Temporary use – magnesium implants biodegrade systematically
In the course of the next four years, the first prototypes of biocompatible magnesium bone implants are to be tested and developed in the scope of the new EU project, “Tailored Biodegradable Magnesium Implant Materials”(MagnIM). This major three million euro project will be coordinated by the Helmholtz-Zentrum Geesthacht (HZG). The head of the HZG department “Structure Research on Macromolecules”, Prof. Dr. Regine Willumeit, will act as project leader. Researchers in Geesthacht have been engaged in the investigation and development of metallic biomaterials based on titanium and magnesium for some time now. Implants made from the light metal magnesium promote the regeneration of bone tissue and biodegrade in situ after a pre-defined period of time.
Screw Prototyp of Biodegradable Magnesium implants. Photo: HZG
Whether as the result of a sports accident or age-related degeneration, the demand for implants such as artificial joints, plates and screws to promote the healing of bone fractures is constantly increasing. Whereas the priority for hip replacements lies in their durability, it is advantageous in some areas if the implant biodegrades in a pre-determined manner. The application of such biomaterials is of special interest in pediatric surgery, as children are still in a state of growth. This also applies for the treatment of injuries in which, for example, ligaments have to be held in place temporarily. Prototypes of biodegradable implants made of magnesium alloys are to be tested in the scope of the new EU project MagnIM. Magnesium is an ideal choice as this element is a natural component of the human body and has, therefore, a particularly high degree of tolerance. Moreover, this material is both hard and malleable which means that it can be adapted to the specific requirements of the human skeleton.
The Participants of the first MagnIM-Meeting. Photo: HZG
Prof. Dr. Regine Willumeit explains the most important considerations in the development of prototypes as follows: “We need materials which are very stable and can provide high mechanical strength over a relatively long period of time.
In the healing process it should be possible for the implant to be totally resorbed i.e. assimilated into the bone.
The bone then takes the place of this implant and it is to be expected that it is no longer possible to determine whether a magnesium implant has previously been fitted to the bone or not.”
Before this stage is reached, however, there is still a great deal of development work on the scientists’ research schedule. As Dr. Norbert Hort, Head of the HZG Magnesium Technology department comments, “The alloying elements e.g. gadolinium from the field of rare earths, ensure, amongst other things, systematic degradation through corrosion. The structural and surface properties are also important in order to promote the in-growth of bone cells. Moreover, only materials which do not entail a health risk can be incorporated. Aluminium, for example, can be ruled out as an alloy partner.”
An important part of Regine Willumeit’s work, therefore, involves cell experiments to test biological tolerability. Do the cells survive contact with the metal? Under which conditions does corrosion take place and how long does the decomposition take? A bioreactor, specially developed in Geesthacht, runs the tests in a manner which is close to reality. From the total of 3.1 million euro granted by Brussels, the researchers in Geesthacht have approximately 1.2 million euro at their disposal for their investigations. Dr Willumeit adds, “In addition to the development of alloys and the extension of the laboratory experiments, we want to use this money to promote three young scientists at the HZG. It is our wish to support committed young people, who are pursuing their doctoral studies in this seminal field of materials research”.
Materials research in Geesthacht
The magnesium-based alloys are developed in the Magnesium Technology department under the direction of Dr. Norbert Hort. The department headed by Prof. Dr. Regine Willumeit is engaged in cell experiments to research the compatibility of the alloys. They are supported by scientists from Leuven and Prague. Medical doctors at the universities of Graz in Austria and Malmö in Sweden will, amongst other investigations, carry out tolerability tests on rats. Furthermore, there are industrial partners based in Germany and Finland. The implant prototypes will be manufactured by these medical technology companies.