Comparative assessment of toxicity of ZnO and amine-functionalized ZnO nanorods toward Daphnia magna in acute and chronic multigenerational tests.

Zinc oxide nanomaterials (ZnO NM) have been used in a large number of applications due to their interesting physicochemical properties. However, the increasing use of ZnO NM has led to concerns regarding their environmental impacts. In this study, the acute and chronic toxicity of ZnO nanorods (NR) bare (ZnONR) and amine-functionalized (ZnONR@AF) toward the freshwater microcrustacean Daphnia magna was evaluated. The ZnO NR were characterized by transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and the zeta potential and hydrodynamic diameter (HD). The acute EC50(48h) values for D. magna revealed that the ZnONR@AF were more toxic than the ZnONR. The generation of reactive oxygen species (ROS) was observed in both NM. Regarding the chronic toxicity, the ZnONR@AF were again found to be more toxic than the ZnONR toward D. magna. An effect on longevity was observed for ZnONR, while ZnONR@AF affected the reproduction, growth and longevity. In the multigenerational recovery test, we observed that maternal exposure can affect the offspring even when these organisms are not directly exposed to the ZnO NR.

Genotoxic effects of copper oxide nanoparticles in Neuro 2A cell cultures.

Copper oxide nanoparticles (CuO NPs) are used for their biocide potential however they were also shown to be highly toxic to mammalian cells. Therefore, the effects of CuO NPs should be carefully investigated to determine the most sensitive processes for CuO NP toxicity. In this study, the genotoxicity of CuO NPs was investigated in vitro, using the mouse neuroblastoma cell line Neuro-2A. Genotoxic effects related to DNA fragmentation, DNA methylation and chromosomal damage, as well as lipid peroxidation, were investigated and compared to cytotoxic effects, measured by the mitochondrial reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide into formazan. Based on mitochondrial activity, CuO NPs were found to be cytotoxic. At the highest concentration tested (400 mg l⁻¹), 63% of cell viability was found in Neuro-2A cells after 24 h of treatment to CuO NPs. CuO NPs were also found to induce DNA fragmentation, lipid peroxidation and micronucleus formation. The micronucleus assay was the most sensitive to evaluate CuO NP genotoxicity and micronucleus frequency was increased significantly at 12.5 mg l⁻¹ CuO NPs after 24h of treatment. At this concentration, no significant change of cell viability was found using the mitochondrial activity assay. These results highlight the important risk of genotoxic effects of CuO NPs and show that genotoxicity assays are a sensitive approach to evaluate the risk of CuO NP toxicity.