Fig. 3

The role of zinc ions in ZnO NPs-induced oxidative stress. a Intercorrelation of cell viability and intracellular free zinc ions levels after exposure to ZnO NPs for 24 h. b Effect of TPEN on the cytotoxicity of ZnO NPs by PI staining. Cells were pretreated with the indicated doses of TPEN for 30 min, and then incubated with 15 μg/mL ZnONPs for 6 h. Effect of TPEN on intracellular zinc ions by zinc ions indicator Fluor™ Zn-520, AM staining (c) and ROS level by DCFH-DA staining (d) in ZnO NPs-treated PC12 cells. Cells were pretreated with 4 μM TPEN for 30 min, followed by exposure to 15 μg/mL ZnO NPs for 6 h. e Effects of NAC and TPEN on the cytotoxicity of ZnO NPs by CCK8 assay. Cells were pretreated with 2 mM NAC or 4 μM TPEN for 30 min, and then cell viability was determined at 12 h after 15 μg/mL ZnO NPs exposure. Data from at least three independent experiments were expressed as the means ± SD. *p < 0.05, **p < 0.01, ***p < 0.001 compared with the untreated control