Hemocompatibility Investigation Of TI-O Thin Films By Ion Implantation

Improving the thromboresistance of cardiovascular biomaterials is an essential problem in biomaterial field. It is influenced by the material surface properties such as surface wettability, surface energy and surface charge. Accordingly, surface modification is regarded as a significant means to improve the thromboresistance of cardiovascular biomaterials. To thoroughly study the interfacial interaction between biomaterial surface and blood and ulteriorly recognize the surface modification mechanism of anti-coagulation materials are a greatly arduous task for researchers. The Titanium oxide(Ti-O) films such as TiO_2-x and H, P, Ta, Nb doped Ti-0 have been proved an outstanding thromboresistance, in addition, these films have a common characteristic of n-type semiconductor. Thereby, the motive of this paper is to develope donor doped Ti-0 films with good thromboresistance, investigate the influence of ion implantation doping on the thromboresistance of Ti-0 film, reveal the thromboresistant mechanism of inorganic films, and direct the design of thromboresistant inorganic films.In this paper, a series of TiO₂ films were obtainted by magnetron sputtering, additionally, phosphorus /aluminium ions were implanted and then annealed in vacuum to adjust their thromboresistant properties. X-ray photcelectron spectrum was used to analyze the bonding and composition of the films both at surfaces and interfaces. Sheet resistence test was applied to characterise the conductivity of these films after annealling. Apart from above tests, the surface energy was evaluated by a contact angle test using the sessile drop method on the contact angle goniometer. Moreover, to research the thromboresistant mechanism, asystem of thromboresistant tests has been applied to evalute the thromboresistance of these doped films.The research reveals that phosphorus doping was activated with the increasing of annealing temperature, accompanying with the increase of conductivity. Phosphorus was re-distributed in the film after annealing at 800 degree and the phosphorus doped Ti-0 film was obtained, furthermore, the thromboresistance has been improved. The re-distribution of phosphorus caused changes of oxide adsorption at surface, suddenly raising of hydrophilicity, the increase of the ratio of polar component to dispersive component and the base component of surface tension.The result shows that the interaction behavior at blood/Ti-O film interfaces is different between phosphorus and aluminium doped Ti-0 films. Fibrinogen absorption/denaturation and platelet adhesion / activation was slight at the surface of phosphorus doped Ti-0 films, and clotting factor was not activated. In contrast, the aluminium doped Ti-0 films cause serious absorption/denaturation of fibrinogen and platelet adhesion / activation, additionally, to some extent, the activatation of clotting factor was caused.The research shows that the phosphorus doped Ti-0 films have excellent thromboresistance, which is mainly because of inhibiting the electron transfer from the fibrinogen to the surface of the film, thus blocking the denaturation of fibrinogen and decreasing the level of platelet adhesion / activation. Consequently, the thromboresistace of the Ti-0 thin film, which is n-type semiconductor, was improved.