Fig. 6
Cytotoxicity and genotoxicity responses in HepG2 spheroids following a prolonged (120 h) exposure using a single, bolus dosing regimen or a fractionated, repeated dosing regimen with 0.5 and 5.0 µg/mL of TiO2 and ZnO ENMs. Cytotoxicity was assessed using the trypan blue exclusion assay and is presented relative to the negative, untreated control. A known liver carcinogen, aflatoxin B1 (0.1 µM) was used as a positive control for genotoxicity. For acute exposures, 1000 binucleated cells were scored per replicate for each dose point using the cytokinesis-block version of the MN assay (2000 binucleate cells scored in total per dose). For prolonged exposures, 2000 mononucleated cells were scored per replicate for each dose point using the mononuclear MN assay (4000 mononucleate cells scored in total per dose). Mean data of two and three biological replicates (n = 2, n = 3) for genotoxicity and cytotoxicity respectively is presented ± SD. Significance indicated in relation to the negative control: * = p ≤ 0.05