Fig. 1

Cellular uptake and cytotoxicity of ZnO NPs by HEK-293 cells. a TEM analysis of ZnO NP morphology. ZnO NPs were mainly spherical in shape. The scale bar represents 100 nm. b Cell viability was measured using the MTS assay. ZnO NPs decreased the viability of HEK-293 cells in a concentration-dependent manner. The cells were treated with 0, 15, 20, 25, 30 or 35 μg/ml ZnO NPs for 24 h. All of the MTS values were normalized to the control values (no particle exposure), which were regarded as 100 % cell viability. *p < 0.05 versus control. c Uptake of ZnO NPs detected by fluorescence confocal microscopy. ZnO NPs are shown in red and DAPI (blue) is a nuclei-specific marker. The cells were treated with 20 μg/ml ZnO NPs for 8 h. d, The results of the SSC data and flow cytometry demonstrated that ZnO NPs were apparently engulfed by HEK-293 cells. e Quantification of the scatter intensity in HEK-293 cells with ZnO NP treatment. The cells were treated with ZnO NPs at 0, 15, 20, or 25 μg/ml for 24 h. The data are presented as the mean ± standard deviation of three independent experiments