Antithrombogenic investigation of surface energy and optical bandgap and hemocompatibility mechanism of Ti(Ta⁺⁵)O₂ thin films

Recent improvements in the antithrombogenic properties of blood contacting biomaterials permit a hybrid design of layers for biomedical applications such as artificial heart valves and stents. Using magnetron sputtering and thermal oxidation, titanium oxide thin films containing tantalum, Ti(Ta⁺⁵)O₂, are fabricated to meet the challenge of enhanced hemocompatibility. The blood compatibility is evaluated in vitro by clotting time and platelet adhesion measurement, and in vivo experiments are also conducted. The Ti(Ta⁺⁵)O₂ films exhibit attractive blood compatibility exceeding that of low isotropic pyrolytic carbon. Physical properties such as surface energy and semiconductivity are found to play important roles. Our calculated results reveal that the smaller surface force γ_s of the film and the smaller blood/film interfacial tension γ_c.blood are partially responsible for the enhancement of the blood compatibility. Based on the optical bandgap model, the film possesses better hemocompatibility because its optical bandgap of 3.2eV is wider than that of fibrinogen having a bandgap of 1.8eV. These factors result in thinner protein layers on the film surface, less protein denaturing, and overall excellent antithrombogenic properties. Copyright © 2002 Elsevier Science Ltd.