Study On Bio-modified TiO₂ Thin Films Prepared On The Surface Of Nanostructured Titanium

The biomedical metallic materials used in the areas of vascular stent mainly contain biomedical stainless steel,titanium and cobalt alloy. However,all of these materials can't meet the needs of clinical application, for example,extravasation of nickel from stainless steel may lead to hidden trouble and knub;vanadium contained in the titanium alloy can cause malignant tissue reaction etc;clinical application shows that cobalt alloy might result in restenosis after insertion.Therefore,to research and develop advanced interventional materials for human body becomes hotspot. Recently,as the development of research,nanostructured titanium has provided advantages to solve the problems mentionded above,but its biocapability(bioactivity and biocompatibility) needs to be further improved.Research shows that the anticoagulation property of TiO₂ film is even better than hydrolytic carbon of clinical application.Common methods of preparation TiO₂ thin film include sol-gel,micro arc oxidation,magnetron sputtering etc.However,the thickness of TiO₂ thin film prepared by sol-gel method is difficult to control;deposition temperature of micro arc oxidation may exceed 3000 Degree Centigrade,which can destroy the structures and properties of nanostructured titanium.This paper prepares TiO₂ films by magnetron sputtering on the surface of nanostructured titanium at a low temperature to modify its biocompatibility and bioactivity.The effect of the parameters for DC magnetron sputtering on the structure and surface morphology of TiO₂ thin films was systematically studied in this paper by X-ray diffraction and Raman spectra(XRD) and scanning electron microscope(SEM);mechanical properties were researched by scratch test detector,friction and wear test detector;and biocapabilities of TiO₂ thin films were also tested by Simulated Body Fluid (SBF),dynamic clotting time and platelet adhesion in vitro respectively. Research reveals that the best technical parameters of preparing TiO₂ thin films are under the power of 160W,the gas pressure of 1.0Pa,the time of 2.5h,the temperature of 125 Degree Centigrade,the O₂/Ar ratio of 1:3 and the distance of substrate-to-target of 80mm.Result of XRD shows that crystalline structure of this film under the technical parameters is an admixture of Anatase and Rutile,with fine grains,low friction coefficient of some 0.08,high adherence between TiO₂ films and nanostructured titanium substrate of 73N.The results for the tests of SBF,dynamic clotting time and platelet adhesion in vitro indicate that the compositor for biocapability of different samples are as follows:TiO₂ thin film on the surface of nanostructured titanium＞TiO₂ thin film on the surface of traditional titanium＞nanostructured titanium＞traditional titanium. Therefore,conclusion can be made that TiO₂ films prepared by magnetron sputtering on the surface of both nanostructured titanium and traditional titanium have improved their bioactivity and biocompatibility obviously, and the TiO₂ film on the surface of nanostructured titanium has better biocapability.