Abstract: Zinc oxide nanoparticles(ZnO NPs) are among the most commonly utilized nanomaterials. They are used in a wide range of applications, including medicine, sunscreens, cosmetics, paints, catalysis, electronics, as well as biosensors, and hence, it is crucial to illustrate their biological effects and risks. In the present study, the effects and mechanism of ZnO NPs(≤ 5 nm) were investigated in rat glioma C6 cells in vitro. The results of transmission electron microscopy(TEM) and X-ray diffraction(XRD) show that ZnO NPs are pure with a uniform diameter of ca. 5 nm. 3-(4,5-Dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide(MTT) assays on C6 cells show that ZnO NPs, at different concentrations(0-5 μg/mL), can induce significant cytotoxicity in C6 cells in a dose-dependent manner. An increased level of reactive oxygen species(ROS), a decreased level of glutathione(GSH), and an elevated level of glutathione disulfide(GSSG) and the toxicity mechanism are primarily attributed to the induced cellular oxidative stress. 4',6-Diamidino-2-phenylindole(DAPI) staining was used to observe the apoptosis. The results show that C6 cells treated with the ZnO NPs at various concentrations(0, 1.25, 2.5 and 5 μg/mL) can induce apoptosis in a dose-dependent manner. These results suggest that ZnO NPs are the killers of the rat glioma C6 cells, and oxidative stress is the underlying mechanism of this process.

Key words: Zinc oxide, Reactive oxygen species (ROS), Glutathione (GSH), Glutathione disulfide (GSSG)