%0 journal article %@ 1944-8244 %A Xu, X., Wang, W., Zou, J., Kratz, K., Deng, Z., Lendlein, A., Ma, N. %D 2023 %J ACS Applied Materials and Interfaces %N 25 %P 29752–29766 %R doi:10.1021/acsami.3c01481 %T Histone modification of osteogenesis related genes triggered by substrate topography promotes human mesenchymal stem cell differentiation %U https://doi.org/10.1021/acsami.3c01481 25 %X The clinical success of orthopedic implants is closely related to their integration in the bone tissue promoted by rough device surfaces. The biological response of precursor cells to their artificial microenvironments plays a critical role in this process. In this study, we elucidated the relation between cell instructivity and surface microstructure of polycarbonate (PC)-based model substrates. The rough surface structure (hPC) with an average peak spacing (Sm) similar to the trabecular spacing of trabecular bone improved osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs), as compared to the smooth surface (sPC) and the surface with a moderate Sm value (mPC). The hPC substrate promoted the cell adhesion and assembling of F-actin and enhanced cell contractile force by upregulating phosphorylated myosin light chain (pMLC) expression. The increased cell contractile force led to YAP nuclear translocation and the elongation of cell nuclei, presenting higher levels of active form of Lamin A/C. The nuclear deformation alternated the histone modification profile, particularly the decrease of H3K27me3 and increase of H3K9ac on the promoter region of osteogenesis related genes (ALPL, RUNX2, and OCN). Mechanism study using inhibitors and siRNAs elucidated the role of YAP, integrin, F-actin, myosin, and nuclear membrane proteins in such a regulatory process of surface topography on stem cell fate. These mechanistical insights on the epigenetic level give a new perspective in understanding of the interaction of substrate and stem cells as well as provide valuable criteria for designing bioinstructive orthopedic implants. %0 journal article %@ 2352-9407 %A Sauter, T., Kratz, K., Farhan, M., Heuchel, M., Lendlein, A. %D 2022 %J Applied Materials Today %P 101562 %R doi:10.1016/j.apmt.2022.101562 %T Design and fabrication of fiber mesh actuators %U https://doi.org/10.1016/j.apmt.2022.101562 %X Soft actuator performance can be tuned by chemistry or mechanical manipulation, but this adjustability is limited especially in view of their growing technological relevance. Inspired from textile engineering, we designed and fabricated fiber mesh actuators and introduced new features like anisotropic behavior and soft-tissue like elastic deformability. Design criteria for the meshes are the formation of fiber bundles, the angle between fiber bundles in different stacked layers and covalent crosslinks forming within and between fibers at their interfacial contact areas. Through crosslinking the interfiber bond strength increased from a bond transmitting neither axial nor rotational loads (pin joint) to a bond strength capable of both (welded joint). For non-linear elastic stiffening, stacked fiber bundles with four embracing fibers were created forming microstructural rhombus shapes. Loading the rhombus diagonally allowed generation of “soft tissue”-like mechanics. By adjustment of stacking angles, the point of strong increase in stress is tuned. While the highest stresses are observed in aligned and crosslinked fiber mats along the direction of the fiber, the strongest shape-memory actuation behavior is found in randomly oriented fiber mats. Fiber mesh actuators controlled by temperature are of high significance as soft robot skins and as for active patches supporting tissue regeneration. %0 journal article %@ 1866-3508 %A Valente, A., Sathyendranath, S., Brotas, V., Groom, S., Grant, M., Jackson, T., Chuprin, A., Taberner, M., Airs, R., Antoine, D., Arnone, R., Balch, W. M., Barker, K., Barlow, R., Bélanger, S., Berthon, J.-F., Beşiktepe, Ş., Borsheim, Y., Bracher, A., Brando, V., Brewin, R. J. W., Canuti, E., Chavez, F. P., Cianca, A., Claustre, H., Clementson, L., Crout, R., Ferreira, A., Freeman, S., Frouin, R., García-Soto, C., Gibb, S. W., Goericke, R., Gould, R., Guillocheau, N., Hooker, S. B., Hu, C., Kahru, M., Kampel, M., Klein, H., Kratzer, S., Kudela, R., Ledesma, J., Lohrenz, S., Loisel, H., Mannino, A., Martinez-Vicente, V., Matrai, P., McKee, D., Mitchell, B. G., Moisan, T., Montes, E., Muller-Karger, F., Neeley, A., Novak, M., O'Dowd, L., Ondrusek, M., Platt, T., Poulton, A. J., Repecaud, M., Röttgers, R., Schroeder, T., Smyth, T., Smythe-Wright, D., Sosik, H. M., Thomas, C., Thomas, R., Tilstone, G., Tracana, A., Twardowski, M., Vellucci, V., Voss, K., Werdell, J., Wernand, M., Wojtasiewicz, B., Wright, S., Zibordi, G. %D 2022 %J Earth System Science Data %N 12 %P 5737-5770 %R doi:10.5194/essd-14-5737-2022 %T A compilation of global bio-optical in situ data for ocean colour satellite applications – version three %U https://doi.org/10.5194/essd-14-5737-2022 12 %X A global in situ data set for validation of ocean colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI) is presented. This version of the compilation, starting in 1997, now extends to 2021, which is important for the validation of the most recent satellite optical sensors such as Sentinel 3B OLCI and NOAA-20 VIIRS. The data set comprises in situ observations of the following variables: spectral remote-sensing reflectance, concentration of chlorophyll-a, spectral inherent optical properties, spectral diffuse attenuation coefficient, and total suspended matter. Data were obtained from multi-project archives acquired via open internet services or from individual projects acquired directly from data providers. Methodologies were implemented for homogenization, quality control, and merging of all data. Minimal changes were made on the original data, other than conversion to a standard format, elimination of some points, after quality control and averaging of observations that were close in time and space. The result is a merged table available in text format. Overall, the size of the data set grew with 148 432 rows, with each row representing a unique station in space and time (cf. 136 250 rows in previous version; Valente et al., 2019). Observations of remote-sensing reflectance increased to 68 641 (cf. 59 781 in previous version; Valente et al., 2019). There was also a near tenfold increase in chlorophyll data since 2016. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) are included in the final table. By making the metadata available, provenance is better documented and it is also possible to analyse each set of data separately. The compiled data are available at https://doi.org/10.1594/PANGAEA.941318 (Valente et al., 2022). %0 conference lecture %@ %A Liu, Y., Kratz, K., Lendlein, A. %D 2022 %J MRS Spring Meeting 2022 %T Actuating micro-bowls with a temperature-memory %U %X %0 journal article %@ 1616-301X %A Tung, W.T., Maring, J.A., Xu, X., Liu, Y., Becker, M., Somesh, D.B., Klose, K., Wang, W., Sun, X., Ullah, I., Kratz, K., Neffe, A.T., Stamm, C., Ma, N., Lendlein, A. %D 2022 %J Advanced Functional Materials %N 31 %P 2110179 %R doi:10.1002/adfm.202110179 %T In Vivo Performance of a Cell and Factor Free Multifunctional Fiber Mesh Modulating Postinfarct Myocardial Remodeling %U https://doi.org/10.1002/adfm.202110179 31 %X Guidance of postinfarct myocardial remodeling processes by an epicardial patch system may alleviate the consequences of ischemic heart disease. As macrophages are highly relevant in balancing immune response and regenerative processes their suitable instruction would ensure therapeutic success. A polymeric mesh capable of attracting and instructing monocytes by purely physical cues and accelerating implant degradation at the cell/implant interface is designed. In a murine model for myocardial infarction the meshes are compared to those either coated with extracellular matrix or loaded with induced cardiomyocyte progenitor cells. All implants promote macrophage infiltration and polarization in the epicardium, which is verified by in vitro experiments. 6 weeks post-MI, especially the implantation of the mesh attenuates left ventricular adverse remodeling processes as shown by reduced infarct size (14.7% vs 28–32%) and increased wall thickness (854 µm vs 400–600 µm), enhanced angiogenesis/arteriogenesis (more than 50% increase compared to controls and other groups), and improved heart function (ejection fraction = 36.8% compared to 12.7–31.3%). Upscaling as well as process controls is comprehensively considered in the presented mesh fabrication scheme to warrant further progression from bench to bedside. %0 journal article %@ 1613-6810 %A Liu, Y., Gould, O., Kratz, K., Lendlein, A. %D 2022 %J Small %N 5 %P 2104621 %R doi:10.1002/smll.202104621 %T On Demand Sequential Release of (Sub)Micron Particles Controlled by Size and Temperature %U https://doi.org/10.1002/smll.202104621 5 %X Polymeric devices capable of releasing submicron particles (subMP) on demand are highly desirable for controlled release systems, sensors, and smart surfaces. Here, a temperature-memory polymer sheet with a programmable smooth surface served as matrix to embed and release polystyrene subMP controlled by particle size and temperature. subMPs embedding at 80 °C can be released sequentially according to their size (diameter D of 200 nm, 500 nm, 1 µm) when heated. The differences in their embedding extent are determined by the various subMPs sizes and result in their distinct release temperatures. Microparticles of the same size (D ≈ 1 µm) incorporated in films at different programming temperatures Tp (50, 65, and 80 °C) lead to a sequential release based on the temperature-memory effect. The change of apparent height over the film surface is quantified using atomic force microscopy and the realization of sequential release is proven by confocal laser scanning microscopy. The demonstration and quantification of on demand subMP release are of technological impact for assembly, particle sorting, and release technologies in microtechnology, catalysis, and controlled release. %0 journal article %@ 1438-7492 %A Farhan, M., Chaudhary, D., Nöchel, U., Behl, K., Kratz, K., Lendlein, A. %D 2021 %J Macromolecular Materials and Engineering %N 2 %P 2000579 %R doi:10.1002/mame.202000579 %T Electrical Actuation of Coated and Composite Fibers Based on Poly[ethylene‐co‐(vinyl acetate)] %U https://doi.org/10.1002/mame.202000579 2 %X Robots are typically controlled by electrical signals. Resistive heating is an option to electrically trigger actuation in thermosensitive polymer systems. In this study electrically triggerable poly[ethylene‐co‐(vinyl acetate)] (PEVA)‐based fiber actuators are realized as composite fibers as well as polymer fibers with conductive coatings. In the coated fibers, the core consists of crosslinked PEVA (cPEVA), while the conductive coating shell is achieved via a dip coating procedure with a coating thickness between 10 and 140 µm. The conductivity of coated fibers σ = 300–550 S m−1 is much higher than that of the composite fibers σ = 5.5 S m−1. A voltage (U) of 110 V is required to heat 30 cm of coated fiber to a targeted temperature of ≈ 65 °C for switching in less than a minute. Cyclic electrical actuation investigations reveal ε′rev = 5 ± 1% reversible change in length for coated fibers. The fabrication of such electro‐conductive polymeric actuators is suitable for upscaling so that their application potential as artificial muscles can be explored in future studies. %0 journal article %@ 1386-0291 %A Braune, S., Bäckemo, J., Lau, S., Heuchel, M., Kratz, K., Jung, F., Reinthaler, M., Lendlein, A. %D 2021 %J Clinical Hemorheology and Microcirculation %N 4 %P 367-380 %R doi:10.3233/CH-201029 %T The influence of different rewetting procedures on the thrombogenicity of nanoporous poly(ether imide) microparticles %U https://doi.org/10.3233/CH-201029 4 %X Nanoporous microparticles prepared from poly(ether imide) (PEI) are discussed as candidate adsorber materials for the removal of uremic toxins during apheresis. Polymers exhibiting such porosity can induce the formation of micro-gas/air pockets when exposed to fluids. Such air presenting material surfaces are reported to induce platelet activation and thrombus formation. Physical or chemical treatments prior to implantation are discussed to reduce the formation of such gas nuclei. Here, we report about the influence of different rewetting procedures – as chemical treatments with solvents – on the thrombogenicity of hydrophobic PEI microparticles and PEI microparticles hydrophilized by covalent attachment of poly(vinyl pyrrolidone) (PVP) of two different chain lengths. Autoclaved dry PEI particles of all types with a diameter range of 200 – 250 μm and a porosity of about 84% ±2% were either rewetted directly with phosphate buffered saline (24 h) or after immersion in an ethanol-series. Thrombogenicity of the particles was studied in vitro using human sodium citrated whole blood (60 min, 5 rpm vertical rotation). Numbers of non-adherent platelets were quantified, and adhesion of blood cells was qualitatively analyzed by bright field microscopy. Platelet activation (percentage of CD62P positive platelets and amounts of soluble P-Selectin) and platelet function (PFA100 closure times) were analysed. Retention of blood platelets on the particles was similar for all particle types and both rewetting procedures. Non-adherent platelets were less activated after contact with ethanol-treated particles of all types compared to those rewetted with phosphate buffered saline as assessed by a reduced number of CD62P-positive platelets and reduced amounts of secreted P-Selectin (P < 0.05 each). Interestingly, the hydrophilic surfaces significantly increased the number of activated platelets compared to hydrophobic PEI regardless of the rewetting agent. This suggests that, apart from wettability, other material properties might be more important to regulate platelet activation. PFA100 closure times were reduced and within the reference ranges in the ethanol group, however, significantly increased in the saline group. No substantial difference was detected between the tested surface modifications. In summary, rewetting with ethanol resulted in a reduced thrombogenicity of all studied microparticles regardless of their wettability, most likely resulting from the evacuation of air from the nanoporous particles. %0 conference lecture (invited) %@ %A Kratz, K., Izraylit, V., Heuchel, M., Lendlein, A. %D 2021 %J Virtual MRS Spring Meeting 2021 %T Shape-memory actuator blends by stereocomplexation of PLA %U %X %0 journal article %@ 2059-8521 %A Izraylit, V., Heuchel, M., Kratz, K., Lendlein, A. %D 2021 %J MRS Advances %N 33 %P 781-785 %R doi:10.1557/s43580-021-00063-8 %T Non-woven shape-memory polymer blend actuators %U https://doi.org/10.1557/s43580-021-00063-8 33 %X The hierarchical design approach provides various opportunities to adjust the structural performance of polymer materials. Electrospinning processing techniques give access to molecular orientation as a design parameter, which we consider here in view of the shape-memory actuation performance. The aim of this work is to investigate how the reversible strain ε′rev can be affected by a morphology change from a bulk material to an electrospun mesh. ε′rev could be increased from 5.5 ± 0.5% to 15 ± 1.8% for a blend from a multiblock copolymer with poly(ε-caprolactone) (PCL) and poly(L-lactide) (PLLA) segments with oligo(D-lactide) (ODLA). This study demonstrates an effective design approach for enhancing soft actuator performance, which can be broadly applied in soft robotics and medicine. %0 journal article %@ 2159-6859 %A Farhan, M., Behl, M., Kratz, K., Lendlein, A. %D 2021 %J MRS Communications %N 4 %P 476-482 %R doi:10.1557/s43579-021-00058-4 %T Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators %U https://doi.org/10.1557/s43579-021-00058-4 4 %X Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg−1 was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling. %0 conference lecture (invited) %@ %A Izraylit, V., Kratz, K., Heuchel, M., Lendlein, A. %D 2021 %J Seminar am Kurchatov Complex of NBICS-nature-like Technologies; National Research Centre Kurchatov Institute %T Shape-memory actuator blends by stereocomplexation of PLA %U %X %0 journal article %@ 0264-1275 %A Sauter, T., Kratz, K., Heuchel, M., Lendlein, A. %D 2021 %J Materials & Design %P 109546 %R doi:10.1016/j.matdes.2021.109546 %T Fiber diameter as design parameter for tailoring the macroscopic shape-memory performance of electrospun meshes %U https://doi.org/10.1016/j.matdes.2021.109546 %X Fibrous shape-memory polymer (SMP) scaffolds were investigated considering the fiber as basic microstructural feature. By reduction of the fiber diameter in randomly oriented electrospun polyetherurethane (PEU) meshes from the micro- to the nano-scale, we observed changes in the molecular orientation within the fibers and its impact on the structural and shape-memory performance. It was assumed that a spatial restriction by reduction of the fiber diameter increases molecular orientation along the orientation of the fiber. The stress-strain relation of random PEU scaffolds is initially determined by the 3D arrangement of the fibers and thus is independent of the molecular orientation. Increasing the molecular orientation with decreasing single fiber diameter in scaffolds composed of randomly arranged fibers did not alter the initial stiffness and peak stress but strongly influenced the elongation at break and the stress increase above the Yield point. Reduction of the single fiber diameter also distinctly improved the shape-memory performance of the scaffolds. Fibers with nanoscale diameters (< 100 nm) possessed an almost complete shape recovery, high recovery stresses and fast relaxation kinetics, while the shape fixity was found to decrease with decreasing fiber diameter. Hence, the fiber diameter is a relevant design parameter for SMP. %0 journal article %@ 1438-7492 %A Sauter, T., Kratz, K., Madbouly, S., Klein, F., Heuchel, M., Lendlein, A. %D 2021 %J Macromolecular Materials and Engineering %N 4 %P 2000730 %R doi:10.1002/mame.202000730 %T Anisotropy Effects in the Shape‐Memory Performance of Polymer Foams %U https://doi.org/10.1002/mame.202000730 4 %X Isotropic and anisotropic shape‐memory polymer foams are prepared by supercritical carbon dioxide foaming from a multiblock copolymer (PDLCL) consisting of poly(ω‐pentadecalactone) and poly(ε‐caprolactone) segments. Analysis by micro‐computed tomography reveals for the anisotropic PDLCL foam cells a high shape anisotropy ratio of R = 1.72 ± 0.62 with a corresponding Young's compression moduli ratio between longitudinal and transversal direction of 4.3. The experimental compression data in the linear elastic range can be well described by the anisotropic open foam model of Gibson and Ashby. A micro‐morphological analysis for single pores using scanning electron microscopy images permits the correlation between the macroscopic stress‐compression behavior and microscale structural changes. %0 journal article %@ 0032-3861 %A Kratz, K., Heuchel, M., Weigel, T., Lendlein, A. %D 2020 %J Polymer %P 123045 %R doi:10.1016/j.polymer.2020.123045 %T Surface hydrophilization of highly porous poly(ether imide) microparticles by covalent attachment of poly(vinyl pyrrolidone) %U https://doi.org/10.1016/j.polymer.2020.123045 %X Here we report on the hydrophilic surface functionalization of porous poly (ether imide) (PEI) microparticles, having a mean diameter of 226 ± 14 μm, a porosity of around 84 ± 2% with a mean pore diameter of 230 ± 40 nm, by covalent attachment of amino-terminated poly (vinyl pyrrolidone) (PVP–NH2) with a number average molecular weight of Mn = 5400 g mol−1. X-ray photoelectron spectroscopy confirmed a successful surface modification by a change in the surface chemistry, in particular the N/C ratio. The PEI-PVP particles exhibited an advancing water contact angle of θadv = 75° ± 5° as determined in environmental scanning electron microscopy microwetting experiments. The obtained results from mercury intrusion porosimetry and nitrogen adsorption experiments documented the preservation of the porous structure of the particles in the cause of the modification, which could be visualized by electron microscopy. The presented approach enables a covalent hydrophilization of porous particles while preserving their nanoporous morphology. %0 journal article %@ 1438-7492 %A Liu, Y., Gould, O., Rudolph, T., Fang, L., Kratz, K., Lendlein, A. %D 2020 %J Macromolecular Materials and Engineering %N 10 %P 2000333 %R doi:10.1002/mame.202000333 %T Polymeric Microcuboids Programmable for Temperature‐Memory %U https://doi.org/10.1002/mame.202000333 10 %X Microobjects with programmable mechanical functionality are highly desirable for the creation of flexible electronics, sensors, and microfluidic systems, where fabrication/programming and quantification methods are required to fully control and implement dynamic physical behavior. Here, programmable microcuboids with defined geometries are prepared by a template‐based method from crosslinked poly[ethylene‐co‐(vinyl acetate)] elastomers. These microobjects could be programmed to exhibit a temperature‐memory effect or a shape‐memory polymer actuation capability. Switching temperatures Tsw during shape recovery of 55 ± 2, 68 ± 2, 80 ± 2, and 86 ± 2 °C are achieved by tuning programming temperatures to 55, 70, 85, and 100 °C, respectively. Actuation is achieved with a reversible strain of 2.9 ± 0.2% to 6.7 ± 0.1%, whereby greater compression ratios and higher separation temperatures induce a more pronounced actuation. Micro‐geometry change is quantified using optical microscopy and atomic force microscopy. The realization and quantification of microparticles, capable of a tunable temperature responsive shape‐change or reversible actuation, represent a key development in the creation of soft microscale devices for drug delivery or microrobotics. %0 journal article %@ 1386-0291 %A Sun, X., Tung, W., Zou, J., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2020 %J Clinical Hemorheology and Microcirculation %N 4 %P 405-415 %R doi:10.3233/CH-190696 %T Elasticity of fiber meshes from multiblock copolymers influences endothelial cell behavior %U https://doi.org/10.3233/CH-190696 4 %X These results suggested that tuning the fiber meshes’ elasticity might be a potential strategy for modulating the formation or regeneration of blood vessels. %0 conference poster %@ %A Liu, Y., Gould, O., Kratz, K., Lendlein, A. %D 2020 %J Virtual MRS Spring/Fall Meeting 2020 %T Reversible Shape-Memory Actuation of Individual Micro-/Nanofibers %U %X %0 journal article %@ 0027-8424 %A Deng, Z., Wang, W., Xu, X., Gould, O.E.C, Kratz, K., Ma, N., Lendlein, A. %D 2020 %J Proceedings of the National Academy of Sciences of the United States of America: PNAS %N 4 %P 1895-1901 %R doi:10.1073/pnas.1910668117 %T Polymeric sheet actuators with programmable bioinstructivity %U https://doi.org/10.1073/pnas.1910668117 4 %X Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSCs). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca2+) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSCs are interconnected via intracellular Ca2+. Up-regulated Ca2+ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects. %0 journal article %@ 1525-7797 %A Izraylit, V., Gould, O., Rudolph, T., Kratz, K., Lendlein, A. %D 2020 %J Biomacromolecules %N 2 %P 338-348 %R doi:10.1021/acs.biomac.9b01279 %T Controlling Actuation Performance in Physically Cross-Linked Polylactone Blends Using Polylactide Stereocomplexation %U https://doi.org/10.1021/acs.biomac.9b01279 2 %X Within the field of shape-changing materials, synthetic chemical modification has been widely used to introduce key structural units and subsequently expand the mechanical functionality of actuator devices. The introduction of architectural elements that facilitate in situ control over mechanical properties and complete geometric reconfiguration of a device is highly desirable to increase the morphological diversity of polymeric actuator materials. The subject of the present study is a multiblock copolymer with semicrystalline poly(l-lactide) and poly(ε-caprolactone) (PLLA–PCL) segments. By harnessing the stereocomplexation of copolymer chains with a poly(d-lactide) oligomer (PDLA), we provide anchoring points for physical network formation and demonstrate how a blending process can be used to efficiently vary the mechanical properties of a shape-memory actuator. We investigate the effect of molecular structure on the actuation performance of the material in cyclic thermomechanical tests, with a maximum reversible shape change εrev′ = 13.4 ± 1.5% measured at 3.1 wt % of polylactide stereocomplex content in the multiblock copolymer matrix. The thermophysical properties, crystalline structure, and phase morphology were analyzed by DSC, WAXS and AFM respectively, elucidating the structure-to-function relationship in physically cross-linked blended materials. The work demonstrates a one-step technique for manufacturing a polymeric actuator and tuning its performance in situ. This approach should greatly improve the efficiency of physically cross-linked actuator fabrication, allowing composition and physical behavior to be precisely and easily controlled. %0 journal article %@ 2059-8521 %A Izraylit, V., Gould, O., Kratz, K., Lendlein, A. %D 2020 %J MRS Advances %N 14 - 15 %P 699-707 %R doi:10.1557/adv.2019.465 %T Investigating the Phase-Morphology of PLLA-PCL Multiblock Copolymer / PDLA Blends Cross-linked Using Stereocomplexation %U https://doi.org/10.1557/adv.2019.465 14 - 15 %X The macroscale function of multicomponent polymeric materials is dependent on their phase-morphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(ε-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 – 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance. %0 journal article %@ 2059-8521 %A Wischke, C., Kersting, M., Welle, A., Lysyakova, L., Braune, S., Kratz, K., Jung, F., Franzreb, M., Lendlein, A. %D 2020 %J MRS Advances %N 14 - 15 %P 773-783 %R doi:10.1557/adv.2020.218 %T Thin hydrogel coatings formation catalyzed by immobilized enzyme horseradish peroxidase %U https://doi.org/10.1557/adv.2020.218 14 - 15 %X Enzymes can be a renewable source of catalytic agents and thus be interesting for sustainable approaches to create and modify functional materials. Here, thin hydrogel layers were prepared as thin coatings on hard substrates by immobilized horseradish peroxidase. Hydrophilic 4-arm star shaped telechelics from oligo(ethylene glycol) bearing on average 55% end groups derived from aromatic amino acids served as monomers and enzymatic substrates. Shifts of the contact angle from 84° to 62° for the wetting process and of zeta potential towards the neutral range illustrated an alteration of physicochemical properties of the model surfaces by a hydrophilic shielding. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), quartz crystal microbalance and atomic force microscopy (AFM) experiments enabled the qualitative and quantitative proof of hydrogel deposition at the interface with thicknesses in the medium nanometer size range. Conceptually, as the immobilized enzyme becomes entrapped in the hydrogel and the crosslinking mechanism bases on a radical reaction after enzymatic activation of the monomers with a limited diffusivity and lifetime, the formed network material can be assumed to be inhomogeneous on the molecular level. On the macroscale, however, relative homogeneity of the coating was observed via ToF-SIMS and AFM mapping. As an exemplary functional evaluation in view of bioanalytical applications, the thrombogenicity of the coating was studied in static tests with human blood from several donors. In the future, this “coating-from” approach may be explored for cell culture substrate coatings, for protein/biofilm repellence in technical applications, or in bioanalytical devices. %0 journal article %@ 2059-8521 %A Xu, X., Wang, W., Nie, Y., Kratz, K., Ma, N., Lendlein, A. %D 2020 %J MRS Advances %N 12 - 13 %P 643-653 %R doi:10.1557/adv.2019.446 %T Fine-tuning of Rat Mesenchymal Stem Cell Senescence via Microtopography of Polymeric Substrates %U https://doi.org/10.1557/adv.2019.446 12 - 13 %X Cellular senescence, a driver of aging and age-related diseases, is a stable state found in metabolically active cells characterized by irreversible cell growth arrest and dramatic changes in metabolism, gene expression and secretome profile. Endogenous regeneration efficacy of mesenchymal stem cells (MSCs) could be attenuated due to senescence. MSCs can be modulated by not only biochemical signals but also by physical cues such as substrate topography. To provide a cell culture substrate that can prevent MSC senescence over an extended period of in vitro cultivation, here, the cell- and immunocompatible poly(ether imide) (PEI) substrate was used. Two distinct levels of roughness were created on the bottom surfaces of PEI inserts via injection molding: Low-R (similar to the thickness of attached single MSC, Rq: 3.9 ± 0.2 µm) and High-R (larger than single MSC thickness. Rq: 22.7 ± 0.8 µm). Cell expansion, lysosomal enzymatic activity, apoptosis and paracrine effects of senescent MSCs were examined by cell counting, detection of senescence-associated β-galactosidase (SA β-gal), Caspase 3/7, and CFSE labeling. MSCs showed high cell viability and similar spindle-shaped morphology on all investigated surfaces. Cells on Low-R presented the highest expansion (80000 ± 1805 cells), as compared to cells on smooth PEI and High-R. The low apoptosis level (0.08 vs 0.12 from smooth PEI) and senescence ratio (35% vs. 54% from smooth PEI) were observed in MSCs cultured on Low-R. The secretome from Low-R effectively prevents senescence and supports the proliferation of neighboring cells (1.5-fold faster) as compared to the smooth PEI secretome. In summary, the Low-R PEI provided a superior surface environment for MSCs, which promoted proliferation, inhibited apoptosis and senescence, and effectively influenced the proliferation of neighboring cells via their paracrine effect. Such microroughness can be considered as a key parameter for improving the therapeutic potential of endogenous regeneration, anti-organismal aging and anti-age-related pathologies via directly promoting cell growth and modulating paracrine effects of the senescence associated secretome. %0 journal article %@ 1386-0291 %A Haase, T., Klopfleisch, R., Krost, A., Sauter, T., Kratz, K., Peter, J., Jung, F., Lendlein, A., Zohlnhöfer, D., Rüder, C. %D 2020 %J Clinical Hemorheology and Microcirculation %N 2 %P 163-176 %R doi:10.3233/CH-190748 %T In vivo biocompatibility study of degradable homo- versus multiblock copolymers and their (micro)structure compared to an established biomaterial %U https://doi.org/10.3233/CH-190748 2 %X Copolyetheresterurethane (PDC) is a biodegradable, shape-memory biomaterial, which has been shown to be of low toxicity and pro-angiogenic in vitro. In the present study we examined the in vivo compatibility of PDC as a compression molded film and as electrospun scaffolds and its well established constituent, the homopolymer poly(p-dioxanone) (PPDO), which were compared with the clinically used poly[(vinylidene fluoride)-co-hexafluoropropene] (PVDF) as reference material. The materials were implanted in the subcutaneous tissue of mice and the host responses were analyzed histologically 7 and 28 days after implantation. All materials induced a foreign body response (FRB) including the induction of foreign body giant cells and a peripheral fibrous capsule. PDC, PPDO and PVDF films showed no signs of degradation after 28 days. PDC films showed a significantly reduced associated macrophage layer and fibrous capsule on their surface. Few fragments of PDC and PPDO scaffolds were present at the implantation site, while PVDF scaffolds were still present in large amounts at day 28. Especially aligned electrospun PDC scaffold induced a significantly thinner fibrous and a slightly reduced inflammatory response after 28 days of implantation. In addition, only PDC aligned fibrous scaffold structures induced a significant increase in angiogenesis. In summary, PDC films outperformed PPDO and PVDF films in terms of compatibility, especially in capsule and macrophage layer thickness. Through microstructuring of PDC and PPDO into scaffolds an almost complete degradation was observed after 28 days, while their respective films remained almost unchanged. However, the capsule thickness of all scaffolds was comparable to the films after 28 days. Finally, the parallel arrangement of PDC fibers enabled a strong enhancement of angiogenesis within the scaffold. Hence, material chemistries influence overall compatibility in vivo, while angiogenesis could be influenced more strongly by microstructural parameters than chemical ones. %0 journal article %@ 2059-8521 %A Liu, Y., Gould, O., Kratz, K., Lendlein, A. %D 2020 %J MRS Advances %N 46 - 47 %P 2391-2399 %R doi:10.1557/adv.2020.276 %T Shape-Memory Actuation of Individual Micro-/Nanofibers %U https://doi.org/10.1557/adv.2020.276 46 - 47 %X Advances in the fabrication and characterization of polymeric nanomaterials has greatly advanced the miniaturization of soft actuators, creating materials capable of replicating the functional physical behavior previously limited to the macroscale. Here, we demonstrate how a reversible shape-memory polymer actuation can be generated in a single micro/nano object, where the shape change during actuation of an individual fiber can be dictated by programming using an AFM-based method. Electrospinning was used to prepare poly(ε-caprolactone) micro-/nanofibers, which were fixed and crosslinked on a structured silicon wafer. The programming as well as the observation of recovery and reversible displacement of the fiber were performed by vertical three point bending, using an AFM testing platform introduced here. A plateau tip was utilized to improve the stability of the fiber contact and working distance, enabling larger deformations and greater rbSMPA performance. Values for the reversible elongation of εrev = 3.4 ± 0.1% and 10.5 ± 0.1% were obtained for a single micro (d = 1.0 ± 0.2 μm) and nanofiber (d = 300 ± 100 nm) in cyclic testing between the temperatures 10 and 60 °C. The reversible actuation of the nanofiber was successfully characterized for 10 cycles. The demonstration and characterization of individual shape-memory nano and microfiber actuators represents an important step in the creation of miniaturized robotic devices capable of performing complex physical functions at the length scale of cells and structural component of the extracellular matrix. %0 journal article %@ 0032-3861 %A Izraylit, V., Heuchel, M., Gould, O., Kratz, K., Lendlein, A. %D 2020 %J Polymer %P 122984 %R doi:10.1016/j.polymer.2020.122984 %T Strain recovery and stress relaxation behaviour of multiblock copolymer blends physically cross-linked with PLA stereocomplexation %U https://doi.org/10.1016/j.polymer.2020.122984 %X Polylactide (PLA) stereocomplexes have attracted attention due to their ability to improve the thermal stability of bioplastics. Here, we evaluate whether PLA stereocomplexes can form stable physical cross-links in blends of a multiblock copolymer with poly(l-lactide) and poly(ε-caprolactone) segments (PLLA-PCL) and a poly(d-lactide) oligomer (PDLA). Through the investigation of the strain recovery in step-cycle experiments and compliance of stress relaxation behaviour with a three-component model for the deformation of semi-crystalline polymers, PLA stereocomplexes were found to possess sufficient stability in the true strain range εH < 2.25 to be described as firm physical netpoints at 70 °C in the studied blends with PLA stereocomplex content ϕc SC ≥ 1.1 wt%, when the PCL domains are melted. Limiting ϕc SC ≤ 6 wt% broadens the behaviour inherent to elastic cross-linked networks to the strain values up until breakage of the samples, while the increase of ϕc SC triggers plastic deformations typical for semi-crystalline polymers. Redistributing of internal stresses from the amorphous to crystalline domains at increase of ϕc calculated with the adopted model was identified as reason of PLA stereocomplexes failure as stable physical network junctions at higher ϕc SC. Within the experimentally determined strain and composition ranges, in which PLA stereocomplexes possess structural stability, they can form robust cross-links in a polymer network. The knowledge gained here provides valuable design criteria for multifunctional thermoplastic elastomers. %0 journal article %@ 2059-8521 %A Bäckemo, J., Heuchel, M., Reinthaler, M., Kratz, K., Lendlein, A. %D 2020 %J MRS Advances %N 12 - 13 %P 621-632 %R doi:10.1557/adv.2019.433 %T Predictive topography impact model for Electrical Discharge Machining (EDM) of metal surfaces %U https://doi.org/10.1557/adv.2019.433 12 - 13 %X Electrical discharge machining (EDM) is a method capable of modifying the microstructure of metal surfaces. Here, we present a predictive computer supported model of the roughness generated on the surface by this process. EDM is a stochastic process, in which charge generated between a metallic substrate and an electrode creates impacts, and thus is suitable for modeling through iterative simulations. The resulting virtual, modified surface structures were evaluated for roughness. Curvatures were analyzed using Abbott-Firestone curves. Three radii of impacts (10, 20, 30 μm) and two values for the depth to radius ratio (0.1, 0.3) were used as input parameters to compute a total of six simulations. It was found that the roughness parameters followed an inverse exponential trend as a function of impact number, and that the strongly concave curvatures reached equilibrium at an earlier impact number for lower depth to radius ratios. %0 journal article %@ 1386-0291 %A Tung, W., Zou, J., Sun, X., Wang, W., Gould, O., Kratz, K., Ma, N., Lendlein, A. %D 2020 %J Clinical Hemorheology and Microcirculation %N 1 %P 53-66 %R doi:10.3233/CH-199235 %T Coaxial electrospinning of PEEU/gelatin to fiber meshes with enhanced mesenchymal stem cell attachment and proliferation %U https://doi.org/10.3233/CH-199235 1 %X Microfibers with a core-shell structure can be produced by co-axial electrospinning, allowing for the functionalization of the outer layer with bioactive molecules. In this study, a thermoplastic, degradable polyesteretherurethane (PEEU), consisting of poly(p-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments with different PPDO to PCL weight ratios, were processed into fiber meshes by co-axial electrospinning with gelatin. The prepared PEEU fibers have a diameter of 1.3±0.5 μm and an elastic modulus of around 5.1±1.0 MPa as measured by tensile testing in a dry state at 37°C, while the PEEU/Gelatin core-shell fibers with a gelatin content of 12±6 wt% and a diameter of 1.5±0.5 μm possess an elastic modulus of 15.0±1.1 MPa in a dry state at 37 °C but as low as 0.7±0.7 MPa when hydrated at 37 °C. Co-axial electrospinning allowed for the homogeneous distribution of the gelatin shell along the whole microfiber. Gelatin with conjugated Fluorescein (FITC) remained stable on the PEEU fibers after 7 days incubation in Phosphate-buffered saline (PBS) at 37 °C. The gelatin coating on PEEU fibers lead to enhanced human adipose tissue derived mesenchymal stem cell (hADSC) attachment and a proliferation rate 81.7±34.1 % higher in cell number in PEEU50/Gelatin fibers after 7 days of cell culture when compared to PEEU fibers without coating. In this work, we demonstrate that water-soluble gelatin can be incorporated as the outer shell of a polymer fiber via molecular entanglement, with a sustained presence and role in enhancing stem cell attachment and proliferation. %0 conference poster %@ %A Sun, X., Tung, W., Zou, J., Liu, Y., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2020 %J Virtual MRS Spring/Fall Meeting %T PEEU fiber mesh elasticity and its regulatory effects on human endothelial cells %U %X %0 journal article %@ 1386-0291 %A Lee, S., Ganesan, R., Krüger-Genge, A., Kratz, K., Franke, R., Lendlein, A., Jung, F. %D 2020 %J Clinical Hemorheology and Microcirculation %N 1 %P 85-98 %R doi:10.3233/CH-190736 %T Substrate-enzyme affinity-based surface modification strategy for endothelial cell-specific binding under shear stress %U https://doi.org/10.3233/CH-190736 1 %X Establishing an endothelial cell (EC) monolayer on top of the blood contacting surface of grafts is considered to be a promising approach for creating a hemocompatible surface. Here we utilized the high affinity interactions between the EC plasma membrane expressed enzyme called endothelin converting enzyme-1 (ECE-1) and its corresponding substrate big Endothelin-1 (bigET-1) to engineer an EC-specific binding surface. Since enzymatic cleavage of substrates require physical interaction between the enzyme and its corresponding substrate, it was hypothesized that a surface with chemically immobilized synthetic bigET-1 will preferentially attract ECs over other types of cells found in vascular system such as vascular smooth muscle cells (VSMCs). First, the expression of ECE-1 was significantly higher in ECs, and ECs processed synthetic bigET-1 to produce ET-1 in a cell number-dependent manner. Such interaction between ECs and synthetic bigET-1 was also detectible in blood. Next, vinyl-terminated self-assembled monolayers (SAMs) were established, oxidized and activated on a glass substrate as a model to immobilize synthetic bigET-1 via amide bonds. The ECs cultured on the synthetic bigET-1-immobilized surface processed larger amount of synthetic bigET-1 to produce ET-1 compared to VSMCs (102.9±5.13 vs. 9.75±0.74 pg/ml). The number of ECs bound to the synthetic bigET-1-immobilized surface during 1 h of shearing (5dyne/cm2) was approximately 3-fold higher than that of VSMCs (46.25±12.61 vs. 15.25±3.69 cells/100×HPF). EC-specific binding of synthetic bigET-1-immobilized surface over a surface modified with collagen, a common substance for cell adhesion, was also observed. The present study demonstrated that using the substrate-enzyme affinity (SEA) of cell type-specific enzyme and its corresponding substrate can be an effective method to engineer a surface preferentially binds specific type of cells. This novel strategy might open a new route toward rapid endothelialization under dynamic conditions supporting the long-term patency of cardiovascular implants. %0 conference lecture %@ %A Izraylit, V., Kratz, K., Lendlein, A. %D 2019 %J MRS Fall Meeting 2019 %T Controlling actuation behaviour in shape-memory polymer blends by tailoring supramolecular interactions %U %X %0 conference lecture %@ %A Tung, W., Zou, J., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J 38. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheoligie (DGKMH %T Coaxial electrospinning of Gelatin/PEEU to fiber meshes with enhanced mesenchymal stem cell attachment and proliferation %U %X %0 conference lecture %@ %A Braune, S., Xourida, M., Maier, A., Reinthaler, M., Kratz, K., Latour, R., Lendlein, A., Jung, F. %D 2019 %J 38. