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

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.