Abstract: OBJECTIVE: To compare the cytotoxicity and DNA damage caused by nano- and micro- zinc oxide particles. METHODS: Cultured A549 human lung adenocarcinoma cells were exposed to nano- (30 nm) and micro-scale ZnO particles(≤1 μm) at the concentrations of 25, 50 and 100 μg/ml for 6, 12, 24 and 48 h. In the mean time, DMEM culture medium was set up as control. Morphological changes were examined after exposure, methyl tetrazolium cytotoxicity (MTT) assay and the single cell gel electrophoresis(comet assay) were used to determine cytotoxicity and DNA damage. RESULTS: The IC50 of the nano-ZnO and micro-ZnO on the A549 cells were 53.91 and 190.15 μg/ml, respectively. It was found that nano-ZnO inhibited A549 cells significantly at 50 μg/ml, showing a dose- and time- dependent manner. But micro-ZnO inhibited A549 cells significantly only when the concentration up to 100 μg/ml. The slope of the dose-response curve and time-effect curve of the nano-and micro-ZnO was significantly different. In addition, nano-ZnO particles demonstrated a DNA-damaging potential compared to control group in the Comet assay after an exposure of 6 h. Micro-ZnO did not induce any DNA damage. CONCLUSION: Nano- and micro-ZnO particles both demonstrated cytoxicity in A549 cells, but the toxic effects of nano-ZnO occurred earlier in time and lower in dose compared with micro-ZnO. Nano-ZnO particles could induce DNA damage, but the micro- ones did not.

Key words: Nano-ZnO, Micro-ZnO, A549 cells, cytoxicity, DNA damage