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie %T Translocation and release of Von Willebrand factor in the adherent platelet %U %X The adsorption of proteins from blood plasma, molecules secreted by blood cells - such as the activated platelet - participates in orchestrating the overall hemocompatibility of cardiovascular implants. Here, we studied the translocation and secretion of von Willebrand factor (VWF) from human platelets on implant materials using three-dimensional super resolution microscopy in order to explore how local secretion processes can influence thrombotic processes. We hypothesize that beyond the secretion of VWF from the platelet granula, also not secreted VWF might be available on blood contacting implant surfaces after the full activation of the adherent platelet. %0 journal article %@ 1386-0291 %A Sun, X., Tung, W., Wang, W., Xu, X., Zou, J., Gould, O., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J Clinical Hemorheology and Microcirculation %N 1 %P 219-228 %R doi:10.3233/CH-199206 %T The effect of stiffness variation of electrospun fiber meshes of multiblock copolymers on the osteogenic differentiation of human mesenchymal stem cells %U https://doi.org/10.3233/CH-199206 1 %X Electrospinning has attracted significant attention as a method to produce cell culture substrates whose fibrous structure mimics the native extracellular matrix (ECM). In this study, the influence of E-modulus of fibrous substrates on the lineage commitment of human adipose-derived stem cells (hADSCs) was studied using fiber meshes prepared via the electrospinning of a polyetheresterurethane (PEEU) consisting of poly(ρ-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments. The PPDO: PCL weight ratio was varied from 40:60 to 70:30 to adjust the physiochemical properties of the PEEU fibers. The cells attached on stiffer PEEU70 (PPDO:PCL,= 70:30) fiber meshes displayed an elongated morphology compared to those cultured on softer fibers. The nuclear aspect ratio (width vs. length of a nucleus) of hADSCs cultured on softer PEEU40 (PPDO:PCL = 40:60) fibers was lower than on stiffer fibers. The osteogenic differentiation of hADSCs was enhanced by culturing on stiffer fibers. Compared to PEEU40, a 73% increase of osteocalcin expression and a 34% enhancement of alkaline phosphatase (ALP) activity was observed in cells on PEEU70. These results demonstrated that the differentiation commitment of stem cells could be regulated via tailoring the mechanical properties of electrospun fibers. %0 journal article %@ 0036-8075 %A Yuan, J., Neri, W., Zakri, C., Merzeau, P., Kratz, K., Lendlein, A., Poulin, P. %D 2019 %J Science %N 6449 %P 155-158 %R doi:10.1126/science.aaw3722 %T Shape memory nanocomposite fibers for untethered high-energy microengines %U https://doi.org/10.1126/science.aaw3722 6449 %X Classic rotating engines are powerful and broadly used but are of complex design and difficult to miniaturize. It has long remained challenging to make large-stroke, high-speed, high-energy microengines that are simple and robust. We show that torsionally stiffened shape memory nanocomposite fibers can be transformed upon insertion of twist to store and provide fast and high-energy rotations. The twisted shape memory nanocomposite fibers combine high torque with large angles of rotation, delivering a gravimetric work capacity that is 60 times higher than that of natural skeletal muscles. The temperature that triggers fiber rotation can be tuned. This temperature memory effect provides an additional advantage over conventional engines by allowing for the tunability of the operation temperature and a stepwise release of stored energy. %0 journal article %@ 2159-6859 %A Jiang, Y., Mansfeld, U., Kratz, K., Lendlein, A. %D 2019 %J MRS Communications %N 1 %P 181-188 %R doi:10.1557/mrc.2019.24 %T Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology %U https://doi.org/10.1557/mrc.2019.24 1 %X Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 °C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 °C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads, optical storage, or cell instructive substrates. %0 journal article %@ 1386-0291 %A Zou, J., Wang, W., Kratz, K., Xu, X., Nie, Y., Ma, N., Lendlein, A. %D 2019 %J Clinical Hemorheology and Microcirculation %N 4 %P 573-583 %R doi:10.3233/CH-189322 %T Evaluation of human mesenchymal stem cell senescence, differentiation and secretion behavior cultured on polycarbonate cell culture inserts %U https://doi.org/10.3233/CH-189322 4 %X Polycarbonate (PC) substrate is well suited for culturing human mesenchymal stem cells (MSCs) with high proliferation rate, low cell apoptosis rate and negligible cytotoxic effects. However, little is known about the influence of PC on MSC activity including senescence, differentiation and secretion. In this study, the PC cell culture insert was applied for human MSC culture and was compared with polystyrene (PS) and standard tissue culture plate (TCP). The results showed that MSCs were able to adhere on PC surface, exhibiting a spindle-shaped morphology. The size and distribution of focal adhesions of MSCs were similar on PC and TCP. The senescence level of MSCs on PC was comparable to that on TCP, but was significantly lower than that on PS. MSCs on PC were capable of self-renewal and differentiation into multiple cell lineages, including osteogenic and adipogenic lineages. MSCs cultured on PC secreted a higher level inflammatory cytokines and pro-angiogenic factors including FGF2 and VEGF. Conclusively, PC represents a promising cell culture material for human MSCs. %0 journal article %@ 0964-1726 %A Zhang, Q., Rudolph, T., Benitez, A.J., Gould, O.E.C., Behl, M., Kratz, K., Lendlein, A. %D 2019 %J Smart Materials and Structures %N 5 %P 055037 %R doi:10.1088/1361-665X/ab10a1 %T Temperature-controlled reversible pore size change of electrospun fibrous shape-memory polymer actuator based meshes %U https://doi.org/10.1088/1361-665X/ab10a1 5 %X Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of ε m = 300% and 100% reversible strain changes of εʹrev = 22% ± 1% and 6% ± 1% were measured, with switching temperature ranges of 10 °C–30 °C and 45 °C–60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11% ± 3% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality. %0 journal article %@ 1386-0291 %A Wang, W., Xu, X., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J Clinical Hemorheology and Microcirculation %N 2 %P 277-289 %R doi:10.3233/CH-189418 %T Modulating human mesenchymal stem cells using poly(Eta-butyl acrylate) networks in vitro with elasticity matching human arteries %U https://doi.org/10.3233/CH-189418 2 %X Non-swelling hydrophobic poly(n-butyl acrylate) network (cPnBA) is a candidate material for synthetic vascular grafts owing to its low toxicity and tailorable mechanical properties. Mesenchymal stem cells (MSCs) are an attractive cell type for accelerating endothelialization because of their superior anti-thrombosis and immune modulatory function. Further, they can differentiate into smooth muscle cells or endothelial-like cells and secret pro-angiogenic factors such as vascular endothelial growth factor (VEGF). MSCs are sensitive to the substrate mechanical properties, with the alteration of their major cellular behavior and functions as a response to substrate elasticity. Here, we cultured human adipose-derived mesenchymal stem cells (hADSCs) on cPnBAs with different mechanical properties (cPnBA250, Young’s modulus (E) = 250 kPa; cPnBA1100, E = 1100 kPa) matching the elasticity of native arteries, and investigated their cellular response to the materials including cell attachment, proliferation, viability, apoptosis, senescence and secretion. The cPnBA allowed high cell attachment and showed negligible cytotoxicity. F-actin assembly of hADSCs decreased on cPnBA films compared to classical tissue culture plate. The difference of cPnBA elasticity did not show dramatic effects on cell attachment, morphology, cytoskeleton assembly, apoptosis and senescence. Cells on cPnBA250, with lower proliferation rate, had significantly higher VEGF secretion activity. These results demonstrated that tuning polymer elasticity to regulate human stem cells might be a potential strategy for constructing stem cell-based artificial blood vessels. %0 journal article %@ 1748-605X %A Bhuvanesh, T., Machatschek, R., Lysyakova, L., Kratz, K., Schulz, B., Ma, N., Lendlein, A. %D 2019 %J Biomedical Materials %N 2 %P 024101 %R doi:10.1088/1748-605X/aaf464 %T Collagen type-IV Langmuir and Langmuir-Schaefer layers as model biointerfaces to direct stem cell adhesion %U https://doi.org/10.1088/1748-605X/aaf464 2 %X In biomaterial development, the design of material surfaces that mimic the extra-cellular matrix (ECM) in order to achieve favorable cellular instruction is rather challenging. Collagen-type IV (Col-IV), the major scaffolding component of Basement membranes, a specialized ECM with multiple biological functions, has the propensity to form networks by self-assembly and supports adhesion of cells such as endothelial cells or stem cells. The preparation of biomimetic Col-IV network like layers to direct cell responses is difficult. We hypothesize that the morphology of the layer, and especially the density of the available adhesion sites, regulates the cellular adhesion to the layer. The Langmuir monolayer technique allows for preparation of thin layers with precisely controlled packing density at the air-water (A-W) interface. Transferring these layers onto cell culture substrates using the Langmuir Schäfer (LS) technique should therefore provide a pathway for preparation of BM mimicking layers with controlled cell adherence properties. In situ characterization using ellipsometry and polarization modulation-infrared reflection absorption spectroscopy of Col-IV layer during compression at the A-W interface reveal that there is linear increase of surface molecule concentration with negligible orientational changes up to a surface pressure of 25 mNcenterdotm<sup>-1</sup>. Smooth and homogeneous Col-IV network-like layers are successfully transferred by LS method at 15 mNcenterdotm<sup>-1</sup> onto poly(ethyleneterepthalate) (PET), which is a common substrate for cell culture. In contrast, the organization of Col-IV on PET prepared by the traditionally employed solution deposition method results in rather inhomogeneous layers with the appearance of aggregates and multilayers. Progressive increase in the number of early adherent mesenchymal stem cells (MSCs) after 24 h by controlling the Col-IV density by LS transfer at 10, 15 and 20 mNcenterdotm<sup>-1</sup> on PET is shown. LS method offers the possibility to control protein characteristics on biomaterial surfaces such as molecular density and thereby, modulate cell responses. %0 conference poster %@ %A Xu, X., Wang, W., Nie, Y., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J MRS Fall Meeting 2019 %T Fine-tuning of Rat Mesenchymal Stem Cell Senescence via Microtopography of Polymeric Substrates %U %X %0 conference poster %@ %A Wischke, C., Kersting, M., Welle, A., Lysyakova, L., Braune, S., Kratz, K., Franzreb, M., Lendlein, A. %D 2019 %J MRS Fall Meeting 2019 %T Thin hydrogel coatings by enzyme-catalyzed mechanism %U %X %0 journal article %@ 1386-0291 %A Tung, W., Wang, W., Liu, Y., Gould, O., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J Clinical Hemorheology and Microcirculation %N 1 %P 229-236 %R doi:10.3233/CH-199201 %T Mechanical characterization of electrospun polyesteretherurethane (PEEU) meshes by atomic force microscopy %U https://doi.org/10.3233/CH-199201 1 %X The mechanical properties of electrospun fiber meshes typically are measured by tensile testing at the macro-scale without precisely addressing the spatial scale of living cells and their submicron architecture. Atomic force microscopy (AFM) enables the examination of the nano- and micro-mechanical properties of the fibers with potential to correlate the structural mechanical properties across length scales with composition and functional behavior. In this study, a polyesteretherurethane (PEEU) polymer containing poly(p-dioxanone) (PPDO) and poly(ɛ-caprolactone) (PCL) segments was electrospun into fiber meshes or suspended single fibers. We employed AFM three point bending testing and AFM force mapping to measure the elastic modulus and stiffness of individual micro/nanofibers and the fiber mesh. The local stiffness of the fiber mesh including the randomized, intersecting structure was also examined for each individual fiber. Force mapping results with a set point of 50 nN demonstrated the dependence of the elasticity of a single fiber on the fiber mesh architecture. The non-homogeneous stiffness along the same fiber was attributed to the intersecting structure of the supporting mesh morphology. The same fiber measured at a point with and without axial fiber support showed a remarkable difference in stiffness, ranging from 0.2 to 10 nN/nm respectively. For the region, where supporting fibers densely intersected, the stiffness was found to be considerably higher. In the region where the degrees of freedom of the fibers was not restricted, allowing greater displacement, the stiffness were observed to be lower. This study elucidates the relationship between architecture and the mechanical properties of a micro/nanofiber mesh. By providing a greater understanding of the role of spatial arrangement and organization on the surface mechanical properties of such materials, we hope to provide insight into the design of microenvironments capable of regulating cell functionality. %0 conference lecture %@ %A Tung, W., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J 38. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheoligie (DGKMH) %T Determining the mechanic properties of electrospun Polyesteretherurethane (PEEU) microfibers using AFM %U %X %0 conference poster %@ %A Pieper, Y., Kratz, K., Heuchel, M., Lendlein, A. %D 2019 %J Microscopy Conference 2019 %T In-situ measurement of contact angles on single multifunctional; porous polymer microparticles utilizing ESEM %U %X %0 journal article %@ 0261-3069 %A Jiang, Y., Mansfeld, U., Fang, L., Kratz, K., Lendlein, A. %D 2019 %J Materials and Design %P 107530 %R doi:10.1016/j.matdes.2018.12.002 %T Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability %U https://doi.org/10.1016/j.matdes.2018.12.002 %X Here, we present switchable underwater aerophobicity of hydrophobic polymeric substrates, which respond to heat with multilevel micro- and nanotopographical changes. The cross-linked poly[ethylene-co-(vinyl acetate)] substrates possess arrays of microcylinders with a nanorough top surface. It is hypothesized that the specific micro-/nanotopography of the surface allows trapping of a water film at the micro interspace and in this way generates the aerophobic behavior. The structured substrates were programmed to a temporarily stable, nanoscale flat substrate showing aerophilic behavior. Upon heating, the topographical changes caused a switch in contact angle from aerophilic to aerophobic for approaching air bubbles. In this way, the initial adhesion of air bubbles to the programmed flat substrate could be turned into repellence for the recovered substrate surface. The temperature at which the repellence of air bubbles starts can be adjusted from 58 ± 3 °C to 73 ± 3 °C by varying the deformation temperature applied during the temperature-memory programming procedure. The presented actively switching polymeric substrates are attractive candidates for applications, where an on-demand gas bubble repellence is advantageous. %0 conference lecture %@ %A Braune, S., Xourida, M., Maier, A., Reinthaler, M., Kratz, K., Latour, R., Lendlein, A., Jung, F. %D 2019 %J 38. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheoligie (DGKMH) %T Translocation and release of von Willebrand factor in the adherent and activated platelet %U %X %0 journal article %@ 1386-0291 %A Krüger-Genge, A., Dietze, S., Yan, W., Liu, Y., Fang, L., Kratz, K., Lendlein, A., Jung, F. %D 2019 %J Clinical Hemorheology and Microcirculation %N 4 %P 511-529 %R doi:10.3233/CH-189317 %T Endothelial cell migration, adhesion and proliferation on different polymeric substrates %U https://doi.org/10.3233/CH-189317 4 %X The study revealed that the wettability of polymers affected not only the initial adherence but also the migration of EC, which is of importance for the proliferation and ultimately the endothelialization of polymer-based biomaterials. %0 conference poster %@ %A Izraylit, V., Kratz, K., Lendlein, A. %D 2019 %J Polydays 2019 - Polymer Science and Engineering in View of Digitalization %T Controlling Actuation Behaviour in Shape-Memory Polymer Blends by Tailoring Supramolecular lnteractions %U %X %0 conference poster %@ %A Sun, X., Tung, W., Zou, J., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J Polydays 2019 - Polymer Science and Engineering in View of Digitalization %T Elasticity of fiber meshes from multiblock copolymers influences endothelial cell behaviors %U %X %0 conference poster %@ %A Sun, X., Wang, W., Tung, W., Zou, J., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J Advanced Functional Polymers for Medicine (AFPM) 2019 %T Elasticity of fiber meshes from multiblock copolymers influences endothelial cell behaviors %U %X %0 conference lecture %@ %A Gould, O., Kratz, K., Lendlein, A. %D 2019 %J BIFTM Seminar %T Implementing and quantifying the shape-memory effect of polymeric micro/nanowires %U %X %0 conference lecture %@ %A Sun, X., Tung, W., Wang, W., Xu, X., Zou, J., Kratz, K., Ma, N., Lendlein, A. %D 2019 %J 38. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheoligie (DGKMH %T Electrospun fiber meshes of multiblock copolymers differing in elasticity affects osteogenic differentiation of hADSCs %U %X %0 conference poster %@ %A Bäckemo Johansson, D., Heuchel, M., Reinthaler, M., Kratz, K., Lendlein, A. %D 2019 %J MRS Fall Meeting 2019 %T Computational Modelling of Electrical Discharge Machining (EDM) for Tuning Surface Roughness andCurvature %U %X The application of such a computational model may be useful in predicting how a surface is deformed, and what input parameters to use to create a surface with certain desired surface function. Future improvements of the model may include volumetric changes, surface charge and heat transfer. %0 journal article %@ 1424-8220 %A Sathyendranath, S., Brewin, R., Brockmann, C., Brotas, V., Calton, B., Chuprin, A., Cipollini, P., Couto, A., Dingle, J., Doerffer, R., Donlon, C., Dowell, M., Grant, M., Groom, S., Horseman, A., Jackson, T., Krasemann, H., Lavender, S., Martinez-Vicente, V., Mazeran, C., Melin, F., Moore, T., Müller, D., Regner, P., Roy, S., Steele, C., Steinmetz, F., Swinton, J., Taberner, M., Thompson, A., Valente, A., Zühlke, M., Brando, V., Feng, H., Feldman, G., Franz, B., Frouin, R., Gould, R., Hooker, S., Kahru, M., Kratzer, S., Mitchell, B., Muller-Karger, F., Sosik, H., Voss, K., Werdell, J., Platt, T. %D 2019 %J Sensors %N 19 %P 4285 %R doi:10.3390/s19194285 %T An Ocean-Colour Time Series for Use in Climate Studies: The Experience of the Ocean-Colour Climate Change Initiative (OC-CCI) %U https://doi.org/10.3390/s19194285 19 %X Ocean colour is recognised as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS); and spectrally-resolved water-leaving radiances (or remote-sensing reflectances) in the visible domain, and chlorophyll-a concentration are identified as required ECV products. Time series of the products at the global scale and at high spatial resolution, derived from ocean-colour data, are key to studying the dynamics of phytoplankton at seasonal and inter-annual scales; their role in marine biogeochemistry; the global carbon cycle; the modulation of how phytoplankton distribute solar-induced heat in the upper layers of the ocean; and the response of the marine ecosystem to climate variability and change. However, generating a long time series of these products from ocean-colour data is not a trivial task: algorithms that are best suited for climate studies have to be selected from a number that are available for atmospheric correction of the satellite signal and for retrieval of chlorophyll-a concentration; since satellites have a finite life span, data from multiple sensors have to be merged to create a single time series, and any uncorrected inter-sensor biases could introduce artefacts in the series, e.g., different sensors monitor radiances at different wavebands such that producing a consistent time series of reflectances is not straightforward. Another requirement is that the products have to be validated against in situ observations. Furthermore, the uncertainties in the products have to be quantified, ideally on a pixel-by-pixel basis, to facilitate applications and interpretations that are consistent with the quality of the data. This paper outlines an approach that was adopted for generating an ocean-colour time series for climate studies, using data from the MERIS (MEdium spectral Resolution Imaging Spectrometer) sensor of the European Space Agency; the SeaWiFS (Sea-viewing Wide-Field-of-view Sensor) and MODIS-Aqua (Moderate-resolution Imaging Spectroradiometer-Aqua) sensors from the National Aeronautics and Space Administration (USA); and VIIRS (Visible and Infrared Imaging Radiometer Suite) from the National Oceanic and Atmospheric Administration (USA). The time series now covers the period from late 1997 to end of 2018. To ensure that the products meet, as well as possible, the requirements of the user community, marine-ecosystem modellers, and remote-sensing scientists were consulted at the outset on their immediate and longer-term requirements as well as on their expectations of ocean-colour data for use in climate research. Taking the user requirements into account, a series of objective criteria were established, against which available algorithms for processing ocean-colour data were evaluated and ranked. The algorithms that performed best with respect to the climate user requirements were selected to process data from the satellite sensors. Remote-sensing reflectance data from MODIS-Aqua, MERIS, and VIIRS were band-shifted to match the wavebands of SeaWiFS. Overlapping data were used to correct for mean biases between sensors at every pixel. The remote-sensing reflectance data derived from the sensors were merged, and the selected in-water algorithm was applied to the merged data to generate maps of chlorophyll concentration, inherent optical properties at SeaWiFS wavelengths, and the diffuse attenuation coefficient at 490 nm. The merged products were validated against in situ observations. The uncertainties established on the basis of comparisons with in situ data were combined with an optical classification of the remote-sensing reflectance data using a fuzzy-logic approach, and were used to generate uncertainties (root mean square difference and bias) for each product at each pixel. %0 journal article %@ 1386-0291 %A Krueger-Genge, A., Braune, S., Walter, M., Krengel, M., Kratz, K., Kuepper, J.-H., Lendlein, A., Jung, F. %D 2018 %J Clinical Hemorheology and Microcirculation %N 1-2 %P 305-316 %R doi:10.3233/CH-189130 %T Influence of different surface treatments of poly(Eta-butyl acrylate) networks on fibroblasts adhesion, morphology and viability %U https://doi.org/10.3233/CH-189130 1-2 %X The applied surface treatments of cPnBA successfully improved the adhesion of viable fibroblasts. Under resting conditions as well as after shearing the highest fibroblast densities were found on surfaces with combined post-treatment. %0 journal article %@ 1386-0291 %A Hiebl, B., Ascher, L., Luetzow, K., Kratz, K., Gruber, C., Mrowietz, C., Nehring, M.E., Lendlein, A., Franke, R.-P., Jung, F. %D 2018 %J Clinical Hemorheology and Microcirculation %N 1-2 %P 317-326 %R doi:10.3233/CH-189108 %T Albumin solder covalently bound to a polymer membrane: New approach to improve binding strength in laser tissue soldering in-vitro %U https://doi.org/10.3233/CH-189108 1-2 %X Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat-denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG-supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250 mW and 1500 mW was utilized. The albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450 mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002 MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1 mm around the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native blood vessel. These in-vitro results confirmed the beneficial effects of solder reinforcement by carrier membranes, and suggest LTS with covalently bound solders on PEI substrates for further studies in animal models. %0 conference lecture %@ %A Kratz, K., Liu, Y., Rudolph, T., Lendlein, A. %D 2018 %J ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018 %T Einfluss von Deformations- und Separationstemperatur auf das Formgedaechtnisverhalten von polymeren Mikroquadern %U %X %0 journal article %@ 0009-286X %A Kratz, K., Liu, Y., Rudolph, T., Lendlein, A. %D 2018 %J Chemie - Ingenieur - Technik %N 9 %P 1331-1332 %R doi:10.1002/cite.201855431 %T Einfluss von Deformations- und Separationstemperatur auf das Formgedaechtnisverhalten von polymeren Mikroquadern %U https://doi.org/10.1002/cite.201855431 9 %X No abstract %0 journal article %@ 2051-6347 %A Wang, L., Razzaq, M.Y., Rudolph, T., Heuchel, M., Noechel, U., Mansfeld, U., Jiang, Y., Gould, O.E.C., Behl, M., Kratz, K., Lendlein, A. %D 2018 %J Materials Horizons %N 5 %P 861-867 %R doi:10.1039/C8MH00266E %T Reprogrammable, magnetically controlled polymeric nanocomposite actuators %U https://doi.org/10.1039/C8MH00266E 5 %X Soft robots and devices with the advanced capability to perform adaptive motions similar to that of human beings often have stimuli-sensitive polymeric materials as the key actuating component. The external signals triggering the smart polymers’ actuations can be transmitted either via a direct physical connection between actuator and controlling unit (tethered) or remotely without a connecting wire. However, the vast majority of such polymeric actuator materials are limited to one specific type of motion as their geometrical information is chemically fixed. Here, we present magnetically driven nanocomposite actuators, which can be reversibly reprogrammed to different actuation geometries by a solely physical procedure. Our approach is based on nanocomposite materials comprising spatially segregated crystallizable actuation and geometry determining units. Upon exposure to a specific magnetic field strength the actuators’ geometric memory is erased by the melting of the geometry determining units allowing the implementation of a new actuator shape. The actuation performance of the nanocomposites can be tuned and the technical significance was demonstrated in a multi-cyclic experiment with several hundreds of repetitive free-standing shape shifts without losing performance. %0 journal article %@ 1386-0291 %A Kumar, R.K., Heuchel, M., Kratz, K., Lendlein, A., Jankowski, J., Tetali, S.D. %D 2018 %J Clinical Hemorheology and Microcirculation %N 1-2 %P 175-185 %R doi:10.3233/CH-189112 %T Effects of extracts prepared from modified porous poly(ether imide) microparticulate absorbers on cytotoxicity, macrophage differentiation and proinflammatory behavior of human monocytic (THP-1) cells %U https://doi.org/10.3233/CH-189112 1-2 %X Remaining uremic toxins in the blood of chronic renal failure patients represent one central challenge in hemodialysis therapies. Highly porous poly(ether imide) (PEI) microparticles have been recently introduced as candidate absorber materials, which show a high absorption capacity for uremic toxins and allow hydrophilic surface modification suitable for minimization of serum protein absorption. In this work, the effects of extracts prepared from PEI microparticles modified by nucleophilic reaction with low molecular weight polyethylene imine (Pei) or potassium hydroxide (KOH), on human monocytic (THP-1) cells are studied. The obtained results suggested that the extracts of Pei and KOH modified PEI absorbers have no negative effect on THP-1 cell viability and do not initiate the critical differentiation towards macrophages. The extracts did not enhance transcript or protein levels of investigated proinflammatory markers in THP-1 cells, namely, TNFμ, MCP1, IL6 and IL8. Based on these findings such modified PEI microparticles should be qualified for further pre-clinical evaluation i.e. in an in vivo animal experiment. %0 journal article %@ 2073-4360 %A Farhan, M., Rudolph, T., Noechel, U., Kratz, K., Lendlein, A. %D 2018 %J Polymers %N 3 %P 255 %R doi:10.3390/polym10030255 %T Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(Epsilon-caprolactone) Networks and Enable Self-Healing %U https://doi.org/10.3390/polym10030255 3 %X Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(ε-caprolactone) thermosets (cPCLs) were prepared from linear starting material, whereby the amount of extractable polymer was varied. Fractions of 5–60 wt % of non-crosslinked polymer chains, which freely interpenetrate the crosslinked network, were achieved leading to differences in the resulting phase of the bulk material. This can be described as “sponge-like” with open or closed compartments depending on the amount of interpenetrating polymer. The crosslinking density and the average network chain length remained in a similar range for all network structures, while the theoretical accessible volume for reptation of the free polymer content is affected. This feature could influence or introduce new functions into the material created by thermomechanical treatment. The effect of interpenetrating PCL in cPCLs on the reversible actuation was analyzed by cyclic, uniaxial tensile tests. Here, high reversible strains of up to ∆ε = 24% showed the enhanced actuation performance of networks with a non-crosslinked PCL content of 30 wt % resulting from the crystal formation in the phase of the non-crosslinked PCL and co-crystallization with network structures. Additional functionalities are reprogrammability and self-healing capabilities for networks with high contents of extractable polymer enabling reusability and providing durable actuator materials. %0 conference lecture %@ %A Maier, A., Braune, S., Kratz, K., Latour, R.A., Lendlein, A., Jung, F. %D 2018 %J 37. Jahrestagung der Deutschen Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie, DGKMH 2018 %T Adsorption and conformation of von Willebrand factor from fresh human plasma on to polymer-based biomaterials %U %X %0 conference poster %@ %A Vijaya Bhaskar, T.B., Machatschek, R., Lysyakova, L., Kratz, K., Schulz, B., Ma, N., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T Collagen type-IV Langmuir-Schaefer films as substrates to direct mesenchymal stem cell adherence %U %X %0 conference lecture %@ %A Gould, O., Lysyakova, L., Kratz, K., Lendlein, A. %D 2018 %J XXVII Int. Materials Research Congress (IMRC) 2018 %T Implementing and Quantifying the Shape-Memory Effect of Single Polymeric Micro/Nanowires with an Atomic Force Microscope %U %X %0 conference lecture %@ %A Kratz, K. %D 2018 %J International Biotech Innovation Days %T Multifunctional polymer particles for detoxification purposes %U %X %0 conference poster %@ %A Gould, O., Lysyakova, L., Kratz, K., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T Quantification of Shape Memory Nano/microfibers by Atomic Force Microscopy %U %X %0 conference poster %@ %A Noechel, U., Behl, M., Kratz, K., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T Tailoring the Thermo-Mechanical Properties of Degradable Copolyetherester Urethanes Comprising Oligo(p-dioxanone) and Oligo(e-caprolactone) segments %U %X %0 conference poster %@ %A Wang, W., Xu, X., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T Tuning polymer elasticity to regulate human mesenchymal stem cells: a potential strategy for tissue-engineering of blood vessels %U %X %0 conference lecture %@ %A Wang, W., Xu, X., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2018 %J Joint Conference of Three Societies: European Society of Clinical Hemorheology and Miclrocirculation, International Society of Biorheology, International Society of Clinical Hemorheology, ESCHM-ISB-ISCH 2018 %T Modulating human mesenchymal stem cells using poly(Eta-butyl acrylate) networks in vitro with elasticity matching human arteries %U %X %0 conference lecture %@ %A Krueger-Genge, A., Dietze, S., Yan, W., Liu, Y., Fang, L., Kratz, K., Lendlein, A., Jung, F. %D 2018 %J 37. Jahrestagung Deutsche Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie %T Endothelial cell migration, adhesion and proliferation on different polymeric substrates %U %X %0 conference poster %@ %A Heuchel, M., Weigel, T., Kratz, K., Lendlein, A. %D 2018 %J International Biotech Innovation Days %T Morphological analysis of porous poly(ether imide) microparticles by mercury porosimetry %U %X %0 conference lecture %@ %A Zou, J., Wang, W., Kratz, K., Xu, X., Nie, Y., Ma, N., Lendlein, A. %D 2018 %J 37. Jahrestagung Deutsche Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie %T Evaluation of human mesenchymal stem cell senescence, differentiation and secretion behavior cultured on polycarbonate cell culture inserts %U %X %0 journal article %@ 2059-8521 %A Yan, W., Fang, L., Noechel, U., Gould, O.E.C., Behl, M., Kratz, K., Lendlein, A. %D 2018 %J MRS Advances %N 63 %P 3741-3749 %R doi:10.1557/adv.2018.590 %T Investigating the Roles of Crystallizable and Glassy Switching Segments within Multiblock Copolymer Shape-Memory Materials %U https://doi.org/10.1557/adv.2018.590 63 %X The variation of the molecular architecture of multiblock copolymers has enabled the introduction of functional behaviour and the control of key mechanical properties. In the current study, we explore the synergistic relationship of two structural components in a shape-memory material formed of a multiblock copolymer with crystallizable poly(ε-caprolactone) and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments (PCL-PIBMD). The thermal and structural properties of PCL-PIBMD films were compared with PCL-PU and PIBMD-PU, investigated by means of DSC, SAXS and WAXS measurements. The shape-memory properties were quantified by cyclic, thermomechanical tensile tests, where deformation strains up to 900% were applied for programming PCL-PIBMD films at 50 °C. Toluene vapor treatment experiments demonstrated that the temporary shape was fixed mainly by glassy PIBMD domains at strains lower than 600%, with the PCL contribution to fixation increasing to 42±2% at programming strains of 900%. This study into the shape-memory mechanism of PCL-PIBMD provides insight into the structure-function relation in multiblock copolymers with both crystallizable and glassy switching segments. %0 conference lecture %@ %A Yan, W., Fang, L., Noechel, U., Gould, O.E.C., Behl, M., Kratz, K., Lendlein, A. %D 2018 %J 27th International Materials Research Congress %T Investigating the Roles of Crystallizable and Glassy Switching Segments within Multiblock Copolymer Shape-Memory Materials %U %X %0 conference lecture %@ %A Farhan, M., Rudolph, T., Kratz, K., Lendlein, A. %D 2018 %J 27th International Materials Research Congress %T Torsional Fiber Actuators from Shape-memory Polymer %U %X %0 conference poster %@ %A Rudolph, T., Farhan, M., Noechel, U., Yan, W., Kratz, K., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T Noncontinuously Responding Polymeric Actuators %U %X %0 journal article %@ 2059-8521 %A Farhan, M., Rudolph, T., Kratz, K., Lendlein, A. %D 2018 %J MRS Advances %N 63 %P 3861-3868 %R doi:10.1557/adv.2018.621 %T Torsional Fiber Actuators from Shape-memory Polymer %U https://doi.org/10.1557/adv.2018.621 63 %X Humanoid robots, prosthetic limbs and exoskeletons require soft actuators to perform their primary function, which is controlled movement. In this work, we explored whether crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, with different vinyl acetate (VA) content can serve as torsional fiber actuators, exhibiting temperature controlled reversible rotational changes. Broad melting transitions ranging from 50 to 90 °C for cPEVA18-165 or from 40 to 80 °C for cPEVA28-165 fibers in combination with complete crystallization at temperatures around 10 °C make them suitable actuating materials with adjustable actuation temperature ranges between 10 and 70 °C during repetitive cooling and heating. The obtained fibers exhibited a circular cross section with diameters around 0.4±0.1 mm, while a length of 4 cm was employed for the investigation of reversible rotational actuation after programming by twist insertion using 30 complete rotations at a temperature above melting transition. Repetitive heating and cooling between 10 to 60 °C or 70 °C of one-end-tethered programmed fibers revealed reversible rotations and torsional force. During cooling 3±1 complete rotations (Δθr = + 1080±360°) in twisting direction were observed, while 4±1 turns in the opposite direction (Δθr = - 1440±360°) were found during heating. Such torsional fiber actuators, which are capable of approximately one rotation per cm fiber length, can serve as miniaturized rotary motors to provide rotational actuation in futuristic humanoid robots. %0 journal article %@ 1439-4235 %A Fang, L., Gould, O.E.C., Lysyakova, L., Jiang, Y., Sauter, T., Frank, O., Becker, T., Schossig, M., Kratz, K., Lendlein, A. %D 2018 %J ChemPhysChem %N 16 %P 2078-2084 %R doi:10.1002/cphc.201701362 %T Implementing and Quantifying the Shape-Memory Effect of Single Polymeric Micro/Nanowires with an Atomic Force Microscope %U https://doi.org/10.1002/cphc.201701362 16 %X The implementation of shape‐memory effects (SME) in polymeric micro‐ or nano‐objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro‐ and nano‐objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro‐spun poly(ether urethane) (PEU) micro‐ or nanowires freely suspended between two micropillars on a micro‐structured silicon substrate. In this way, programming strains of 10±1% or 21±1% were realized, which could be successfully fixed. An almost complete restoration of the original free‐suspended shape during heating confirmed the excellent shape‐memory performance of the PEU wires. Apparent recovery stresses of σmax,app=1.2±0.1 and 33.3±0.1 MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro‐ and nanosystems. %0 conference lecture %@ %A Braune, S., Xourida, M., Maier, A., Kratz, K., Latour, B., Lendlein, A., Jung, F. %D 2018 %J 37. Jahrestagung der Deutschen Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie, DGKMH 2018 %T Translocation and release of von Willebrand factor in platelets adherent on polymer-based biomaterial surfaces %U %X %0 conference poster %@ %A Eschborn, J., Loewenberg, C., Benitez, A.J., Thiels, K., Kratz, K., Ghods, M., Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %T pH Changes of Aqueous Media Caused by Degradation of Suture Materials %U %X %0 journal article %@ 0024-9297 %A Yan, W., Rudolph, T., Noechel, U., Gould, O., Behl, M., Kratz, K., Lendlein, A. %D 2018 %J Macromolecules %N 12 %P 4624-4632 %R doi:10.1021/acs.macromol.8b00322 %T Reversible Actuation of Thermoplastic Multiblock Copolymers with Overlapping Thermal Transitions of Crystalline and Glassy Domains %U https://doi.org/10.1021/acs.macromol.8b00322 12 %X Polymeric materials possessing specific features like programmability, high deformability, and easy processability are highly desirable for creating modern actuating systems. In this study, thermoplastic shape-memory polymer actuators obtained by combining crystallizable poly(ε-caprolactone) (PCL) and poly(3S-isobutylmorpholin-2,5-dione) (PIBMD) segments in multiblock copolymers are described. We designed these materials according to our hypothesis that the confinement of glassy PIBMD domains present at the upper actuation temperature contribute to the stability of the actuator skeleton, especially at large programming strains. The copolymers have a phase-segregated morphology, indicated by the well-separated melting and glass transition temperatures for PIBMD and PCL, but possess a partially overlapping Tm of PCL and Tg of PIBMD in the temperature interval from 40 to 60 °C. Crystalline PIBMD hard domains act as strong physical netpoints in the PIBMD−PCL bulk material enabling high deformability (up to 2000%) and good elastic recoverability (up to 80% at 50 °C above Tm,PCL). In the programmed thermoplastic actuators a high content of crystallizable PCL actuation domains ensures pronounced thermoreversible shape changes upon repetitive cooling and heating. The programmed actuator skeleton, composed of PCL crystals present at the upper actuation temperature Thigh and the remaining glassy PIBMD domains, enabled oriented crystallization upon cooling. The actuation performance of PIBMD-PCL could be tailored by balancing the interplay between actuation and skeleton, but also by varying the quantity of crystalline PIBMD hard domains via the copolymer composition, the applied programming strain, and the choice of Thigh. The actuator with 17 mol% PIBMD showed the highest reversible elongation of 11.4% when programmed to a strain of 900% at 50 °C. It is anticipated that the presented thermoplastic actuator materials can be applied as modern compression textiles. %0 journal article %@ 1386-0291 %A Krueger-Genge, A., Schulz, C., Kratz, K., Lendlein, A., Jung, F. %D 2018 %J Clinical Hemorheology and Microcirculation %N 3 %P 437-445 %R doi:10.3233/CH-189904 %T Comparison of two substrate materials used as negative control in endothelialization studies: Glass versus polymeric tissue culture plate %U https://doi.org/10.3233/CH-189904 3 %X In conclusion, these findings indicate that both reference materials are almost comparable and can be used equivalently as control materials in in vitro endothelialization studies. %0 conference lecture %@ %A Farhan, M., Rudolph, T., Kratz, K., Lendlein, A. %D 2018 %J XXVII Int. Materials Research Congress (IMRC) 2018 %T Non-continuously responding polymeric actuators %U %X %0 conference lecture %@ %A Jiang, Y., Mansfeld, U., Fang, L., Kratz, K., Lendlein, A. %D 2018 %J XXVII Int. Materials Research Congress (IMRC) 2018 %T Multilevel topographical changes of polymeric surfaces control their aerophobic behavior %U %X %0 conference lecture %@ %A Rudolph, T., Liu, Y., Razzaq, M., Fang, L., Kratz, K., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies Conference 2017 %T Miniaturized polymeric micro-cuboids prepared from crystallizable copolymer networks investigated on the nano- and micro-level %U %X %0 conference lecture %@ %A Farhan, M., Kratz, K., Lendlein, A. %D 2017 %J MRS Spring Meeting 2017; Symposium SM8 %T Reversible shape-memory effect of crosslinked thermoplastic polymer blends %U %X %0 journal article %@ 1042-7147 %A Bhuvanesh, T., Saretia, S., Roch, T., Schoene, A.