Effects of a Titanium Dioxide Thin Film for Improving the Biocompatibility of Diamond-Like Coated Coronary Stents

This study was performed to evaluate the effects of a diamond-like carbon (DLC) layer on the biological properties of a pre-treated titanium dioxide (TiO₂) coronary stent surface. TiO₂ and DLC were coated onto a cobalt-chromium stent surface in consecutive order using the plasma-enhanced chemical vapor deposition method (TiO₂/DLC). To investigate the effect of TiO₂, a group treated only with DLC was also prepared as a control. The surface characteristics were investigated by SEM, ESCA, AFM, and contact angle analyses. To estimate the effect of surface modification on biological response, endothelial cell migration was carried out. As a result, cracking of the coating layer on the strut curved portion in the DLC group was restored in the TiO₂/DLC group. ESCA result showed that the peaks sp² and sp³ were slightly shifted and higher in the TiO₂/DLC group. The surface roughness average was highly increased in the TiO₂/DLC group (Ra; 18.033) compared to the BMS (Ra; 9.258) and DLC groups (Ra; 10.144). By the increment of Ra, the surface property became hydrophilic in the TiO₂/DLC group (39.8° ± 5.88°) compared to the non-treated (72.7° ± 2.24°) and DLC (78.6° ± 2.24°) groups. Endothelial cell migration was significantly increased in the TiO₂/DLC group (68.9 ± 13.52%) compared to the non-treated (5.4 ± 3.14%) and DLC groups (22.3 ± 8.22%). Therefore, the improvement of surface properties and endothelial cell migration in the TiO₂/DLC group could improve the physiological response in the human body.