Abstract
The present study investigated the cytotoxic effects of ZnO, CuO, and mixed combinations of them on SH-SY5Y cells. For this purpose, the cells were exposed to various concentrations of these NPs alone for 24-96 h and as a mixture for 24 h. Variations in cell viability were noted. MTT results showed that ZnO and/or CuO NPs decreased cell survival by about 59% at 200 (ZnO, at 24 h) and 800 µg/ml (ZnO and/or CuO, at 72 and 96 h). When the NR assay was used, slight decreases were noted with ZnO NPs at 72 and 96 h. With CuO NPs alone and NPs in a mixture, only the highest concentrations caused 40 and 70% decreases in cell survival, respectively. Especially with NR assays, DTPA, NAC, or taurine provided marked protection. ROS levels were increased with the highest concentration of CuO NPs and with all concentrations of the mixture. The highest concentration of ZnO NPs and the lowest concentration of CuO NPs caused slight decreases in mitochondrial membrane potential levels. Additionally, increases were noted in caspase 3/7 levels with ZnO and CuO NPs alone or with a mixture of them. Intracellular calcium levels were decreased in this system. These findings demonstrated that ZnO and CuO NPs, either separately or in combination, had a modest cytotoxic effect on SH-SY5Y cells. Protection obtained with DTPA, NAC, or taurine against the cytotoxicity of these NPs and the ROS-inducing effect of CuO NPs and the NPs' mixture suggests that oxidative stress might be involved in the cytotoxicity mechanisms of these NPs.