Ultraviolet irradiation confers titanium oxide oleophilicity

Ultraviolet irradiation confers titanium dioxide amphiphilicity. Unlike the UV-induced hydrophilic properties that had a long history of academic interest, oleophilicity has not received much attention. This study aims to investigate the molecular evidence of lipid adsorption onto UV-treated TiO₂ surface by in vitro and in silico approaches. Artificial lipid vesicles were fabricated for empirical confirmation of the increased oleophilicity of the TiO₂ surface after UV irradiation and in silico model was developed for computational simulation of the underlying molecular dynamics. After UV treatment and application of a synthetic liposome solution, the TiO₂ surfaces were analyzed for surface roughness and the trace of lipid molecules by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and fluorescence confocal microscopy. The surface roughness was reduced and the increased liposome residues on the surface of TiO₂ were observed after UV irradiation. The in silico simulation of molecular dynamics predicted higher non-covalent bonding energy to phospholipids and a closer atomic distance between the lipid molecules and the TiO₂ surface after UV irradiation. These data suggested that UV irradiation enhanced the oleophilicity of the TiO₂, presumably by the result of the hydrogen bonds between lipid and TiO₂. Further studies on the oleophilicity of TiO₂ are required to elucidate the osseointegration process of UV-treated implant fixtures in hyperlipidemic patients.