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Anatase titanium dioxide nanoparticles (TiO 2 NPs) are used in a large range of industrial applications mainly due to their photocatalytic properties. Before entering the lung, virtually all TiO 2 NPs are exposed to some UV light, and lung toxicity of TiO 2 NPs might be influenced by photoexcitation that is known to alter TiO 2 surface properties. Although the TiO 2 NPs toxicity has been extensively investigated, limited data are available regarding the toxicity of TiO 2 NPs that have been pre-exposed to UV light, and their impact on humans remains unknown. In this study, five types of TiO 2 NPs 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 TiO 2 NPs, and the average aggregate size was slightly increased. A higher cytotoxic effect was observed for preirradiated TiO 2 NPs compared to nonirradiated samples. Preirradiation of TiO 2 NPs 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.

The concern about titanium dioxide nanoparticles (TiO 2 -NPs) toxicity and their possible harmful effects on human health has increased. Their biological impact is related to some key physicochemical properties, that is, particle size, charge, crystallinity, shape, and agglomeration state. However, the understanding of the influence of such features on TiO 2 -NP toxicity remains quite limited. In this study, cytotoxicity, proinflammatory response, and oxidative stress caused by five types of TiO 2 -NPs with different physicochemical properties were investigated on A549 cells used either as monoculture or in co-culture with macrophages differentiated from the human monocytic THP-1 cells. We tailored bulk and surface TiO 2 physicochemical properties and differentiated NPs for size/specific surface area, shape, agglomeration state, and surface functionalization/charge (aminopropyltriethoxysilane). An impact on the cytotoxicity and to a lesser extent on the proinflammatory responses depending on cell type was observed, namely, smaller, large-agglomerated TiO 2 -NPs were shown to be less toxic than P25, whereas rod-shaped TiO 2 -NPs were found to be more toxic. Besides, the positively charged particle was slightly more toxic than the negatively charged one. Contrarily, TiO 2 -NPs, whatever their physicochemical properties, did not induce significant ROS production in both cell systems compared to nontreated control groups. These results may contribute to a better understanding of TiO 2 -NPs toxicity in relation with their physicochemical features.