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

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.