Titanium dioxide nanomaterials - induced DNA damage in intestinal cells following simulated in vitro digestion

Introduction: The increased use of titanium dioxide nanomaterials (TiO2) in food products has raised oral exposure to those nanomaterials, with subsequent risks to human health, particularly genotoxicity and, ultimately, cancer development. In humans, the digestion process may modify the physicochemical properties of TiO2, thereby shaping the potential biological outcomes. Thus, such process should be considered when assessing their hazard upon oral exposure. This work aimed to investigate the genotoxic effects of three TiO2 (NM-102, NM-103 and NM-105, JRC repository) after the simulation of the human digestive process using the standardized INFOGEST in vitro digestion method. The secondary physicochemical properties and DNA damage levels, using the comet assay, were analysed in two intestinal cell lines exposed for 24h to digested or undigested TiO2. Results: An increase in the level of DNA strand breaks in two intestinal cell lines(Caco-2 and HT29-MTX-E12) was observed after exposure to digested NM-105, concomitantly with a decrease in its hydrodynamic size, comparatively to the undigested nanomaterial. Moreover, the digested NM-103 induced DNA damage in Caco-2 cells whereas the undigested nanomaterial did not. The FPG-modified comet assay also revealed an increase in oxidative DNA lesions upon treatment of Caco-2 with NM-103 and HT29-MTX-E12 with NM-102. Conclusions: One of the digested TiO2(NM-105) can be classified as potentially genotoxic in both cell lines, while the digested NM-103 induced an equivocal genotoxic response in Caco-2 cells. Therefore, the digestion simulation is of relevance to investigate the potential genotoxic effects of ingested nanomaterials.