-C., Rottke, F.O., Kratz, K., Wang, W., Ma, N., Schulz, B., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1305-1311 %R doi:10.1002/pat.3910 %T Langmuir–Schaefer films of fibronectin as designed biointerfaces for culturing stem cells %U https://doi.org/10.1002/pat.3910 10 %X Glycoproteins adsorbing on an implant upon contact with body fluids can affect the biological response in vitro and in vivo, depending on the type and conformation of the adsorbed biomacromolecules. However, this process is poorly characterized and so far not controllable. Here, protein monolayers of high molecular cohesion with defined density are transferred onto polymeric substrates by the Langmuir–Schaefer (LS) technique and were compared with solution deposition (SO) method. It is hypothesized that on polydimethylsiloxane (PDMS), a substrate with poor cell adhesion capacity, the fibronectin (FN) layers generated by the LS and SO methods will differ in their organization, subsequently facilitating differential stem cell adhesion behavior. Indeed, atomic force microscopy visualization and immunofluorescence images indicated that organization of the FN layer immobilized on PDMS was uniform and homogeneous. In contrast, FN deposited by SO method was rather heterogeneous with appearance of structures resembling protein aggregates. Human mesenchymal stem cells showed reduced absolute numbers of adherent cells, and the vinculin expression seemed to be higher and more homogenously distributed after seeding on PDMS equipped with FN by LS in comparison with PDMS equipped with FN by SO. These divergent responses could be attributed to differences in the availability of adhesion molecule ligands such as the Arg-Gly-Asp (RGD) peptide sequence presented at the interface. The LS method allows to control the protein layer characteristics, including the thickness and the protein orientation or conformation, which can be harnessed to direct stem cell responses to defined outcomes, including migration and differentiation. %0 journal article %@ 1042-7147 %A Heuchel, M., Gerber, D., Kratz, K., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1269-1277 %R doi:10.1002/pat.3973 %T Morphological analysis of differently sized highly porous poly(ether imide) microparticles by mercury porosimetry %U https://doi.org/10.1002/pat.3973 10 %X Highly porous poly(ether imide) (PEI) microparticles prepared by a spraying/coagulation process are discussed as candidate adsorber materials for apheresis applications, i.e. removal of uremic toxins from the blood of renal failure patients. PEI particles obtained by the aforementioned procedure can have a broad size distribution with particle diameters ranging from 20 to 800 µm. In order to further estimate the adsorption behavior of PEI microparticles packed in application relevant apheresis modules, a quantitative information about the relation between particle size and pore morphology is required. In this study, we explored whether the intraparticle porosity of PEI microparticles varies with altering the diameter of the particulate adsorbers. By an analytical wet sieving procedure, the obtained PEI microparticles were separated into five size fractions, which were analyzed by mercury intrusion porosimetry, nitrogen adsorption, and scanning electron microscopy. Mercury intrusion porosimetry revealed for all size fractions high porosity values in the range from 78% to 84% with pore diameters in the range from 10 to 1000 nm. A bimodal pore size distribution was found having a first peak at around 100 nm, while a second pronounced peak maximum was found at higher pore sizes that increased with raising particle diameter from 300 nm for the smallest particle size fraction (50–100 µm) to 700 nm for particles with a diameter of 200 to 250 µm. %0 conference lecture %@ %A Li, Z., Xu, X., Wang, W., Kratz, K., Sun, X., Zou, J., Deng, Z., Jung, F., Gossen, M., Ma, N., Lendlein, A. %D 2017 %J 36th Conference of the German Society for Clinical Microcirculation and Hemorheology %T Modulation of the mesenchymal stem cell migration capacity via preconditioning with topographic microstructure %U %X %0 conference poster %@ %A Heuchel, M., Gerber, D., Weigel, T., Kratz, K., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies Conference 2017 %T Morphological analysis of porous poly(ether imide) microparticles %U %X %0 conference poster %@ %A Liu, Y., Razzaq, M., Rudolph, T., Kratz, K., Lendlein, A. %D 2017 %J XXVI International Materials Research Congress (IMRC) 2017; Symp. F4: Shape-memory and self-repairing materials %T Polymeric Microcuboids Exhibiting Micro- and Nano-Level Shape Changes %U %X %0 conference poster %@ %A Zhang, Q., Kratz, K., Lendlein, A. %D 2017 %J XXVI International Materials Research Congress (IMRC) 2017; Symp. F4: Shape-memory and self-repairing materials %T Reversible bidirectional shape-memory properties of electrospun fibrous meshes %U %X %0 conference lecture %@ %A Liu, Y., Razzaq, M., Rudolph, T., Kratz, K., Lendlein, A. %D 2017 %J BIFTM PhD Symposium - BioInterfaces in Technology and Medicine %T Two-level shape changes of polymeric microcuboids prepared from crystallizable copolymer networks %U %X %0 conference lecture %@ %A Kratz, K., Liu, Y., Jiang, Y., Fang, L., Lendlein, A. %D 2017 %J MRS Spring Meeting; Symposium SM8 %T Characterizing shape-memory effects of polymeric micro-scale objects %U %X %0 book part %@ %A Lendlein, A., Razzaq, M.Y., Wischke, C., Kratz, K., Heuchel, M., Zotzmann, J., Hiebl, B., Neffe, A.T., Behl, M. %D 2017 %J Comprehensive Biomaterials II - Reference Module in Materials Science and Materials Engineering, Metallic, Ceramic, and Polymeric Biomaterials %P 620-647 %R doi:10.1016/B978-0-12-803581-8.10213-9 %T Shape-Memory Polymers %U https://doi.org/10.1016/B978-0-12-803581-8.10213-9 %X Medical devices such as implants, surgical instruments, extracorporal devices, and wound covers, as well as controlled drug delivery systems (CDDS) require a specific combination of material properties and functions including, for example, mechanical stability, biocompatibility, and biofunctionality. Polymeric biomaterials are of high relevance for such applications, as properties and functions can be tuned in a wide range by only small defined variations of their chemical or morphological structure. The rapid progress in surgical techniques, especially in minimally invasive surgery, requires smart materials, which are capable of an active on-demand movement and which do not need to be removed in a second surgery. These challenges can be addressed by shape-memory polymers (SMPs) described in this chapter. SMPs are of high technological significance for biomedical applications as they enable on-demand predefined changes in the shape of a device upon exposure to a suitable stimulus such as heat or alternating magnetic field (AMF). Multifunctional materials are obtained when the shape-memory effect is combined with an additional function such as hydrolytic degradability, biofunctionality, and controlled drug release. Selected biomaterials with shape-memory capability are presented, including data on their biocompatibility. The potential of SMPs as a platform technology for biomedical applications is sketched by an overview on SMP-based medical devices being developed and the potential use of SMPs as matrix for CDDS. %0 journal article %@ 1386-0291 %A Li, Z., Xu, X., Wang, W., Kratz, K., Sun, X., Zou, J., Deng, Z., Jung, F., Gossen, M., Ma, N., Lendlein, A. %D 2017 %J Clinical Hemorheology and Microcirculation %N 3-4 %P 267-278 %R doi:10.3233/CH-179208 %T Modulation of the mesenchymal stem cell migration capacity via preconditioning with topographic microstructure %U https://doi.org/10.3233/CH-179208 3-4 %X Controlling mesenchymal stem cells (MSCs) behavior is necessary to fully exploit their therapeutic potential. Various approaches are employed to effectively influence the migration capacity of MSCs. Here, topographic microstructures with different microscale roughness were created on polystyrene (PS) culture vessel surfaces as a feasible physical preconditioning strategy to modulate MSC migration. By analyzing trajectories of cells migrating after reseeding, we demonstrated that the mobilization velocity of human adipose derived mesenchymal stem cells (hADSCs) could be promoted by and persisted after brief preconditioning with the appropriate microtopography. Moreover, the elevated activation levels of focal adhesion kinase (FAK) and mitogen-activated protein kinase (MAPK) in hADSCs were also observed during and after the preconditioning process. These findings underline the potential enhancement of in vivo therapeutic efficacy in regenerative medicine via transplantation of topographic microstructure preconditioned stem cells. %0 journal article %@ 1042-7147 %A Blocki, A., Loewenberg, C., Jiang, Y., Kratz, K., Neffe, A.T., Jung, F., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1245-1251 %R doi:10.1002/pat.3947 %T Response of encapsulated cells to a gelatin matrix with varied bulk and microenvironmental elastic properties %U https://doi.org/10.1002/pat.3947 10 %X Gelatin-based hydrogels offer various biochemical cues that support encapsulated cells and are therefore suitable as cell delivery vehicles in regenerative medicine. However, besides the biochemical signals, biomechanical cues are crucial to ensure an optimal support of encapsulated cells. Hence, we aimed to correlate the cellular response of encapsulated cells to macroscopic and microscopic elastic properties of glycidylmethacrylate (GMA)-functionalized gelatin-based hydrogels. To ensure that different observations in cellular behavior could be attributed to differences in elastic properties, an identical concentration as well as degree of functionalization of biopolymers was utilized to form covalently crosslinked hydrogels. Elastic properties were merely altered by varying the average gelatin-chain length. Hydrogels exhibited an increased degree of swelling and a decreased bulk elastic modulus G′ with prolonged autoclaving of the starting solution. This was accompanied by an increase of hydrogel mesh size and thus by a reduction of crosslinking density. Tougher hydrogels retained the largest amount of cells; however, they also interfered with cell viability. Softer gels contained a lower cell density, but supported cell elongation and viability. Observed differences could be partially attributed to differences in bulk properties, as high crosslinking densities interfere with diffusion and cell spreading and thus can impede cell viability. Interestingly, a microscopic elastic modulus in the range of native soft tissue supported cell viability and elongation best while ensuring a good cell entrapment. In conclusion, gelatin-based hydrogels providing a soft tissue-like microenvironment represent adequate cell delivery vehicles for tissue engineering approaches. %0 journal article %@ 2050-750X %A Li, Z., Wang, W., Xu, X., Kratz, K., Zou, J., Lysyakova, L., Heuchel, M., Kurtz, A., Gossen, M., Ma, N., Lendlein, A. %D 2017 %J Journal of Materials Chemistry B %N 35 %P 7415-7425 %R doi:10.1039/C7TB01232B %T Integrin β1 activation by micro-scale curvature promotes pro-angiogenic secretion of human mesenchymal stem cells %U https://doi.org/10.1039/C7TB01232B 35 %X Fine tuning of the substrate properties to modulate the function of mesenchymal stem cells (MSCs) has emerged as an attractive strategy to optimize their therapeutic potential. In the context of the mechanotransduction process, the conformational change of integrin (integrin activation) plays a critical role in perceiving and transmitting various signals. In this study, polymeric cell culture inserts with defined bottom roughness were fabricated as a model system for cell cultivation. We showed that the conformational change of integrin and its downstream signaling cascade of human adipose-derived mesenchymal stem cells (hADSCs) could be modulated by the curvature of the cell–material interface. The curvature of the substrate surface with a roughness in the size range of a single cell could strongly increase the high-affinity β1 integrin level of hADSCs without alteration of the total β1 integrin level. Further, the integrin downstream FAK/ERK and Rho/ROCK pathways were activated and resulted in upregulated VEGF secretion of hADSCs. A conditioned medium on such a surface exhibited a strong pro-angiogenic effect, with an increased formation of the tubular structure, a higher migration velocity of endothelial cells and an enhanced blood vessel density in an ex vivo hen's egg test-chorioallantoic membrane (HET-CAM). These results highlighted the clinical potential to manipulate the topographic features of the cell culture substrate, whereby to regulate integrin affinity states and further control MSC functions. %0 journal article %@ 2059-8521 %A Xu, X., Wang, W., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2017 %J MRS Advances %N 47 %P 2561-2570 %R doi:10.1557/adv.2017.487 %T Microwell Geometry Modulates Interleukin-6 Secretion in Human Mesenchymal Stem Cells %U https://doi.org/10.1557/adv.2017.487 47 %X The therapeutic effect of mesenchymal stem cells (MSCs) has been investigated in various clinical applications, in which their functional benefits are mainly attributed to the secretion of soluble factors. The enhancement of their therapeutic potential by physical and chemical properties of cell culture substrate is a safe and effective strategy, since they are highly sensitive to their microenvironment such as the elasticity and surface topography. In this study, we demonstrated that the geometry of polymeric substrate regulated the interleukin-6 (IL-6) secretion of human adipose derived MSCs. Polystyrene substrates comprising arrays of square-shaped (S50) or round-shaped (R50) microwells (side length or diameter of 50 μm and depth of 10 μm) were prepared by injection molding. Cellular apoptototic rate of MSCs was not affected by the microwell geometry, while the upregulated secretion of IL-6 and the enhancement of nuclear transcription factor STAT3 were detected in MSCs seeded on S50 substrate. The geometry-dependent modulatory effect was highly associated with ROCK signaling cascade. The inhibition of ROCK abolished the disparity in IL-6 secretion. These findings highlight the possibility to steer the secretion profile of stem cells via microwell geometry in combination with the manipulation of ROCK signaling pathway. %0 journal article %@ 1932-6254 %A Haase, T., Krost, A., Sauter, T., Kratz, K., Peter, J., Kamann, S., Jung, F., Lendlein, A., Zohlnhöfer, D., Rüder, C. %D 2017 %J Journal of Tissue Engineering and Regenerative Medicine %N 4 %P 1034-1044 %R doi:10.1002/term.2002 %T In vivo biocompatibility assessment of poly (ether imide) electrospun scaffolds %U https://doi.org/10.1002/term.2002 4 %X Poly(ether imide) (PEI), which can be chemically functionalized with biologically active ligands, has emerged as a potential biomaterial for medical implants. Electrospun PEI scaffolds have shown advantageous properties, such as enhanced endothelial cell adherence, proliferation and low platelet adhesion in in vitro experiments. In this study, the in vivo behaviour of electrospun PEI scaffolds and PEI films was examined in a murine subcutaneous implantation model. Electrospun PEI scaffolds and films were surgically implanted subcutaneously in the dorsae of mice. The surrounding subcutaneous tissue response was examined via histopathological examination at 7 and 28 days after implantation. No serious adverse events were observed for both types of PEI implants. The presence of macrophages or foreign body giant cells in the vicinity of the implants and the formation of a fibrous capsule indicated a normal foreign body reaction towards PEI films and scaffolds. Capsule thickness and inflammatory infiltration cells significantly decreased for PEI scaffolds during days 7–28 while remaining unchanged for PEI films. The infiltration of cells into the implant was observed for PEI scaffolds 7 days after implantation and remained stable until 28 days of implantation. Additionally some, but not all, PEI scaffold implants induced the formation of functional blood vessels in the vicinity of the implants. Conclusively, this study demonstrates the in vivo biocompatibility of PEI implants, with favourable properties of electrospun PEI scaffolds regarding tissue integration and wound healing. %0 conference lecture %@ %A Li, Z., Xu, X., Wang, W., Kratz, K., Sun, X., Zou, J., Deng, Z., Jung, F., Gossen, M., Ma, N., Lendlein, A. %D 2017 %J 36. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Preconditioning with topographic microstructure of materials promotes the migration capacity of adipose derived mesenchymal stem cells %U %X transplantation of topographic microstructure preconditioned stem cells. %0 conference poster %@ %A Quinn, S., Kratz, K., Tirelli, N., Lendlein, A., Blaker, J. %D 2017 %J Polymers for Advanced Technologies Conference %T Solution blow spinning of poly(vinylidene fluoride) at different temperatures %U %X %0 conference lecture %@ %A Ma, N., Xu, X., Wang, W., Li, Z., Zou, J., Kratz, K., Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %T Regulation of mesenchymal stem cell behavior and secretion via microscale surface roughness %U %X %0 conference poster %@ %A Xu, X., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %T Microstructured stubstrates modulate interleukin-6 secretion in human mesenchymal stem cells %U %X %0 journal article %@ 1944-8244 %A Farhan, M., Rudolph, T., Noechel, U., Yan, W., Kratz, K., Lendlein, A. %D 2017 %J ACS Applied Materials and Interfaces %N 39 %P 33559-33564 %R doi:10.1021/acsami.7b11316 %T Noncontinuously Responding Polymeric Actuators %U https://doi.org/10.1021/acsami.7b11316 39 %X Reversible movements of current polymeric actuators stem from the continuous response to signals from a controlling unit, and subsequently cannot be interrupted without stopping or eliminating the input trigger. Here, we present actuators based on cross-linked blends of two crystallizable polymers capable of pausing their movements in a defined manner upon continuous cyclic heating and cooling. This noncontinuous actuation can be adjusted by varying the applied heating and cooling rates. The feasibility of these devices for technological applications was shown in a 140 cycle experiment of free-standing noncontinuous shape shifts, as well as by various demonstrators. %0 conference lecture %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2017 %J 36. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Standard elution protocols are insufficient to determine the endotoxin burden of biomaterials %U %X %0 journal article %@ 0024-9297 %A Liu, Y., Razzaq, M.Y., Rudolph, T., Fang, L., Kratz, K., Lendlein, A. %D 2017 %J Macromolecules %N 6 %P 2518-2527 %R doi:10.1021/acs.macromol.6b02237 %T Two-Level Shape Changes of Polymeric Microcuboids Prepared from Crystallizable Copolymer Networks %U https://doi.org/10.1021/acs.macromol.6b02237 6 %X Polymeric microdevices bearing features like nonspherical shapes or spatially segregated surface properties are of increasing importance in biological and medical analysis, drug delivery, and bioimaging or microfluidic systems as well as in micromechanics, sensors, information storage, or data carrier devices. Here, a method to fabricate programmable microcuboids with shape-memory capability and the quantification of their recovery at different levels is reported. The method uses the soft lithographic technique to create microcuboids with well-defined sizes and surface properties. Microcuboids having an edge length of 25 μm and a height of 10 μm were prepared from cross-linked poly[ethylene-co-(vinyl acetate)] (cPEVA) with different vinyl acetate contents and were programmed by compression with various deformation degrees at elevated temperatures. The microlevel shape-recovery of the cuboidal geometry during heating was monitored by optical microscopy (OM) and atomic force microscopy (AFM) studying the related changes in the projected area (PA) or height, while the nanolevel changes of the nanosurface roughness were investigated by in situ AFM. The shape-memory effect at the microlevel was quantified by the recovery ratio of cuboids (Rr,micro), while at the nanolevel, the recovery ratio of the nanoroughness (Rr,nano) was measured. The values of Rr,micro could be tailored in a range from 42 ± 1% to 102 ± 1% and Rr,nano from 89 ± 6% to 136 ± 21% depending on the applied compression ratio and the amount of vinyl acetate content in the cPEVA microcuboids. %0 journal article %@ 1860-7314 %A Roch, T., Hahne, S., Kratz, K., Ma, N., Lendlein, A. %D 2017 %J Biotechnology Journal %N 12 %P 1700334 %R doi:10.1002/biot.201700334 %T Transparent Substrates Prepared From Different Amorphous Polymers Can Directly Modulate Primary Human B cell functions %U https://doi.org/10.1002/biot.201700334 12 %X Manipulation of B cell functions such as antibody and cytokine secretion, is of clinical and biotechnological interest and can be achieved by soluble ligands activating cell surface receptors. Alternatively, the exposure to suitable solid substrates would offer the possibility to transiently induced cell signaling, since the signaling is interrupted when the cells are removed from the substrate. Cell/substrate interactions are mediated by physical valences such as, hydrogen bonds or hydrophobic forces on the substrate surface. Therefore, in this study B cells were cultivated on polymeric substrates, differing in their chemical composition and thus their capacity to undergo physical interactions. Activated B cells cultivated on polystyrene (PS) showed an altered cytokine response indicated by increased IL-10 and decreased IL-6 secretion. Interestingly, B cells cultivated on polyetherurethane (PEU), which has among all tested polymers the highest potential to form strong hydrogen bonds showed an impaired activation, which could be restored by re-cultivation on tissue culture polystyrene. The results indicate that B cell behavior can transiently be manipulated solely by interacting with polymeric surface, which could be explained by receptor activation mediated by physical interaction with the substrate or by altering the availability of the soluble stimulatory reagents by adsorption processes. %0 journal article %@ 1042-7147 %A Yan, W., Fang, L., Weigel, T., Behl, M., Kratz, K., Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1339-1345 %R doi:10.1002/pat.3953 %T The influence of thermal treatment on the morphology in differently prepared films of a oligodepsipeptide based multiblock copolymer %U https://doi.org/10.1002/pat.3953 10 %X In this study, we explored the influence of applying different thermal treatments on the resulting morphologies of solution-cast and spin-coated PCL-PIBMD thin films, which showed different initial surface morphologies. Differential scanning calorimetry results and atomic force microscopy images after different thermal treatments indicated that PCL and PIBMD domains showed similar crystallization behaviors in 270 ± 30 µm thick solution-cast films as well as in 30 ± 2 and 8 ± 1 nm thick spin-coated PCL-PIBMD films. Existing PIBMD crystalline domains highly restricted the generation of PCL crystalline domains during cooling when the sample was annealed at 180 °C. By annealing the sample above 120 °C, the PIBMD domains crystallized sufficiently and covered the free surface, which restricted the crystallization of PCL domains during cooling. The PCL domains can crystallize by hindering the crystallization of PIBMD domains via the fast vitrification of PIBMD domains when the sample was cooled/quenched in liquid nitrogen after annealing at 180 °C. These findings contribute to a better fundamental understanding of the crystallization mechanism of multi-block copolymers containing two crystallizable domains whereby the Tg of the higher melting domain type is in the same temperature range as the Tm of the lower melting domain type. %0 conference lecture %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J 18th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2016 %T Dendritic cell responses towards clinically used polydimethylsiloxane and polytetrafluoroethylene %U %X %0 conference lecture %@ %A Braune, S., Baeckemo-Johansson, J., Kratz, K., Jung, F., Lendlein, A. %D 2016 %J 18th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2016 %T The Influence of different rewetting procedures on the thrombogenicity of nanoporous poly(ether imide) microparticles %U %X %0 conference poster %@ %A Farhan, M., Kratz, K., Lendlein, A. %D 2016 %J Advanced Functional Polymers for Medicine, AFPM 2016 %T Two-way shape-memory networks with large reversible changes %U %X %0 journal article %@ 0887-6266 %A Yan, W., Fang, L., Noechel, U., Kratz, K., Lendlein, A. %D 2016 %J Journal of Polymer Science B %N 19 %P 1935-1943 %R doi:10.1002/polb.24097 %T Influence of programming strain rates on the shape-memory performance of semicrystalline multiblock copolymers %U https://doi.org/10.1002/polb.24097 19 %X Multiblock copolymers named PCL-PIBMD consisting of crystallizable poly(ε-caprolactone) segments and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments coupled by trimethyl hexamethylene diisocyanate provide a versatile molecular architecture for achieving shape-memory effects (SMEs) in polymers. The mechanical properties as well as the SME performance of PCL-PIBMD can be tailored by the variation of physical parameters during programming such as deformation strain or applied temperature protocols. In this study, we explored the influence of applying different strain rates during programming on the resulting nanostructure of PCL-PIBMD. Programming was conducted at 50 °C by elongation to εm = 50% with strain rates of 1 or 10 or 50 mm min−1. The nanostructural changes were visualized by atomic force microscopy (AFM) measurements and investigated by in situ wide and small angle X-ray scattering experiments. With increasing the strain rate, a higher degree of orientation was observed in the amorphous domains. Simultaneously the strain-induced formation of new PIBMD crystals as well as the fragmentation of existing large PIBMD crystals occurred. The observed differences in shape fixity ratio and recovery stress of samples deformed with various strain rates can be attributed to their different nanostructures. The achieved findings can be relevant parameters for programming the shape-memory polymers with designed recovery forces. %0 journal article %@ 1386-0291 %A Kumar, R.K., Basu, S., Lemke, H.-D., Jankowski, J., Kratz, K., Lendlein, A., Tetali, S.D. %D 2016 %J Clinical Hemorheology and Microcirculation %N 4 %P 931-940 %R doi:10.3233/CH-168046 %T Influence of nanoporous poly(ether imide) particle extracts on human aortic endothelial cells (HAECs) %U https://doi.org/10.3233/CH-168046 4 %X It is essential to make sure that these synthetic polymers should not evoke any inflammatory or apoptotic response during dialysis. Therefore in our study we evaluated in vitro effect of PEI microparticle extracts in human aortic endothelial cells (HEACs) concerning toxicity, inflammation and apoptosis. No cell toxicity was observed when HAECs were treated with PEI extracts and inflammatory/apoptotic markers were not upregulated in presence of PEI extracts. Our results ensure biocompatibility of PEI particles and further hemocompatibility of particles will be tested. %0 conference lecture %@ %A Kumar, R.K., Basu, S., Lemke, H.-D., Jankowski, J., Kratz, K., Lendlein, A., Tetali, S.D. %D 2016 %J 18th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2016 %T Influence of nanoporous poly(ether imide) particle extracts on human aortic endothelial cells (HAECs) %U %X %0 journal article %@ 2059-8521 %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2016 %J MRS Advances %N 27 %P 1985-1993 %R doi:10.1557/adv.2016.389 %T Influence of Compression Direction on the Shape-Memory Effect of Micro-Cylinder Arrays Prepared from Semi-Crystalline Polymer Networks %U https://doi.org/10.1557/adv.2016.389 27 %X In this study, we explored the influence of the applied compression direction during programming, i.e. vertical compression and tilted compression, on the SME of microstructured crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) films comprising arrays of micro-cylinders with a height of 10 µm and different diameters of 10 µm, 25 µm, and 50 µm. The shape recovery of the microstructures during heating was visualized online by optical microscopy, while atomic force microscopy (AFM) was utilized to investigate the temperature-induced shape change of single micro-cylinders. Here, the changes in micro-cylinder height and the characteristic angle θ were followed and analyzed for quantification of the shape-memory performance. Both compression modes resulted in almost flat programmed surfaces as indicated by high shape fixity ratios of R f ≥ 93±1%. A nearly complete recovery of the micro-cylinders was obtained for all investigated cPEVA samples documented by high shape recovery values of R r ≥ 97±1%, while the obtained shape change of the micro-cylinders during recovery almost reversely recalled the applied deformation during programming. The presented capability of SMP microstructured substrates to memorize the way of deformation during programming could be a new tool for controlling particular shape changes of microstructures during recovery and in such a way the generated local recovery forces can be adjusted. %0 journal article %@ 1616-5187 %A Schulz, C., Hecht, J., Krueger-Genge, A., Kratz, K., Jung, F., Lendlein, A. %D 2016 %J Macromolecular Bioscience %N 12 %P 1776-1791 %R doi:10.1002/mabi.201600319 %T Generating Aptamers Interacting with Polymeric Surfaces for Biofunctionalization %U https://doi.org/10.1002/mabi.201600319 12 %X Common strategies for biofunctionalization of surfaces comprise the immobilization of bioactive molecules used as cell-binding ligands for cell recruitment. Besides covalent binding, multivalent noncovalent physical forces between substrate and ligand are an alternative way to equip surfaces with biomacromolecules. In this study, polymer binding ligands are screened by means of a DNA-based in vitro selection process. As candidate biomaterials poly(ether imide) (PEI), polystyrene, and poly[ethylene-co-(vinyl acetate)] are selected, due to their different chemical structure, but similar macroscopic interface properties, allowing physical interaction with nucleotide bases by varying valences. Multivalent interacting aptamers are successfully enriched by SELEX method and an area-wide surface functionalization is achieved, which can be used for further binding of bioactive molecules. In vitro selection against the polymers result in thymine-dominated aptamer binding motifs. The preferential interaction with thymine is attributed to its chemical structure, connected with a decreased electrostatic repulsion of the π-system and the hydrophobic character maximizing entropy. The aptamer binding stability correlates with available valences for interaction, resulting in a more stable functionalization of PEI. %0 conference lecture (invited) %@ %A Behl, M., Neffe, A., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J Medtec Europe %T Design Principles of Multifunctional Materials Interacting With Cells %U %X %0 journal article %@ 1386-0291 %A Braune, S., Basu, S., Kratz, K., Johansson, J.B., Reinthaler, M., Lendlein, A., Jung, F. %D 2016 %J Clinical Hemorheology and Microcirculation %N 3 %P 345-353 %R doi:10.3233/CH-168114 %T Strategy for the hemocompatibility testing of microparticles %U https://doi.org/10.3233/CH-168114 3 %X The reported in vitro dynamic whole blood test system allowed the sensitive analysis of the hemocompatibility of polymer-based microparticles and was successfully validated for porous PEI microparticles with different water wettabilities. Beyond the qualitative and quantitative analysis of cell-material interactions, the test also allowed the functional evaluation of platelets in whole blood. %0 conference lecture %@ %A Xu, X., Wang, W., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J 35th Conference of the German Society for Clinical Microcirculation and Hemorheology %R doi:10.3233/CH-168107 %T Surface geometry of poly(ether imide) boosts mouse pluripotent stem cell spontaneous cardiomyogenesis via modulating the embryoid body formation process %U https://doi.org/10.3233/CH-168107 %X %0 journal article %@ 1386-0291 %A Tetali, S.D., Jankowski, V., Luetzow, K., Kratz, K., Lendlein, A., Jankowski, J. %D 2016 %J Clinical Hemorheology and Microcirculation %N 4 %P 657-665 %R doi:10.3233/CH-152026 %T Adsorption capacity of poly(ether imide) microparticles to uremic toxins %U https://doi.org/10.3233/CH-152026 4 %X Uremia is a phenomenon caused by retention of uremic toxins in the plasma due to functional impairment of kidneys in the elimination of urinary waste products. Uremia is presently treated by dialysis techniques like hemofiltration, dialysis or hemodiafiltration. However, these techniques in use are more favorable towards removing hydrophilic than hydrophobic uremic toxins. Hydrophobic uremic toxins, such as hydroxy hipuric acid (OH-HPA), phenylacetic acid (PAA), indoxyl sulfate (IDS) and p-cresylsulfate (pCRS), contribute substantially to the progression of chronic kidney disease (CKD) and cardiovascular disease. Therefore, objective of the present study is to test adsorption capacity of highly porous microparticles prepared from poly( ether imide) (PEI) as an alternative technique for the removal of uremic toxins. Two types of nanoporous, spherically shaped microparticles were prepared from PEI by a spraying/coagulation process. PEI particles were packed into a preparative HPLC column to which a mixture of the four types of uremic toxins was injected and eluted with ethanol. Eluted toxins were quantified by analytical HPLC. PEI particles were able to adsorb all four toxins, with the highest affinity for PAA and pCR. IDS and OH-HPA showed a partially non-reversible binding. In summary, PEI particles are interesting candidates to be explored for future application in CKD. %0 journal article %@ 1386-0291 %A Kumar, R.K., Basu, S., Lemke, H.-D., Jankowski, J., Kratz, K., Lendlein, A., Tetali, S.D. %D 2016 %J Clinical Hemorheology and Microcirculation %N 4 %P 667-680 %R doi:10.3233/CH-152027 %T Effect of extracts of poly(ether imide) microparticles on cytotoxicity, ROS generation and proinflammatory effects on human monocytic (THP-1) cells %U https://doi.org/10.3233/CH-152027 4 %X examined. %0 book part %@ %A Albert, C., Buerger-Arndt, R., Evers, M., Fischer, C., Freese, J., Galler, C., Haaren, C.v., Jedicke, E., Job, H., Kannen, A., Kraetzig, S., Lichter, F., Mewes, M., Moeckel, S., Reck, H., Reisert, J., Wende, W., Woltering, M. %D 2016 %J Oekosystemleistungen in laendlichen Raeumen - Grundlage fuer menschliches Wohlergehen und nachhaltige wirtschaftliche Entwicklung %P 246-307 %T Stand und Potenziale der Integration des Oekosystemleistungskonzeptes in bestehende Planungs-, Regelungs- und Anreizmechanismen %U %X Das Ökosystemleistungskonzept hat jedoch auch Schwachpunkte und diese müssen beachtet und, wo möglich, vermieden werden. Die Beweisführung für kausale Wirkungen von Maßnahmen auf Ökosystemleistungen ist, insbesondere in kürzeren Zeiträumen, nur schwer zu realisieren. Der Anspruch, verschiedenste Ökosystemleistungen gleichzeitig zu berücksichtigen, ist sinnvoll, dieses bislang jedoch auch aufwändig. Ein einfacher, aber ausreichender Leitfaden zur vergleichbaren Bewertung von Ökosystemleistungen fehlt bislang als Grundlage für Planungsprozesse. %0 journal article %@ 2073-4360 %A Zharinova, E., Heuchel, M., Weigel, T., Gerber, D., Kratz, K., Lendlein, A. %D 2016 %J Polymers %N 12 %P 412 %R doi:10.3390/polym8120412 %T Water-Blown Polyurethane Foams Showing a Reversible Shape-Memory Effect %U https://doi.org/10.3390/polym8120412 12 %X Water-blown polyurethane (PU) foams are of enormous technological interest as they are widely applied in various fields, i.e., consumer goods, medicine, automotive or aerospace industries. The discovery of the one-way shape-memory effect in PU foams provided a fresh impetus for extensive investigations on porous polymeric actuators over the past decades. High expansion ratios during the shape-recovery are of special interest when big volume changes are required, for example to fill an aneurysm during micro-invasive surgery or save space during transportation. However, the need to program the foams before each operation cycle could be a drawback impeding the entry of shape-memory polymeric (SMP) foams to our daily life. Here, we showed that a reversible shape-memory effect (rSME) is achievable for polyurethane water-blown semicrystalline foams. We selected commercially available crystallizable poly(ε-caprolactone)-diols of different molecular weight for foams synthesis, followed by investigations of morphology, thermal, thermomechanical and shape-memory properties of obtained compositions. Densities of synthesized foams varied from 110 to 180 kg∙m−3, while peak melting temperatures were composition-dependent and changed from 36 to 47 °C, while the melting temperature interval was around 15 K. All semicrystalline foams exhibited excellent one-way SME with shape-fixity ratios slightly above 100% and shape-recovery ratios from the second cycle of 99%. The composition with broad distribution of molecular weights of poly(ε-caprolactone)-diols exhibited an rSME of about 12% upon cyclic heating and cooling from Tlow = 10 °C and Thigh = 47 °C. We anticipate that our experimental study opens a field of systematic investigation of rSMEs in porous polymeric materials on macro and micro scale and extend the application of water-blown polyurethane foams to, e.g., protective covers with zero thermal expansion or even cushions adjustable to a certain body shape. %0 conference lecture %@ %A Li, Z., Wang, W., Kratz, K., Kuechler, J., Xu, X., Zou, J., Deng, Z., Sun, X., Gossen, M., Ma, N., Lendlein, A. %D 2016 %J 35th Conference of the German Society for Clinical Microcirculation and Hemorheology %T Influence of surface roughness on neural differentiation of human induced pluripotent stem cells %U %X %0 journal article %@ 1386-0291 %A Li, Z., Wang, W., Kratz, K., Kuechler, J., Xu, X., Zou, J., Deng, Z., Sun, X., Gossen, M., Ma, N., Lendlein, A. %D 2016 %J Clinical Hemorheology and Microcirculation %N 3 %P 355-366 %R doi:10.3233/CH-168121 %T Influence of surface roughness on neural differentiation of human induced pluripotent stem cells %U https://doi.org/10.3233/CH-168121 3 %X Induced pluripotent stem cells (iPSCs) own the capacity to develop into all cell types of the adult body, presenting high potential in regenerative medicine. Regulating and controlling the differentiation of iPSCs using the surface topographic cues of biomaterials is a promising and safe approach to enhance their therapeutic efficacy. In this study, we tested the effects of surface roughness on differentiation of human iPSCs into neural progenitor cells and dopaminergic neuron cells using polystyrene with different roughness (R0: flat surface; R1: rough surface, Rq ∼ 6 μm; R2: rough surface, Rq ∼ 38 μm). Neural differentiation of human iPSCs could be influenced by surface roughness. Up-regulated neuronal markers were found in cells on rough surface, as examined by real-time PCR and immunostaining. Particularly, the R1 surface significantly improved the neuronal marker expression, as compared to R0 and R2 surface. This study demonstrates the significance of surface roughness, depending on the roughness level, in promoting differentiation of human iPSCs towards the neuronal lineage. Our study suggests the potential applications of surface roughness in iPSCs based treatment of neural disorder diseases, and highlights the importance of design and development of biomaterials with effective surface structures to regulate stem cells. %0 conference poster %@ %A Li, Z., Wang, W., Kratz, K., Küchler, J., Xu, X., Zou, J., Deng, Z., Sun, X., Gossen, M., Ma, N., Lendlein, A. %D 2016 %J 35. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Neural differentiation of human induced pluripotent stem cells on the structured surface %U %X lnduced pluripotent stem cells (iPSCs) own the capacity to develop into all cell types of the adult body, presenting high potential in regenerative medicine. Regulating and controlling the differentiation of iPSCs via the surface topographic cues of biomaterials is a promising and safe approach to enhance their therapeutic efficacy. In this study, we tested the effects of microscale roughness on differentiation of human iPSCs into neural progenitor cells and dopaminergic neuron cells using polystyrene surface with different roughness levels. Neural differentiation of human iPSCs could be strongly influenced by microscale roughness. Upregulated neuronal markers were detected in iPSCs cells seeded on rougher surface, as examined by real-time PCR and immunost aini ng. Particularly, the intermedium rough surface significantly improved the neuronal marker expression as compared other surfaces. This study demonstrates that a surface with an appropriated microscale roughness level can promote the differentiation of human iPSCs towards the neuronal lineage. Our study suggests the potential applications of controllable iPSCs cell differentiation via surface structure, and highlights the strategy of design and development of structured surface on regulating stem cell development. %0 conference lecture %@ %A Braune, S., Basu, S., Kratz, K., Johansson, J.B., Reinthaler, M., Lendlein, A., Jung, F. %D 2016 %J 35th Conference of the German Society for Clinical Microcirculation and Hemorheology %T Strategy for the hemocompatibility testing of microparticles %U %X %0 conference lecture %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J 18th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2016 %T Inflammatory responses of primary human dendritic cells towards polydimethylsiloxane and polytetrafluoroethylene %U %X %0 journal article %@ 1386-0291 %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J Clinical Hemorheology and Microcirculation %N 4 %P 899-910 %R doi:10.3233/CH-168033 %T Inflammatory responses of primary human dendritic cells towards polydimethylsiloxane and polytetrafluoroethylene %U https://doi.org/10.3233/CH-168033 4 %X Although frequently used as implants materials, both polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE) are often associated with adverse effects including foreign body responses. Dendritic cells (DC) are crucial for the initiation of immune reactions and could also play a role in foreign body associated inflammations. Therefore, the interaction of DC with PDMS and PTFE was investigated regarding their capacity to induce undesired cell activation. Medical grade PDMS and PTFE films were embedded into polystyrene PS inserts via injection molding to prevent the DC from migrating below the substrate and thereby, interacting not only with the test sample but also with the culture vessel material. The viability, the expression of co-stimulatory molecules, and the cytokine/chemokine profiles were determined after 24 hours incubation of the DC with PDMS or PTFE. Blank PS inserts and tissue culture polystyrene (TCP) served as reference materials. The viability of DC was not substantially influenced after incubation with PDMS and PTFE. However, both polymers induced DC activation indicated by the upregulation of co-stimulatory molecules. The release profiles of 14 soluble inflammatory mediators showed substantial differences between PDMS, PTFE, PS, and TCP. This study showed the potential of PTFE and PDMS to activate primary human dendritic cells, which could be an explanation for the often observed inflammatory events associated with the implantation of these polymers. %0 conference lecture (invited) %@ %A Kratz, K., Lendlein, A. %D 2016 %J Cross - Innovation - Workshop: Polymere, Neue Perspektiven fuer IVD, Bioanalytik und Medizin %T Multifunktionale Materialien fuer Technologie und Medizin %U %X %0 journal article %@ 0141-3910 %A Schoene, A.-C., Kratz, K., Schulz, B., Lendlein, A. %D 2016 %J Polymer Degradation and Stability %P 114-121 %R doi:10.1016/j.polymdegradstab.2016.07.010 %T Polymer architecture versus chemical structure as adjusting tools for the enzymatic degradation of oligo(Epsilon-caprolactone) based films at the air-water interface %U https://doi.org/10.1016/j.polymdegradstab.2016.07.010 %X The enzymatic degradation of oligo(ε-caprolactone) (OCL) based films at the air-water interface is investigated by Langmuir monolayer degradation (LMD) experiments to elucidate the influence of the molecular architecture and of the chemical structure on the chain scission process. For that purpose, the interactions of 2D monolayers of two star-shaped poly(ε-caprolactone)s (PCLs) and three linear OCL based copolyesterurethanes (P(OCL-U)) with the lipase from Pseudomonas cepacia are evaluated in comparison to linear OCL. While the architecture of star-shaped PCL Langmuir layers slightly influences their degradability compared to OCL films, significantly retarded degradations are observed for P(OCL-U) films containing urethane junction units derived from 2, 2 (4), 4-trimethyl hexamethylene diisocyanate (TMDI), hexamethylene diisocyanate (HDI) or lysine ethyl ester diisocyanate (LDI). The enzymatic degradation of the OCL based 2D structures is related to the presence of hydrophilic groups within the macromolecules rather than to the packing density of the film or to the molecular weight. The results reveal that the LMD technique allows the parallel analysis of both the film/enzyme interactions and the degradation process on the molecular level. %0 journal article %@ 0032-3861 %A Fang, L., Yan, W., Noechel, U., Kratz, K., Lendlein, A. %D 2016 %J Polymer %P 54-62 %R doi:10.1016/j.polymer.2016.08.105 %T Programming structural functions in phase-segregated polymers by implementing a defined thermomechanical history %U https://doi.org/10.1016/j.polymer.2016.08.105 %X These findings provide insights about the structure function relation in multiblock copolymers with two crystalline phases exhibiting a temperature-memory effect by implementation of specific thermomechanical histories, which might be a general principle for tailoring other functions like mechanical strength or deformability in polymers. %0 journal article %@ 0032-3861 %A Schoene, A.