Nitrogen-doped TiO2 films as drug-binding matrices for the preparation of drug-eluting stents

Abstract

Nitrogen doped-TiO2 thin film was deposited by plasma enhanced chemical vapour deposition (PECVD) process and its applicability as a drug-binding matrix was investigated in the preparation of drug eluting stents. N–TiO2 film was deposited at 5 W and uniformly covered metallic stent surfaces. Films showed excellent mechanical stability and good adhesion. Alpha lipoic acid, heparin, and abciximab could then be grafted onto the N–TiO2 film through ester bond formation after water plasma modification of the films' surfaces. Drug-grafted N–TiO2 films showed smooth surfaces and good blood compatibility in in vitro platelet adhesion tests. The films maintained uniform coverings, without peeling, even after expansion by a balloon catheter. Grafted-heparin and abciximab could be released continuously for three weeks from drug-grafted N–TiO2 stents in in vitro drug release test. Such immunosuppressive and antiproliferative drug-grafted N–TiO2 film is expected to minimize potential problems related to organic polymers and the risk of direct contact of a bare metal surface with a blood vessel. Hence, the N–TiO2 films prepared in this study are promising alternatives to organic polymers for the preparation of drug-eluting stents.