Abstract: Self-polymerization of dopamine and immobilization of heparin were applied for surface-modification of titanium in order to improve its blood compatibility. Surface modification was developed via self-polymerization of dopamine and covalent graft of heparin. Surface elemental composition was analyzed qualitatively by X-ray photoelectron spectroscopy(XPS). Surface heparin content was detected by toluidine blue O(TBO). Surface hydrophilicity and hydrophobicity were characterized by water contact angle measurement. Hemolysis rate test, which was applied for detection ofhemolytic ability, was combined with activated partial thromboplastin time test(APTT) and platelet adhesion test to evaluate blood compatibility. The results showed that self-polymerization of dopamine was achieved on titanium surface. Heparin was successfully immobilized onto polydopamine layer by covalent graft. The heparin-modified surface could result in a significantly improved hydrophilicity, low hemolysis rate, prolonged APTT and a remarkablely decrease both in adhesion amount and activation degree of platelet. The blood compatibility of titanium could be significantly improved by the method of self-polymerization of dopamine and covalent graft of heparin. This study provides potential application for cardiovascular implants materials with anticoagulant properties.

Key words: Titanium, Dopamine, Heparin, Blood compatibility