-C., Kratz, K., Schulz, B., Lendlein, A. %D 2016 %J Polymer %P 92-98 %R doi:10.1016/j.polymer.2016.09.001 %T The relevance of hydrophobic segments in multiblock copolyesterurethanes for their enzymatic degradation at the air-water interface %U https://doi.org/10.1016/j.polymer.2016.09.001 %X The interplay of an enzyme with a multiblock copolymer PDLCL containing two segments of different hydrophilicity and degradability is explored in thin films at the air-water interface. The enzymatic degradation was studied in homogenous Langmuir monolayers, which are formed when containing more than 40 wt% oligo(ε-caprolactone) (OCL). Enzymatic degradation rates were significantly reduced with increasing content of hydrophobic oligo(ω-pentadecalactone) (OPDL). The apparent deceleration of the enzymatic process is caused by smaller portion of water-soluble degradation fragments formed from degradable OCL fragments. Beside the film degradation, a second competing process occurs after adding lipase from Pseudomonas cepacia into the subphase, namely the enrichment of the lipase molecules in the polymeric monolayer. The incorporation of the lipase into the Langmuir film is experimentally revealed by concurrent surface area enlargement and by Brewster angle microscopy (BAM). Aside from the ability to provide information about the degradation behavior of polymers, the Langmuir monolayer degradation (LMD) approach enables to investigate polymer-enzyme interactions for non-degradable polymers. %0 journal article %@ 2190-4286 %A Rottke, F.O., Schulz, B., Richau, K., Kratz, K., Lendlein, A. %D 2016 %J Beilstein Journal of Nanotechnology %P 1156-1165 %R doi:10.3762/bjnano.7.107 %T An ellipsometric approach towards the description of inhomogeneous polymer-based Langmuir layers %U https://doi.org/10.3762/bjnano.7.107 %X The applicability of nulling-based ellipsometric mapping as a complementary method next to Brewster angle microscopy (BAM) and imaging ellipsometry (IE) is presented for the characterization of ultrathin films at the air–water interface. First, the methodology is demonstrated for a vertically nonmoving Langmuir layer of star-shaped, 4-arm poly(ω-pentadecalactone) (PPDL-D4). Using nulling-based ellipsometric mapping, PPDL-D4-based inhomogeneously structured morphologies with a vertical dimension in the lower nm range could be mapped. In addition to the identification of these structures, the differentiation between a monolayer and bare water was possible. Second, the potential and limitations of this method were verified by applying it to more versatile Langmuir layers of telechelic poly[(rac-lactide)-co-glycolide]-diol (PLGA). All ellipsometric maps were converted into thickness maps by introduction of the refractive index that was derived from independent ellipsometric experiments, and the result was additionally evaluated in terms of the root mean square roughness, Rq. Thereby, a three-dimensional view into the layers was enabled and morphological inhomogeneity could be quantified. %0 conference poster %@ %A Kratz, K., Jiang, Y., Liu, Y., Lendlein, A. %D 2016 %J International Conference on Molecular Interaction Engineering, MIE 2016 %T Active Polymer Substrates for 3D Printable Biology %U %X %0 journal article %@ 1386-0291 %A Xu, X., Wang, W., Li, Z., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J Clinical Hemorheology and Microcirculation %N 3 %P 367-382 %R doi:10.3233/CH-168107 %T Surface geometry of poly(ether imide) boosts mouse pluripotent stem cell spontaneous cardiomyogenesis via modulating the embryoid body formation process %U https://doi.org/10.3233/CH-168107 3 %X The permanent loss of cardiomyocytes may lead to the irreversible damage of myocardium in cardiovascular diseases. The induced pluripotent stem cells (iPSCs) with the capacity of differentiation into a variety of cell types including cardiomyocytes showed high potential for efficient heart regeneration. The iPSCs and iPSC-derived embryoid bodies (EBs) as well as the differentiated cardiomyocytes are highly sensitive to the biophysical cues of their microenvironment, and accordingly their behavior and function can be largely modulated by microstructure of the cell culture surface. In this study, we investigated the regulatory effect of microscale roughness on both cardiomyogenesis and secretion of EBs using poly(ether imide) (PEI) cell culture inserts with different levels of bottom roughness (R0: flat surface; R1: rough surface, Rq ∼ 4 μm; R2: rough surface, Rq ∼ 23 μm). The proliferation rate and cardiomyogenesis of EBs increased with the increase of surface roughness. The EB secretome derived from R2 surface remarkably enhanced the in vitro new vessel formation of endothelial cells, as compared to those from R0 and R1. These findings highlight the potential to improve the iPSC/EB-based restoration of cardiovascular function via microstructured biomaterials. %0 conference poster %@ %A Liu, Y., Razzaq, M.Y., Kratz, K., Lendlein, A. %D 2016 %J Integrating Function Into Polymers, Polydays 2016 %T Two Level Shape Changes of Programmed Micro-cuboids %U %X %0 conference poster %@ %A Farhan, M., Noechel, U., Kratz, K., Lendlein, A. %D 2016 %J Integrating Function Into Polymers, Polydays 2016 %T Two-way shape-memory properties of surface functionalizable crosslinked crystallizable Terpolymers %U %X %0 conference poster %@ %A Yan, W., Behl, M., Kratz, K., Lendlein, A. %D 2016 %J Integrating function into polymers, Polydays 2016 %T Insights in the shape-memory mechanism of multiblock copolymers having crystallizable as well as glassy switching segments %U %X %0 conference poster %@ %A Xu, X., Li, Z., Wang, W., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J 18th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2016 %T Geometry of Microwells modulate IL-6 secretion of human adipose derived mesenchymal stem cells via ROCK signaling pathway %U %X %0 conference lecture %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2016 %J Multifunctional Biomaterials for Medicine, HVI Symposium 2016 %T Dendritic cell responses towards clinically used polydimethylsiloxane and polytetrafluoroethylene %U %X %0 conference lecture %@ %A Kratz, K., Noechel, U., Behl, M., Lendlein, A. %D 2016 %J Shape Memory Applications, Research and Technology Symposium, SMART 2016 %T Decoding Temperature - Memory Effects in Copolymer Networks Having Crystallizable Controlling Units %U %X %0 conference lecture %@ %A Wischke, C., Kratz, K., Lendlein, A. %D 2016 %J International Conference on Molecular Interaction Engineering, MIE 2016 %T Functional Materials and Interfaces %U %X %0 conference poster %@ %A Blocki, A., Loewenberg, C., Jiang, Y., Kratz, K., Neffe, A.T., Jung, F., Lendlein, A. %D 2016 %J RegMed Forum - 10 Jahre BCRT %T Response of encapsulated cells to a gelatin matrix with varied bulk and microenvironmental elastic properties %U %X %0 conference poster %@ %A Kumar Reddi, K., Krishna D., Jankowski, J., Heuchel, M., Kratz, K., Lendlein, A., Tetali, S. %D 2016 %J 35. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Influence of extracts from hydrophilic modified poly(ether imide) microparticles on cytotoxicity; ROS generation and proinflammatory behavior of human monocytic (THP-1) cells %U %X %0 journal article %@ 1042-7147 %A Farhan, M., Chaganti, S.R., Noechel, U., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1421-1427 %R doi:10.1002/pat.3702 %T Reversible shape-memory properties of surface functionalizable, crystallizable crosslinked terpolymers %U https://doi.org/10.1002/pat.3702 12 %X There is a high demand for polymer actuators comprising reactive groups at their surface in biotechnological or bioanalytical devices especially in microfluidics. In this work, we explored whether a thermoplastic poly[ethylene-co-(ethyl acylate)-co-(maleic anhydride)] (PEEAMA) terpolymer can be converted to a multifunctional shape-memory actuator by introducing covalent netpoints. In crosslinked PEEAMA (cPEEAMA) crystalline polyethylene (PE) domains with melting temperatures below 70°C should serve as actuation domains, responsible for the reversible shape change during cyclic heating and cooling, while higher melting PE crystals act as skeleton forming domains; finally maleic anhydride (MAH) groups enable surface modification of the polymeric substrate. cPEEAMAs with a fixed composition and various crosslink densities were prepared by thermally crosslinking of PEEAMA using different dicumyl peroxide (DCP) concentrations in the starting reaction mixture. A broad melting transition in the range of 50 to 90°C with a melting temperature interval of ∆Tm = 40°C, related to the crystalline PE domains, was observed for all polymer networks in differential scanning calorimetric experiments. Cyclic, thermomechanical uniaxial tensile tests revealed high reversible strains up to 17 ± 2%. A reversible change in long period during repetitive heating and cooling was observed in in situ small angle X-ray scattering experiments. Finally, a successful functionalization of the MAH groups at the cPEEAMA surface by reaction with ethylene diamine was confirmed by infrared spectroscopy analysis. The presented amino functionalized cPEEAMA substrates could be a candidate material for the preparation of adaptive microfluidic devices. %0 conference poster %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2015 %J 34th Conference of the German Society for Clinical Microcirculation and Hemorheology %T Polymeric inserts differing in their chemical composition as substrates for dendritic cell cultivation %U %X %0 journal article %@ 1386-0291 %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2015 %J Clinical Hemorheology and Microcirculation %N 2 %P 347-357 %R doi:10.3233/CH-152004 %T Polymeric inserts differing in their chemical composition as substrates for dendritic cell cultivation %U https://doi.org/10.3233/CH-152004 2 %X Dendritic cells (DC) contribute to immunity by presenting antigens to T cells and shape the immune response by the secretion of cytokines. Due to their immune stimulatory potential DC-based therapies are promising approaches to overcome tolerance e.g. against tumors. In order to enforce the immunogenicity of DCs, they have to be matured and activated in vitro , which requires an appropriate cell culture substrate, supporting their survival expansion and activation. Since most cell culture devices are not optimized for DC growth, it is hypothesized that polymers with certain physicochemical properties can positively influence the DC cultures. With the aim to evaluate the effects that polymers with different chemical compositions have on the survival, the activation status, and the cytokine/chemokine secretion profile of DC, their interaction with polystyrene (PS), polycarbonate (PC), poly(ether imide) (PEI), and poly(styrene-co -acrylonitrile) (PSAN)-based cell culture inserts was investigated. By using this insert system, which fits exactly into 24 well cell culture plates, effects induced from the culture dish material can be excluded. The viability of untreated DC after incubation with the different inserts was not influenced by the different inserts, whereas LPS-activated DC showed an increased survival after cultivation on PC, PS, and PSAN compared to tissue culture polystyrene (TCP). The activation status of DC estimated by the expression of CD40, CD80, CD83, CD86 and HLA-DR expression was not altered by the different inserts in untreated DC but slightly reduced when LPS-activated DC were cultivated on PC, PS, PSAN, and PEI compared to TCP. For each polymeric cell culture insert a distinct cytokine profile could be observed. Since inserts with different chemical compositions of the inserts did not substantially alter the behavior of DC all insert systems could be considered as alternative substrate. The observed increased survival on some polymers, which showed in contrast to TCP a hydrophobic surface, could be beneficial for certain applications such as T cell expansion and activation. %0 conference poster %@ %A Vijaya Bhaskar, T., Roch, T., Ma, N., Kratz, K., Lendlein, A. %D 2015 %J Advanced Functional Polymers for Medicine (AFPM) %T Single and competitive protein adsorption on polymeric surfaces %U %X %0 journal article %@ 1386-0291 %A Wang, W., Kratz, K., Behl, M., Yan, W., Liu, Y., Xu, X., Baudis, S., Li, Z., Kurtz, A., Lendlein, A., Ma, N. %D 2015 %J Clinical Hemorheology and Microcirculation %N 2 %P 301-321 %R doi:10.3233/CH-152001 %T The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone %U https://doi.org/10.3233/CH-152001 2 %X Polyether ether ketone (PEEK) as a high-performance, thermoplastic implant material entered the field of medical applications due to its structural function and commercial availability. In bone tissue engineering, the combination of mesenchymal stem cells (MSCs) with PEEK implants may accelerate the bone formation and promote the osseointegration between the implant and the adjacent bone tissue. In this concept the question how PEEK influences the behaviour and functions of MSCs is of great interest. Here the cellular response of human adipose-derived MSCs to PEEK was evaluated and compared to tissue culture plate (TCP) as the reference material. Viability and morphology of cells were not altered when cultured on the PEEK film. The cells on PEEK presented a high proliferation activity in spite of a relatively lower initial cell adhesion rate. There was no significant difference on cell apoptosis and senescence between the cells on PEEK and TCP. The inflammatory cytokines and VEGF secreted by the cells on these two surfaces were at similar levels. The cells on PEEK showed up-regulated BMP2 and down-regulated BMP4 and BMP6 gene expression, whereas no conspicuous differences were observed in the committed osteoblast markers (BGLAP, COL1A1 and Runx2). With osteoinduction the cells on PEEK and TCP exhibited a similar osteogenic differentiation potential. Our results demonstrate the biofunctionality of PEEK for human MSC cultivation and differentiation. Its clinical benefits in bone tissue engineering may be achieved by combining MSCs with PEEK implants. These data may also provide useful information for further modification of PEEK with chemical or physical methods to regulate the cellular processes of MSCs and to consequently improve the efficacy of MSC-PEEK based therapies. %0 journal article %@ 1946-4274 %A Heuchel, M., Al-Qaisi, L., Kratz, K., Noechel, U., Behl, M., Lendlein, A. %D 2015 %J MRS Online Proceedings Library %P 127-134 %R doi:10.1557/opl.2015.527 %T Thermomechanical Characterization of a Series of Crosslinked Poly[ethylene-co-(vinyl acetate)] (PEVA) Copolymers %U https://doi.org/10.1557/opl.2015.527 %X The influence of VA content and extent of crosslinking on the appearance of the respective melting (Tm) and glass transition (Tg) as well as the thermomechanical properties of cPEVA systems could be demonstrated by discussing both DSC and DMTA results. The temperature range of mechanical stability correlates with the VA content and is determined by decreasing Tm values. The cross links do barely alter the stiffness of a PEVA up to the Tm rang, but lead to constant mechanical rigidity in the rubbery range above Tm. %0 journal article %@ 1042-7147 %A Schoene, A.-C., Falkenhagen, S., Travkova, O., Schulz, B., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1402-1410 %R doi:10.1002/pat.3701 %T Influence of intermediate degradation products on the hydrolytic degradation of poly[(rac-lactide)-co-glycolide] at the air–water interface %U https://doi.org/10.1002/pat.3701 12 %X The influence of intermediate degradation products on the hydrolytic degradation of poly[(rac-lactide)-co-glycolide] (PLGA, 50 mol% lactide) at the air–water interface is investigated using the Langmuir film balance. For that purpose, PLGA bulk samples were degraded in aqueous solution for different time periods to generate different sized fragments with varying water solubility. After dissolution in chloroform the water-insoluble degradation products are able to form Langmuir monolayers with an increased elasticity modulus by decreasing molecular weights. Water-soluble degradation products of PLGA were found to be surface active and form an adsorption layer at the air–water interface, which can be further compressed, and revealing a different adsorption behavior in dependence on their composition. The obtained results imply that measured surface area reduction as it is determined in Langmuir monolayer degradation (LMD) experiment is restricted by the effect of the surface activity of adsorbed oligomer fragments during the degradation process. The surface activity of the formed degradation products makes it difficult to derive degradation mechanism from a common LMD experiment. To elucidate the mechanism in detail, dimers, trimers and longer oligomers with known composition and end-groups have to be investigated. %0 journal article %@ 1946-4274 %A Noechel, U., Kratz, K., Behl, M., Lendlein, A. %D 2015 %J MRS Online Proceedings Library %P 41-48 %R doi:10.1557/opl.2015.427 %T Relation -between Nanostructural Changes and Macroscopic Effects during Reversible Temperature-Memory Effect under Stress-Free Conditions in Semicrystalline Polymer Networks %U https://doi.org/10.1557/opl.2015.427 %X Temperature-memory effects in polymers under stress-free conditions are typically limited to one way effects. Recently, crosslinked polymer networks comprising crystallizable domains, which were capable of a reversible temperature-memory effect (rTME) under stress-free conditions, were introduced. The utilization of crystallizable actuator domains (AD) and shape determining domains (SD) where related to two different temperature ranges of a single broad melting temperature transition in case of rTME. In this study we investigated the nanostructure of crosslinked poly[ethylene-co-(vinyl acetate)] cPEVA capable of rTME in situ during actuation cycles utilizing X-ray scattering techniques and related the changes on the nanoscale to effects on the macroscopic scale. It was observed that 23% of SD obtained at a separation temperature of 75 °C gave the highest reversible strain and when exceeding 80 °C only isotropic crystallization occurred and no rTME was observed. Furthermore, distances between oriented crystalline lamellae correlated to the macroscopic actuation during heating-cooling cycles, exhibiting long-periods from 14 to 17 nm as function of temperature. %0 journal article %@ 0033-4545 %A Wang, L., Baudis, S., Kratz, K., Lendlein, A. %D 2015 %J Pure and Applied Chemistry %N 11-12 %P 1085-1097 %R doi:10.1515/pac-2015-0607 %T Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization %U https://doi.org/10.1515/pac-2015-0607 11-12 %X A versatile strategy to integrate multiple functions in a polymer based material is the formation of polymer networks with defined nanostructures. Here, we present synthesis and comprehensive characterization of covalently surface functionalized magnetic nanoparticles (MNPs) comprising a bi-layer oligomeric shell, using Sn(Oct)2 as catalyst for a two-step functionalization. These hydroxy-terminated precursors for degradable magneto- and thermo-sensitive polymer networks were prepared via two subsequent surface-initiated ring-opening polymerizations (ROPs) with ω-pentadecalactone and ε-caprolactone. A two-step mass loss obtained in thermogravimetric analysis and two distinct melting transitions around 50 and 85°C observed in differential scanning calorimetry experiments, which are attributed to the melting of OPDL and OCL crystallites, confirmed a successful preparation of the modified MNPs. The oligomeric coating of the nanoparticles could be visualized by transmission electron microscopy. The investigation of degrafted oligomeric coatings by gel permeation chromatography and 1H-NMR spectroscopy showed an increase in number average molecular weight as well as the presence of signals related to both of oligo(ω-pentadecalactone) (OPDL) and oligo(ε-caprolactone) (OCL) after the second ROP. A more detailed analysis of the NMR results revealed that only a few ω-pentadecalactone repeating units are present in the degrafted oligomeric bi-layers, whereby a considerable degree of transesterification could be observed when OPDL was polymerized in the 2nd ROP step. These findings are supported by a low degree of crystallinity for OPDL in the degrafted oligomeric bi-layers obtained in wide angle X-ray scattering experiments. Based on these findings it can be concluded that Sn(Oct)2 was suitable as catalyst for the preparation of nanosized bi-layered coated MNP precursors by a two-step ROP. %0 journal article %@ 1042-7147 %A Basu, S., Heuchel, M., Weigel, T., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1447-1455 %R doi:10.1002/pat.3684 %T Integrated process for preparing porous, surface functionalized polyetherimide microparticles %U https://doi.org/10.1002/pat.3684 12 %X Highly porous polyetherimide (PEI) microparticles achieved by a spraying/coagulation process are candidate absorber materials for apheresis applications. Hydrophobic PEI surfaces tend to be rapidly coated with proteins when in contact with blood. Therefore, a hydrophilic modification of such particles is required. In this study, we explored the formation of porous, surface functionalized PEI microparticles by low molecular weight polyethyleneimine (Pei) or potassium hydroxide (KOH) in an integrated process combining chemical modification and particle formation. The integrated process resulted in smaller microparticles with diameters of 70 to 80 µm compared to the chemical two-step process. All particles exhibited similar bulk densities, ranging from 0.09 to 0.015 g cm−3, and average pore sizes around 180–250 nm. A successful modification of the particles' surface by both processing approaches could be confirmed by X-ray photoelectron spectroscopy measurements and microwetting experiments, where hydrophilic advancing contact angles of 57° to 64° were determined. Integrated particle processing further resulted in changes of the bulk properties, i.e. molecular weight, thermal decomposition behavior or glass transition temperature. Hydrophilic modified PEI microparticles have been successfully prepared by different approaches. In a next step their absorption capacity for uremic toxins will be investigated with regard to a potential application in blood detoxification. %0 journal article %@ 1022-1336 %A Schoene, A.-C., Richau, K., Kratz, K., Schulz, B., Lendlein, A. %D 2015 %J Macromolecular Rapid Communications %N 21 %P 1910-1915 %R doi:10.1002/marc.201500316 %T Influence of Diurethane Linkers on the Langmuir Layer Behavior of Oligo[(rac-lactide)-co-glycolide]-based Polyesterurethanes %U https://doi.org/10.1002/marc.201500316 21 %X Three oligo[(rac-lactide)-co-glycolide] based polyesterurethanes (OLGA-PUs) containing different diurethane linkers are investigated by the Langmuir monolayer technique and compared to poly[(rac-lactide)-co-glycolide] (PLGA) to elucidate the influence of the diurethane junction units on hydrophilicity and packing motifs of these polymers at the air–water interface. The presence of diurethane linkers does not manifest itself in the Langmuir layer behavior both in compression and expansion experiments when monomolecular films of OLGA-PUs are spread on the water surface. However, the linker retard the evolution of morphological structures at intermediate compression level under isobaric conditions (with a surface pressure greater than 11 mN m−1) compared to the PLGA, independent on the chemical structure of the diurethane moiety. The layer thicknesses of both OLGA-PU and PLGA films decrease in the high compression state with decreasing surface pressure, as deduced from ellipsometric data. All films must be described with the effective medium approximation as water swollen layers. %0 journal article %@ 1042-7147 %A Schoene, A.-C., Kratz, K., Schulz, B., Reiche, J., Santer, S., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1411-1420 %R doi:10.1002/pat.3638 %T Surface pressure-induced isothermal 2D- to 3D-transitions in Langmuir films of poly(Epsilon-caprolactone)s and oligo(Epsilon-caprolactone) based polyesterurethanes %U https://doi.org/10.1002/pat.3638 12 %X Surface pressure-induced isothermal 2D- to 3D-transitions in Langmuir films of biodegradable poly(ε-caprolactone) (PCL) and oligo(ε-caprolactone) based polyester-urethanes P(OCL-U)s are investigated in order to gain deeper insights into the influence of the linker species on the crystallization and aggregation behavior of macromolecules in a biomimetic aqueous environment. The presence of three urethane linkers derived from 2, 2 (4), 4-trimethyl-hexamethylene-diisocyanate (TMDI), hexamethylene diisocyanate (HDI) and lysine ethylester diisocyanate (LDI) induces remarkable changes in the mesoscopic structure compared to PCL Langmuir films. The pronounced changes in the morphology of the 3D structures co-existing with the Langmuir film above a collapse surface pressure are visualized by Brewster angle microscopy (BAM). Hysteresis of the compression–expansion isotherm in the surface pressure range of the 2D- to 3D-transition indicates the influence of the urethane linkers on the diffusion-limited kinetics and on the reversibility of this phase transition. %0 journal article %@ 1042-7147 %A Vijaya Bhaskar, T.B., Roch, T., Romero, O., Ma, N., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1387-1393 %R doi:10.1002/pat.3639 %T Single and competitive protein adsorption on polymeric surfaces %U https://doi.org/10.1002/pat.3639 12 %X The biological response to material surfaces is often influenced by protein layers formed at the bio-interface. Understanding this protein layer is of paramount importance for biomedical materials and cell culture devices, which often require protein coating for optimal cell growth. An insert system fitting exactly into standard tissue culture plates was developed and can be used for biological investigations without the influence of the cell culture material. Inserts prepared from polystyrene (PS), polycarbonate (PC), poly(styrene-co-acrylonitrile) (PSAN) and poly(ether imide) (PEI) exhibit a similar surface roughness and wettability so that only the chemistry is varied. Previously, stem cell adhesion responses were found to be different for these inserts, possibly because of their different protein adsorption profiles. This work investigated if the surface functional groups of these inserts influence their protein binding ability. Single and competitive adsorption of two most abundant blood proteins, human serum albumin (HSA) and immunoglobulin G (IgG) on these polymers was investigated by labeling both proteins with different near-infrared (IR) dyes. PEI showed the highest protein adsorption propensity in single and competitive adsorption of IgG and HSA while PS exhibited the least adsorption capability, whereas PSAN and PC showed an intermediate protein adsorption profile. Chemical inertness of PS could be the reason for this low protein binding ability and limited cell growth. Conclusively, a novel method to efficiently detect protein adsorption on polymer surfaces was established, and using this method the high relevance of the chemical composition of polymeric substrates on their protein adsorption profile could be proven. %0 journal article %@ 1042-7147 %A Zhang, Q., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1468-1475 %R doi:10.1002/pat.3630 %T Shape-memory properties of degradable electrospun scaffolds based on hollow microfibers %U https://doi.org/10.1002/pat.3630 12 %X Multifunctional thermo-responsive and degradable porous materials exhibiting a shape-memory effect are explored in biomedicine as actively moving scaffolds or switchable substrates. One example are electrospun shape-memory polymer-based scaffolds comprising solid microfibers or nanofibers. In this work, we explored whether fibrous scaffolds composed of hollow microfibers can be prepared from a degradable shape-memory copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(ε-caprolactone) (OCL) switching segments. Scaffolds based on PDC microfibers with identical outer diameter around 1.4 ± 0.3 µm and different hollowness of 0%, 13%, and 33% related to the outer diameter (determined by scanning electron microscopy) were prepared by coaxial electrospinning using poly(ethylene glycol) (PEG) as sacrificial core. Thermal characterization of the scaffolds by differential scanning calorimetry (DSC) and thermogravimetric analysis confirmed a successful removal of PEG. DSC results revealed that the degree of crystallinity increased with increasing microfiber hollowness. The Young's modulus and the failure stress of the prepared scaffolds determined by tensile tests at ambient temperature and 50 °C were found to increase with rising hollowness, while the elongation at break decreased. Cyclic, thermomechanical uniaxial tensile tests showed a pronounced dual-shape effect for all tested materials. Scaffolds comprising microfibers with a hollowness of 33% exhibited the highest shape recovery ratio. Here, we could demonstrate that the degree of hollowness of microfibers, which alters the degree of macromolecular chain orientation, is a suitable design parameter to tailor the mechanical properties as well as the shape-memory performance of electrospun shape-memory polymer fibrous scaffolds. %0 conference poster %@ %A Schöne, A., Travkova, O., Falkenhagen, S., Schulz, B., Kratz, K., Lendlein, A. %D 2015 %J 14th European Conference on Organised Films (ECOF 14) %T Influence of poly[(rac-lactide)-co-glycolide] degradation fragments on hydrolytic Langmuir monolayer degradationexperiments %U %X %0 journal article %@ 1788-618X %A Yan, W., Fang, L., Noechel, U., Kratz, K., Lendlein, A. %D 2015 %J eXPRESS Polymer Letters %N 7 %P 624-635 %R doi:10.3144/expresspolymlett.2015.58 %T Influence of deformation temperature on structural variation and shape-memory effect of a thermoplastic semi-crystalline multiblock copolymer %U https://doi.org/10.3144/expresspolymlett.2015.58 7 %X was mainly fixed by PCL crystals generated via strain-induced crystallization. %0 journal article %@ 1042-7147 %A Sauter, T., Geiger, B., Kratz, K., Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 10 %P 1209-1216 %R doi:10.1002/pat.3583 %T Encasement of metallic cardiovascular stents with endothelial cell-selective copolyetheresterurethane microfibers %U https://doi.org/10.1002/pat.3583 10 %X Cardiovascular metallic stents established in clinical application are typically coated by a thin polymeric layer on the stent struts to improve hemocompatibility, whereby often a drug is added to the coating to inhibit neointimal hyperplasia. Besides such thin film coatings recently nano/microfiber coated stents are investigated, whereby the fibrous coating was applied circumferential on stents. Here, we explored whether a thin fibrous encasement of metallic stents with preferentially longitudinal aligned fibers and different local fiber densities can be achieved by electrospinning. An elastic degradable copolyetheresterurethane, which is reported to selectively enhance the adhesion of endothelial cells, while simultaneously rejecting smooth muscle cells, was utilized for stent coating. The fibrous stent encasements were microscopically assessed regarding their single fiber diameters, fiber covered area and fiber alignment at three characteristic stent regions before and after stent expansion. Stent coatings with thicknesses in the range from 30 to 50 µm were achieved via electrospinning with 1,1,1,3,3,3-hexafluoro-2-propanol (HFP)-based polymer solution, while a mixture of HFP and formic acid as solvent resulted in encasements with a thickness below 5 µm comprising submicron sized single fibers. All polymeric encasements were mechanically stable during expansion, whereby the fibers deposited on the struts remained their position. The observed changes in fiber density and diameter indicated diverse local deformation mechanisms of the microfibers at the different regions between the struts. Based on these results it can be anticipated that the presented fibrous encasement of stents might be a promising alternative to stents with polymeric strut coatings releasing anti-proliferative drugs. %0 journal article %@ 0032-3861 %A Heuchel, M., Razzaq, M.Y., Kratz, K., Behl, M., Lendlein, A. %D 2015 %J Polymer %P 215-222 %R doi:10.1016/j.polymer.2015.03.063 %T Modeling the heat transfer in magneto-sensitive shape-memory polymer nanocomposites with dynamically changing surface area to volume ratios %U https://doi.org/10.1016/j.polymer.2015.03.063 %X Here we present a heat transfer model for predicting Tmax of SMPNCs samples with different S/V ratios when exposed to an AMF. The obtained temperature difference between sample and surrounding in an AMF of constant magnetic field strength decreases at uni-axial deformation with the square root of the stretching ratio. The model was validated with magnetically heating experiments of two different SMPNC systems (comprising crystallizable or amorphous switching segments) containing the same magnetic nanoparticles, while H was varied from 7 to 27 kA m−1 at a fixed frequency of 258 kHz. The experimentally achieved temperatures at deformations up to 50% could be predicted with a divergence below 6%. Finally the model was applied in a principle design study of a device consisting of a rolled SMPNC stripe, which was stepwise opened by increasing H. The modeling approach might be helpful to predict the temperature profiles of SMPNCs which were heated by other mechanisms, e.g., radiofrequency or near IR. %0 journal article %@ 1386-0291 %A Roch, T., Ma, N., Kratz, K., Lendlein, A. %D 2015 %J Clinical Hemorheology and Microcirculation %N 1 %P 51-63 %R doi:10.3233/CH-151939 %T Cell-based detection of microbial biomaterial contaminations %U https://doi.org/10.3233/CH-151939 1 %X A major challenge in biomaterial synthesis and functionalization is the prevention of microbial contaminations such as endotoxins (lipopolysaccharides (LPS)). In addition to LPS, which are exclusively expressed by Gram negative bacteria, also other microbial products derived from fungi or Gram positive bacteria can be found as contaminations in research laboratories. Typically, the Limulus amebocyte lysate (LAL)-test is used to determine the endotoxin levels of medical devices. However, this test fails to detect material-bound LPS and other microbial contaminations and, as demonstrated in this study, detects LPS from various bacterial species with different sensitivities. In this study a cell-based assay using genetically engineered RAW macrophages, which detect not only soluble but also material-bound microbial contaminations is introduced. The sensitivity of this cell-line towards different LPS species and different heat-inactivated microbes was investigated. As proof of principle a soft hydrophobic poly(n-butyl acrylate) network (cPnBA), which may due to adhesive properties strongly bind microbes, was deliberately contaminated with heat-inactivated bacteria. While the LAL-test failed to detect the microbial contamination, the cell-based assay clearly detected material-bound microbial contaminations. Our data demonstrate that a cell-based detection system should routinely be used as supplement to the LAL-test to determine microbial contaminations of biomaterials. %0 journal article %@ 1386-0291 %A Fang, L., Wischke, C., Kratz, K., Lendlein, A. %D 2015 %J Clinical Hemorheology and Microcirculation %N 1 %P 77-87 %R doi:10.3233/CH-151934 %T Influence of film thickness on the crystalline morphology of a copolyesterurethane comprising crystallizable poly(Epsilon-caprolactone) soft segments %U https://doi.org/10.3233/CH-151934 1 %X BACKGROUND: In this work a model approach to investigate changes in crystalline morphology during heating/cooling procedures in the context of programming and induction of the shape-memory effect is presented. OBJECTIVE AND METHOD: Atomic-force microscopy (AFM) was performed to investigate the variations in poly(ε-caprolactone) (PCL) crystalline morphology in nm thin films on a silicon substrate and a film with 20 μm thickness, prepared from a copolyesterurethane (named PDLCL) consisting of crystallizable poly(ω-pentadecalactone) (PPDL) hard segments and crystallizable PCL segments forming switching domains. RESULTS: PCL crystals in switching domains melted/recrystallized repeatedly during heating/cooling cycles between 20 and 70°C, while evident variation in PPDL crystals forming hard domains remained was not observed. When film thickness was 20 nm, PCL edge-on lamellae were observed, confined in the phase-separated morphology, while flat-on PCL lamellae, which broke out from the previous phase-separated morphology, were obtained at a film thickness of 170 nm. In contrast, large PCL spherulites were observed in the 20 μm thick film. CONCLUSION: PCL crystalline morphology in PDLCL as well as the competition between crystallization and phase separation can be tailored by the film thickness and the substrate. Such AFM investigations on thin films can be a helpful approach for predicting the crystal morphology in micro-/nanoscaled objects. %0 journal article %@ 1386-0291 %A Yan, W., Fang, L., Heuchel, M., Kratz, K., Lendlein, A. %D 2015 %J Clinical Hemorheology and Microcirculation %N 1 %P 109-120 %R doi:10.3233/CH-151940 %T Modeling of stress relaxation of a semi-crystalline multiblock copolymer and its deformation behavior %U https://doi.org/10.3233/CH-151940 1 %X Stress relaxation can strongly influence the shape-memory capability of polymers. Recently a modified Maxwell-Wiechert model comprising two Maxwell units and single spring unit in parallel has been introduced to successfully describe the shape recovery characteristics of amorphous polyether urethanes. In this work we explored whether such a modified Maxwell-Wiechert model is capable to describe the stress relaxation behavior of a semi-crystalline multiblock copolymer named PCL-PIBMD, which consists of crystallizable poly(ε-caprolactone) (PCL) segments and crystallizable poly(3S-isobutylmorpholine-2,5-dione) (PIBMD) segments. The stress relaxation behavior of PCL-PIBMD was explored after uniaxial deformation to different strains ranging from 50 to 900% with various strain rates of 1 or 10 or 50 mm·min−1. The modeling results indicated that under the assumption that in PCL-PIBMD both PCL and PIBMD blocks have narrow molecular weight distributions and are arranged in sequence, the two relaxation processes can be related to the amorphous PCL and PIBMD domains and the spring element can be associated to the PIBMD crystalline domains. The first Maxwell unit representing the faster relaxation process characterized by the modulus E1 and the relaxation time τ1 is related to the amorphous PCL domains (which are in the rubbery state), while the second Maxwell unit (E2 ;τ2) represents the behavior of the amorphous PIBMD domains, which are in the glassy state at 50°C. Increasing strain rates resulted in an increase of E1 and a significantly reduction in τ1, whereas the elastic modulus as well as the relaxation time related to the amorphous PIBMD domains remained almost constant. When a higher deformation was applied (ε ≥ 200%) lower values for the elastic moduli of the three model elements were obtained. In general the applied model was also capable to describe the relaxation behavior of PCL-PIBMD at a deformation temperature of 20°C, where additional crystalline PCL domains are existent. The presented approach using a modified Maxwell-Wiechert model to analyze the stress relaxation behavior can be useful to understand the changes in structure-function relation of amorphous as well as semi-crystalline polymers occurring during its uniaxial deformation. %0 conference poster %@ %A Schöne, A., Schulz, B., Kratz, K., Lendlein, A. %D 2015 %J Advanced Functional Polymers for Medicine (AFPM) %T Reduced enzymatic degradation of poly( -caprolactone) based Langmuir films at the air- water interface by introduction of urethane linkers in the polymer backbone %U %X %0 conference lecture %@ %A Braune, S., Kratz, K., Lendlein, A., Jung, F. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Strategy for the hemocompatibility testing of polymer based microparticles %U %X %0 journal article %@ 2050-7488 %A Noechel, U., Reddy, C.S., Wang, K., Cui, J., Zizak, I., Behl, M., Kratz, K., Lendlein, A. %D 2015 %J Journal of Materials Chemistry A %N 16 %P 8284-8293 %R doi:10.1039/C4TA06586G %T Nanostructural changes in crystallizable controlling units determine the temperature-memory of polymers %U https://doi.org/10.1039/C4TA06586G 16 %X Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 °C related to a broad melting transition ([similar]100 °C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (Tdeform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 °C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low Tdeform (<50 °C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units. %0 journal article %@ 1438-7492 %A Zhang, Q., Sauter, T., Fang, L., Kratz, K., Lendlein, A. %D 2015 %J Macromolecular Materials and Engineering %N 5 %P 522-530 %R doi:10.1002/mame.201400267 %T Shape-Memory Capability of Copolyetheresterurethane Microparticles Prepared via Electrospraying %U https://doi.org/10.1002/mame.201400267 5 %X Multifunctional thermo-responsive and degradable microparticles exhibiting a shape-memory effect (SME) have attracted widespread interest in biomedicine as switchable delivery vehicles or microactuators. In this work almost spherical solid microparticles with an average diameter of 3.9 ± 0.9 μm are prepared via electrospraying of a copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(ε-caprolactone) (OCL) switching segments. The PDC microparticles are programmed via compression at different pressures and their shape-memory capability is explored by off-line and online heating experiments. When a low programming pressure of 0.2 MPa is applied a pronounced thermally-induced shape-memory effect is achieved with a shape recovery ratio about 80%, while a high programming pressure of 100 MPa resulted in a weak shape-memory performance. Finally, it is demonstrated that an array of PDC microparticles deposited on a polypropylene (PP) substrate can be successfully programmed into a smart temporary film, which disintegrates upon heating to 60 °C. %0 conference poster %@ %A Schöne, A., Kratz, K., Schulz, B., Lendlein, A. %D 2015 %J 14th European Conference on Organised Films (ECOF 14) %T Enzymatic degradation of Langmuir films based on star-shaped poly(Ɛ-caprolactone) %U %X %0 conference lecture %@ %A Wang, W., Kratz, K., Behl, M., Yan, W., Liu, Y., Xu, X., Baudis, S., Li, Z., Kurtz, A., Lendlein, A., Ma, N. %D 2015 %J 34th Conference of the German Society for Clinical Microcirculation and Hemorheology %T The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone %U %X %0 conference poster %@ %A Rottke, F., Schulz, B., Richau, K., Kratz, K., Lendlein, A. %D 2015 %J 14th European Conference on Organised Films (ECOF 14) %T Visualization of inhomogeneous; biodegradable polymeric Langmuir layers by imaging ellipsometry and mapping technique %U %X %0 conference poster %@ %A Tetali, S., Jankowski, V., Brettschneider, F., Lützow, K., Kratz, K., Lendlein, A., Jankowski, J. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Adsorption capacity of poly(etherimide) microparticles to uremic toxins %U %X %0 conference lecture %@ %A Yan, W., Fang, L., Nöchel, U., Kratz, K., Lendlein, A. %D 2015 %J MRS Fall Meeting 2015; Symposium H “Multifunctionality in Polymer-Based Materials; Gels and Interfaces” %T Effect of Strain Rate on the Nanostructure and Shape-Memory Properties of Semi-crystallineMultiblock Copolymers %U %X %0 conference lecture %@ %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2015 %J MRS Fall Meeting 2015; Symposium H “Multifunctionality in Polymer-Based Materials; Gels and Interfaces” %T Temperature-Memory Polymers as Active Substrates for Printable Biology on 3D Structures %U %X %0 conference lecture %@ %A Liu, Y., Fang, L., Kratz, K., Lendlein, A. %D 2015 %J MRS Fall Meeting 2015; Symposium H “Multifunctionality in Polymer-Based Materials; Gels and Interfaces” %T Preparation and characterization of polymer-based cubic micro actuators %U %X %0 conference poster %@ %A Kumar, R., Basu, S., Kratz, K., Lendlein, A., Tetali, S. