Antibacterial Properties of TiO₂ Layers Formed by Au-Sputtering and Thermal Oxidation of Titanium under Visible Light

Abstract

To prevent infection in dental implants using photocatalytic activity under visible-light irradiation, the fabrication of Au-added TiO₂ layers on Ti substrates and their antibacterial properties were studied. Pure Au and Ti–(60, 40) mol%Au alloy films with thicknesses of 10–47 nm were sputtered onto Ti, followed by thermal oxidation in air at 873 K for 1.8 ks to form TiO₂ layers. The antibacterial properties against Escherichia coli, cytotoxicity, and bonding strength to Ti substrates were evaluated. The highest antibacterial activity under visible-light irradiation was obtained when the sputtered film was pure Au and its thickness was 38 nm. Compared with as-polished commercially pure Ti, the number of viable mouse osteoblast-like cells and human gingival fibroblasts on Au-added TiO₂ layers increased after placement in the dark but decreased after visible-light irradiation. The best antibacterial property-bonding strength balance was achieved when the Ti–40 mol%Au sputtered film with a thickness of 42 nm was formed on Ti. To the best of our knowledge, this study is the first to report the formation of TiO₂ layers with antibacterial activity under visible-light irradiation by combining Au-sputtering and thermal oxidation of Ti.