Biological responses at the interface of Ti-doped diamond-like carbon surfaces for indoor environment application

Diamond-like carbon (DLC) and titanium-doped DLC coatings were prepared by hybrid PECVD/direct current magnetron sputtering (DCMS). In this study, we show that the operating conditions of titanium-doped DLC coatings used for implants in surgical devices significantly modify their surface properties and consequently their interaction with cells. The coatings showed uniform distribution on the substrate and their biocompatibility was tested by way of rat calvaria osteoblasts. Doping DLC with Ti changed the roughness and wettability of the film interface. The autoclaving of the samples led to the surface oxidation and the formation of TiO₂ on the top-most layers of Ti-doped DLC. This was quantitatively assessed by X-ray photoelectron spectroscopy (XPS) and revealed the presence of Ti³⁺ and Ti⁴⁺ species in redox reactions during their interactions with cells. By XPS analysis, the oxidative carbonaceous species C=O and O=C-C were detected during the bacterial inactivation. Reactive oxygen species (ROS) were identified on the sputtered samples and the ^⦁OH radical was identified as the most important oxidative radical intermediate leading to bacterial disinfection. The position of the intra-gap of the oxidized C species is suggested within the TiO₂ bandgap.