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Examining the influence of poly(etherimide) microparticles on cytotoxicity and proinflammatoryeffects on human monocytic cells as well as apoptosis of human aortic endothelial cells %U %X %0 conference poster %@ %A Jiang, J., Liu, Y., Seifert, B., dal Bianco, A., Wischke, C., Kratz, K., Lendlein, A. %D 2015 %J Design von Biosystemen - Vom fundamentalen Verständnis zu neuen Anwendungen %T Multifunktionale Materialien für die Biotechnologie %U %X %0 conference poster %@ %A Basu, S., Kratz, K., Lendlein, A. %D 2015 %J 5. Int. Seminar “Advanced Functional Polymers for Medicine (AFPM)” %T Surface modification of porous polyetherimide microparticles prepared via a spraying/coagulation process %U %X %0 conference poster %@ %A Zhang, Q., Kratz, K., Lendlein, A. %D 2015 %J 5. Int. Seminar “Advanced Functional Polymers for Medicine (AFPM)” %T Shape-memory properties of degradable electrospun scaffolds based on hollow microfibers %U %X %0 conference poster %@ %A Farhan, M., Kratz, K., Lendlein, A. %D 2015 %J 5. Int. Seminar “Advanced Functional Polymers for Medicine (AFPM)” %T Bidirectional Shape-memory Effect of Poly (Ɛ-caprolactone) Based Polymer Networks %U %X %0 conference poster %@ %A Rottke, F., Schulz, B., Richau, K., Kratz, K., Behl, M., Lendlein, A. %D 2015 %J 9th Workshop on Ellipsometry (WSE 2015) %T Visualization of inhomogeneous; biodegradable polymeric Langmuir AClayers by imaging ellipsometry and mapping technique %U %X %0 conference lecture %@ %A Wang, W., Kratz, K., Behl, M., Xu, X., Baudis, S., Li, Z., Kurtz, A., Ma, N., Lendlein, A. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T The interaction of human adipose-derived mesenchymal stem cells and polyether ether ketone %U %X %0 conference poster %@ %A Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %T Polymeric inserts differing in their chemical composition as substrates for dendritic cell cultivation %U %X %0 conference lecture %@ %A Li, Z., Wang, W., Kratz, K., Xu, X., Roch, M., Kurtz, A., Gossen, M., jung, F., Ma, N., Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %T Scaffold Roughness Regulates the Endothelial Differentiation of Human Adipose Derived Mesenchymal Stem Cells %U %X %0 conference paper %@ 1927-7938 %A Kazakeviciute-Makovska, R., Heuchel, M., Kratz, K., Steeb, H. %D 2014 %J Proceedings of ICAST 2014, 25th International Conference on Adapitive Structures and Technologies %P 085 %T Macroscopic characterization and phenomenological modeling of thermally-responsive shape memory polymers %U %X The rational design of shape memory polymer based adaptive structures requires a comprehensive examination of these materials under general multiaxial stress and strain states. This is also necessary for the identification of response functions and the evaluation of predictive capabilities of theoretical models proposed in the literature for this class of smart materials. In this paper we discuss different testing procedures and related methods of data analysis that furnish a firm experimental basis for the evaluation of functional properties of shape memory polymers (SMPs). Moreover, two broad classes of models are discussed, thermoelastic models used in the analysis of rate independent problems and thermo-viscoelastic models, which account for time effects typical for polymer materials. It is shown that the tensor-valued response functions of the general three-dimensional theory presented in this paper may be determined directly from strain/stress storage/recovery profiles measured in strain-controlled shape memory cycles performed in different deformation modes. Finally, the influence of thermo-temporal conditions on functional properties of SMPs is shortly discussed with the view of the evaluation of different classes of these materials and the corresponding theoretical models. %0 conference lecture %@ %A Kazakeviciute-Makovska, R., Heuchel, M., Kratz, K., Steeb, H. %D 2014 %J 25th International Conference on Adapitive Structures and Technologies, ICAST 2014 %T Macroscopic characterization and phenomenological modeling of thermally-responsive shape memory polymers %U %X %0 journal article %@ 1022-1360 %A Wang, L., Noechel, U., Fang, L., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 82-90 %R doi:10.1002/masy.201400141 %T Impact of Molecular Architectures on the Thermal and Mechanical Properties of Multi-Phase Polymer Networks %U https://doi.org/10.1002/masy.201400141 1 %X Multiphase copolymer networks (CLEG) composed of crystallizable poly(ε-caprolactone) (PCL) and crystallizable poly(ethylene glycol) (PEG) segments can exhibit a pronounced triple-shape effect in the dry state or a dual-shape effect in the water swollen, hydrogel state. We hypothesize that by adjusting the network architecture of CLEG copolymers networks the swelling behavior, the thermal and mechanical properties, as well as the crystal structure of PEG and PCL domains can be tailored. Here, we studied CLEG materials with a fixed PCL/PEG weight ratio but different polymer network architectures, whereby the PEG segments were incorporated as grafted side chains or as network chains connecting two netpoints. The prepared CLEGs were analyzed regarding their gel contents, swelling behavior, thermal and mechanical properties and finally the crystallinity of the polymer networks were determined by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) measurements. High gel content values of G  ≥ 98% were achieved for all copolymer network samples, indicating an almost complete conversion of the reaction precursors. The degree of swelling (Q) determined with water increased from Q ≈ 150% to 223% with increasing poly(ethylene glycol) monomethyl monomethacrylate (PEGMMA) content to create more PEG grafted side chains. Only when PEGMMA moieties were present in the CLEG networks two separated melting transitions related to the PCL and PEG segments were obtained, whereby Tm,PEG was found to increase with increasing the PEGMMA weight fraction. Based on this observation it can be assumed that the incorporated poly(ε-caprolactone) diisocyanoethyl methacrylate PEGDIMA segments forming the main network were not able to form crystallites in CLEG networks. An almost two-fold decrease in the Younǵs modulus was observed with increasing amounts of grafted PEG side chains, while the elongation at break increased significantly. Based on Mooney-Rivlin Equations, the crosslinking density increased from 0.10% to 0.21% when PEG segments switched from grafted chains to the network. WAXS and DSC investigations revealed an increase in the degree of crystallinity (DOC) of PEG segments with increasing PEGMMA moieties, while the DOC related to the crystalline PCL domains remained almost constant. The obtained results clearly demonstrated the importance of the molecular architecture in designing polymer networks. %0 conference lecture %@ %A Braune, S., Gross, M., Walter, M., Zhou, S., Dietze, S., Kratz, K., Lendlein, A., Tschoepe, C., Jung, F. %D 2014 %J 33. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Platelet adhesion and activation on polymer-based biomaterials - A comparative pilot study of platelets from patients with coronary artery disease and apparently healthy donors %U %X %0 conference lecture %@ %A Krueger, A., Dietze, S., Kratz, K., Jung, F., Lendlein, A. %D 2014 %J 33. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Endothelial cell migration on different polymer-based biomaterials %U %X %0 journal article %@ 1022-1360 %A Zhang, Q., Sauter, T., Wang, L., Fang, L., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 66-74 %R doi:10.1002/masy.201400140 %T Preparation of Magneto-Sensitive Polymer Nanocomposite Microparticles from Copolyesterurethanes via Electrospraying %U https://doi.org/10.1002/masy.201400140 1 %X Small stimuli-responsive magneto-sensitive microparticles (<5 μm) have attracted broad interest for biomedical applications, since they can be delivered minimal-invasively (e.g. via injection) and guided to a specific site or organ, while using their magnetic properties. In addition, such particles can be remotely heated, e.g., for hyperthermia therapy approaches. In this study, we prepared magneto-sensitive polymer-based nanocomposite microparticles by electrospraying of a 1,1,1,3,3,3 hexafluoro-2-propanol solution containing a mixture of a copolyetheresterurethane (PDC) and magnetic Fe3O4 nanoparticles (MNPs). Thermal gravimetric analysis (TGA) revealed a weight content of 23 ± 0.5 wt-% MNPs in the PDC magneto-sensitive nanocomposite microparticles, which was identical with the initial starting composition. Scanning electron microscopy (SEM) results indicated a bimodal particle size distribution for the prepared magneto-sensitive nanocomposite microparticles around 1.2 ± 0.3 μm and 400 ± 100 nm, respectively. Decreasing the size of the magneto-sensitive nanocomposite microparticles resulted in an increase in their reduced modulus, which was obtained via nanoindentation testing. The PDC magneto-sensitive nanocomposite microparticles could be successfully manipulated in dispersion medium suspension with a permanent magnet, demonstrating their magneto-sensitivity. In addition, the inductive heating capability of the microparticulate nanocomposites could be demonstrated for a thin compression molded test specimen, which could be heated to 44 °C in an alternating magnetic field. The results indicated that such magneto-sensitive nanocomposite microparticles can be potentially used as magneto-responsive shape-memory microparticles for on-demand and remotely controlled drug delivery. %0 journal article %@ 1022-1360 %A Kusmierczuk, M., Noechel, U., Baudis, S., Behl, M., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 98-104 %R doi:10.1002/masy.201400150 %T Shape-Memory Polymer Networks Prepared from Star-Shaped Poly[(L-lactide)-co-glycolide] Precursors %U https://doi.org/10.1002/masy.201400150 1 %X Amorphous degradable copolymer networks such as poly[(L-lactide)-co-glycolide] (PLGA) are promising multifunctional polymers with tailorable degradation profiles and capable of a thermally-induced shape-memory effect. Currently, the shape-memory performance for covalently crosslinked networks based on linear PLGA dimethacrylate precursors (cPLGA) is limited. In this study we explored the shape-memory properties of cPLGA networks prepared from three-armed 2-isocyanatoethyl methacrylate functionalized precursors via photopolymerization. cPLGA exhibited excellent dual-shape properties characterized by an almost complete fixation of the temporary shape as well as an almost perfect recovery of the original shape. In the dry state cPLGA exhibited a switching temperature (Tsw) of 60 °C with a narrow recovery temperature interval of ΔTrec = 5 °C, while a significant lower Tsw of 40 °C with a ΔTrec = 15 °C was obtained when the polymer network was investigated in an aqueous environment. A concomitant decrease in the glass transition temperature could be observed in differential scanning calorimetry heating curves for copolymer networks after storage in aqueous buffer solution at 37 °C for 7 days, which can be attributed to the up-take of water molecules (1.5 wt%). The shape-memory properties achieved for cPLGA, in particular the shape recovery ratio and ΔTrec were superior to those of analogous polymer networks based on linear PLGA dimethacrylates. %0 journal article %@ 2192-2659 %A Xu, X., Wang, W., Kratz, K., Fang, L., Li, Z., Kurtz, A., Ma, N., Lendlein, A. %D 2014 %J Advanced Healthcare Materials %N 12 %P 1933 %R doi:10.1002/adhm.201470060 %T Cover Picture - Stem Cells: Controlling Major Cellular Processes of Human Mesenchymal Stem Cells using Microwell Structures %U https://doi.org/10.1002/adhm.201470060 12 %X The geometry of polymeric matrices is a powerful tool to control cell behavior. On page 1991 N. Ma, A. Lendlein, and co-workers demonstrate human adipose-derived stem cells that show ROCK pathway-mediated differences in their response to square- and round-shaped microwells with respect to their morphology, proliferation, migration, and differentiation. Phagocytes react differently to spherical and ellipsoid microparticles, which now can shift their shape upon stimulation due to an internal polymer micronetwork structure. %0 journal article %@ 1022-1360 %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 75-82 %R doi:10.1002/masy.201400142 %T Effect of the Fixation Temperature Tlow on the Crystallization Behavior and Shape-Memory Performance of Crystallizable Copolyesterurethanes %U https://doi.org/10.1002/masy.201400142 1 %X Multiblock copolymers (PDLCL) composed of crystallizable poly(ω-pentadecalactone) (PPDL) segments forming hard domains and crystallizable poly(ε-caprolactone) (PCL) segments forming switching domains, have been recently introduced as multifunctional shape-memory material. The shape-memory properties of PDLCL are related to the crystallization and melting behavior of PCL switching domains, which enable the temporary fixation of an applied deformation via crystallization as well as the recovery of the original shape by melting of the PCL crystals upon heating. In this work, we explored the effect of different fixation temperatures (Tlow = 0, 10, 20 and 25 °C) on the crystallization behavior of PCL domains in compression-molded films prepared from PDLCL with identical weight contents of PCL and PPDL segments in the starting composition by atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The results demonstrated that lower Tlows ≤ 10 °C supported the nucleation of PCL domains, while a Tlow ≥ 20 °C facilitated the growth of PCL crystals. Reducing Tlow, on one hand, increased the degree of crystallinity of PCL domains, which resultantly improved the shape fixation ratio (Rf) from 83% at 25 °C to 89% at 0 °C. Furthermore, the onset temperature of the recovery process (Ts) related to the crystalline PCL domains, was shifted from Ts = 29 °C to 14 °C when Tlow decreased from 25 to 0 °C, causing an increase in the width of the shape-memory transition. In contrast, the shape recovery ratio, with constant high values of Rr ≥ 96% and the almost identical characteristic switching temperature at Tsw ≈ 42 °C, were found to be independent from the applied Tlow. The obtained results confirmed that the shape-memory performance of multiblock copolymers with crystallizable switching domains can be tailored by altering the fixation temperature during programming. %0 journal article %@ 1022-1360 %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 59-65 %R doi:10.1002/masy.201400138 %T Crystallization Behavior of Copolyesterurethanes Containing Different Weight Contents of Crystallizable Poly(Epsilon-caprolactone) Segments %U https://doi.org/10.1002/masy.201400138 1 %X Multiblock copolymers composed of crystallizable poly(ω-pentadecalactone) (PPDL) and poly(ε-caprolactone) (PCL) segments, which are linked via an aliphatic urethane unit, named PDLCL, have been recently introduced as temperature-memory materials. In this work, we studied the effect of different PCL weight content on the crystallization behavior of both PCL and PPDL domains in PDLCLs by differential scanning calorimetry (DSC), optical microscopy (OM) and atomic force microscopy (AFM). The results demonstrated that the nucleation mechanism of PCL crystals, the crystallization and melting temperatures of PCL domains, as well as their crystal morphology and size were found to change with varying composition, i.e., PCL weight content. %0 journal article %@ 1022-1360 %A Fang, L., Yan, W., Zierke, M., Richau, K., Behl, M., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 83-90 %R doi:10.1002/masy.201400143 %T Crystallization and Phase Segregation of Multifunctional Multiblock Copolymers in Spin Coated Thin Films Altered by Diurethane Junction Units %U https://doi.org/10.1002/masy.201400143 1 %X A multiblock copolymer named PDC is composed of crystallizable oligo(p-dioxanone) (OPDO) and oligo(ε-caprolactone) (OCL) as hard and switching segments. PDC has been synthesized via connecting two oligomeric macrodiols using a diisocyanate linker such as 2,2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) or 1,6-hexamethylene diisocyanate (HDI). In this work, the surface morphologies of spin coated thin films from two PDCs (PDC-HDI and PDC-TMDI) were investigated via in-situ atomic force microscopy (AFM) to examine how the diisocyanate linkers affect the balance between crystallization and phase segregation behavior. The results demonstrated that in PDC-HDI, the crystallization of poly(ε-caprolactone) (PCL) crystals provoked a “break out” from the phase segregated morphology. On contrary, the crystallization of PCL crystals in PDC-TMDI was strictly confined in the phase segregated morphology. %0 journal article %@ 2192-2659 %A Xu, X., Wang, W., Kratz, K., Fang, L., Li, Z., Kurtz, A., Ma, N., Lendlein, A. %D 2014 %J Advanced Healthcare Materials %N 12 %P 1991-2003 %R doi:10.1002/adhm.201400415 %T Controlling Major Cellular Processes of Human Mesenchymal Stem Cells using Microwell Structures %U https://doi.org/10.1002/adhm.201400415 12 %X Directing stem cells towards a desired location and function by utilizing the structural cues of biomaterials is a promising approach for inducing effective tissue regeneration. Here, the cellular response of human adipose-derived mesenchymal stem cells (hADSCs) to structural signals from microstructured substrates comprising arrays of square-shaped or round-shaped microwells is explored as a transitional model between 2D and 3D systems. Microwells with a side length/diameter of 50 μm show advantages over 10 μm and 25 μm microwells for accommodating hADSCs within single microwells rather than in the inter-microwell area. The cell morphologies are three-dimensionally modulated by the microwell structure due to differences in focal adhesion and consequent alterations of the cytoskeleton. In contrast to the substrate with 50 μm round-shaped microwells, the substrate with 50 μm square-shaped microwells promotes the proliferation and osteogenic differentiation potential of hADSCs but reduces the cell migration velocity and distance. Such microwell shape-dependent modulatory effects are highly associated with Rho/ROCK signaling. Following ROCK inhibition, the differences in migration, proliferation, and osteogenesis between cells on different substrates are diminished. These results highlight the possibility to control stem cell functions through the use of structured microwells combined with the manipulation of Rho/ROCK signaling. %0 journal article %@ 1022-1352 %A Schoene, A.-C., Schulz, B., Richau, K., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 24 %P 2437-2445 %R doi:10.1002/macp.201400377 %T Characterization of Langmuir Films Prepared from Copolyesterurethanes Based on Oligo(Ômega-pentadecalactone) and Oligo(Epsilon-caprolactone) Segments %U https://doi.org/10.1002/macp.201400377 24 %X A series of multiblock copolymers (PDLCL) synthesized from oligo(ω-pentadecalactone)diol (OPDL) and oligo(ε-caprolactone)diol (OCL), which are linked by 2,2(4),4-trimethyl-hexa­methylene diisocyanate (TMDI), is investigated by the Langmuir monolayer technique at the air–water interface. Brewster angle microscopy (BAM) and spectroscopic ellipsometry are employed to characterize the polymer film morphologies in situ. PDLCL containing ≥40 wt% OCL segments form homogeneous Langmuir monofilms after spreading. The film elasticity modulus decreases with increasing amounts of OPDL segments in the copolymer. In contrast, the OCL-free polyesterurethane OPDL-TMDI cannot be spread to monomolecular films on the water surface properly, and movable slabs are observed by BAM even at low surface pressures. The results of the in situ morphological characterization clearly show that essential information concerning the reliability of Langmuir monolayer degradation (LMD) experiments cannot be obtained from the evaluation of the π–A isotherms only. Consequently, in situ morphological characterization turns out to be indispensable for characterization of Langmuir layers before LMD experiments. %0 journal article %@ 1022-1352 %A Noechel, U., Kumar, U.N., Wang, K., Kratz, K., Behl, M., Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 24 %P 2446-2456 %R doi:10.1002/macp.201400445 %T Triple-Shape Effect with Adjustable Switching Temperatures in Crosslinked Poly[ethylene-co-(vinyl acetate)] %U https://doi.org/10.1002/macp.201400445 24 %X A triple-shape capability of copolymer networks enabling a variation of the two switching temperatures Tsws by purely physical functionalization is introduced. The polymer networks obtained by covalently crosslinking of poly[ethylene-co-(vinyl acetate)] exhibit a broad melting transition. The influence of the two deformation temperatures Tdeforms applied during programming of the triple-shape effect (TSE) on the two Tsws is explored. Interestingly, it turns out that the deformation geometry plays an important role in the realizability of this concept. Tensile deformations allow adjusting only one Tsw in the lower melting temperature range of 45 to 60 °C, whereas in bending tests, both Tsws can be varied. Finally, two independent TSEs associated to four different Tsws between 45 and 90 °C can be realized in the same specimen. Shape fixity and shape recovery ratios generally exceed 90%, demonstrating an excellent performance of the triple-shape function. %0 journal article %@ 0020-7225 %A Kazakeviciute-Makovska, R., Heuchel, M., Kratz, K., Steeb, H. %D 2014 %J International Journal of Engineering Science %P 140-158 %R doi:10.1016/j.ijengsci.2014.05.009 %T Universal relations in linear thermoelastic theories of thermally-responsive shape memory polymers %U https://doi.org/10.1016/j.ijengsci.2014.05.009 %X In this paper we formulate a one-dimensional linear thermo-elastic (LTE) model in integral form for describing the behavior of thermally-responsive shape memory polymers (SMPs), which unifies and slightly generalizes numerous theories proposed in the literature starting with the seminal approach proposed by Liu et al. (2006). The presented model in its most general form requires the calibration of three response functions. Detailed analysis of four types of shape memory cycles (SMCs) used to quantify the shape memory effect in thermally-responsive SMPs and the corresponding forms of constitutive relations derived within LTE model display a number of critical properties. In particular, two of three response functions may be determined in many different ways from strain and stress storage/recovery profiles measured in SMCs (the third response function may be determined from an independent test). As implication of this fact, we show that the LTE model predicts a number of inter-relations between the measured strain and stress storage/recovery profiles. All these relations are universal in the sense that for any shape memory polymer, which may be correctly described by LTE model, the strain/stress storage/recovery profiles measured in SMCs must satisfy (at least approximately) these relations. Their role within the LTE model is analogous to the role of universal relations in the theory of finite deformation elasticity. In particular, these universal relationships provide a theoretical basis for the validation of any model within the LTE class. The basic theoretical results derived in this paper are illustrated using data obtained by Liu et al. (2006). %0 journal article %@ 1022-1352 %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 1 %P 65-75 %R doi:10.1002/macp.201300507 %T Atomistic Simulation of the Shape-Memory Effect in Dry and Water Swollen Poly[(rac-lactide)-co-glycolide] and Copolyester Urethanes Thereof %U https://doi.org/10.1002/macp.201300507 1 %X An atomistic molecular dynamics simulation approach is applied to model the influence of urethane linker units as well as the addition of water molecules on the simulated shape-memory properties of poly[(rac-lactide)-co-glycolide] (PLGA) and PLGA-based copolyester urethanes comprising different urethane linkers. The shape-memory performance of these amorphous packing models is explored in a simulated heating–deformation–cooling–heating procedure. Depending on the type of incorporated urethane linker, the mechanical properties of the dry copolyester urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the urethane units. Good shape-memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated. %0 journal article %@ 1042-7147 %A Karimi, M., Heuchel, M., Weigel, T., Kratz, K., Lendlein, A. %D 2014 %J Polymers for Advanced Technologies %N 11 %P 1349-1355 %R doi:10.1002/pat.3371 %T Influence of expansion cooling regime on morphology of poly(Epsilon-caprolactone) foams prepared by pressure quenching using supercritical CO2 %U https://doi.org/10.1002/pat.3371 11 %X Creation of foam structures from hydrolytically degradable poly(ε-caprolactone) (PCL) is a current task in biomaterial research. One example are degradable scaffolds. The thermodynamic and kinetic conditions in a supercritical CO2 (scCO2) supported foaming process of PCL can influence the resulting morphology of the foam. PCL foaming with scCO2 was systematically investigated in the pressure range from 78 to 200 bar at temperatures between 25°C and 50°C with the help of a view cell. PCL foams could be obtained at both conditions above the pressure dependent melting temperature as well as below this temperature, i.e. from supercooled melt states. Differential scanning calorimetry investigations of the PCL foam samples were used for the analysis of the relationship between pore morphology and foaming conditions. Three characteristic regions could be distinguished in the PCL/CO2 phase diagram. Only when the foaming was conducted above the critical temperature of CO2, a significant influence of the depressurization rate could be observed. Here, an increase in the quenching rate resulted in a decreasing pore size while the pore density was found to increase. %0 conference lecture %@ %A Kratz, K., Behl, M., Nöchel, U., Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting; Symp. B Multifunctional Polymeric and Hybrid Materials %T Crystallizable Polymer Networks Capable of Reversible Shape-Memory- Effects %U %X %0 conference lecture %@ %A Noechel, U., Kratz, K., Behl, M., Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting & Exhibit, Symposium B %T Relation -between Nanostructural Changes and Macroscopic Effects during Reversible Temperature-Memory Effect under Stress-Free Conditions in Semicrystalline Polymer Networks %U %X %0 conference lecture (invited) %@ %A Behl, M., Kratz, K., Noechel, U., Sauter, T., Lendlein, A. %D 2014 %J 248th ACS National Meeting & Exposition %T Polymer networks capable of reversible shape-memory effects %U %X %0 conference lecture %@ %A Behl, M., Kratz, K., Noechel, U., Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %T Reversible Actuation of Polymer Networks by Directed Crystallization %U %X %0 conference poster %@ %A Roch, T., Ma, N., Kratz, K., Lendlein, A. %D 2014 %J Advanced Functional Polymers for Medicine, AFPM 2014 %T Cell-based detection of microbial biomaterial contaminations %U %X %0 conference lecture %@ %A Braune, S., Dietze, S., Roch, T., Krueger, A., Baudis, S., Behl, M., Kratz, K., Jung, F., Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %T Bicompatibility of a Degradable Poly[(L-lactide)-coglycolide] Network %U %X %0 conference poster %@ %A Xu, X., Wang, W., Kratz, K., Fang, L., Li, Z., Kurtz, A., Ma, N., Lendlein, A. %D 2014 %J Advanced Functional Polymers for Medicine, AFPM 2014 %T 3D geometric cues regulate stem cell self-renewal, migration and differentiation %U %X %0 conference poster %@ %A Rossberg, J., Schulz, B., Kratz, K., Lendlein, A. %D 2014 %J Advanced Functional Polymers for Medicine, AFPM 2014 %T Interactions of Langmuir monolayers based on boronic acid end-capped oligo(ε-caprolactone) with saccharides as model compounds for diol containing biomolecules %U %X %0 conference poster %@ %A Yan, W., Fang, L., Heuchel, M., Kratz, K., Lendlein, A. %D 2014 %J Advanced Functional Polymers for Medicine, AFPM 2014 %T Modeling of Stress Relaxation of a Semi-Crystalline Multiblock Copolymer and its Deformation Behavior %U %X %0 conference poster %@ %A Fang, L., Wischke, C., Kratz, K., Lendlein, A. %D 2014 %J Advanced Functional Polymers for Medicine, AFPM 2014 %T Influence of Film Thickness on the Morphology of a Copolyesterurethane Comprising Crystallizable Poly(Epsilon-caprolactone) Segments %U %X %0 conference lecture %@ %A Kratz, K., Jung, F., Lendlein, A. %D 2014 %J 33. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Development of shape-memory polymer-based Implants at HZG %U %X %0 conference lecture (invited) %@ %A Behl, M., Razzaq, M., Kratz, K., Lendlein, A. %D 2014 %J SPIE BiOS 2014 %T Magnetically triggered active Hybrid- Nanocomposites %U %X %0 conference lecture (invited) %@ %A Kratz, K., Behl, M., Noechel, U., Sauter, T., Lendlein, A. %D 2014 %J Polymermischungen 2014, Polymerblends und Nanocomposites %T Reversible Shape- Memory- Effects in Polymer Networks %U %X %0 conference lecture %@ %A Wang, L., Baudis, S., Kratz, K., Lendlein, A. %D 2014 %J 2nd International Conference on Bioinspired and Biobased Chemistry and Materials: Nature Inspires Chemical Engineers, NICE 2014 %T Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization %U %X %0 conference lecture %@ %A Heuchel, M., Al-Qaisi, L., Kratz, K., Noechel, U., Behl, M., Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting & Exhibit %T Thermomechanical Characterization of a Series of Crosslinked Poly[ethylene-co-(vinyl acetate)] (PEVA) Copolymers %U %X %0 conference lecture %@ %A Heuchel, M., Razzaq, M., Kratz, K., Behl, M., Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting; Symp. B Multifunctional Polymeric and Hybrid Materials %T Modeling the heat transfer behavior of magnetosensitive shape-polymer nanocomposites with changing surface area to volume ratios %U %X %0 conference lecture %@ %A Rueder, C., Haase, T., Sauter, T., Kratz, K., Peter, J., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T In Vivo Assessment of Poly(ether imide) (PEI) Electrospun Scaffold and Film by Subcutaneous Implantation in Mice %U %X %0 conference lecture %@ %A Behl, M., Kratz, K., Noechel, U., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Reversible, Bidirectional Shape-memory Polymers by Directed Crystallization %U %X %0 conference lecture %@ %A Wang, W., Kratz, K., Xu, X., Li, Z., Jung, F., Ma, N., Lendlein, A. %D 2013 %J 17th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2013 %T Interaction of human mesenchymal stem cells with soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli comparable to arteries %U %X %0 conference lecture %@ %A Roch, T., Schmidt, S., Kratz, K., Ma, N., Lendlein, A. %D 2013 %J 17th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2013 %T The influence of polymeric substrates differing in their chemical structure on survival, proliferation, and activation of primary human B cells %U %X %0 conference lecture %@ %A Ma, N., Luetzow, C., Kratz, K., Furlani, D., Li, W., Wang, W., Pittermann, E., Neffe, A.T., Sauter, T., Jung, F., Lendlein, A. %D 2013 %J 17th Conference of the European Society for Clinical Hemorheology and Microcirculation, ESCHM 2013 %T A three-dimensional stem cell culture system by polyurethane scaffold material %U %X %0 conference lecture %@ %A Kratz, K., Lendlein, A. %D 2013 %J Helmholtz Graduate School for Macromolecular Bioscience, Summer School 2013 %T Equipment of Polymers with Memory Effects by Physical Approaches %U %X %0 conference lecture %@ %A Kratz, K., Behl, M., Noechel, U., Sauter, T., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Polymer Networks Exhibiting a Reversible Temperature-Memory Effect %U %X %0 conference poster %@ %A Zhang, Q., Sauter, T., Kratz, K., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T Microparticles prepared from degradable copolyetherester urethanes via electrospraying %U %X %0 conference poster %@ %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T Atomistic simulation of the shape-memory effect of switching segments in poly[(rac-lactide)-co-glycolide] polyesterurethanes %U %X %0 conference lecture %@ %A Braune, S., Alagoez, G., Zhou, S., Roch, T., Kratz, K., Lendlein, A., Jung, F. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Static in vitro hemocompatibility testing of hydrophobic poly(n-butyl acrylate) networks with high crosslink densities %U %X %0 conference lecture %@ %A Rueder, C., Sauter, T., Kratz, K., Haase, T., Peter, J., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Influence of fiber diameter and orientation of electrospun copolyetheresterurethanes on smooth muscle and endothelial cell behaviour %U %X %0 conference poster %@ %A Fang, L., Yan, W., Noechel, U., Zierke, M., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit, Symposium MM – Advanced Materials for Biological and Biomedical Applications %T Influence of Coupling Agent on the Morphology of Multifunctional, Degradable Shape-Memory Polymers %U %X %0 conference lecture %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2013 %J 245th National ACS Spring Meeting, Symposium on Stimuli-Responsive Polymers %T Pore Size Distribution as Structural Parameter to Tailor the Shape-Memory Effect of Polyurethane Foams %U %X %0 conference lecture %@ %A Kratz, K., Cui, J., Lendlein, A. %D 2013 %J 245th National ACS Spring Meeting, Symposium on Stimuli-Responsive Polymers %T Temperature-Memory Polymers %U %X %0 conference lecture %@ %A Ma, N., Xu, X., Kratz, K., Wang, W., Li, Z., Jung, F., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T The Influence of Geometrically Patterned Polymer Surfaces on the Development of Human Mesenchymal Stem Cells %U %X %0 conference poster %@ %A Wang, L., Noechel, U., Fang, L., Kratz, K., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T Impact of Polymer Network Architecture on the Thermal and Mechanical Properties of Multi-phase Polymer Networks Containing Crystallizable Poly(ethylene glycol) (PEG) and Poly(ε-caprolactone) (PCL) Segments %U %X %0 conference lecture (invited) %@ %A Behl, M., Kratz, K., Lendlein, A. %D 2013 %J Soft Control - Switching Surface Properties with Stimulus Responsive Polymers at Interfaces %T Shape-Memory Polymers – From One Way Effects to Programmable Actuators %U %X %0 journal article %@ 1558-3724 %A Sauter, T., Heuchel, M., Kratz, K., Lendlein, A. %D 2013 %J Polymer Reviews %N 1 %P 6-40 %R doi:10.1080/15583724.2012.756519 %T Quantifying the Shape-Memory Effect of Polymers by Cyclic Thermomechanical Tests %U https://doi.org/10.1080/15583724.2012.756519 1 %X Shape-memory polymers (SMPs) can be deformed and fixed in defined temporary shapes, which significantly differ from their original shape and remain unchanged until exposed to heat or other stimuli. The shape-memory effect (SME) of polymers is generally quantified in cyclic thermomechanical experiments, which allow to simultaneously control stress or strain and temperature during programming and recovery. Characteristic shape-memory quantities such as the shape-fixity ratio R f and shape-recovery ratio R r as well as the specific response temperatures can be determined from the obtained stress-temperature-strain curves. This review reports on the most common cyclic testing methods utilizing tensile, bending, and compression experiments for examination of dual-shape polymers. Furthermore, recently developed testing protocols for triple- and multi-shape polymers as well as materials that exhibit a temperature-memory effect or can show a two-way SME under constant stress are discussed. %0 journal article %@ 1386-0291 %A Xu, X., Kratz, K., Wang, W., Li, Z., Roch, T., Jung, F., Lendlein, A., Ma, N. %D 2013 %J Clinical Hemorheology and Microcirculation %N 1 %P 143-156 %R doi:10.3233/CH-131698 %T Cultivation and spontaneous differentiation of rat bone marrow-derived mesenchymal stem cells on polymeric surfaces %U https://doi.org/10.3233/CH-131698 1 %X Accumulating evidence demonstrated many physical and chemical cues from the local microenvironment could influence mesenchymal stem cells (MSCs) maintenance and differentiation. In this study, we systematically investigated the interaction of rat bone marrow-derived mesenchymal stem cells (rBMSCs) and polymeric substrates. Adhesion, proliferative capacity, cytoskeleton alteration, cytotoxicity, apoptosis, senescence, and adipogenesis potential of rBMSCs were determined on these polymeric inserts prepared from polyetherurethane (PEU) and poly(ether imide) (PEI). Inserts for culture plates were applied to ensure that the rBMSCs were solely in contact to the tested material. The explored inserts exhibited advancing contact angles of 84° (PEU) and 93° (PEI). Finally, the micromechanical properties determined by atomic force microscopy (AFM) indentation varied in the range from 6 GPa (PEU) to 13 GPa (PEI). We found that both PEU and PEI showed a good cell compatibility to rBMSCs. rBMSCs could adherent on both polymeric surfaces with the similar adhesion ratio and subsequent division rate. However, cells cultured on PEU exhibited higher apoptosis level and senescence ratio, which resulted in lower cell density (22061 ± 3000/cm2) compared to that on PEI (68395 ± 8000/cm2) after 20 days cultivation. Morphological differences of rBMSCs were detected after 5 days cultivation. Cells on PEU exhibited flat and enlarged shape with rearranged filamentous actin (F-actin) cytoskeleton, while cells on PEI and tissue culture plate (TCP) had similar spindle-shape morphology and oriented F-actin. After 20 days, lipid droplets were spontaneously formed in rBMSCs on PEU and PEI but not on TCP. Both PEU and PEI might trigger rBMSCs towards spontaneous adipogenic commitment, whereas PEI provided better cell compatibility on rBMSCs apoptosis, senescence and proliferation. %0 conference poster %@ %A Behl, M., Kratz, K., Noechel, U., Zotzmann, J., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T Directed Crystallization turns Poly(Omega-pentadecalactone)-based Multiphase Polymer Networks into Active Polymers %U %X %0 conference object %@ %A Lendlein, A., Razzaq, M.Y., Kratz, K., Behl, M. %D 2013 %J Abstracts of Papers of the American Chemical Society, 245th National Spring Meeting of the American-Chemical-Society %P 164-PMSE %T Magnetically triggered memory-effects of active nanocomposites %U %X %0 journal article %@ 1022-1352 %A Sauter, T., Kratz, K., Lendlein, A. %D 2013 %J Macromolecular Chemistry and Physics %N 11 %P 1184-1188 %R doi:10.1002/macp.201300062 %T Pore-Size Distribution Controls Shape-Memory Properties on the Macro- and Microscale of Polymeric Foams %U https://doi.org/10.1002/macp.201300062 11 %X Open porous foams with identical foam density but different pore-size distributions (bimodal or monomodal) are prepared from a shape-memory polyetherurethane (PEU) by thermally induced phase separation. The shape-memory effect of the two PEU foams is explored by cyclic thermomechanical compression tests and microstructural analysis. The obtained results reveal that the PEU foam with a bimodal pore-size distribution exhibits an increased shape-recovery under stress-free conditions, both on the macro- (foam level) as well as the microscale (pore level). While bimodal pore-size distributions induce microscale bending during compression, buckling occurs in foams with monomodal pore-size distributions, leading to both a reduced and delayed shape recovery. %0 journal article %@ 0014-3057 %A Noechel, U., Reddy, C.S., Uttamchand, N.K., Kratz, K., Behl, M., Lendlein, A. %D 2013 %J European Polymer Journal %N 9 %P 2457-2466 %R doi:10.1016/j.eurpolymj.2013.01.022 %T Shape-memory properties of hydrogels having a poly(Epsilon-caprolactone) crosslinker and switching segment in an aqueous environment %U https://doi.org/10.1016/j.eurpolymj.2013.01.022 9 %X Here we study the thermomechanical properties as well as the shape-memory behavior of a series of CLEG copolymer networks in an aqueous environment. The mechanical properties of the networks at 25 °C in aqueous environment were found to increase from 4 MPa to 77 MPa with increasing crosslink density. The shape-memory properties of the copolymer networks were examined in an aqueous environment by both bending as well as uniaxial elongation experiments. Excellent dual-shape properties with high shape fixity ratios around Rf = 79–100% and shape recovery ratios in the range of Rr = 59% to Rr = 100% were obtained for copolymers with a PCLDIMA weight fraction ⩾50 wt% in the starting composition. The swelling of CLEG in H2O resulted in a reduction of the switching temperature. Furthermore the structural changes during programming of CLEG were assessed in situ by small and wide angle X-ray scattering (SAXS, WAXS) experiments, which confirmed that the overall degree of crystallinity as well as the orientation of the crystalline domains controlled the dual-shape performance. We have found that an appropriate switching segment should result in a degree of crystallinity higher than 10–20% to enable high strain fixity ratios. Furthermore, hydrogels having dual shape-memory capability could be created by using semi-crystalline crosslinker simultaneously acting as the switching segment. %0 journal article %@ 0887-6266 %A Heuchel, M., Sauter, T., Kratz, K., Lendlein, A. %D 2013 %J Journal of Polymer Science B %N 8 %P 621-637 %R doi:10.1002/polb.23251 %T Thermally induced shape-memory effects in polymers: Quantification and related modeling approaches %U https://doi.org/10.1002/polb.23251 8 %X Thermo-sensitive polymers, which are capable to exhibit a dual-, triple-, or multi-shape effect or a temperature-memory effect (TME), characterized by a controlled shape change in a predefined way, are of current technological interest for designing and realization of actively moving intelligent devices. Here, the methods for the quantitative characterization of shape-memory effects in polymers and recently developed thermomechanical modeling approaches for the simulation of dual-, triple-, and multi-shape polymers as well as materials that exhibit a TME are discussed and some application oriented models are presented. Standardized methods for comprehensive quantification of the different effects and reliable modeling approaches form the basis for a successful translation of the extraordinary achievements of fundamental research into technological applications. %0 journal article %@ 1022-1352 %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2013 %J Macromolecular Chemistry and Physics %N 11 %P 1273-1283 %R doi:10.1002/macp.201200450 %T Simulating the Shape-Memory Behavior of Amorphous Switching Domains of Poly(L-lactide) by Molecular Dynamics %U https://doi.org/10.1002/macp.201200450 11 %X The thermally induced shape-memory effect of polymers is typically characterized by cyclic uniaxial thermomechanical tests. Here, a molecular-dynamics (MD) simulation approach of such a cyclic uniaxial thermomechanical test is presented for amorphous switching domains of poly(L-lactide) (PLLA). Uniaxial deformation of the constructed PLLA models is simulated with a Parinello–Rahman scheme, as well as a pragmatic geometrical approach. We are able to describe two subsequent test cycles using the presented simulation approach. The obtained simulated shape-memory properties in both test cycles are similar and independent of the applied deformation protocols. The simulated PLLA shows high shape fixity ratios (Rf ≥ 94%), but only a moderate shape recovery ratio is obtained (Rr ≥ 30%). Finally, the structural changes during the simulated test are characterized by analysis of the changes in the dihedral angle distributions. %0 journal article %@ 0032-3861 %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2013 %J Polymer %N 16 %P 4204-4211 %R doi:10.1016/j.polymer.2013.05.064 %T Influence of the addition of water to amorphous switching domains on the simulated shape-memory properties of poly(l-lactide) %U https://doi.org/10.1016/j.polymer.2013.05.064 16 %X All simulated PLLA models showed high shape fixity ratio of Rf ≥ 84%. The shape-memory properties obtained at εm = 100% for the dry PLLA and the models containing 1 wt% water were almost identical with a shape recovery ratio in the first and second test cycle around Rr = 61%–64%. In contrast PLLA with 2 wt% water exhibited higher values of Rr = 76% during the first test cycle, but a lower Rr = 52% in the subsequent second cycle. Furthermore, increasing the applied εm resulted in a decrease of Rr from 82% to 42% for the dry PLLA, whereas PLLA with 2 wt% water did not show a dependence of Rr on εm. We anticipate that these observations can be attributed to differences in the initial structure of the various simulated PLLA models e.g. the different distribution of the free volume elements. %0 conference lecture %@ %A Krueger, A., Trescher, K., Scharnagl, N., Kratz, K., Roch, T., Lendlein, A., Jung, F. