Preparation of a drug-eluting stent using a TiO2 film deposited by plasma enhanced chemical vapour deposition as a drug-combining matrix

Abstract

A TiO₂ thin film was deposited onto a bare metal stent by the plasma enhanced chemical vapour deposition (PECVD) process and its potential as a drug-combining matrix was investigated. When deposited at a discharge power of 5 W, the film showed a highly smooth surface with a surface roughness of 9.4 nm, mechanical stability with good adhesion, and good blood compatibility. The film was surface-modified with water plasma to introduce hydroxyl groups on the TiO₂ surface. Then, drugs could be chemically grafted to the modified surface through the formation of ester bonds between hydroxyl groups on the modified TiO₂ film and carboxyl groups in the drugs. When heparin, α-lipoic acid, and abciximab were grafted onto the TiO₂-deposited and surface-modified stents, the grafted amount was measured to be 106.1 μg for α-lipoic acid, 32.5 μg for abciximab, and 53.9 μg for heparin on average. In the in vitro drug-release test, heparin and abciximab were released continuously for 4 weeks but ALA showed a burst release within 6 days.