Electrochemical Investigation Of Anti-Thrombogenic Ti-O Film

Ti-O film was widely accepted as a bio-compatible inorganic material particularly for anti-thrombogenic surface modification of cardiovascular implants such as artificial heart valves and vascular stents. Nevertheless the underlying mechanism of anti-thrombogenicity remains unclear up to now. In order to research the Electrochemical behaviors of Ti-O anticoagulation films, Ti-O Films with different composition, structure were deposited on Ti by unbalanced magnetron sputtering system, the phase structure and composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. The surface resistisity and band gap were characterized through four probe method and optical analysis respectively. In vitro blood compatibilities were evaluated by platelets adhesion testing, LDH test and fibrinogen denaturation test. Electrochemical impedance spectroscopy (EIS) and Mott-schottky measurements were used to investigate the interfacial electrochemical behaviors. The main results obtained and conclusions reached in this research are as follows:XPS results dictated that all the films were nonstoichiometric titanium oxides and the O/Ti ratio was reduced from 1.83 to 1.80 and 1.78 with decreasing of oxygen partial pressure. XRD patterns dictated that mixture structure existence of rutile TiO2 and anatase TiO2 phases were obtained at higher oxygen pressure, while Ti2O3 and TiO structure achieved at lower oxygen pressure.In-vitro blood compatibility evaluations showed that Ti-O films with defined characteristics of O/Ti ratio 1.80, mixed crystalline structures of rutile and anatase TiO2, Ti2O3 phase, and exhibit significantly lower thrombotic reactions compared with others.According to electrochemical impedance spectroscopy (EIS) and Mott-schottky results, the Ti-O films show also typical n type semiconducting characteristic with relatively high space charge layer carrier concentration about 5.6～7.4×1020cm-3, as well as comparatively negative values of flat-band potential Efb of around-1.14V vs. S.C.E. in fibrinogen containing(2mg/mL) PBS solutions.Based on the semiconductor electrochemistry theory:the Ti-O film owns higher surface conduction band Esc, thus there is little probability of charge transfer from fibrinogen to the conducting band of Ti-O film from the thermodynamic perspective. Accordingly, the charge transfer from the fibrinogen (as the first coagulating factor) to the film can, therefore, be effectively impeded owing to the negative flat-band potential corresponding to the high energy level of Esc.