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %R doi:10.1007/s00382-011-1220-0 %T Adherence and viability of primary human dermal keratinocytes and primary human dermal fibroblasts on acrylonitrile-based copolymers with systematic variations of positively and negatively charged functional groups %U https://doi.org/10.1007/s00382-011-1220-0 %X %0 conference poster %@ %A Dietze, S., Braune, S., Krueger, A., Baudis, S., Behl, M., Kratz, K., Jung, F., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Hemocompatibility of degradable poly[(rac-lactide)-co-glycolide] polymer network %U %X %0 conference poster %@ %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T AFM Study of the Crystallization Behavior of Temperature-Memory Polymers Containing Different Weight Contents of Crystallizable Poly(ε-caprolactone) Switching Segments %U %X %0 conference lecture (invited) %@ %A Lendlein, A., Razzaq, M.Y., Kratz, K., Behl, M. %D 2013 %J 245th National Spring Meeting of the American-Chemical-Society %T Magnetically triggered memory-effects of active nanocomposites %U %X %0 journal article %@ 0168-1656 %A Trescher, K., Roch, T., Cui, J., Kratz, K., Lendlein, A., Jung, F. %D 2013 %J Journal of Biotechnology %N 1-2 %P 58-64 %R doi:10.1016/j.jbiotec.2013.04.012 %T Test system for evaluating the influence of polymer properties on primary human keratinocytes and fibroblasts in mono- and coculture %U https://doi.org/10.1016/j.jbiotec.2013.04.012 1-2 %X Poly(n-butyl acrylate) networks (cPnBAs) as model biomaterials were used to demonstrate the applicability of our newly developed coculture screening system for differential cell growth. The apparent Young's modulus of the cPnBAs differentially regulated fibroblasts and keratinocytes. Particularly, cPnBA73 with an apparent Young's modulus of 930 ± 140 kPa measured in phosphate buffered saline (PBS) solution at ambient temperature seemed to have favoring properties for keratinocyte adhesion, while fibroblast adhesion was not affected. For keratinocytes the concentration of some pro-inflammatory cytokines was lower on cPnBA73 and a decreased deposition of collagen, elastin and fibronectin was observed in the coculture. %0 conference poster %@ %A Krueger, A., Scharnagl, N., Trescher, K., Zierke, M., kratz, K., Behl, M., Jung, F., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Behaviour of fibroblasts on water born acrylonitrile based copolymers with varying hydrophilicities %U %X %0 conference lecture %@ %A Li, Z., Ma, N., Kratz, K., Wang, W., Xu, X., Gossen, M., Roch, T., Kurtz, A., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Effects of Roughness on Angiogenesis of Human Adipose Derived Stem Cells %U %X %0 conference poster %@ %A Schoene, A.-C., Schulz, B., Richau, K., Kratz, K., Lendlein, A. %D 2013 %J 28. Tag der Chemie %T Characterization of Langmuir Layers Prepared from Copolyesterurethanes Containing Different Poly(ε-caprolactone) Moieties %U %X %0 conference poster %@ %A Roch, T., Behl, M., Zierke, M., Pierce, B.F., Weigel, T., Ma, N., Kratz, K., Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit, Symposium NN – Multifunctional Biomaterials %T The influence of the co-monomer ratio of poly[acrylonitrile-co-(N-vinylpyrrolidone)]s on primary human monocyte-derived dendritic cells %U %X %0 conference poster %@ %A Fang, L., Yan, W., Zierke, M., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %T Morphology of Spin-coated Films from Copolyetheresterurethanes Containing Different Aliphatic Diisocyanate Linkers %U %X %0 journal article %@ 1946-4274 %A Fang, L., Yan, W., Noechel, U., Zierke, M., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J MRS Online Proceedings Library %P 57-64 %R doi:10.1557/opl.2013.805 %T Influence of Coupling Agent on the Morphology of Multifunctional, Degradable Shape-Memory Polymers %U https://doi.org/10.1557/opl.2013.805 %X Multifunctional polymer-based biomaterials, which combine degradability and shapememory capability, are promising candidate materials for biomedical implants. An example is a degradable multiblock copolymer (PDC), composed of poly(p-dioxanone) (PPDO) as hard and poly(ε-caprolactone) (PCL) as switching segments. PDC exhibits a unique linear mass loss during hydrolytic degradation, which can be tailored by the PPDO to PCL weight ratio, as well as an excellent thermally induced dual-shape effect. PDC can be synthesized by co-condensation of two oligomeric macrodiols (PCL-diol and PPDO-diol) using aliphatic diisocyanates as coupling agent. Here, we investigated whether different morphologies could be obtained for PDCs synthesized from identical oligomeric macrodiols (PCL-diol with M n = 2000 g·mol-1 and PPDO-diol with M n = 5300-5500 g·mol-1) with 2, 2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) and 1, 6-hexamethylene diisocyanate (HDI), respectively. More specifically, atomic force microscopy (AFM) was utilized for an investigation of the surface morphologies in solution casted PDC thin films in the temperature range from 20 °C to 60 °C. The results obtained in differential scanning calorimetry (DSC) and AFM demonstrated that different morphologies were obtained when TMDI (PDC-TMDI) or HDI (PDC-HDI) were used as linker. PCL related crystals in PDC-HDI were more heterogeneous and less ordered than those in PDCTMDI, while HDI resulted in a larger degree of crystallinity than TMDI. This research provides some new suggestions for choosing a suitable coupling agent to tailor the required morphologies and properties of SMPs with crystallizable switching segments. %0 journal article %@ 1386-0291 %A König, J., Kohl, B., Kratz, K., Jung, F., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2013 %J Clinical Hemorheology and Microcirculation %N 4 %P 523-533 %R doi:10.3233/CH-131788 %T Effect of polystyrene and polyether imide cell culture inserts with different roughness on chondrocyte metabolic activity and gene expression profiles of aggrecan and collagen %U https://doi.org/10.3233/CH-131788 4 %X In vitro cultured autologous chondrocytes can be used for implantation to support cartilage repair. For this purpose, a very small number of autologous cells harvested from a biopsy have to be expanded in monolayer culture. Commercially available polymer surfaces lead to chondrocyte dedifferentiation. Hence, the demanding need for optimized polymers and surface topologies supporting chondrocytes' differentiated phenotypes in vitro arises. In this study we explored the effect of tailored cell culture plate inserts prepared from polystyrene (PS) and polyether imide (PEI) exhibiting three different roughness levels (R0, RI, RII) on chondrocyte morphology, metabolism and gene expression profile. As a control, commercially available tissue culture plastic (TCP) dishes were included. Primary porcine articular chondrocytes were seeded on tailored PS and PEI inserts with three different roughness levels. The metabolic activity of the chondrocytes was determined after 24 hours using alamar blue assay. Chondrocyte gene expression profiles (aggrecan, type I and type II collagen) were monitored after 48 hours using Real Time Detection (RTD)-PCR. Chondrocytes cultured on PS and PEI surfaces formed cell clusters after 24 and 48 hours, which was not observed on TCP. The metabolic activity of chondrocytes cultured on PS was lower than of chondrocytes cultured on PEI, but also lower than on TCP. Gene expression analyses revealed an elevated expression of cartilage-specific aggrecan and an impaired expression of both collagen types by chondrocytes on PS and PEI compared with TCP. In summary, PEI is a biocompatible biomaterial suitable for chondrocyte culturing, which can be further chemically functionalized for generating specific surface interactions or covalent binding of biomolecules. %0 journal article %@ 1386-0291 %A Rüder, C., Sauter, T., Kratz, K., Haase, T., Peter, J., Jung, F., Lendlein, A., Zohlnhöfer, D. %D 2013 %J Clinical Hemorheology and Microcirculation %N 4 %P 513-522 %R doi:10.3233/CH-131787 %T Influence of fibre diameter and orientation of electrospun copolyetheresterurethanes on smooth muscle and endothelial cell behaviour %U https://doi.org/10.3233/CH-131787 4 %X Polymers exhibiting cell-selective effects represent an extensive research field with high relevance for biomedical applications e.g. in the cardiovascular field supporting re-endothelialization while suppressing smooth muscle cell overgrowth. Such an endothelial cell-selective effect could be recently demonstrated for a copolyetheresterurethane (PDC) containing biodegradable poly(p-dioxanone) and poly(ε-caprolactone) segments, which selectively enhanced the adhesion of human umbilical vein endothelial cells (HUVEC) while suppressing the attachment of smooth muscle cells (SMC). In this study we investigated the influence of the fibre orientation (random and aligned) and fibre diameter (2 μm and 500 nm) of electrospun PDC scaffolds on the adhesion, proliferation and apoptosis of HUVEC and SMC. Adhesion, viability and proliferation of HUVEC was diminished when the fibre diameter was reduced to a submicron scale, while the orientation of the microfibres did only slightly influence the cellular behaviour. In contrast, a submicron fibre diameter improved SMC viability. In conclusion, PDC scaffolds with micron-sized single fibres could be promising candidate materials for cell-selective stent coatings. %0 journal article %@ 1386-0291 %A Hashimdeen, S.S., Römhild, A., Schmueck, M., Kratz, K., Lendlein, A., Kurtz, A., Reinke, P. %D 2013 %J Clinical Hemorheology and Microcirculation %N 4 %P 501-512 %R doi:10.3233/CH-131786 %T Culture surface influence on T-cell phenotype and function %U https://doi.org/10.3233/CH-131786 4 %X When dealing with T lymphocyte culture there is currently very less information available about the interaction between T-cells and the culture system. In this study we look at the influence of the culture chamber on T-cell proliferation in two main aspects of the culture system, namely: culture chamber material and geometry. The study was carried out using unique polymeric closed cell culture inserts, which were processed via injection moulding from polystyrene (PS), polycarbonate (PC), polyetherurethane (PEU), polystyrene-co-acrylonitrile (PSAN) and polyetherimide (PEI). Furthermore culture chamber geometry was studied using commercially available 24, 12 and 6-well plates prepared from tissue culture plastic (TCP). For T lymphocyte stimulation two methods were used involving either EBV peptide pools or MACS iBead particles depending on the experiment performed. Culture was done with 1645 RPMI medium supplemented with foetal calf serum, penicillin, streptomycin and rhIL-2. We found four materials out of five we tested (PS, PC, PSAN and PEI) exhibited similar fold expansions with minimal influence on proportions of CD4 and CD8, while PEU had a negative influence on T cell growth along with adversely affected CD4/CD8 proportions. Changes in the geometry of TCP had no effect on T cell growth or maturation rather the size of geometry seems to have more influence on proliferation. T-cells appear to prefer smaller geometries during initial stages of culture while towards the end of the culture size becomes less significant to cell proliferation. The parameters tested in this study have significant influences on T-cell growth and are necessary to consider when designing and constructing expansion systems for antigen specific T lymphocytes. This is important when culturing T-cells for immunotherapeutic applications where antigen specificity, T-cell maturation and function should remain unaffected during culture. %0 journal article %@ 0027-8424 %A Behl, M., Kratz, K., Noechel, U., Sauter, T., Lendlein, A. %D 2013 %J Proceedings of the National Academy of Sciences of the United States of America: PNAS %N 31 %P 12555-12559 %R doi:10.1073/pnas.1301895110 %T Temperature-memory polymer actuators %U https://doi.org/10.1073/pnas.1301895110 31 %X Reading out the temperature-memory of polymers, which is their ability to remember the temperature where they were deformed recently, is thus far unavoidably linked to erasing this memory effect. Here temperature-memory polymer actuators (TMPAs) based on cross-linked copolymer networks exhibiting a broad melting temperature range (ΔTm) are presented, which are capable of a long-term temperature-memory enabling more than 250 cyclic thermally controlled actuations with almost constant performance. The characteristic actuation temperatures Tacts of TMPAs can be adjusted by a purely physical process, guiding a directed crystallization in a temperature range of up to 40 °C by variation of the parameter Tsep in a nearly linear correlation. The temperature Tsep divides ΔTm into an upper Tm range (T > Tsep) forming a reshapeable actuation geometry that determines the skeleton and a lower Tm range (T < Tsep) that enables the temperature-controlled bidirectional actuation by crystallization-induced elongation and melting-induced contraction. The macroscopic bidirectional shape changes in TMPAs could be correlated with changes in the nanostructure of the crystallizable domains as a result of in situ X-ray investigations. Potential applications of TMPAs include heat engines with adjustable rotation rate and active building facades with self-regulating sun protectors. %0 journal article %@ 0935-9648 %A Razzaq, M.Y., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J Advanced Materials %N 40 %P 5730-5733 %R doi:10.1002/adma.201302485 %T Multifunctional Hybrid Nanocomposites with Magnetically Controlled Reversible Shape–Memory Effect %U https://doi.org/10.1002/adma.201302485 40 %X Magneto-sensitivity and a thermo-sensitive reversible shape–memory effect have been successfully integrated into a hybrid nanocomposite, resulting in a magnetically controlled actuator. The complex requirements for gaining this multifunctionality are fulfilled by combining netpoints on the molecular and nano level in a polyesterurethane network prepared from hydroxyl group decorated magnetic nanoparticles, crystallizable star-shaped poly(ω-pentadecalactone) precursors, and a diisocyanate. %0 journal article %@ 0935-9648 %A Razzaq, M.Y., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J Advanced Materials %N 38 %P 5514-5518 %R doi:10.1002/adma.201301521 %T Triple-Shape Effect in Polymer-Based Composites by Cleverly Matching Geometry of Active Component with Heating Method %U https://doi.org/10.1002/adma.201301521 38 %X A triple-shape effect is created for a segmented device consisting of an active component encapsulated in a highly flexible polymer network. Segments with the same composition but different interface areas can be recovered independently either at specific field strengths (Hsw) during inductive heating, at a specific time during environmentally heating, or at different airflow during inductive heating at constant H. Herein the type of heating method regulates the sequence order. %0 journal article %@ 0935-9648 %A Behl, M., Kratz, K., Zotzmann, J., Nöchel, U., Lendlein, A. %D 2013 %J Advanced Materials %N 32 %P 4466-4469 %R doi:10.1002/adma.201300880 %T Reversible Bidirectional Shape-Memory Polymers %U https://doi.org/10.1002/adma.201300880 32 %X Free-standing copolymer network samples with two types of crystallizable domains are capable of a fully reversible bidirectional shape-memory effect. One set of crystallizable domains determines the shape-shifting geometry while the other provides the thermally controlled actuation capability. %0 journal article %@ 1946-4274 %A Wang, L., Nöchel, U., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J MRS Online Proceedings Library %P 123-128 %R doi:10.1557/opl.2013.799 %T Comparison of memory effects in multiblock copolymers and covalently crosslinked multiphase polymer networks composed of the same types of oligoester segments and urethane linker %U https://doi.org/10.1557/opl.2013.799 %X A pronounced temperature-memory effect was achieved for thermoplastic as well as crosslinked copolyesterurethanes. Hereby, the switching temperatureTsw could be adjusted via the variation of the applied deformation temperatureTdeform in the range from 32 °C to 53 °C for MBC and in the range from 29 °C to 78 °C for multiphase polymer networks. %0 journal article %@ 1946-4274 %A Landsberger, P., Boenke, V., Gorbushina, A.A., Rodenacker, K., Pierce, B.F., Kratz, K., Lendlein, A. %D 2013 %J MRS Online Proceedings Library %P 85-90 %R doi:10.1557/opl.2013.832 %T Bacterial attachment on poly[acrylonitrile-co-(2-methyl-2-propene-1-sulfonic acid)] surfaces %U https://doi.org/10.1557/opl.2013.832 %X We found a reduced colonized area ofE. coli for NaMAS containing copolymers in comparison to pure PAN materials, whereby the bacterial colonization was similar for copolymers with different nNaMAS amounts. A different adhesion behavior was obtained for the second tested organismB. subtilis, where the implementation of negative charges into PAN did not change the overall adhesion pattern. Furthermore, it was observed thatB. subtilis adhesion was significantly increased on copolymer samples that exhibited a more irregular surface roughness. %0 conference lecture %@ %A Schmidt, S., Roch, T., Kratz, K., Ma, N., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Investigations of Cell Culture Inserts Engineered from Polystyrene and Poly(ether imide) for B Cell Cultivation %U %X %0 conference lecture (invited) %@ %A Behl, M., Kratz, K., Lendlein, A. %D 2013 %J International Workshop on Biodegradable Polymers in Medicine %T Shape-Memory Polymers %U %X %0 conference lecture %@ %A Xu, X., Wang, W., Kratz, K., Li, Z., Jung, F., Ma, N., Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Cultivation of rat mesenchymal stem cells on poly(ether imide) surfaces with different microscaled roughness %U %X %0 journal article %@ 1386-0291 %A Roch, T., Kratz, K., Ma, N., Jung, F., Lendlein, A. %D 2013 %J Clinical Hemorheology and Microcirculation %N 1 %P 157-168 %R doi:10.3233/CH-131699 %T The influence of polystyrene and poly(ether imide) inserts with different roughness, on the activation of dendritic cells %U https://doi.org/10.3233/CH-131699 1 %X Dendritic cells (DC) have a pivotal role during inflammation. DC efficiently present antigens to T cells and shape the subsequent immune response by the secretion of pro- or anti-inflammatory cytokines and by the expression of co-stimulatory molecules. They respond to “danger signals” such as microbial products or fragments from necrotic cells or tissues, but were also described to be reactive towards biomaterials. However, how mechanical and physical properties of the subjacent substrate influences the DC activation is currently poorly understood. In this study micro patterned inserts prepared from polystyrene (PS) as well as from poly (ether imide) (PEI) with three different roughness levels of i) Rq = 0.29 μm (PS) and 0.23 μm (PEI); ii) Rq = 3.47 μm (PS) and 3.92 μm (PEI); and iii) Rq = 22.16 μm (PS) and 22.65 μm (PEI) were analyzed for their capacity to influence the activation of human monocytes derived DC. Since the DC were directly cultured in the inserts, the effects of the testing material alone could be investigated and influences from additional culture dish material could be excluded. The viability, the expression of the DC activation markers, and their cytokine/chemokine secretion were determined after the incubation with the different inserts in vitro. Both the PS and the PEI inserts did not influence the survival of the DC and their expression of co-stimulatory molecules. The expression of inflammatory cytokines was not altered by the PEI and PS inserts. However, the secretion of chemokines such as CCL2, CCL3, and CCL4 was influenced by the different roughness levels, indicating that material roughness has the capacity to modulate the DC phenotype. The data presented here will help to understand the interaction of DC with structured polymer surfaces. Biomaterial-induced immuno-modulatory effects mediated by DC may promote tissue regeneration or could potentially reduce inflammation caused by the implant material. %0 journal article %@ 1946-4274 %A Roch, T., Behl, M., Zierke, M., Pierce, B.F., Kratz, K., Weigel, T., Ma, N., Lendlein, A. %D 2013 %J MRS Online Proceedings Library %P 21-26 %R doi:10.1557/opl.2013.830 %T The influence of the co-monomer ratio of poly[acrylonitrile-co-(N-vinylpyrrolidone)]s on primary human monocyte-derived dendritic cells %U https://doi.org/10.1557/opl.2013.830 %X A major goal in the field of regenerative medicine is to improve our understanding of how biomaterial properties affect cells of the immune system. Systematic variation of defined chemical properties could help to understand which factors determine and modulate cellular responses. A series of copolymers poly[acrylonitrile-co-(N-vinylpyrrolidone)]s (P(AN-co-NVP)) served as model system, in which increasing hydrophilicity was adjusted by increasing the content related to the NVP based repeating units (nNVP) (0, 4.6, 11.8, 22.3, and 29.4 mol%). The influence of increasing nNVP contents on cellular response of human primary monocyte derived dendritic cells (DC), which play a key role in the initiation of immune responses, was investigated. It was shown using the LAL-Test as well as a macrophage-based assay, that the materials were free of endotoxins and other microbial contaminations, which could otherwise bias the readout of the DC experiments. The increasing nNVP content led to a slightly increased cell death of DC, whereas the activation status of DC was not systematically altered by the different P(AN-co-NVP)s as demonstrated by the expression of co-stimulatory molecule and cytokine secretion. Similarly, under inflammatory conditions mimicked by the addition of lipopolysaccharides (LPS), neither the expression of co-stimulatory molecules nor the release of cytokines was influenced by the different copolymers. Conclusively, our data showed that this class of copolymers does not substantially influence the viability and the activation status of DC. %0 conference poster %@ %A Yan, W., Fang, L., Noechel, U., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Influence of Strain Rate on the Shape-Memory Performance of Multiblock Copolymers Comprising Crystallizable Poly(Epsilon-caprolactone) Switching and Poly[3-(S)-isobutylmorpholine-2,5-dione] Hard Segments %U %X %0 conference poster %@ %A Fang, L., Yan, W., Zierke, M., Richau, K., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Crystallization Behavior and Phase Separation in Spin Coated Copolyetherester Urethane Films with Different Diisocyanate Linkers %U %X %0 conference poster %@ %A Schoene, A.-C., Kratz, K., Schulz, B., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Morphological Investigation of Oligo[(rac-lactide)-co-glycolide]-based Polyesterurethanes at the Water-Air Interface via Brewster Angle Microscopy and Ellipsometry %U %X %0 conference poster %@ %A Jiang, Y., Fang, L., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T The Effect of Fixation Temperature on Crystallization Behaviors and Shape-Memory Properties of a Semi-Crystalline Multiblock Copolymer %U %X %0 conference poster %@ %A Wang, L., Fang, L., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Preparation of Two-Layered Magnetic Nanoparticles via a Two Step Surface-Initiated Ring-Opening Polymerization of Omega-Pentadecalactone and Epsilon-Caprolactone %U %X %0 conference poster %@ %A Kusmierczuk, M., Baudis, S., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Investigating the Influence of Water Uptake on the Mechanical Properties of Covalently Crosslinked Poly[(L-lactide)-co-glycolide] Polymer Networks %U %X %0 conference poster %@ %A Karimi, M., Heuchel, M., Weigel, T., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Influence of expansion cooling regime on morphology of poly(Epsilon-caprolactone) foams prepared by pressure quenching technique using supercritical CO2 %U %X %0 conference poster %@ %A Farhan, M., Reddy, C., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Two-way shape-memory properties of crystallizable, covalently crosslinked terpolymer networks %U %X %0 conference poster %@ %A Schoene, A.-C., Reuter, F., Richau, K., Kratz, K., Schulz, B., Reiche, J., Santer, S., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Langmuir Film Morphology of Poly(Epsilon-caprolactone) (PCL) and PCL-based Polyesterurethanes %U %X %0 conference poster %@ %A Fang, L., Yan, W., Richau, K., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Crystallization Behaviors of Biodegradable Multiblock Copolymers Based on Oligodepsipeptides in Spin-coated Films %U %X %0 conference poster %@ %A Reddy, C., Noechel, U., Wang, K., Cui, J., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Influence of co-monomer composition and covalent netpoint density on temperature-memory performance of crystallizable copolymer networks %U %X %0 conference poster %@ %A Heuchel, M., Albrecht, W., Kosmella, H.-J., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Experimental determination of vitrification points in ternary polymer/solvent/non-solvent/ systems %U %X %0 conference poster %@ %A Razzaq, M., Behl, M., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Geometrically Controlled Triple-Shape Effect of Polymer Nanocomposites %U %X %0 conference poster %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %T Controlling the Shape-Memory Properties in Polymeric Foams by Microstructural Design %U %X %0 conference lecture %@ %A Schneider, T., Kohl, B., Sauter, T., Kratz, K., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Influence of fiber orientation in electrospun polymer scaffolds on viability, adhesion and differentiation of articular chondrocytes %U %X %0 journal article %@ 1386-0291 %A Krueger, A., Braune, S., Kratz, K., Lendlein, A., Jung, F. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 283-294 %R doi:10.3233/CH-2012-1605 %T The influence of poly(n-butyl acrylate) networks on viability and function of smooth muscle cells and vascular fibroblasts %U https://doi.org/10.3233/CH-2012-1605 2-4 %X Background: The patency of small-diameter vascular prostheses is limited by several factors such as thrombogenicity, which is strongly influenced by surface roughness and chemical composition, or a mechanical mismatch between the elastic modulus of an artery and of the vascular prosthesis. A confluent layer of endothelial cells onto the inner surface of vascular prostheses could improve the hemocompatibility of the device. Biomaterials with adjustable elastic properties could be tailored to the values of human arteries so that a prothesis mismatch could be avoided. It was recently demonstrated that a co-culture of endothelial cells with angiogenically stimulated monocytes (aMO2) shows an accelerated formation of a functional confluent endothelial cell monolayer on soft hydrophobic poly(n-butyl acrylate) (cPnBA) networks. In addition, the cell compatibility with vascular smooth muscle cells and aortic fibroblasts, which are other important cell types of the vessel wall, is essential for a vascular prosthesis material and must therefore be explored. Purpose: Here we investigated the interaction of human vascular smooth muscle cells and aortic fibroblasts with cPnBA04 and cPnBA73. Material and methods: Human primary vascular smooth muscle cells and aortic fibroblasts were seeded on the two cPnBAs with different elastic moduli (cPnBA04 - 250 kPa and cPnBA73 - 1100 kPa) over 72 h. A live-dead staining (fluorescein diacetate/propium iodide) was performed to determine the morphology and viability of adherent cells. Furthermore, the extracellular matrix components, the actin cytoskeleton, the cell-material-contacts and the cytokine profiles were analysed. Results: Both cell types adhered and were viable on cPnBA04 and cPnBA73. The level of pro-inflammatory cytokine secretion (IFN-γ and TNF-α) by smooth muscle cells and vascular fibroblasts was comparable to that of cells cultivated on a control material. The release of these cytokines by human fibroblasts was higher on cPnBA73 compared to cPnBA04. Both cell types secreted an extracellular matrix comparable to cells seeded on a control material. Conclusion: The study revealed, that cPnBA with varying elastic moduli are not only suitable for the cultivation of endothelial cells, but also for human vascular smooth muscle cells and aortic fibroblasts. Therefore, cPnBA could be a potential candidate material for the development of cardiovascular prostheses. %0 journal article %@ 1386-0291 %A Schneider, T., Kohl, B., Sauter, T., Kratz, K., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 325-336 %R doi:10.3233/CH-2012-1608 %T Influence of fiber orientation in electrospun polymer scaffolds on viability, adhesion and differentiation of articular chondrocytes %U https://doi.org/10.3233/CH-2012-1608 2-4 %X Degradable polymers with a tailorable degradation rate might be promising candidate materials for biomaterial-based cartilage repair. In view of the poor intrinsic healing capability of cartilage, implantation of autologous chondrocytes seeded on a biocompatible slow degrading polymer might be an encouraging approach to improve cartilage repair in the future. This study was undertaken to test if the fiber orientation (random versus aligned) of two different degradable polymers and a polymer intended for long term applications could influence primary articular chondrocytes growth and ultrastructure. A degradable copoly(ether)esterurethane (PDC) was synthesized via co-condensation of poly(p-dioxanone)diol and poly(ε-caprolactone)diol using an aliphatic diisocyanate as linker. Poly(p-dioxanone) (PPDO) was applied as commercially available degradable polymer, while polyetherimide (PEI) was chosen as biomaterial enabling surface functionalization. The fibrous scaffolds of PDC and PPDO were obtained by electrospinning using 1,1,1,3,3,3 hexafluoro-2-propanol (HFP), while for PEI dimethyl acetamide (DMAc) was applied as solvent. Primary porcine articular chondrocytes were seeded at different cell densities on the fibrous polymer scaffolds and analyzed for viability (fluorescein diacetate/ethidiumbromide staining), for type II collagen synthesis (immunolabelling), ultrastructure and orientation on the fibers (SEM: scanning electron microscopy). Vital chondrocytes adhered on all electrospun scaffolds irrespective of random and aligned topologies. In addition, the chondrocytes produced the cartilage-specific type II collagen on all tested polymer topologies suggesting their differentiated functions. SEM revealed an almost flattened chondrocytes shape on scaffolds with random fiber orientation: whereby chondrocytes growth remained mainly restricted to the scaffold surface. On aligned fibers the chondrocytes exhibited a more spindle-shaped morphology with rougher cell surfaces but only a minority of the cells aligned according to the fibers. As a next step the reduction of the fiber diameter of electrospun scaffolds should be addressed as an important parameter to mimic cartilage ECM structure. %0 journal article %@ 1438-1656 %A Sauter, T., Luetzow, K., Schossig, M., Kosmalla, H., Weigel, T., Kratz, K., Lendlein, A. %D 2012 %J Advanced Engineering Materials %N 9 %P 818-824 %R doi:10.1002/adem.201200127 %T Shape-Memory Properties of Polyetherurethane Foams Prepared by Thermally Induced Phase Separation %U https://doi.org/10.1002/adem.201200127 9 %X In this study, we report the preparation of two structurally different shape-memory polymer foams by thermally induced phase separation (TIPS) from amorphous polyetherurethanes. Foams with either a homogeneous, monomodal, or with a hierarchically structured, bimodal, pore size distribution are obtained by adoption of the cooling protocol. The shape-memory properties have been investigated for both foam structures by cyclic, thermomechanical experiments, while the morphological changes on the micro scale (pore level) have been compared to the macro scale by an in situ micro compression device experiment. The results show that the hierarchically structured foam achieves higher shape-recovery rates and a higher total recovery as compared to the homogeneous foam, which is due to an increased energy storage capability by micro scale bending of the hierarchically structured foam compared to pure compression of the homogeneous foam. %0 journal article %@ 1788-618X %A Kumar, U.N., Kratz, K., Behl, M., Lendlein, A. %D 2012 %J eXPRESS Polymer Letters %N 1 %P 26-40 %R doi:10.3144/expresspolymlett.2012.4 %T Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments %U https://doi.org/10.3144/expresspolymlett.2012.4 1 %X materials as here the temporary shape (A) was predominantly fixed by PCL crystallites. %0 journal article %@ 1386-0291 %A Rueder, C., Sauter, T., Kratz, K., Peter, J., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 313-323 %R doi:10.3233/CH-2012-1607 %T Smooth muscle and endothelial cell behaviour on degradable copolyetheresterurethane films %U https://doi.org/10.3233/CH-2012-1607 2-4 %X Stent thrombosis and restenosis after drug-eluting stent (DES) implantation remains a relevant problem in the cardiovascular field. The polymer-based biomaterial (e.g. stent coating) requirements are comprehensive, since the polymeric material ideally should ensure an effective re-endothelialization by recruiting endothelial cells (EC) and endothelial progenitor cells (EPC). Simultaneously, the polymer should effectively prevent adherence of smooth muscle cells (SMC) and thereby inhibiting restenosis. The aim of this study was to gain a basic understanding on the interaction of SMC and human umbilical vein endothelial cells (HUVEC) with nonporous polymer films. A multifunctional copolyetheresterurethane (PDC) was chosen as candidate material: PDC consists of poly(p-dioxanone) (PPDO) and poly(ε-caprolactone)-segments (PCL). In our study it was compared to the degradable PPDO homopolymer and poly(vinylidene fluoride-co-hexafluoropropene) (PVDF), an established coating material of DES in clinical applications intended for longterm applications. The films were analyzed according to their thermomechanical and surface properties before being examined in contact with HUVEC and SMC concerning cell viability, proliferation and adhesion. Experimental results showed that adhesion could be improved for HUVEC on PDC compared to PPDO and PVDF. In contrast, SMC attachment is largely suppressed on PDC polymeric films indicating a cell-specific response of HUVEC towards PDC. In conclusion, PDC represents a promising candidate material for future cardiovascular applications like e.g. biodegradable (PDC) stent coatings. %0 journal article %@ 1386-0291 %A Trescher, K., Scharnagl, N., Kratz, K., Roch, T., Lendlein, A., Jung, F. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 391-401 %R doi:10.3233/CH-2012-1613 %T Adherence and viability of primary human keratinocytes and primary human dermal fibroblasts on acrylonitrile-based copolymers with different concentrations of positively charged functional groups %U https://doi.org/10.3233/CH-2012-1613 2-4 %X As shown in several studies, various properties of biomaterials such as stiffness, surface roughness, chemical composition or the amount of functional groups at the surface can influence adhesion, viability, proliferation and functionalities of cells. The aim of this work was to explore whether a cell-selective effect could be achieved for acrylonitrile-based copolymers containing different contents of positively charged functional groups, which were introduced by incorporation of methacrylic acid-2-aminoethylester hydrochloride (AEMA) units. The p(AN-co-AEMA) copolymers were synthesized by suspension polymerization in water and processed into disk shaped test specimen via a sintering process to ensure the absence of organic solvents in the copolymers. Copolymers with an AEMA content of 1.4, 1.6, and 4.4 mol-% were investigated according to their cell-selective capacity, which should support the adhesion, viability and proliferation of keratinocytes, while the adherence of fibroblasts should rather be disabled. The test samples were seeded with primary human keratinocytes and primary human dermal fibroblasts in mono- as well as in co-cultures. Tissue culture plate polystyrene (TCP) was used to control the physiologic growth of the cells. Density and viability of attached and non-adherent cells were analyzed by live/dead staining, lactate dehydrogenase (LDH) assay and flow cytometry with DAPI staining. For the assured discrimination of adherent cell types in coculture a keratin/vimentin-staining was performed. On copolymers with 4.4 mol-% AEMA adherent keratinocytes in monoculture and cocultured keratinocytes and fibroblasts showed a higher viability, a lower impairment of cell membranes and higher densities of viable cells compared to both other copolymers. For adherent fibroblasts these parameters did not differ between the copolymers and an increasing ratio of keratinocytes to fibroblasts in cocultures were found with increasing AEMA content. The results showed that keratinocytes and fibroblasts can be influenced by copolymers with different contents of positively charged functional groups. Since the tendency of a better adherence and viability of keratinocytes with increasing amounts of positively charged functional groups was shown, the potential enhancement by further increase of the amount of positively charged functional groups shall be tested in a future study. %0 journal article %@ 1793-9844 %A Sauter, T., Weigel, T., Kratz, K., Lendlein, A. %D 2012 %J Nano LIFE %N 1 %P 1230005 %R doi:10.1142/S1793984411000372 %T Polymer Scaffolds for Regenerative Therapies – Design of Hierarchically Organized Structures and their Morphological Characterization %U https://doi.org/10.1142/S1793984411000372 1 %X Read More: http://www.worldscientific.com/doi/abs/10.1142/S1793984411000372 %0 journal article %@ 1386-0291 %A Wang, W., Ma, N., Kratz, K., Xu, X., Li, Z., Roch, T., Bieback, K., Jung, F., Lendlein, A. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 357-373 %R doi:10.3233/CH-2012-1611 %T The influence of polymer scaffolds on cellular behaviour of bone marrow derived human mesenchymal stem cells %U https://doi.org/10.3233/CH-2012-1611 2-4 %X Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into a variety of cell types. Therefore, they are widely explored in regenerative medicine. The interaction of MSCs with biomaterials is of great importance for cell proliferation, differentiation and function, and can be strongly influenced by numerous factors, such as the chemical nature and the mechanical properties of the material surface. In this study, we investigated the interaction of bone marrow derived human MSCs with different amorphous and transparent polymers namely polystyrene (PS), polycarbonate (PC), poly(ether imide) (PEI), polyetherurethane (PEU) and poly(styrene-co-acrylonitrile) (PSAN). To ensure that the MSCs were solely in contact to the testing material we applied polymeric inserts, which were prepared from the aforementioned polymers via injection molding. The explored inserts exhibited a similar wettability with advancing contact angles ranging from 84 ± 7° (PEU) to 99 ± 5° (PS) and a surface roughness of Rq ≤ 0.86 μm. The micromechanical properties determined by AFM indentation varied from 6 ± 1 GPa (PEU) to 24 ± 5 GPa (PSAN). Cells presented different adhesion rates on the polymer surfaces 24 hours after seeding (45 ± 7% (PS), 63 ± 1% (PC), 75 ± 4% (PEI), 69 ± 2% (PEU) and 61 ± 5% (PSAN)). The cells could proliferate on the polymer surfaces, and the fold change of cell number after 16 days of culture reached to 1.93 ± 0.07 (PS), 3.38 ± 0.11 (PC), 3.65 ± 0.04 (PEI), 2.24 ± 0.15 (PEU) and 3.36 ± 0.09 (PSAN). Differences in cell apoptosis could be observed during the culture. After 7 days, the apoptosis of cells on PC, PEI and PSAN decreased to a level comparable to that on standard tissue culture plate (TCP). All of the tested polymers exhibited low cytotoxicity and allowed high cell viability. Compared to cells on TCP, cells on PC and PEI showed similar morphology, distribution as well as F-actin cytoskeleton organization, whereas cells on PSAN were distributed less evenly and cells on PEU were less oriented. Cells were more likely to form clusters on PS. Conclusively, we demonstrated the influence of polymer substrates on the cellular behaviour of MSCs, which could be included in the development of novel design concepts based on polymeric biomaterials. %0 journal article %@ 0014-3057 %A Matsumoto, H., Ishiguro, T., Konosu, Y., Minagawa, M., Tanioka, A., Richau, K., Kratz, K., Lendlein, A. %D 2012 %J European Polymer Journal %N 11 %P 1866-1874 %R doi:10.1016/j.eurpolymj.2012.07.008 %T Shape-memory properties of electrospun non-woven fabrics prepared from degradable polyesterurethanes containing poly(Omega-pentadecalactone) hard segments %U https://doi.org/10.1016/j.eurpolymj.2012.07.008 11 %X Microscaled non-woven fabrics with fiber diameters in the range 1.8–3.1 μm were prepared by electrospinning from a chloroform solution of a degradable multiblock copolymer (PDLCL) consisting of crystallizable poly(ω-pentadecalactone) hard segments (PPDL) and poly(ε-caprolactone) switching segments (PCL). The surface morphology and microstructure of the non-woven fabrics were characterized by scanning electron microscopy, temperature-controlled scanning probe microscopy, wide angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS). The microstructural analysis demonstrated that the rod-like domains of hard segment (PPDL) formed in the electrospun PDLCL fiber functioned as physical crosslinks. Cyclic, thermomechanical tensile tests showed that the electrospun PDLCL fabrics exhibited good shape-memory properties with strain recovery rates of Rr = 89–95% and strain fixity rates of Rf = 82–83% after the 2nd cycle, when small deformations were applied at clinically relevant temperatures. %0 journal article %@ 1386-0291 %A Scharnagl, N., Hiebl, B., Trescher, K., Zierke, M., Behl, M., Kratz, K., Jung, F., Lendlein, A. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 295-311 %R doi:10.3233/CH-2012-1606 %T Behaviour of fibroblasts on water born acrylonitrile-based copolymers containing different cationic and anionic moieties %U https://doi.org/10.3233/CH-2012-1606 2-4 %X The chemical composition of a substrate can influence the adhesion, viability and proliferation of cells seeded on the substrate. The aim of this work was to investigate the influence of different cationic or anionic moieties in acrylonitrile-based copolymers on the interaction with fibroblasts. A series of ten different types of acrylonitrile-based copolymers with a random sequence structure was prepared using a water born synthesis process to exclude potential residues of organic solvents. As charged comonomers cationic methacrylic acid-2-aminoethylester hydrochloride (AEMA), N-3-amino-propyl-methacrylamide hydrochloride (APMA) and anionic 2-methyl-2-propene-1-sulfonic acid sodium salt (NaMAS) were utilized. By application of a specific sintering procedure the copolymer materials were processed into transparent disks for conducting cell tests in direct contact. The copolymers were analyzed with respect to their composition and surface properties. Cytotoxicity tests of the polymer extracts, as well as of the disks were performed with L929 mouse fibroblasts. All copolymers showed no cytotoxic effects. Furthermore, for higher molar ratios of AEMA an increase in cell growth could be observed, which might be a hint that higher charge densities are favorable for the proliferation of L929 cells. %0 journal article %@ 1386-0291 %A Roch, T., Krueger, A., Kratz, K., Ma, N., Jung, F., Lendlein, A. