Surface modification of PVDF porous membranes via poly(DOPA) coating and heparin immobilization

Based on the strong adhesive behavior of poly(3,4-dihydroxy-l-phenylalanine) (or poly(DOPA)) on solid surface, poly(vinylidene fluoride) (PVDF) microporous membranes were surface-modified by the self-polymerization of DOPA in aqueous solution. Subsequently, heparin was immobilized covalently onto the obtained PVDF/poly(DOPA) composite membranes by the coupling between heparin and poly(DOPA) coating. The modified membranes were subjected to a long-term washing, and the firm immobilization of poly(DOPA) and heparin was confirmed by X-ray photoelectron spectroscopy (XPS). The results of water contact angle measurements showed that the hydrophilicity of PVDF membranes was significantly improved by the incorporation of poly(DOPA) and heparin. The effects of poly(DOPA) and heparin on membrane surface morphologies were also investigated by scanning electron microscopy (SEM).