Plasma protein adsorption and thrombus formation on surface functionalized polypyrrole with and without electrical stimulation

A surface modification technique was developed in which heparin was covalently immobilized onto electrically conductive polypyrrole (PPY) film through poly(ethylene glycol) methacrylate (PEGMA) graft copolymerization and subsequent cyanuric chloride activation. In vitro plasma protein adsorption and thrombus formation experiments were carried out on the various films. The PEGMA-graft-copolymerized PPY surfaces with immobilized heparin have good bioactivity indicated by low level of protein adsorption, high ratio of albumin to fibrinogen adsorption, and low thrombus formation, making them potentially good candidates for biomedical applications. Since the PPY film retained significant electrical conductivity after surface modification, the effect of electrical stimulation on protein adsorption and thrombus formation was also evaluated. The covalently immobilized heparin on the PPY film was able to retain its bioactivity after 4 days of immersion in PBS. The film after long-term immersion in PBS also retained sufficient electrical conductivity for electrical stimulation still to be effective for reducing protein adsorption.