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 375-389 %R doi:10.3233/CH-2012-1612 %T Immunological evaluation of polystyrene and poly(ether imide) cell culture inserts with different roughness %U https://doi.org/10.3233/CH-2012-1612 2-4 %X For the successful clinical and biological application of polymers, their interaction with cells, tissues, and body fluids has to be well characterized. In order to investigate how the physical, chemical, and mechanical properties of candidate biomaterials influence cell behaviours, the testing sample is usually placed in commercially available cell culture plates. Thus, not only the testing sample itself but also the culture dish material might influence the cell behaviour. Therefore, an insert system was created to exclude this influence and allow investigations of the testing material solely. In this study micropatterned inserts prepared from polystyrene (PS) as well as from poly(ether imide) (PEI) with three different roughness levels of i) Rq = 0.12 μm (PS) and 0.23 μm (PEI); ii) Rq = 3.52 μm (PS) and 3.92 μm (PEI); and iii) Rq = 16.04 μm (PS) and 22.65 μm (PEI) were explored with regard of their immuno-compatibility including the determination of potential contaminations with endotoxins or other microbial products. The endotoxin levels of the inserts were determined to be less than 0.07 EU/mL, which is well below the U.S. Food and Drug Administration limit of 0.5 EU/mL and the survival of murine macrophages cultured in the inserts was not impaired. Activation of early immune mechanisms such as complement activation and the generation of reactive oxygen species could not be observed. All tested materials had no influence on the cytokine secretion from cells of whole human blood. The investigated inserts were immuno-compatible and apparently free of contaminations with microbial products. The roughness of the inserts had no stimulatory or inhibitory effect on early immune mechanisms. Conclusively, the 24-well plate insert systems introduced in this study allow investigating the interactions of tailored surface properties such as roughness with many other cell types, without the disadvantage of the standard commercially available culture vessels influencing the biomaterial testing. %0 journal article %@ 0906-6705 %A Trescher, K., Kratz, K., Roch, T., Juenger, M., Jung, F., Lendlein, A. %D 2012 %J Experimental Dermatology %N 3 %P e1-e58 %R doi:10.1111/j.1600-0625.2011.01428.x %T Behaviour of primary human keratinocytes and fibroblasts on soft poly(n-butyl acrylate) networks with tailored mechanical properties %U https://doi.org/10.1111/j.1600-0625.2011.01428.x 3 %X No abstract %0 journal article %@ 1742-7061 %A Mayer, A., Roch, T., Kratz, K., Lendlein, A., Jung, F. %D 2012 %J Acta Biomaterialia %N 12 %P 4253-4259 %R doi:10.1016/j.actbio.2012.08.011 %T Pro-angiogenic CD14++ CD16+ CD163+ monocytes accelerate the in vitro endothelialization of soft hydrophobic poly(n-butyl acrylate) networks %U https://doi.org/10.1016/j.actbio.2012.08.011 12 %X As the majority of the polymers used as cardiovascular grafts so far do not match the elasticity of human arteries (100–1000 kPa) and the required endothelialization, a multifunctional material approach is needed to allow the adjustment of the mechanical properties while at the same time exhibiting a haemocompatible surface. Recently soft poly(n-butyl acrylate) networks (cPnBA) with adjustable mechanical properties were introduced as candidate materials with a surface that can be endothelialized. In this study, angiogenically stimulated intermediate CD163+ monocytes/macrophages (aMO2) were utilized as a cellular cytokine release system to realize the functional endothelialization of the hydrophobic cPnBA surface. We investigated the influence of co-cultured aMO2 on the morphology, density and cytokine secretion of human umbilical venous endothelial cells (HUVEC) seeded on cPnBA with an elastic modulus of around 250 kPa (cPnBA0250). A functional confluent HUVEC monolayer could be developed in the co-culture within 3 days. In contrast, the HUVEC in the monoculture exhibited stress fibres, broadened marginal filament bands and significantly more and larger cell-free areas in the monolayer, indicating incomplete cell–substrate binding. Remarkably, a functional confluent monolayer formation could only be achieved in co-cultures; it did not develop with the sole supplementation of recombinant VEGF-A165 to the HUVEC monocultures (unpublished data). The study demonstrated the multifunctional potential of cPnBA in combination with aMO2 as a cellular cytokine release system, adapting their secretion to the demand of HUVEC. In this way, a functional confluent monolayer could be generated within 3 days. %0 conference lecture (invited) %@ %A Lendlein, A., Wischke, C., Mathew, S., Roch, T., Kratz, K. %D 2012 %J 12th European Symposium on Controlled Drug Delivery, ESCDD 2012 %T Multifunctional Polymer-based Carrier Systems %U %X %0 conference lecture %@ %A Krueger, A., Braune, S., Kratz, K., Lendlein, A., Jung, F. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T The influence of poly(n-butyl acrylate) networks on viability and function of smooth muscle cells and vascular fibroblasts %U %X %0 conference poster %@ %A Trescher, K., Kratz, K., Roch, T., Juenger, M., Jung, F., Lendlein, A. %D 2012 %J 39. Annual Meeting of the Arbeitsgemeinschaft Dermatologische Forschung %T Behaviour of primary human keratinocytes and fibroblasts on soft poly(n-butyl acrylate) networks with tailored mechanical properties %U %X %0 journal article %@ 1520-6106 %A Yoshikawa, Y.Y., Cui, J., Kratz, K., Matsuzaki, T., Nakabayashi, S., Marx, A., Engel, U., Lendlein, A., Tanaka, M. %D 2012 %J The Journal of Physical Chemistry B %N 28 %P 8024-8030 %R doi:10.1021/jp212385p %T Quantitative Evaluation of Adhesion of Osteosarcoma Cells to Hydrophobic Polymer Substrate with Tunable Elasticity %U https://doi.org/10.1021/jp212385p 28 %X We investigated a potential application of hydrophobic poly(n-butyl acrylate) networks (cPnBA) as substrates with tunable elasticity for culturing, maintenance, and regulation of human osteosarcoma cells (U2OS). Nanoindentation experiments with an atomic force microscope revealed that the mechanical properties of cPnBA films are maintained under aqueous conditions, confirming that the substrate elasticity can be controlled simply by the degree of cross-linking, independent from the culture medium. We found that the adhesion U2OS cells to cPnBA substrates could be improved by surface treatments such as oxgen plasma and serum proteins. To determine the strength of cell adhesion, the critical pressure to detach cells from cPnBA substrates was measured using a shock wave induced by an intensive picosecond laser pulse. A monotonic increase in the cell adhesion strength in accordance with the substrate elasticity demonstrated the potential of intrinsically hydrophobic cPnBA as a new class of substrate material with tunable mechanical properties that are not influenced by the culture medium. %0 journal article %@ 1946-4274 %A Sauter, T., Kratz, K., Lendlein, A. %D 2012 %J MRS Online Proceedings Library %P 49-54 %R doi:10.1557/opl.2012.251 %T Shape-Memory Properties of Electrospun Non-wovens Prepared from Amorphous Polyetherurethanes Under Stress-free and Constant Strain Conditions %U https://doi.org/10.1557/opl.2012.251 %X The shape-memory properties of electrospun polyetherurethanes (PEU) non-wovens with a single fiber diameter of around 1 μm were explored. In uniaxial cyclic, thermomechanical tensile tests a dual-shape shape-memory creation procedure (SMCP) was applied and the shape recovery was examined under stress-free and constant strain conditions. The thermal properties of the electrospun PEU non-wovens were found to be similar to those obtained for bulk PEU samples, whereas the mechanical properties revealed differences with respect to the elongation at break (εb) at increased temperatures. Excellent dual-shape properties were achieved for the PEU non-wovens with a high shape fixity rate (Rf) and shape recovery rate (Rr). A significant higher recovery stress (σmax) was obtained under constant strain recovery conditions for the electrospun non-wovens compared to the bulk PEU samples, which might be attributed to the higher degree of orientation of the polymer chains in the microfibers. Therefore the influence of different (single) fiber diameters as well as the variation of the programming elongation εm and temperature Tprog on σmax is an interesting issue for future investigations. %0 journal article %@ 1386-0291 %A Rueder, C., Sauter, T., Becker, T., Kratz, K., Hiebl, B., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2012 %J Clinical Hemorheology and Microcirculation %N 1-2 %P 101-112 %R doi:10.3233/CH-2011-1447 %T Viability, proliferation and adhesion of smooth muscle cells and human umbilical vein endothelial cells on electrospun polymer scaffolds %U https://doi.org/10.3233/CH-2011-1447 1-2 %X A major clinical problem of high relevance in the cardiovascular field is late stent thrombosis after implantation of drug eluting stents (DES). Clinical widely used DES currently utilize durable polymer coatings, which can induce persistent arterial wall inflammation and delayed vascular healing resulting in an impaired endothelialization. In this study we explored the interaction of smooth muscle cells (SMC) and human umbilical vein endothelial cells (HUVEC) with electrospun scaffolds prepared from resorbable polyetheresterurethane (PDC) and poly(p-dioxanone) (PPDO), as well as polyetherimide (PEI), which can be surface modified, in comparison to poly(vinylidene fluoride-co-hexafluoropropene) (PVDF) as reference material, which is established as coating material of DES in clinical applications. Our results show that adhesion could be improved for HUVEC on PDC, PPDO and PEI compared to PVDF, whereas almost no SMC attached to the scaffolds indicating a cell-specific response of HUVEC towards the different fibrous structures. Proliferation and apoptosis results revealed that PPDO and PEI have no significant negative influence on vitality and cell cycle behaviour compared to PVDF. Hence, they represent promising candidates for temporary blood vessel support that induce HUVEC attachment and prevent SMC proliferation. %0 journal article %@ 1386-0291 %A Roch, T., Cui, J., Kratz, K., Lendlein, A., Jung, F. %D 2012 %J Clinical Hemorheology and Microcirculation %N 1-2 %P 131-142 %R doi:10.3233/CH-2010-1449 %T Immuno-compatibility of soft hydrophobic poly (n-butyl acrylate) networks with elastic moduli for regeneration of functional tissues %U https://doi.org/10.3233/CH-2010-1449 1-2 %X The need for engineered devices to treat cardiovascular diseases is increasing due to an aging population and a changing lifestyle. Soft poly(n-butyl acrylate) (cPnBA) networks were recently described as polymer networks with adjustable mechanical properties and suggested as soft substrates for cells, which could potentially be used for cardiovascular implants. Vascular prostheses designed to be implanted in arteries should have an elasticity similar to blood vessels (elastic modulus at body temperature between 100 and 1200 kPa). Therefore, cPnBA networks with E-moduli of 250 kPa (cPnBA0250) and 1100 kPa (cPnBA1100) were developed. Recently, it was shown that both materials were non-cytotoxic for murin fibroblasts, human primary endothelial cells and human monocytes. However, before such newly developed polymers can be used in vivo, it has to be assured that the sterilized materials have a very low endotoxin load to avoid an unspecific activation of the immune system, which otherwise might cause local or systemic inflammatory responses and could lead to severe pathologies. In this study we investigated the immuno-compatibility of sterilized cPnBA0250 and cPnBA1100 with the help of an immuno-competent macrophage cell line as well as with whole human blood. %0 conference poster %@ %A Wang, W., Kratz, K., Xu, X., Li, Z., Roch, T., Jung, F., Ma, N., Lendlein, A. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T The influence of polymeric materials on cellular behaviors of bone marrow derived human mesenchymal stem cells %U %X %0 conference poster %@ %A Roch, T., Krueger, A., Kratz, K., Ma, N., Jung, F., Lendlein, A. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Immuno-compatibility of polystyrene and poly(ether imide) with different roughness %U %X %0 journal article %@ 0160-564X %A Mayer, A., Kratz, K., Hiebl, B., Lendlein, A., Jung, F. %D 2012 %J Artificial Organs %N 3 %P E28-E38 %R doi:10.1111/j.1525-1594.2011.01410.x %T Interaction of angiogenically stimulated intermediate CD163+ monocytes/macrophages with soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli matched to that of human arteries %U https://doi.org/10.1111/j.1525-1594.2011.01410.x 3 %X Seeded on cPnBA, aMO2 – unaffected by the elastic moduli of both substrates – seemed to remain in their subset status and secreted VEGF-A165 without release of pro-inflammatory cytokines. These in vitro results might indicate that this MO subset can be used as cellular delivery system for pro-angiogenic and non-inflammatory mediators to support the endothelialization of cPnBA. %0 journal article %@ 1616-301X %A Kratz, K., Voigt, U., Lendlein, A. %D 2012 %J Advanced Functional Materials %N 14 %P 3057-3065 %R doi:10.1002/adfm.201200211 %T Temperature-Memory Effect of Copolyesterurethanes and their Application Potential in Minimally Invasive Medical Technologies %U https://doi.org/10.1002/adfm.201200211 14 %X Minimally invasive surgery often requires devices that can change their geometry or shape when placed inside the body. Here, the potential of thermoplastic temperature-memory polymers (TMP) for the design of intelligent devices, which can be programmed by the clinician to individually adapt their shifting geometry and their response temperature Tsw to the patient's needs, is explored. Poly(ω-pentadecalactone) as hard segments and poly(ϵ-caprolactone) segments acting as crystallizable controlling units for the temperature-memory effect (TME) are chosen to form multiblock copolymers PDLCL. These components are selected according to their thermal properties and their good biocompatibility. Response temperatures obtained under stress-free and constant strain recovery can be systematically adjusted by variation of the deformation temperature in a temperature range from 32 °C to 65 °C, which is the relevant temperature range for medical applications. The working principle of TMP based instruments for minimally invasive surgical procedures is successfully demonstrated using three temperature-memory catheter concepts: individually programmable TM-catheter, an in-situ programmable TM-catheter, and an intelligent drainage catheter for gastroenterology. %0 journal article %@ %A Wischke, C., Kratz, K., Jung, F., Lendlein, A. %D 2012 %J BioTOPics : Journal of Biotechnology in Berlin-Brandenburg %P 5-7 %T Helmholtz Virtual Institute „Multifunctional Materials for Medicine“ %U %X into the regional cluster “Healthcare Industry Berlin-Brandenburg – Health Capital”. %0 conference lecture %@ %A Xu, X., Wang, W., Kratz, K., Li, Z., Roch, T., Jung, F., Ma, N., Lendlein, A. %D 2012 %J 14th International Congress of Biorheology, 7th International Conference on Clinical Hemorheology %T Different polymer surfaces influence in vitro cultivation of rat mesenchymal stem cells %U %X %0 conference poster %@ %A Kumar, U.N., Kratz, K., Noechel, U., Lendlein, A. %D 2012 %J Advanced Macromolecular Systems Across the Length Scales, AMSALS 2012 %T Shape-Memory Properties of Copolymer Networks Containing a Poly(ε-caprolactone) Crosslinker in an Aqueous Environment %U %X %0 conference lecture %@ %A Braune, S., Krueger, A., Walter, M., Schiemann, M., Kratz, K., Kuepper, J.-H., Jung, F., Lendlein, A. %D 2012 %J 39th Congress of the European Society for Artificial Organs, ESAO 2012 %T Influence of different surface treatment of poly(n-butyl acrylate) networks on L929 mouse fibroblasts adhesion and viability %U %X %0 conference lecture %@ %A Ma, N., Xu, X., Kratz, K., Li, Z., Roch, T., Jung, F., Lendlein, A. %D 2012 %J 14th International Congress of Biorheology, 7th International Conference on Clinical Hemorheology %T The influence of polymeric materials on mesenchymal stem cells cellular behaviors %U %X %0 conference lecture %@ %A Kratz, K. %D 2012 %J Materialien fuer medizinische Anwendungen, 2. Arbeitsgruppentreffen %T Multifunctional Polymer-Based Biomaterials %U %X %0 conference paper %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2012 %J MRS Symposium Proceedings, Multifunctional Polymer-Based Materials, 2011 MRS Fall Meeting %P 105-112 %T Shape-Memory Properties of Electrospun Non-wovens Prepared from Amorphous Polyetherurethanes Under Stress-free and Constant Strain Conditions %U %X %0 conference lecture %@ %A Kratz, K., Lendlein, A. %D 2012 %J Materials Science and Engineering, MSE 2012 %T Processing of Biomaterials %U %X %0 journal article %@ 1946-4274 %A Kratz, K., Kumar, U., Noechel, U., Lendlein, A. %D 2012 %J MRS Online Proceedings Library %P 7-12 %R doi:10.1557/opl.2012.454 %T Thermal Properties and Crystallinity of Grafted Copolymer Networks containing a Crystallizable Poly(ε-caprolactone) Crosslinker in an aqueous environment %U https://doi.org/10.1557/opl.2012.454 %X The water swelling capability of the CLEG polymer networks was found to increase from 120% to 240% with increasing weight content of PEG. In contrast to the dry state, where two well separated melting temperatures could be observed for all CLEG samples, in aqueous environment only one melting temperature slightly above 40 °C, was obtained, whereby the overall crystallinity after swelling with water was strongly related to the PCL content in the CLEG polymer networks. %0 journal article %@ 2280-8000 %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2012 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 293-301 %R doi:10.5301/JABFM.2012.10432 %T Simulation of volumetric swelling of degradable poly[(rac-lactide)-co-glycolide] based polyesterurethanes containing different urethane-linkers %U https://doi.org/10.5301/JABFM.2012.10432 3 %X The hydrolytic degradation behavior of degradable aliphatic polyester-based polymers is strongly influenced by the up-take or transport of water into the polymer matrix and also the hydrolysis rate of ester bonds.
Methods: We examined the volumetric swelling behavior of poly[(rac-lactide)-co-glycolide] (PLGA) and PLGA-based polyurethanes (PLGA-PU) with water contents of 0 wt%, 2 wt% and 7 wt% water at 310 K using a molecular modeling approach. Polymer systems with a number average molecular weight of Mn = 10,126 g∙mol-1 were constructed from PLGA with a lactide content of 67 mol%, whereby PLGA-PU systems were composed of five PLGA segments with Mn = 2052 g∙mol-1, which were connected via urethane linkers originated from 2,2,4–trimethyl hexamethylene-1,6-diisocyanate (TMDI), hexamethyl-1,6–diisocyanate (HDI), or L-lysine-1,6–diisocyanate (LDI).
Results: The calculated densities of the dry PLGA-PU systems were found to be lower than for pure PLGA. The obtained volumetric swelling of the PLGA-PU was depending on the type of urethane linker, whereby all swollen PLGA-PUs contained larger free volume distribution compared to pure PLGA. The mean square displacement curves for dry PLGA and PLGA-PUs showed that urethane linker units reduce the mobility of the polymer chains, while an increase in backbone atoms mobility was found, when water was added to these systems. Consequently, an increased water uptake of PLGA-PU matrices combined with a higher mobility of the chain segments should result in an accelerated hydrolytic chain scission rate in comparison to PLGA. Conclusions: It can be anticipated that the incorporation of urethane linkers might be a helpful tool to adjust the degradation behavior of polyesters. %0 journal article %@ 2280-8000 %A Ghobadi, E., Heuchel, M., Kratz, K., Lendlein, A. %D 2012 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 259-264 %R doi:10.5301/JABFM.2012.10440 %T Influence of different heating regimes on the shape-recovery behavior of poly(L-lactide) in simulated thermomechanical tests %U https://doi.org/10.5301/JABFM.2012.10440 3 %X Multifunctional polymer-based biomaterials, which combine degradability with a shape-memory capability and in this way enable the design of actively moving implants such as self-anchoring implants or controlled release systems, have been recently introduced. Of particular interest are approved degradable polymers such as poly(L-lactide) (PLLA), which can be easily functionalized with a shape-memory effect. In the case of semicrystalline PLLA, the glass transition can be utilized as shape-memory switching domain.
Methods: In this work we applied a fully atomistic molecular dynamics simulation to study the shape-memory behavior of PLLA. A heating-deformation-cooling programming procedure was applied to atomistic PLLA packing models followed by a recovery module under stress-free conditions allowing the shape recovery. The recovery was simulated by heating the samples from Tlow = 250 K to Thigh = 500 K with different heating rates β of 125, 40 and 4 K⋅ns-1. 
Results: We could demonstrate that the obtained strain recovery rate (Rr) was strongly influenced by the applied simulation time and heating rate, whereby Rr values in the range from 46% to 63% were achieved. On its own the application of a heating rate of 4 K⋅ns-1 enabled us to determine a characteristic switching temperature of Tsw = 473 K for the modeled samples. 
Conclusions: We anticipate that the atomistic modeling approach presented should be capable of enabling further study of Tsw with respect to the molecular structure of the investigated SMP and therefore could be applied in the context of design and development of new shape-memory (bio)materials. %0 conference lecture (invited) %@ %A Kratz, K., Heuchel, M., Razzaq, M., Lendlein, A. %D 2012 %J 8th European Solid Mechanics Conference, ESMC 2012 %T Heating and Stretching of Magneto-Sensitive and Mechanically Active Polymer Composites %U %X %0 conference poster %@ %A Kumar, U.N., Kratz, K., Behl, M., Lendlein, A. %D 2012 %J German-Russian Conference on Fundamentals and Applications of Nanoscience %T Triple-shape Nanocomposites with Adaptable Apparent Switching Temperatures %U %X %0 conference poster %@ %A Braune, S., Krueger, A., Kratz, K., Lendlein, A., Jung, F. %D 2012 %J 14th International Congress of Biorheology, 7th International Conference on Clinical Hemorheology %T Influence of randomized biomaterial micropatterning on platelet adhesion and activation %U %X %0 conference lecture %@ %A Kratz, K., Heuchel, M., Lendlein, A. %D 2012 %J 9th World Biomaterials Congress %T Shape-memory polymer based active scaffolds with adjustable self-sufficiently moving capability %U %X %0 conference poster %@ %A Scharnagl, N., Hiebl, B., Trescher, K., Zierke, M., Behl, M., Kratz, K., Jung, F., Lendlein, A. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Behaviour of fibroblasts on water born acrylonitrile based copolymers with different densities of positive and negative surface charges %U %X %0 conference lecture %@ %A Kratz, K., Lendlein, A. %D 2012 %J Intelligente Oberflaechen, Forschungspolitischer Dialog %T Cell- and Tissue Specific Polymer-Based Biomaterials %U %X %0 conference poster %@ %A Noechel, U., Kratz, K., Behl, M., Zizak, I., Lendlein, A. %D 2012 %J Advanced Macromolecular Systems Across the Length Scales, AMSALS 2012 %T Nanostructural Changes of Temperature-Memory Polymers With Crystallizable Controlling Units Explored by SAXS/WAXS %U %X %0 conference poster %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2012 %J Materials Science and Engineering, MSE 2012 %T Shape-Memory Properties of Electrospun Non-Wovens %U %X %0 conference lecture %@ %A Lendlein, A., Behl, M., Kratz, K. %D 2012 %J 24th International Liquid Crystal Conference, ILCC 2012 %T Multifunctional Shape-Memory Polymers %U %X %0 conference lecture (invited) %@ %A Rueder, C., Sauter, T., Kratz, K., Peter, J., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %T Smooth muscle and endothelial cell behaviour on polymeric films with different chemical compositions %U %X %0 journal article %@ 2280-8000 %A Wang, L., Heuchel, M., Fang, L., Kratz, K., Lendlein, A. %D 2012 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 203-209 %R doi:10.5301/JABFM.2012.10293 %T Influence of a polyester coating of magnetic nanoparticles on magnetic heating behavior of shape-memory polymer-based composites %U https://doi.org/10.5301/JABFM.2012.10293 3 %X Background: Magnetic composites of thermosensitive shape-memory polymers (SMPs) and magnetite nanoparticles (MNPs) allow noncontact actuation of the shape-memory effect in an alternating magnetic field. In this study, we investigated whether the magnetic heating capability of cross-linked poly(ε-caprolactone)/MNP composites (cPCLC) could be improved by covalent coating of MNPs with oligo(ε-caprolactone) (OCL). Methods: Two different types of cPCLC containing uncoated and OCL-coated MNP with identical magnetite weight content were prepared by thermally induced polymerization of poly(ε-caprolactone) diisocyanatoethyl methacrylate. Both cPCLCs exhibited a melting transition at Tm = 48°C, which could be used as switching transition. Results: The dispersion of the embedded nanoparticles within the polymer matrix could be substantially improved, when the OCL-coated MNPs were used, as visualized by scanning electron microscopy. We could further demonstrate that in this way the maximal achievable bulk temperature (Tbulk) obtained within the cPCLC test specimen in magnetic heating experiments at a magnetic field strength of H = 30 kA⋅m-1 could be increased from Tbulk = 48°C to Tbulk = 74°C. %0 conference lecture %@ %A Kratz, K., Heuchel, M., Lendlein, A. %D 2012 %J 9th World Biomaterials Congress %T Non-contact activation of triple-shape effect in magneto-sensitive polymer network composites %U %X %0 journal article %@ 1381-5148 %A Kaiser, C., Behl, M., Schroeter, M., Kratz, K., Lendlein, A. %D 2012 %J Reactive and Functional Polymers %N 8 %P 533-541 %R doi:10.1016/j.reactfunctpolym.2012.04.015 %T Dicarboxy-telechelic cooligomers with sequence structure tunable light absorption %U https://doi.org/10.1016/j.reactfunctpolym.2012.04.015 8 %X Alternating cooligomers of 5 pyrrole (P) and thiophene (T) units with a PTPTP sequence and carboxylic telechelic groups in α,α′-position are supposed to provide a low band gap and might be incorporated into degradable polymers. In this study we explored whether such new α,α′-ester linked π-conjugated alternating electron rich PTPTP cooligomers of defined size could be created following a Stille coupling synthesis pathway. The obtained cooligomers displayed in the absorption spectra λmax between 341 and 379 nm in solution and between 346 and 410 nm in the solid state, which could be tuned by the substitution with donor type alkyl and alkoxy functions. A strong red shift of the absorption bands into the IR region of the spectrum with absorption maxima between 550 and 650 nm and further to 850 and 1000 nm could be obtained when additional charges by deprotonation or oxidation were introduced. The prepared semi conducting materials could be applied potentially as dyes for photoacoustic imaging or in sensors for oxidation monitoring. %0 journal article %@ 0920-5063 %A Hiebl, B., Cui, J., Kratz, K., Frank, O., Schossig, M., Richau, K., Lee, S., Jung, F., Lendlein, A. %D 2012 %J Journal of Biomaterials Science - Polymer Edition %N 7 %P 901-915 %R doi:10.1163/092050611X566144 %T Viability, Morphology and Function of Primary Endothelial Cells on Poly(Eta-Butyl Acrylate) Networks Having Elastic Moduli Comparable to Arteries %U https://doi.org/10.1163/092050611X566144 7 %X Soft hydrophobic poly(n-butyl acrylate) networks (cPnBA) were developed as entropy elastic substrates for passive mechanical stimulation of cells, where the elastic modulus of the cPnBAs could be systematically adjusted by variation of the cross-link density. The networks were synthesized by thermally-induced radical polymerization from n-butyl acrylate, with poly(propylene glycol) dimethacrylate (PPGDMA) acting as cross-linker, whereby the purity of the cPnBAs was confirmed by (1)H-NMR spectroscopy and gas chromatography. In this work two cPnBA polymer networks with an elastic modulus around 200 kPa and 1 MPa were investigated having an elastic modulus similar to that of arteries. Both cPnBAs exhibited an almost smooth surface with a surface roughness (R(q)) in the wet state ranging from 17 to 37 nm and a similar zeta-potential, indicating an almost identical chemical composition within the topmost surface layer in terms of functional groups. In contrast, wettability of the samples was found to be different with an advancing angle (θ(advancing)) of 1233.8 for cPnBA0250, while for cPnBA1100 significantly lower values for θ(advancing) (1113.8) were obtained. First in vitro tests were performed with primary endothelial cells (HUVEC) to study its effects on vascular cell functions. Within the time period of cultivation (72 h), the cells on the cPnBA samples reached subconfluence and showed a viability rate of almost 100%. Although cell density differed after 72 h with more cells on cPnBA0250 than on cPnBA1100, both materials showed no significant effect on the cell morphology, the cellular LDH-release, which was used as marker for the integrity of the cell membrane, and the organisation of the VE-cadherin. However, lower cell density and less actin stress fibre formation on cPnBA1100 might indicate that cell-material interaction was weaker on cPnBA1100 than on cPnBA0250. The secretion of the vasoactive cytokines prostacyclin (PGI2) and thromboxane A2 (TXA2) was low compared to previously reported values. However, the anti-thrombogenic ratio of PGI2/TXA2 - which is balanced under physiological conditions - with much higher PGI2 compared to TXA2 (up to 17.6-fold after 72 h for cPnBA1100) suggests that this material might be effective to preventing thrombosis. %0 book part %@ %A Lendlein, A., Wischke, C., Kratz, K., Heuchel, M., Zotzmann, J., Hiebl, B., Neffe, A., Behl, M. %D 2011 %J Comprehensive Biomaterials %P 479-496 %T Shape- Memory Polymers %U %X Medical devices such as implants, surgical instruments, extracorporal devices or wound covers, as well as controlled drug delivery systems (CDDS) require a specific combination of material properties and functions including, e.g., mechanical stability, biocompatibility, or biofunctionality. Polymeric biomaterials are of high relevance for such applications, as properties and functions can be tuned in a wide range by only small defined variations of their chemical or morphological structure. The rapid progress in surgical techniques, especially in minimally-invasive surgery, requires smart materials, which are capable of an active on-demand movement and which do not need to be removed in a second surgery. These challenges can be addressed by shape-memory polymers (SMPs) described in this chapter. SMPs are of high technological significance for biomedical applications as they enable on demand predefined changes in the shape of a device upon exposure to a suitable stimulus. Multifunctional materials are obtained when the shape-memory effect is combined with an additional function such as hydrolytic degradability, biofunctionality, and controlled drug release. Selected biomaterials with shape-memory capability are presented, including data on their biocompatibility. The potential of SMPs as a platform technology for biomedical applications is sketched by an overview on SMP-based medical devices being developed and the potential use of SMPs as matrix for CDDS. %0 conference poster %@ %A Uttamchand, N., Kratz, K., Reiche, J., Lendlein, A. %D 2011 %J Workshop an der Universitaet Potsdam %T Non-contact actuation of triple-shape effect in magnetic polymer network nanocomposites %U %X %0 conference poster %@ %A Kratz, K., Reiche, J., Lendlein, A. %D 2011 %J Workshop an der Universitaet Potsdam %T Monolayer degradation experiments of polyester-based (co)polymers %U %X %0 conference lecture %@ %A Mayer, A., Kratz, K., Hiebl, B., Lendlein, A., Jung, F. %D 2011 %J 16th International Conference of the European Society for Clinical Hemorheology and Microcirculation (ESCHM) and the 30th Annual Conference of the German Society for Clinical Microcirculation and Hemorheology (DGKMH) %T Interaction of primary CD14+ CD163+ VEGF-A165+ monocytes/macrophages with soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli matched to human arteries %U %X %0 journal article %@ 1042-7147 %A Cui, J., Kratz, K., Heuchel, M., Hiebl, B., Lendlein, A. %D 2011 %J Polymers for Advanced Technologies %N 1 %P 180-189 %R doi:10.1002/pat.1733 %T Mechanically active scaffolds from radio-opaque shape-memory polymer-based composites %U https://doi.org/10.1002/pat.1733 1 %X composites, while Tsw was found to be close to the applied Tprog. The feasibility of actively moving scaffolds was demonstrated using model scaffolds, where originally square-shaped pores were temporarily fixed in an expanded circular shape at different Tprog. We found that the kinetics of the shape change obtained under physiological conditions could be adjusted by variation of Tprog between 1 and 6 hr. Such radio-opaque scaffolds could serve as model scaffolds for investigating the active mechanical stimulation of cells in vitro or in vivo. %0 journal article %@ 1042-7147 %A Cui, J., Kratz, K., Hiebl, B., Jung, F., Lendlein, A. %D 2011 %J Polymers for Advanced Technologies %N 1 %P 126-132 %R doi:10.1002/pat.1816 %T Soft poly(Eta-butyl acrylate) networks with tailored mechanical properties designed as substrates for in vitro models %U https://doi.org/10.1002/pat.1816 1 %X Mechanical conditioning can serve as a potent tool to influence mechano-responsive cells, which plays a prominent role during formation and regeneration of functional tissue. Recently, the differentiation of mesenchymal stem cells could be influenced by the local stiffness of hydrogels used as 2D substrates. However, the mechanical properties and the swellability of hydrogels in physiological liquids are difficult to control precisely as their properties strongly depend on physical parameters like ionic strength or pH value. Here, we explored amorphous, hydrophobic poly(n-butyl acrylate) networks (cPnBA) as soft substrates for cell culture system with adjustable mechanical properties. cPnBAs were synthesized via bulk radical polymerization from n-butyl acrylate (nBA) and poly(propylene glycol) dimethacrylate (PPGDMA) as crosslinker. The Young's modulus for cPnBAs determined by tensile tests could be systematically adjusted from 100 kPa to 10 MPa by increasing the PPGDMA-content at ambient temperature, while the glass transition temperature (Tg) was found to increase from −46 to −22°C. All cPnBAs exhibited similar surface properties with a surface roughness (Rq) in the range from 1.4 to 0.4 µm and advancing contact angles from 115° to 100°, which remained constant after ethylene oxide sterilization. The extracts of sterilized materials were tested for cytotoxic effects with L929 cells. All tested samples were non-cytotoxic. The functional integrity of cell membranes and mitochondrial activity stayed unaffected. The investigated polymer networks are promising candidates as soft substrates for passive mechanical stimulation of cells in vitro in cell culture devices or in vivo as implant coatings. %0 conference lecture %@ %A Mayer, A., Kratz, K., Hiebl, B., Lendlein, A., Jung, F. %D 2011 %J 16th International Conference of the European Society for Clinical Hemorheology and Microcirculation (ESCHM) and the 30th Annual Conference of the German Society for Clinical Microcirculation and Hemorheology (DGKMH) %T Support of HUVEC proliferation by pro-angiogenic intermediate CD163+ monocytes/macrophages: A co-culture experiment %U %X %0 conference poster %@ %A Schneider, T., Kohl, B., Sauter, T., Becker, T., Kratz, K., Schossig, M., Hiebl, B., Jung, F., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2011 %J Advanced Functional Polymers for Medicine, AFPM 2011 %T Viability, adhesion and differentiated phenotype of articular chondrocytes on degradable polymers and electro-spun structures thereof %U %X %0 conference poster %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2011 %J MRS Fall 2011 Meeting, Symposium V %T Impact of Different Single Fiber Diameter and Variation of the Programming Temperature on the Shape-Memory Properties of Electro-spun Scaffolds Prepared from Amorphous Polyetherurethanes %U %X %0 journal article %@ 1549-9634 %A Kohl, Y., Kaiser, C., Bost, W., Stracke, F., Fournelle, M., Wischke, C., Thielecke, H., Lendlein, A., Kratz, K., Lemor, R. %D 2011 %J Nanomedicine: Nanotechnology, Biology and Medicine %N 2 %P 228-237 %R doi:10.1016/j.nano.2010.07.006 %T Preparation and Biological Evaluation of Multifunctional PLGA-Nanoparticles designed for Photoacoustic Imaging %U https://doi.org/10.1016/j.nano.2010.07.006 2 %X The excellent photoacoustic properties in combination with the positive biological results qualify the dye-loaded PLGA particles as promising candidates for a resorbable photoacoustic contrast system. %0 conference poster %@ %A Sauter, T., Kratz, K., Lendlein, A. %D 2011 %J ESAO Winter School 2011 %T Hydrolytic and Enzymatic Degradation Behaviour of Multiblock Copolymers with Different Fiber Dimension %U %X %0 conference poster %@ %A Roch, T., Mayer, A., Kratz, K., Cui, J., Lendlein, A., Jung, F. %D 2011 %J 16th International Conference of the European Society for Clinical Hemorheology and Microcirculation (ESCHM) and the 30th Annual Conference of the German Society for Clinical Microcirculation and Hemorheology (DGKMH) %T Immuno-compatibility of soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli for regeneration of functional tissues %U %X %0 journal article %@ 0391-3988 %A Kohl, Y., Kaiser, C., Bost, W., Stracke, F., Thielecke, H., Wischke, C., Lendlein, A., Kratz, K., Lemor, R. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 249-252 %R doi:10.5301/IJAO.2011.6405 %T Near-infrared dye-loaded PLGA nanoparticles prepared by spray drying for photoacoustic applications %U https://doi.org/10.5301/IJAO.2011.6405 2 %X Conclusion: The high optical absorption at the relevant NIR-wavelength around 800 nm in combination with absence of cytotoxicity qualifies the ICG-loaded PLGA particles as promising candidates for degradable photoacoustic contrast agents. %0 conference poster %@ %A Rueder, C., Sauter, T., Becker, T., Kratz, K., Hiebl, B., Jung, F., Lendlein, A., Zohlnhoefer, D. %D 2011 %J 16th International Conference of the European Society for Clinical Hemorheology and Microcirculation (ESCHM) and the 30th Annual Conference of the German Society for Clinical Microcirculation and Hemorheology (DGKMH) %T Viability, proliferation, apoptosis and adhesion of smooth muscle cells (SMCs) and endothelial cells (HUVECs) on degradable electro-spun structures %U %X %0 journal article %@ 0391-3988 %A Reiche, J., Kratz, K., Hofmann, D., Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 123-128 %R doi:10.5301/IJAO.2011.6401 %T Current status of Langmuir monolayer degradation of polymeric biomaterials %U https://doi.org/10.5301/IJAO.2011.6401 2 %X Langmuir monolayer degradation (LMD) experiments with polymers possessing outstanding biomedical application potential yield information regarding the kinetics of their hydrolytic or enzymatic chain scission under well-defined and adjustable degradation conditions. A brief review is given of LMD investigations, including the author’s own work on 2-dimensional (2D) polymer systems, providing chain scission data, which are not disturbed by simultaneously occurring transport phenomena, such as water penetration into the sample or transport of scission fragments out of the sample. A knowledge-based approach for the description and simulation of polymer hydrolytic and enzymatic degradation based on a combination of fast LMD experiments and computer simulation of the water penetration is briefly introduced. Finally, the advantages and disadvantages of this approach are discussed. %0 journal article %@ 0935-9648 %A Kratz, K., Madbouly, S.A., Wagermeier, W., Lendlein, A. %D 2011 %J Advanced Materials %N 35 %P 4058-4062 %R doi:10.1002/adma.201102225 %T Temperature-Memory Polymer Networks with Crystallizable Controlling Units %U https://doi.org/10.1002/adma.201102225 35 %X The switching temperature,Tsw, which must be exceeded to initialize a shape-memory effect (SME), and Tσ,max, a temperature related to the recovery stress maximum under constant strain-activation conditions, are adjusted systematically over a wide temperature range for temperature-memory polymers. The polymers are based on crosslinked poly[ethylene-ran-(vinyl acetate)] with crystallizable controlling units and exhibit a broad melting temperature range. %0 journal article %@ 1076-3279 %A Cui, J., Kratz, K., Hiebl, B., Jung, F., Lendlein, A. %D 2011 %J Tissue Engineering A %N 3-4 %P 531-584 %R doi:10.1089/ten.tea.2010.1502 %T Poly(n-butyl acrylate) networks with tailored mechanical properties designed as model substrates for mechano-responsive cells %U https://doi.org/10.1089/ten.tea.2010.1502 3-4 %X No abstract %0 conference lecture (invited) %@ %A Behl, M., Zotzmann, J., Kratz, K., Feng, Y., Lendlein, A. %D 2011 %J Vortrag at the Hong Kong Polytechnic University, Institute of Textiles and Clothing %T Triple-Shape Polymers %U %X %0 conference poster %@ %A Luetzow, K., Weigel, T., Kosmalla, H.