Genotoxic testing of titanium dioxide anatase nanoparticles using the wing-spot test and the comet assay in Drosophila

Abstract Titanium dioxide nanoparticles (TiO 2 NPs) are widely used for preparations of sunscreens, cosmetics, food and personal care products. However, the possible genotoxic risk associated with this nano-scale material exposure is not clear, especially in whole organisms. In the present study, we explored the in vivo genotoxic activity of TiO 2 NPs as well as their TiO 2 bulk form using two well-established genotoxic assays, the wing spot test and the comet assay in Drosophila melanogaster . To determine the extent of tissue damage induced by TiO 2 NPs in Drosophila larvae, the trypan blue dye exclusion test was also applied. Both compounds were supplied to third instar larvae by ingestion at concentration ranging from 0.08 to 1.60 mg/mL. The results obtained in the present study indicate that TiO 2 NPs can reach and induce cytotoxic effects on midgut and imaginal disc tissues of larvae, but they do not promote genotoxicity in the wing-spot test of Drosophila . However, when both nano- and large-size forms of TiO 2 were evaluated with the comet assay in Drosophila hemocytes, a significant increase in DNA damage, with a direct dose-response pattern, was observed for TiO 2 NPs. The results obtained with the comet assay suggest that the primary DNA damage associated with TiO 2 NPs exposure in Drosophila could be associated with specific physico-chemical properties of nano-TiO 2 , since no effects were observed with the bulk form. This study remarks the usefulness of using more than one genetic end-point in the evaluation of the genotoxic potential of nanomaterials.