Rapid Protein Fractionation with Tunable Amphiphilic Isoporous Block Copolymer Membranes

Isoporous block copolymer membranes have emerged as a promising platform for high-performance protein separation. However, it remains a significant challenge to achieve a robust protein fractionation system with both high selectivity and permeance. Herein, we established the tunable isoporous membranes derived from the amphiphilic polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) block copolymer. The membrane characteristics, i.e., pore size, surface porosity, hydrophilicity, and surface charge, were tuned by varying the PS-b-PHEMA molecular weight and composition. The protein separation performance of the designed tunable membranes was thoroughly investigated under application-relevant cross-flow mode by varying the cross-flow rate. Different mixed protein systems, including bovine serum albumin (BSA) and lysozyme (LZ), β-lactoglobulin (LG) and BSA, hemoglobin (HB) and BSA, were tested in a readily accessible and stable physiological buffer at pH = 7.4. The separation behavior is governed by the synergistic effects of size sieving, electrostatic interactions, and competition among the permeating proteins. The prepared membranes achieved an unprecedented selectivity of 88.8 and a high permeance of 67 L m⁻² h⁻¹ bar⁻¹ for the LZ/BSA protein mixture, overcoming the conventional trade-off between permeance and selectivity.