-J., Schossig, M., Kratz, K., Lendlein, A. %D 2011 %J Advanced Functional Polymers for Medicine, AFPM 2011 %T Preparation of Three-Dimensional Scaffolds from Degradable Poly(Ether)Esterurethane by Thermally Induced Phase Separation Technique %U %X %0 journal article %@ 0391-3988 %A Schneider, T., Kohl, B., Sauter, T., Becker, T., Kratz, K., Schossig, M., Jung, F., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2011 %J The International Journal of Artificial Organs %N 8 %P 688 %R doi:10.5301/IJAO.2011.8702 %T Interaction of chondrocytes with electrospun polymer scaffolds depending on the fibre orientation %U https://doi.org/10.5301/IJAO.2011.8702 8 %X No abstract %0 journal article %@ 1386-0291 %A Mayer, A., Kratz, K., Hiebl, B., Lendlein, A., Jung, F. %D 2011 %J Clinical Hemorheology and Microcirculation %N 1-4 %P 423-430 %R doi:10.3233/CH-2011-1492 %T Support of HUVEC proliferation by pro-angiogenic intermediate CD163+ monocytes/macrophages: A co-culture experiment %U https://doi.org/10.3233/CH-2011-1492 1-4 %X So called intermediate (MO2) monocytes/macrophages possess anti-inflammatory properties and express the MO lineage marker CD163. On a hydrophilic, acrylamide-based hydrogel human intermediate (CD14++ CD16+) CD163++ monocytes/macrophages (aMO2) which were angiogenically stimulated, maintained a pro-angiogenic and non-inflammatory status for at least 14 days. Here we explored, whether this aMO2 subset can positively influence the proliferation of human umbilical venous endothelial cells (HUVECs) without switching back into a pro-inflammatory (MO1) phenotype. aMO2 or HUVEC were seeded alone on glass cover slips (0.5 × 105 cells / 1.33 cm2) in a HUVEC specific cell culture medium (EGM-2) for 3 hrs, 24 hrs and 72 hrs or under co-culture conditions (0.5 × 105 HUVEC + 0.25 × 105 aMO2 / 1.33 cm2) in EGM-2 for the same time window as well (n = 6 each). Under co-culture conditions the numbers of adherent HUVEC per unit area were significantly higher (p < 0.01; 525 ± 52 HUVEC/mm2) compared to control mono-cultures (473 ± 76 HUVEC/mm2) after 72 hrs of cultivation and showed their typically spread morphology. The aMO2 remained in their subset status and secreted VEGF-A165 without release of pro-inflammatory cytokines until the end of the 72 hrs cultivation time period, thereby supporting the HUVEC proliferation. These in vitro results might indicate that this MO subset can be used as cellular delivery system for pro-angiogenic and non-inflammatory mediators to support the endothelialisation of biomaterials like e.g. cPnBA. %0 journal article %@ 1022-1360 %A Schneider, T., Kohl, B., Sauter, T., Becker, T., Kratz, K., Schossig, M., Hiebl, B., Jung, F., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2011 %J Macromolecular Symposia %N 1 %P 28-39 %R doi:10.1002/masy.201100057 %T Viability, adhesion and differentiated phenotype of articular chondrocytes on degradable polymers and electro-spun structures thereof %U https://doi.org/10.1002/masy.201100057 1 %X Degradable polymers are essential to enable biomaterial-based regenerative therapies, particularly, in articular cartilage defect healing, which remains a major clinical challenge. The aim of this study was to investigate the effect of two degradable polymers (as a film or scaffold) on primary articular chondrocytes vitality, adherence, differentiated phenotype and morphology. Films and electro-spun scaffolds were prepared from degradable poly(ether)ester urethane (PDC), which was synthesized via co-condensation of poly(p-dioxanone)diol and poly(ε-caprolactone)diol with an aliphatic diisocyanate and poly(p-dioxanone) (PPDO). The thermal and mechanical properties and the surface roughness of the films and scaffolds were examined by differential scanning calorimetry, dynamic mechanical thermal analysis, tensile tests and optical profilometry. Primary porcine articular chondrocytes were seeded on the polymers and analysed for viability, ultrastructure (scanning electron microscopy) and immunolabelled for type II collagen. All films and scaffolds exhibited a low endotoxin load < 0.06 EU/ml and only moderate cytotoxic effects when tested with L929 cells. The results of the seeding experiments revealed that survival and adhesion of chondrocytes depended strongly on seeding density. Vital chondrocytes could be detected on both PPDO and PDC films and scaffolds. They produced the cartilage-specific protein type II collagen indicating differentiated functions. However, they exhibited a mixed morphology on the films and a more flattened cell shape on the scaffolds. The cell/biomaterial interaction in the PPDO scaffolds or films was more intense compared to that in PDC topologies. %0 journal article %@ 1076-3279 %A Kommareddy, K.P., Lange, C., Cui, J., Boergermann, J.H., Manjubala, I., Rumpler, M., Dunlop, J.W.C., Kratz, K., Lendlein, A., Knaus, P., Fratzl, P. %D 2011 %J Tissue Engineering A %N 3-4 %P 531-584 %R doi:10.1089/ten.tea.2010.1502 %T Three-dimensional tissue growth in polymer scaffolds with different stiffness and in-vitro influence of BMP-2 on tissue formation in hydroxyapatite scaffolds %U https://doi.org/10.1089/ten.tea.2010.1502 3-4 %X No abstract %0 conference poster %@ %A Schneider, T., Kohl, B., Sauter, T., Becker, T., Kratz, K., Schossig, M., Jung, F., Lendlein, A., Ertel, W., Schulze-Tanzil, G. %D 2011 %J 38th Congress of the European Society for Artificial Organs, ESAO 2011 %T Interaction of chondrocytes with electrospun polymer scaffolds depending on the fibre orientation %U %X %0 journal article %@ 0935-9648 %A Kumar, U.N., Kratz, K., Heuchel, M., Behl, M., Lendlein, A. %D 2011 %J Advanced Materials %N 36 %P 4157-4162 %R doi:10.1002/adma.201102251 %T Shape-Memory Nanocomposites with Magnetically Adjustable Apparent Switching Temperatures %U https://doi.org/10.1002/adma.201102251 36 %X The apparent switching temperatures (Tsw,app), which need to be exceeded by the environmental temperature (Tenv) to initialize a shape-memory effect (SME) in magnetosensitive dual- or triple-shape composites, are systematically adjusted by application of a constant weak alternating magnetic field. This adaptation of Tsw,app is fully reversible and results from the combination of environmental and inductive heating. %0 journal article %@ 0391-3988 %A Kratz, K., Habermann, R., Becker, T., Richau, K., Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 225-230 %R doi:10.5301/IJAO.2011.6404 %T Shape-memory properties and degradation behavior of multifunctional electro-spun scaffolds %U https://doi.org/10.5301/IJAO.2011.6404 2 %X Multifunctional polymer-based biomaterials, which combine degradability and shape-memory capability, are promising candidate materials for the realization of active self-anchoring implants. In this work we explored the shape-memory capability as well as the hydrolytic and enzymatic in vitro degradation behavior of electro-spun scaffolds prepared from a multiblock copolymer, containing hydrolytically degradable poly(p-dioxanone) (PPDO) and poly(e-caprolactone) (PCL) segments, which we have named PDC.?Electro-spun PDC scaffolds with an average deposit thickness of 80 ± 20 µm and a porosity in the range from 70% to 80% were prepared, where the single fiber diameter was around 3 µm. Excellent shape-memory properties were achieved with high recovery rate (Rr) values in the range of Rr = 92% to 98% and a recovery stress of smax = 4.6 MPa to 5.0 MPa. The switching temperature (Tsw) and the characteristic temperature obtained under constant strain recovery conditions (Ts,max) were found in the range from 32°C to 35°C, which was close to the melting temperature (Tm,PCL) associated to the poly(e-caprolactone) domains. ?A linear mass loss was observed in both hydrolytic and enzymatic degradation experiments. The mass loss was substantially accelerated, in enzymatic degradation when Pseudomonas cepacia lipase was added, which was reported to accelerate the degradation of PCL. During hydrolytic degradation a continuous decrease in elongation at break (eB) from eB = 800% to 15% was observed in a time period of 92 days, while in enzymatic degradation experiments a complete mechanical failure was obtained after 4 days. %0 conference poster %@ %A Kommareddy, K.P., Lange, C., Cui, J., Boergermann, J.H., Manjubala, I., Rumpler, M., Dunlop, J.W.C., Kratz, K., Lendlein, A., Knaus, P., Fratzl, P. %D 2010 %J 4th Congress on Regenerative Biology and Medicine, BioStar 2010 %T Three-dimensional tissue growth in polymer scaffolds with different stiffness and in-vitro influence of BMP-2 on tissue formation in hydroxyapatite scaffolds %U %X %0 conference lecture (invited) %@ %A Hofmann, D., Entrialgo, M., Reiche, J., Kratz, K., Lendlein, A. %D 2010 %J 9th International Conference Medical Applications of Novel Biomaterials and Nano-Biotechnology, CIMTEC 2010 %T Molecular Modeling and experimental investigation of hydrolytically degradable polymeric biomaterials %U %X %0 journal article %@ 0168-1656 %A Hiebl, B., Luetzow, K., Lange, M., Jung, F., Seifert, B., Klein, f., Weigel, T., Kratz, K., Lendlein, A. %D 2010 %J Journal of Biotechnology %N 1 %P 76-82 %R doi:10.1016/j.jbiotec.2010.01.006 %T Cytocompatibility testings using cell culture modules fabricated from specific candidate biomaterials using injection molding %U https://doi.org/10.1016/j.jbiotec.2010.01.006 1 %X Most polymers used in clinical applications today are materials that have been developed originally for application areas other than biomedicine. Testing the cell- and tissue-compatibility of novel materials in vitro and in vivo is of key importance for the approval of medical devices and is regulated according to the Council Directive 93/42 of the European communities concerning medical devices. In the standardized testing methods the testing sample is placed in commercially available cell culture plates, which are often made from polystyrene. Thus not only the testing sample itself influences cell behavior but also the culture vessel material. In order to exclude this influence, a new system for cell testing will be presented allowing a more precise and systematic investigation by preparing tailored inserts which are made of the testing material. Inserts prepared from polystyrene, polycarbonate and poly(ether imide) were tested for their cytotoxity and cell adherence. Furthermore a proof of principle concerning the preparation of inserts with a membrane-like surface structure and its surface modification was established. Physicochemical investigations revealed a similar morphology and showed to be very similar to the findings to analogous preparations and modifications of flat-sheet membranes. %0 conference poster %@ %A Reiche, J., Kratz, K., Hofmann, D., Lendlein, A. %D 2010 %J 13th International Conference on Organized Molecular Films LB-13 %T Separation of chain scission kinetics and water diffusion involved in polymer hydrolytic / enzymatic degradation based on monolayer experiments %U %X %0 conference lecture %@ %A Lendlein, A., Kratz, K., Hiebl, B., Behl, M. %D 2010 %J Makromolekulares Kolloquium %T Active Biomaterials %U %X %0 conference lecture %@ %A Kohl, Y., Bost, W., Kaiser, C., Henkel, A., Schroeter, M., Soennichsen, C., Kratz, K., Thielecke, H., Lemor, R. %D 2010 %J 34th International Conference and Exposition on Advanced Ceramics and Composites, ICACC 2010 %T Evaluation of Nanoparticles as Contrast Agent for Photoacoustic Imaging in Living Cells %U %X %0 journal article %@ 0964-1726 %A Cui, J., Kratz, K., Lendlein, A. %D 2010 %J Smart Materials and Structures %N 6 %P 065019 %R doi:10.1088/0964-1726/19/6/065019 %T Adjusting shape-memory properties of amorphous polyether urethanes and radio-opaque composites thereof by variation of physical parameters during programming %U https://doi.org/10.1088/0964-1726/19/6/065019 6 %X Various composites have been prepared to improve the mechanical properties of shape-memory polymers (SMPs) or to incorporate new functionalities (e.g. magneto-sensitivity) in polymer matrices. In this paper, we systematically investigated the influence of the programming temperature Tprog and the applied strain εm as parameters of the shape-memory creation procedure (SMCP) on the shape-memory properties of an amorphous polyether urethane and radio-opaque composites thereof. Recovery under stress-free conditions was quantified by the shape recovery rate Rr and the switching temperature Tsw, while the maximum recovery stress σmax was determined at the characteristic temperature Tσ, max under constant strain conditions. Excellent shape-memory properties were achieved in all experiments with Rr values in between 80 and 98%. σmax could be tailored from 0.4 to 3.7 MPa. Tsw and Tσ, max could be systematically adjusted from 33 to 71 °C by variation of Tprog for each investigated sample. The investigated radio-opaque shape-memory composites will form the material basis for mechanically active scaffolds, which could serve as an intelligent substitute for the extracellular matrix to study the influence of mechanical stimulation of tissue development. %0 journal article %@ 1559-4106 %A Kommareddy, K.P., Lange, C., Rumpler, M., Dunlop, J.W.C., Manjubala, I., Cui, J., Kratz, K., Lendlein, A., Fratzl, P. %D 2010 %J Biointerphases %N 2 %P 45 %R doi:10.1116/1.3431524 %T Two stages in three-dimensional in vitro growth of tissue generated by osteoblastlike cells %U https://doi.org/10.1116/1.3431524 2 %X Bone regeneration is controlled by a variety of biochemical, biomechanical, cellular, and hormonal mechanisms. In particular, physical properties of the substrate such as stiffness and architecture highly influence the proliferation and differentiation of cells. The aim of this work is to understand the influence of scaffold stiffness and cell seeding densities on the formation of tissue by osteoblast cells within polyether urethane scaffolds containing pores of different sizes. MC3T3-E1 preosteoblast cells were seeded on the scaffold, and the amount of tissue formed within the pores was analyzed for culture times up to 49 days by phase contrast microscopy. The authors show that the kinetics of three-dimensional tissue growth in these scaffolds follows two stages and can be described by a universal growth law. The first stage is dominated by cell-material interactions with cell adherence and differentiation being strongly dependent on the polymer material. After a delay time of a few weeks, cells begin to grow within their own matrix, the delay being strongly dependent on substrate stiffness and seeding protocols. In this later stage of growth, three-dimensional tissue amplification is controlled rather by the pore geometry than the scaffold material properties. This emphasizes how geometric constraints may guide tissue formation in vitro and shows that optimizing scaffold architectures may improve tissue formation independent of the scaffold material used. %0 journal article %@ 0959-9428 %A Ganesan, R., Kratz, K., Lendlein, A. %D 2010 %J Journal of Materials Chemistry %P 7322-7331 %R doi:10.1039/b926690a %T Multicomponent protein patterning of material surfaces %U https://doi.org/10.1039/b926690a %X Micro- and nano-scale protein patterns have gained significant technological interest. While certain techniques for single-component protein patterning are well-established, multicomponent protein patterning approaches are a current topic of intensive research, which might enable complex biosensor systems and expand the knowledge in protein-protein and protein-cell or cell-cell interactions. Only a few patterning methods are suitable for the realization of three dimensional patterns, which are essential for many applications e.g. in the design of scaffolds for regenerative therapies. In this feature article representative approaches for creating multicomponent protein patterning are presented and their potential for tailoring microenvironments for cells on biomaterials surfaces is discussed. %0 journal article %@ 0032-3861 %A Heuchel, M., Cui, J., Kratz, K., Kosmella, H., Lendlein, A. %D 2010 %J Polymer %N 26 %P 6212-6218 %R doi:10.1016/j.polymer.2010.10.051 %T Relaxation based modeling of tunable shape recovery kinetics observed under isothermal conditions for amorphous shape-memory polymers %U https://doi.org/10.1016/j.polymer.2010.10.051 26 %X The presented modeling approach might be helpful to define design criteria for self sufficiently moving scaffolds within a knowledge-based development process. %0 journal article %@ 1386-0291 %A Cui, J., Trescher, K., Kratz, K., Jung, F., Hiebl, B., Lendlein, A. %D 2010 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 401-411 %R doi:10.3233/CH-2010-1322 %T Melt-processable hydrophobic acrylonitrile-based copolymer systems with adjustable elastic properties designed for biomedical applications %U https://doi.org/10.3233/CH-2010-1322 2-4 %X Acrylonitrile-based polymer systems (PAN) are comprehensively explored as versatile biomaterials having various potential biomedical applications, such as membranes for extra corporal devices or matrixes for guided skin reconstruction. The surface properties (e.g. hydrophilicity or charges) of such materials can be tailored over a wide range by variation of molecular parameters such as different co-monomers or their sequence structure. Some of these materials show interesting biofunctionalities such as capability for selective cell cultivation. So far, the majority of AN-based copolymers, which were investigated in physiological environments, were processed from the solution (e.g. membranes), as these materials are thermo-sensitive and might degrade when heated. In this work we aimed at the synthesis of hydrophobic, melt-processable AN-based copolymers with adjustable elastic properties for preparation of model scaffolds with controlled pore geometry and size. For this purpose a series of copolymers from acrylonitrile and n-butyl acrylate (nBA) was synthesized via free radical copolymerisation technique. The content of nBA in the copolymer varied from 45 wt% to 70 wt%, which was confirmed by 1H-NMR spectroscopy. The glass transition temperatures (Tg) of the P(AN-co-nBA) copolymers determined by differential scanning calorimetry (DSC) decreased from 58°C to 20°C with increasing nBA-content, which was in excellent agreement with the prediction of the Gordon-Taylor equation based on the Tgs of the homopolymers. The Young’s modulus obtained in tensile tests was found to decrease significantly with rising nBA-content from 1062 MPa to 1.2 MPa. All copolymers could be successfully processed from the melt with processing temperatures ranging from 50°C to 170°C, whereby thermally induced decomposition was only observed at temperatures higher than 320°C in thermal gravimetric analysis (TGA). Finally, the melt processed P(AN-co-nBA) biomaterials were sterilized with ethylene oxide and tested for cytotoxicity in direct contact tests with L929 cells according to the EN DIN ISO standard 10993-5. All tested samples exhibited non-toxic effects on the functional integrity of the cell membrane and the mitochondrial activity. However, the morphology of the cells on the samples was different from that observed on polystyrene as control, indicating slightly cytotoxic effects according to the evaluation guide of the US Pharmacopeial Convention. Thus, the melt-processable, hydrophobic P(AN-co-nBA) copolymers with adjustable mechanical properties are promising candidates for in vitro investigations of tissue growth kinetics. %0 journal article %@ 1022-1336 %A Wagermaier, W., Zander, T., Hofmann, D., Kratz, K., Kumar, U.N., Lendlein, A. %D 2010 %J Macromolecular Rapid Communications %N 17 %P 1546-1553 %R doi:10.1002/marc.201000122 %T In Situ X-Ray Scattering Studies of Poly(Epsilon-caprolactone) Networks with Grafted Poly(ethylene glycol) Chains to Investigate Structural Changes during Dual- and Triple-Shape Effect %U https://doi.org/10.1002/marc.201000122 17 %X The dual- and triple-shape effects of multiphase polymer networks that contain two crystallizable chain segments have been assessed in situ by combining X-ray measurements with thermomechanical investigations. The studied polymer, named CLEG, is a multiphase polymer network of crystallizable poly(ε-caprolactone) (PCL) with grafted poly(ethylene glycol) (PEG) side chains. Wide-angle (WAXS) and small-angle X-ray scattering (SAXS) measurements were combined with temperature-controlled in situ tensile testing experiments. This integrated approach enables systematic investigation and interpretation of relevant structural features during the programming procedures and the thermally-induced recovery process. Main results concern the combined effect of PCL and PEG crystals on shape fixation, the specific role of low-melting PCL crystallites in the fixation of the low temperature temporary shape, and the different orientation behavior of PCL and PEG crystals during certain stages of the programming procedure. These results demonstrate that crystal orientation effects are dominant for the PCL crystals. The effects of the low temperature PCL crystals could only be investigated when synchrotron radiation was applied. These findings indicate the great potential of in situ X-ray investigations for the creation of design-relevant knowledge about the microscopic foundations of dual- and triple-shape effects in appropriate polymer systems. %0 journal article %@ 1386-0291 %A Hiebl, B., Mrowietz, C., Goers, J., Bahramsoltani, M., Plendl, J., Kratz, K., Lendlein, A., Jung, F. %D 2010 %J Clinical Hemorheology and Microcirculation %N 2-3 %P 233-238 %R doi:10.3233/CH-2010-1350 %T In vivo evaluation of the angiogenic effects of the multiblock copolymer PDC using the hen's egg chorioallantoic membrane test %U https://doi.org/10.3233/CH-2010-1350 2-3 %X Multiblock copolymers with shape-memory capability attracted tremendous interest as promising candidate materials for smart, degradable implants. In the present study the hen's egg-chorioallantoic membrane test (HET-CAM test) was used to investigate the angiogenic properties of a thermoplastic, biodegradable multiblock copolymer PDC composed of poly(p-dioxanone) hard segments (PPDO) and crystallizable poly(ε-caprolactone) switching segments (PCL), whereby PPDO and PCL homopolymers were investigated as controls. According to our HET-CAM test data, only PDC induced significant microvessel attraction and formation in the contact area of the test specimen after 48hours of incubation showing newly formed blood vessels along the outer edge of the material. In contrast, no newly formed blood vessels were observed around the PPDO or PCL specimen after the same incubation period. These in vivo results indicate that the multiblock copolymer PDC possibly possesses an angiogenic effect and it can induce blood vessel formation in its direct vicinity when it is implanted in vivo. %0 journal article %@ 0959-9428 %A Kumar, U.N., Kratz, K., Wagermaier, W., Behl, M., Lendlein, A. %D 2010 %J Journal of Materials Chemistry %N 17 %P 3404-3415 %R doi:10.1039/b923000a %T Non-contact actuation of triple-shape effect in multiphase polymer network nanocomposites in alternating magnetic field %U https://doi.org/10.1039/b923000a 17 %X Triple-shape polymers (TSP) can memorize two independent shapes, which are recovered when the temperature is subsequently increased. Certain applications do not allow triggering of the triple-shape effect (TSE) by environmental heating (e.g. potential damaging of surrounding tissue) and therefore require a non-contact activation. Here we explored whether polymer nanocomposites can be designed, which enable non-contact activation of TSE in an alternating magnetic field. %0 conference poster %@ %A Cui, J., Kratz, K., Hiebl, B., Jung, F., Lendlein, A. %D 2010 %J 4th Congress on Regenerative Biology and Medicine, BioStar 2010 %T Poly(n-butyl acrylate) networks with tailored mechanical properties designed as model substrates for mechano-responsive cells %U %X %0 journal article %@ 1313-2458 %A Hiebl, B., Kratz, K., Fuhrmann, R., Jung, F., Lendlein, A., Franke, R.-P. %D 2010 %J Series on BIOMECHANICS %N 3-4 %P 61-65 %T Changes in the subcutaneous tissue and the chorioallantois membrane of eggs caused by poly(p-dioxanone)- and poly(ε- caprolactone) multiblock copolymers %U 3-4 %X %0 book part %@ %A Wagermaier, W., Kratz, W., Heuchel, M., Lendlein, A. %D 2010 %J Advances in Polymer Science - Shape-memory Polymers %P 97-145 %R doi:10.1007/12_2009_25 %T Characterization Methods for Shape-Memory Polymers %U https://doi.org/10.1007/12_2009_25 %X Finally, as part of a comprehensive characterization, modeling approaches for simulating the thermomechanical behavior of SMPs are presented. At the beginning linear viscoelastic models were applied consisting of coupled spring, dashpot and frictional elements. More recent approaches consider in detail the specific molecular transition underlying the SME, e.g. glass or melting transition. Currently models that incorporate the strain rate dependence and time dependent behavior are under development. %0 book part %@ %A Kratz, K., Wagermaier, W., Heuchel, M., Lendlein, A. %D 2010 %J Shape-Memory Polymers and Multifunctional Composites %P 91-107 %T Thermomechanical Characterizations of Shape-Memory Polymers (Dual/Triple-Shape) and Modeling Approaches %U %X In each chapter, industry experts discuss different key aspects of novel smart materials, from their properties and fabrication to the actuation approaches used to trigger shape recovery. This comprehensive analysis explores the different functions of SMPs, the fundamentals behind them, and the ways in which polymers may reshape product design in general. %0 journal article %@ 1662-0356 %A Hofmann, D., Entrialgo, M., Reiche, J., Kratz, K., Lendlein, A. %D 2010 %J Advances in Science and Technology, 5th Forum on new Materials Part E %P 16-24 %R doi:10.4028/www.scientific.net/AST.76.16 %T Molecular Modeling and experimental investigation of hydrolytically degradable polymeric biomaterials %U https://doi.org/10.4028/www.scientific.net/AST.76.16 %X (PLGA)] and copoly(ether)esteruretanes as multiblock copolymers. The molecular modeling approach permits to efficiently investigate the influence of micro-structural properties like free volume distribution, cohesive energy density and concentration of polar functional groups on the bulk water uptake as one constituent part of hydrolytic degradation. The Langmuir monolayer investigations on polymer degradation on the other hand yield the dynamics of bond splitting during degradation within hours separately from time consuming diffusion processes, which may take months in bulk samples. %0 journal article %@ 1386-0291 %A Hiebl, B., Fuhrmann, R., Jung, F., Kratz, K., Lendlein, A., Franke, R.-P. %D 2010 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 117-122 %R doi:10.3233/CH-2010-1289 %T Degradation of and angiogenesis around multiblock copolymers containing poly(Rho-dioxanone)- and poly(Epsilon-caprolactone)-segments subcutaneously implanted in the rat neck %U https://doi.org/10.3233/CH-2010-1289 2-4 %X The degradation behavior and the effect on angiogenesis of multiblock copolymers based on poly(p-dioxanone)- and poly(ε-caprolactone)-segments (PDC) were studied in vivo. PDC is a multifunctional biomaterial combining degradability and shape-memory capabilities. The “in vivo” degradation of PDC is characterized by a fragmentation occurring at the material tissue interface. This observation is consistent with the enzyme supported degradation behaviour, which was determined “in vitro”. PDC revealed to induce the formation of blood micro-vessels nearby in the periimplantary tissues. Both might explain the good PDC integration into tissues in terms of a strong connection between the implant and the periimplantary tissue. Micro blood-vessels might be involved in the clearance of the small particles, which appear in the periimplantary tissue when PDC degrades. %0 conference paper %@ %A Kratz, K., Voigt, U., Wagermaier, W., Lendlein, A. %D 2009 %J Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging, MRS Symposium Proceedings, MRS Fall Meeting 2008 %P HH03-01 %R doi:10.1557/PROC-1140-HH03-01 %T Shape-memory Properties of Multiblock Copolymers Consisting of Poly(?-pentadecalactone) Hard Segments and Crystallisable Poly(e-caprolactone) Switching Segments %U https://doi.org/10.1557/PROC-1140-HH03-01 %X %0 conference paper %@ %A Razzaq, M.Y., Behl, M., Kratz, K., Lendlein, A. %D 2009 %J Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging, MRS Symposium Proceedings, MRS Fall Meeting 2008 %P HH05-07 %R doi:10.1557/PROC-1140-HH05-07 %T Controlled Actuation of Shape-Memory nanocomposites by Application of an Alternating Magnetic Field %U https://doi.org/10.1557/PROC-1140-HH05-07 %X %0 conference lecture %@ %A Kumar, U.N., Kratz, K., Behl, M., Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %T Triple-Shape Capability of Thermo-Sensitive Nanocomposites from Multiphase Polymer Networks and Magnetic Nanoparticles %U %X %0 conference poster %@ %A Mrowietz, C., Hiebl, B., Goers, J., Bahramsoltani, M., Plendl, J., Kratz, K., Lendlein, A., Jung, F. %D 2009 %J 28. Jahrestagung der Deutschen Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie %T In vitro testing of angiogenic effects derived from polymer based biomaterials using the Hen’s egg test-chorioallantoic membrane method %U %X %0 journal article %@ 0935-9648 %A Hofmann, D., Entrialgo-Castano, M., Kratz, K., Lendlein, A. %D 2009 %J Advanced Materials %N 32-33 %P 3237-3245 %R doi:10.1002/adma.200802213 %T Knowledge-Based Approach towards Hydrolytic Degradation of Polymer-Based Biomaterials %U https://doi.org/10.1002/adma.200802213 32-33 %X The concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.[1] A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge-based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir-Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided. %0 conference paper %@ %A Kumar, U.N., Kratz, K., Behl, M., Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %P NN03-21 %R doi:10.1557/PROC-1190-NN03-21 %T Triple-Shape Capability of Thermo-Sensitive Nanocomposites from Multiphase Polymer Networks and Magnetic Nanoparticles %U https://doi.org/10.1557/PROC-1190-NN03-21 %X %0 conference lecture %@ %A Cui, J., Kratz, K., Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %T Shape-Memory Properties of Radiopaque Micro-Composites from Amorphous Polyether Urethanes Designed for Medical Application %U %X %0 conference paper %@ %A Cui, J., Kratz, K., Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %P NN03-22 %R doi:10.1557/PROC-1190-NN03-22 %T Shape-Memory Properties of Radiopaque Micro-Composites from Amorphous Polyether Urethanes Designed for Medical Application %U https://doi.org/10.1557/PROC-1190-NN03-22 %X %0 conference poster %@ %A Hiebl, B., Kratz, K., Fuhrmann, R., Jung, F., Lendlein, A., Franke, R.-P. %D 2009 %J MRS Spring Meeting 2009 %T In vivo degradation behavior of PDC multiblock copolymers containing poly(para-dioxanone) hard segments and crystallizable poly(epsilon-caprolactone) switching segments %U %X %0 conference paper %@ %A Hiebl, B., Kratz, K., Fuhrmann, R., Jung, F., Lendlein, A., Franke, R.-P. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %P NN06-05 %R doi:10.1557/PROC-1190-NN06-05 %T In vivo degradation behavior of PDC multiblock copolymers containing poly(para-dioxanone) hard segments and crystallizable poly(epsilon-caprolactone) switching segments %U https://doi.org/10.1557/PROC-1190-NN06-05 %X %0 conference lecture %@ %A Lee, S., Ganesan, R., Braune, S., Kratz, K., Lendlein, A., Jung, F. %D 2009 %J 28. Jahrestagung der Deutschen Gesellschaft fuer Klinische Mikrozirkulation und Haemorheologie %T Big ET-1 derived peptides enhances endothelial cell shear resistancy %U %X %0 conference lecture (invited) %@ %A Lendlein, A., Tronci, G., Zaupa, A., Pierce, B., Neffe, A., Cui, J., Kratz, K. %D 2009 %J Biomechanics and Biology of Bone Healing, International Symposium 2009 %T Biomimetic Scaffolds supporting Bone Regeneration in Critical Defects %U %X %0 conference lecture %@ %A Madbouly, S., Kratz, K., Klein, F., Luetzow, K., Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %T Thermomechanical Behaviour of Biodegradable Shape-memory Polymer Foams %U %X %0 conference paper %@ %A Madbouly, S., Kratz, K., Klein, F., Luetzow, K., Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %P NN04-04 %R doi:10.1557/PROC-1190-NN04-04 %T Thermomechanical Behaviour of Biodegradable Shape-memory Polymer Foams %U https://doi.org/10.1557/PROC-1190-NN04-04 %X %0 conference lecture %@ %A Wagermaier, W., Hofmann, D., Kratz, K., Behl, M., Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %T X-ray Scattering Studies to Investigate Triple-shape Capability of Polymer Networks Based on poly(?-caprolactone) and poly(cyclohexyl methacrylate) Segments %U %X %0 conference paper %@ %A Wagermaier, W., Hofmann, D., Kratz, K., Behl, M., Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %P NN03-18 %R doi:10.1557/PROC-1190-NN03-18 %T X-ray Scattering Studies to Investigate Triple-shape Capability of Polymer Networks Based on poly(?-caprolactone) and poly(cyclohexyl methacrylate) Segments %U https://doi.org/10.1557/PROC-1190-NN03-18 %X %0 conference lecture %@ %A Hiebl, B., Fuhrmann, R., Jung, F., Kratz, K., Lendlein, A., Franke, R.-P. %D 2009 %J 15th Conference of the European Society of Clinical Hemorheology and Microcirculation %T Degradation of and angiogenesis around multiblock copolymers containing poly(Rho-dioxanone)- and poly(Epsilon-caprolactone)-segments subcutaneously implanted in the rat neck %U %X %0 conference poster %@ %A Kommareddy, K.P., Lange, C., Rumpler, M., Inderchand, M., Cui, J., Kratz, K., Boergermann, J.H., Lendlein, A., Knaus, P., Fratzl, P. %D 2009 %J 36th European Symposium on Calcified Tissues %T Influence on three-dimensional tissue growth by scaffold architecture %U %X %0 journal article %@ 8756-3282 %A Kommareddy, K.P., Lange, C., Rumpler, M., Inderchand, M., Cui, J., Kratz, K., Boergermann, J.H., Lendlein, A., Knaus, P., Fratzl, P. %D 2009 %J Bone %N S 2 %P S261-S262 %R doi:10.1016/j.bone.2009.03.450 %T Influence on three-dimensional tissue growth by scaffold architecture %U https://doi.org/10.1016/j.bone.2009.03.450 S 2 %X No abstract %0 conference poster %@ %A Kratzer, J., Ahrens, L., Sturm, R., Ebinghaus, R. %D 2009 %J Protecting ecosystem health: facing the challenge of a globally changing environment, SETAC Europe 19th Annual Meeting %T Polyfluoroalkyl compounds in biles of common dabs (Limanda limanda) collected at the coasts of Germany, Denmark, Great Britain, Iceland and in the central North Sea %U %X %0 journal article %@ 0939-6411 %A Kulkarni, A., Reiche, J., Hartmann, J., Kratz, K., Lendlein, A. %D 2008 %J European Journal of Pharmaceutics and Biopharmaceutics %N 1 %P 46-56 %R doi:10.1016/j.ejpb.2007.05.021 %T Selective enzymatic degradation of poly (Epsilon-caprolactone) containing multiblock copolymers %U https://doi.org/10.1016/j.ejpb.2007.05.021 1 %X The hydrolytic and Pseudomonas lipase catalysed enzymatic degradation was studied for PDC multiblock copolymers consisting of poly(e-caprolactone) (PCL) segments and poly(p-dioxanone) (PPDO) segments with variable composition. The enzymatic degradation of these multiblock copolymers is significantly accelerated by Pseudomonas lipase in contrast to the hydrolytic degradation where the deg-radation behaviour is determined by the PPDO segments. Degradation time intervals up to 200 h are selected, where the PPDO segments remain stable and do not contribute to the degradation process. A linear correlation between weight loss and increasing PCL content of the multiblock copolymers was found. X-ray diffraction data confirm that both crystalline and amorphous PCL are attacked by the enzymes. SEM cross-section images reveal that Pseudomonas lipase penetrates into the PDC polymers. The present study impressively demonstrates that selective enzymatic degradation of PCL containing multifunctional polymers is a beneficial tool for controlling their degradation properties. %0 journal article %@ 0040-6090 %A Reiche, J., Kulkarni, A., Kratz, K., Lendlein, A. %D 2008 %J Thin Solid Films %N 24 %P 8821-8828 %R doi:10.1016/j.tsf.2007.11.053 %T Enzymatic Monolayer Degradation Study of Multiblock Copolymers consisting of Poly(epsilon-caprolactone) and Poly(p-dioxanone) Blocks %U https://doi.org/10.1016/j.tsf.2007.11.053 24 %X monolayers is developed. %0 conference lecture %@ %A Lange, C., Rumpler, M., Manjubula, I., Kratz, K., Lendlein, A., Fratzl, P. %D 2008 %J Osteologie-Tagung %T Porengroesse und Substratsteifigkeit beeinflussen die dreidimensionale Gewebeentstehung in vitro %U %X %0 conference lecture %@ %A Reiche, J., Kulkarni, A., Sokolov, I., Kratz, K., Lendlein, A. %D 2008 %J 11th European Conference on Organized Films %T Hydrolytic Fragmentation of Polymer Chains %U %X %0 conference poster %@ %A Kommareddy, K.P., Lange, C., Manjubala, I., Rumpler, M., Fratzl, P., Cui, J., Kratz, K., Lendlein, A. %D 2008 %J Polydays 2008 %T Growth of Extracellular Matrix tissue controlled by pore size and stiffness of scaffolds %U %X %0 conference lecture (invited) %@ %A Lendlein, A., Luetzow, K., Madbouly, S., Weigel, T., Reiche, J., Kratz, K., Tronci, G., Neffe, A.T. %D 2008 %J Biomechanics and Biology of Bone Healing, Symposium und Gruendung des Julius Wolff Instituts %T Formation of Foams from Biodegradable Artificial Materials and Biopolymers %U %X %0 conference lecture %@ %A Kratz, K., Voigt, U., Wagermaier, W., Lendlein, A. %D 2008 %J MRS Fall Meeting 2008, Symposium HH, Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging %T Shape-memory Properties of Multiblock Copolymers Consisting of Poly(?-pentadecalactone) Hard Segments and Crystallisable Poly(e-caprolactone) Switching Segments %U %X %0 conference lecture %@ %A Razzaq, M.Y., Behl, M., Kratz, K., Lendlein, A. %D 2008 %J MRS Fall Meeting 2008, Symposium HH, Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging %T Controlled Actuation of Shape-Memory nanocomposites by Application of an Alternating Magnetic Field %U %X %0 conference poster %@ %A Kratz, K., Reiche, J., Kulkarni, A., Lendlein, A. %D 2008 %J Polydays 2008 %T Biodegradation Behaviour of Thermo-Sensitive Dual Shape Polymers desired for Biomedical Applications %U %X %0 journal article %@ 1746-0751 %A Weigel, T., Kratz, K., Mohr, R., Lendlein, A. %D 2007 %J Regenerative Medicine %N 5 %P 712-713 %T Shape memory polymer nanocomposites responsive to alternating magnetic fields %U 5 %X Typically heat [1] or irradiation by light [2] is used to initiate the shape-shifting process. A remote triggering of the shape memory effect could improve the application possibilities decisively, and composites with magnetic nanoparticles should be able to trigger this effect by heating in alternating magnetic fields [3]. %0 journal article %@ 0743-7463 %A Kulkarni, A., Reiche, J., Kratz, K., Kamusewitz, H., Sokolov, I.M., Lendlein, A. %D 2007 %J Langmuir %N 24 %P 12202-12207 %R doi:10.1021/la701523e %T Enzymatic chain scission kinetics of poly(Epsilon-caprolactone) monolayers %U https://doi.org/10.1021/la701523e 24 %X The hydrolytic and enzymatic degradation behavior of poly(-caprolactone) (PCL) is investigated using the Langmuir monolayer technique, and an improved data acquisition and data reduction procedure is presented. Hydrolytic and enzymatic monolayer degradation experiments of PCL with various molecular weights by Pseudomonas cepacia lipase have been carried out to analyze the influence of subphase pH, subphase temperature, enzyme concentration, and the packing density of polymer chains on the degradation kinetics. The enzymatic monolayer degradation results in an exponential increase in the number of dissolved degradation fragments with increasing degradation time, which confirms random chain scission to be the dominant scission mechanism. The increase in the enzymatic scission rate constant with decreasing initial average molecular weight of the polymers is assigned to the influence of the area density of polar terminal groups on the substrate-enzyme complex formation. %0 conference lecture (invited) %@ %A Kratz, K., Reiche, J., Kulkarni, A., Lendlein, A. %D 2007 %J 3rd World Congress on Regenerative Medicine %T Biodegradation studies of aliphatic polyesters using the Langmuir monolayer technique %U %X %0 conference poster %@ %A Weigel, T., Kratz, K., Mohr, R., Lendlein, A. %D 2007 %J 3rd World Congress of Regenerative Medcine %T Shape-Memory Polymer Nanocomposites Responsive to Alternating Magnetic Fields %U %X %0 conference poster %@ %A Kratz, K., Mohr, R., Lendlein, A., Moneke, M., Lucka-Gabor, M. %D 2006 %J Polydays 2006 %T Properties of Shape-Memory Polymer Nanocompounds Responsive to Alternating Magnetic Fields %U %X %0 conference poster %@ %A Volkmann, A., Kratz, K. %D 2006 %J Intelligente Hydrogele, Schwerpunktprogramm %T Stimuli-sensitive Mikrogele als Modellsysteme für Molecular Imprinting – Vergleichende Untersuchungen zu Makrogelen gleicher Komposition %U %X %0 journal article %@ 0027-8424 %A Mohr, R., Kratz, K., Weigel, T., Lucka-Gabor, M., Moneke, M., Lendlein, A. %D 2006 %J Proceedings of the National Academy of Sciences of the United States of America: PNAS %N 10 %P 3540-3545 %R doi:10.1073/pnas.0600079103 %T Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers %U https://doi.org/10.1073/pnas.0600079103 10 %X triggering are comparable to those obtained by increasing the environmental temperature. %0 journal article %@ 0023-5563 %A Lendlein, A., Kelch, S., Kratz, K. %D 2006 %J Kunststoffe : KU %N 2 %P 54-59 %T Kunststoffe mit programmiertem Gedaechtnis: Implantate %U 2 %X Kunststoffe mit Formgedächtnis können sich an ihre ursprüngliche Form erinnern und nehmen diese nach Anwendung von Temperaturerhöhung oder Bestrahlung mit UV-Licht wieder ein. Bedeutung für die Medizintechnik, z.B. in der minimalinvasiven Chirurgie, haben besonders multifunktionale Materialien, die eine unerwartete Kombination von Funktionalitäten, wie Biofunktionalität, kontrollierte Wirkstofffreisetzung, Degradierbarkeit und Formgedächtnis, aufweisen. %0 journal article %@ 1862-4243 %A Lendlein, A., Kelch, S., Kratz, K. %D 2006 %J Kunststoffe International %N 2 %P 54-59 %T Implantats: Plastics with Programmed Memory %U 2 %X Plastics with shape-memory can "remember" their original shape and resume it again on exposure to heat or UV radiation. Multifunctional materials with an unexpected combination of functionalities, such as biofunctionality, controlled active ingredient release, degradability and shape-memory have a special importance for medical technology, e.g. in minimally invasive surgery. %0 journal article %@ 0032-1338 %A Kratz, K., Lendlein, A. %D 2006 %J Der Plastverarbeiter %N 4 %P 50 %T Rohstoffe - Beruehrungslos Verformen, Nanokomposite aendern ihre Form im Magnetfeld %U 4 %X eröffnen sich neue Einsatzmöglichkeiten in der Medizin. %0 conference poster %@ %A Reiche, J., Kulkarni, A., Hartmann, J., Kratz, K., Lendlein, A. %D 2006 %J 2nd International Symposium Interface Biology of Implants %T Monolayer Degradation Kinetics of Polymer Implant Materials %U %X %0 conference lecture %@ %A Reiche, J., Koehler, A., Kulkarni, A., Kratz, K., Lendlein, A. %D 2006 %J European Conference on Organized Films, ECOF-10 %T Degradation Kinetics of Polymers obtained via the Lanmuir-Monolayer method %U %X %0 conference lecture %@ %A Lucka-Gabor, M., Moneke, M., Mohr, R., Kratz, K., Weigel, T., Lendlein, A. %D 2006 %J Polydays 2006 %T Characterization of Morphology in Shape Memory Compounds and their Warming and Deformation Upon Inductive Heating %U %X %0 conference lecture %@ %A Kulkarni, A., Reiche, J., Koehler, A., Kratz, K., Hartmann, J., Lendlein, A. %D 2006 %J Polydays 2006 %T Chain Scission Kinetics of Polymers Derived from Langmuir-Monolayer- and Bulk Degradation %U %X %0 conference lecture %@ %A Kulkami, A., Reiche, J., Sokolov, I., Kratz, K., Lendlein, A. %D 2006 %J International Symposium Biomaterials and Hamburg Macromolecular Symposium 2006 %T Kinetics of enzymatic degradation of polymer monolayers %U %X %0 journal article %@ 1616-0177 %A Reiche, J., Kulkarni, A., Hartmann, J., Kratz, K., Lendlein, A. %D 2006 %J Biomaterialien %N S 1 %P 107 %T Monolayer Degradation Kinetics of Polymer Implant Materials %U S 1 %X No abstract %0 conference paper %@ %A Richau, K., Kosmella, H.-J., Ziegler, H.-J., Malsch, G., Kamusewitz, H., Kelch, S., Lendlein, A., Zierke, M., Kratz, K., Jarosz, G., Reiche, J. %D 2005 %J Poster-Abstracts, 2nd Max Bergmann Symposium at The Max Bergmann Center of Biomaterials Dresden %P 23 %T Characterization of the degradation behaviour of bioresorbable shape memory polymers %U %X %0 conference lecture %@ %A Richau, K., Kosmella, H.-J., Ziegler, H.-J., Malsch, G., Kamusewitz, H., Kelch, S., Lendlein, A., Zierke, M., Kratz, K., Jarosz, G., Reiche, J. %D 2005 %J 2nd Max Bergmann Symposium at The Max Bergmann Center of Biomaterials Dresden %T Characterization of the degradation behaviour of bioresorbable shape memory polymers %U %X %0 conference lecture %@ %A Tanioka, A., Ishiguro, T., Matsumoto, H., Minagawa, M., Richau, K., Kratz, K. %D 2005 %J American Society for Composites, 20th Annual Technical Conference %T Electrospinning of Biocompatible Shape-Memory Polymer %U %X %0 journal article %@ 1048-6690 %A Lendlein, A., Kratz, K., Kelch, S. %D 2005 %J Medical Device Technology %N 3 %P 12-14 %T Smart Implant Materials - Capabilities and applications of new biodegradable shape-memory elastomers %U 3 %X Biodegradable polymers are widely used as implant materials e.g. as surgical suture material. A group of biodegradable implant materials with shape-memory has been developed for applications in biomedicine. Biodegradable thermoplastic elastomers, as example for a biodegradable shape-memory polymer system, are presented and a smart suture is given as example for a potential application. The combination of stimuli-sensitive implant materials with techniques of minimally invasive surgery is expected to have high potential for applications. %0 conference lecture %@ %A Kelch, S., Kratz, K., Seifert, B., Lendlein, A. %D 2005 %J Jahrestagung der deutschen Gesellschaft fuer Chirurgie %T Entwicklung neuer, intelligenter Nahtmaterialien mit Formgedaechtniseffekt fuer die Visceralchirurgie %U %X %0 book part %@ %A Lendlein, A., Kelch, S., Kratz, K., Schulte, J. %D 2005 %J Encyclopedia of Materials: Science and Technology (Second Edition) %P 1-9 %R doi:10.1016/B0-08-043152-6/02033-7 %T Shape-memory Polymers %U https://doi.org/10.1016/B0-08-043152-6/02033-7 %X %0 journal article %@ 0921-4526 %A Havermeyer, F., Rupp, R.A., Schubert, D.W., Kraetzig, E. %D 2000 %J Physica B %P 330-331 %T Neutron diffraction from holographic gratings in PMMA %U %X %0 conference lecture %@ %A Havermeyer, F., Rupp, R.A., Schubert, D.W., Kraetzig, E. %D 1999 %J 2nd European Conference on Neutron Scattering, ECNS 99, Session C 04 %P 95 %T Neutron diffraction from holographic gratings in PMMA %U %X %0 conference lecture %@ %A Havermeyer, F., Pruner, C., Rupp, R.A., Kraetzig, E., Vollbrandt, J. %D 1999 %J Verhandlungen der Deutschen Physikalischen Gesellschaft, Fruehjahrstagung Leipzig %N 34 %T Untersuchung der Kinetik lichtinduzierter Gitter in PMMA mit Licht- und Neutronenbeugung %U 34 %X %0 conference lecture %@ %A Havermeyer, F., Pruner, C., Rupp, R. A., Kraetzig, E., Vollbrandt, J. %D 1999 %J Fruehjahrstagung der Deutschen Physikalischen Gesellschaft e. V. %T Untersuchung der Kinetik lichtinduzierter Gitter in PMMA mit Licht- und Neutronenbeugung %U