Short Preirradiation of TiO2Nanoparticles Increases Cytotoxicity on Human Lung Coculture System

Anatase titanium dioxide nanoparticles (TiO2NPs) are used in a large range of industrial applications mainly due to their photocatalytic properties. Before entering the lung, virtually all TiO2NPs are exposed to some UV light, and lung toxicity of TiO2NPs might be influenced by photoexcitation that is known to alter TiO2surface properties. Although the TiO2NPs toxicity has been extensively investigated, limited data are available regarding the toxicity of TiO2NPs that have been pre-exposed to UV light, and their impact on humans remains unknown. In this study, five types of TiO2NPs with tailored physicochemical features were characterized and irradiated by UV for 30 min. Following irradiation, cytotoxicity, pro-inflammatory response, and oxidative stress on a human lung coculture system (A549 epithelial cells and macrophages differentiated from THP-1 cells) were assessed. The surface charge of all samples was less negative after UV irradiation of TiO2NPs, and the average aggregate size was slightly increased. A higher cytotoxic effect was observed for preirradiated TiO2NPs compared to nonirradiated samples. Preirradiation of TiO2NPs had no significant impact on the pro-inflammatory response and oxidative stress as shown by a similar production of IL-8, TNF-α, and reactive oxygen species.