Comparing the toxic mechanism of synthesized zinc oxide nanomaterials by physicochemical characterization and reactive oxygen species properties.

We studied the toxicity of ZnO nanomaterials in terms of physicochemical characteristics and reactive oxygen species (ROS) properties. ZnO nanorods [synthesized at room temperature (ZnO-RT, length; 18.0±4.2 nm) and at 60 °C (ZnO-60, length; 80.5±6.8 nm)] were used to evaluate the potential toxicity upon growth velocity-related particle size. The cytotoxicity of ZnO-60 was higher than that of ZnO-RT. We observed that the toxicity of ZnO-RT and ZnO-60 was related with ROS formation by using antioxidant N-acetylcysteine and electron spin resonance. Also, we found that the source of toxicity was not related to Zn(2+) ions released from ZnO in 24h treatment. Our results indicate that toxicity of ZnO nanorods is caused by the amounts of ROS. Our study strongly suggests that size of nanomaterial is not the sole factor to be considered, thus, the development of appropriate criteria based on morphological/physicochemical characteristics as well as synthesis procedures is needed to evaluate the precise toxicity.