Assessment of the genotoxic potential of two zinc oxide sources (amorphous and nanoparticles) using the in vitro micronucleus test and the in vivo wing somatic mutation and recombination test

- ZnO NPs, in V79 cells, were toxic at concentrations equal to or higher than 240.0 μM.
- ZnO NPs, in V79 cells, were genotoxic at 120.0 μM but not cytotoxic.
- Amorphous ZnO and ZnO NPs were not mutagenic in the ST cross of SMART.
- In HB cross, ZnO (6.25 mM) and ZnO NPs (12.50 mM) increased mutant spots.
- Mutagenicity of ZnO may depend on the concentration, size and/or particle shape.

In this study, we evaluated the toxic and genotoxic potential of zinc oxide nanoparticles (ZnO NPs) of 20 nm and the mutagenic potential of these ZnO NPs as well as that of an amorphous ZnO. Toxicity was assessed by XTT colorimetric assay. ZnO NPs were toxic at concentrations equal to or higher than 240.0 μM. Genotoxicity was assessed by in vitro Cytokinesis Block Micronucleus Assay (CBMN) in V79 cells. ZnO NPs were genotoxic at 120.0 μM. The mutagenic potential of amorphous ZnO and the ZnO NPs was assayed using the wing Somatic Mutation and Recombination Test (SMART) of Drosophila melanogaster. In the Standard cross, the amorphous ZnO and ZnO NPs were not mutagenic. Nevertheless, Marker trans-heterozygous individuals from the High bioactivation cross treated with amorphous ZnO (6.25 mM) and ZnO NPs (12.50 mM) displayed a significant increased number of mutant spots when compared with the negative control. In conclusion, the results were not dose related and indicate that only higher concentrations of ZnO NPs were toxic and able to induce genotoxicity in V79 cells. The increase in mutant spots observed in D. melanogaster was generated due to mitotic recombination, rather than mutational events.