The Studies Of Titanium Oxide Films Modification On Vascular Stent Surface

Vascular stents are widely used in intervention treatment, and stents implantation became a standard surgery of coronary angioplasty. However, in-stent restenosis introduced by tissue hyperplasia and thrombosis is the major problem in clinic application. Drug-eluting stents have been reported that thrombosis was formed in months after implantation.Stent coated with thin film can resolve the thrombosis problem. But bad adhesion is an obstacle to thin film for being applied on the surface modification of stent. And the reactive mechanism between biomaterials and blood is still unclear until now.In this paper, Ti-O films were deposited by unbalanced magnetron sputtering. Adhesion of Ti-O films on 316L stainless steel substrate was investigated by tensile test. The results indicate that adhesion of TiO₂ film is better than adhesion of TiO film. The adhesion of the Ti-O film deposited at 400℃is better than those deposited at 50℃and 200℃. The adhesion of Ti-O film applied 50V bias voltage is better than the one applied 150V bias voltage. Thickness of films affects its adhesion on substrate. The adhesion of the 88nm thick Ti-O film is better than the 270nm thick one. Ti interlayer can improve adhesion of Ti-O film on stainless steel substrate. The adhesion of the Ti-O film with Ti interlayer is better than the one without Ti interlayer. The investigation of TiO₂ adhesion on the surface of vascular stents indicates that the adhesion of the thinner Ti film is better than that of the thicker films. The result indicates that the adhesion of the TiO₂ film fabricated at lower deposition rate is better than the one deposited at higher deposition rate. The adhesion of the films decreased as the Ti interlayer thickness increasing.In this paper, Ti-O-N films with different structures and compositions were synthesized on silicon wafer by reactive unbalanced magnetron sputtering. By controlling the proportion of N₂ in the reactive gas (O₂+N₂), Ti-O-N films with different structures, composites, properties and blood compatibilities were obtained. With increasing proportion of N₂, the structure of Ti-O-N film changes from anatase and rutile to Ti₃O₅, finally to TiN. XPS results reveal that the content of nitrogen in the films increased with increasing proportion of N₂. The band gap and the sheet resistance of Ti-O-N films decreased with the increasing content of nitrogen inside Ti-O-N films. After ultraviolet radiation of two hours, water contact angle of Ti-O-N films decreases and the surface energy increases. The blood compatibility of Ti-O-N films is worse than TiO₂ film. After ultraviolet radiation of two hours, the blood compatibility of Ti-O-N films is obviously improved.