Surface Characterization and Hemocompatibility of Heparinized 316l Stainless Steel

Poor compatibility between blood and metallic coronary artery stents is one reason for arterial restenosis. Immobilization of heparin on stent's surface is feasible for improving compatibility. We examined possible surface- coupling agents for anticoagulant agent immobilization. Hexamethylene diisocyanate (HMDI) was examined as surface- coupling agent to activate 316L stainless steel (e.g. stent material). Afterwards, we grafted PEG on the HMDI activated surface to provide heparin with higher conformational freedom and a more hydrophilic environment. The effectiveness of HMDI activated and PEG grafted surface was confirmed by FTIR, XPS, and water contact angle test. Heparin was then immobilized onto the activated 316L stainless steel. The heparin surface density was 9.5 mu g/cm (2). Sessile drop water contact angles showed that the heparin- grafted surface is even more hydrophilic than the PEG grafted one. The function of grafted heparin was evaluated by antithrombrin III (ATIII) adsorption testing and SEM. The surface with heparin grafting shows better ATIII binding ability and hemocompatibility than the native one.