The Toxic Effect of Cu and CuO Nanoparticles on Euplotes Aediculatus

Abstract

\n Toxicology tests were carried out by choosing Cu nanoparticles (CuNPs) and CuO nanoparticles (CuONPs) as experimental materials and Euplotes aediculatus as the experimental organism. To investigate the toxicity effect and mechanism of two NPs on E. aediculatus, we determined antioxidant enzyme activity and observed morphologic changes using optical and electron microscopes, combined with the Fourier infrared spectrum technique. The results showed that the 24 h-LC50 of CuNPs and CuONPs was 0.46 µg/L and 1.24×103 µg/L. The movement ability of cells was decreased and surface cilia gradually shed with CuNPs and CuONPs at 24 h-LC50. In addition, the cell body swelled and finally ruptured. There were varying extents of damage to the nucleus and mitochondria. With CuNPs, disappearance of nucleoli and condensation of chromatin were observed, while the mitochondria were wrinkled in an irregular shape and cristae were partially fractured. With CuONPs, changes of nucleus were not obvious, and the mitochondria were merely irregular. While neither CuNPs nor CuONPs had major effect on the ultrastructure of the membrane, some functional groups were oxidized with CuNPs, e.g. PO2-, C-O-C, δ(COH) of carbohydrates. The 24 h-EC50, 48 h-EC50 and 72 h-EC50 of CuNPs on E. aediculatus were 2.10×10-3 µg/L, 7.92×10-4 µg/L and 2.77×10-4 µg/L. The EC50 of CuONPs in same period was 7.20 µg/L, 0.86 µg/L and 0.19 µg/L. The above concentration of CuNPs and CuONPs could increase the activities of SOD, CAT and GPx, which were dose-dependent. The above results indicate that CuNPs and CuONPs inhibited reproduction and caused death. CuNPs were more toxic to E. aediculatus and more destructive to cell structure. Oxidative stress and destruction to cell structures may be toxic mechanisms. The E. aediculatus was more sensitive to CuNPs or CuONPs, and the value of 24 h-LC50 was much lower than other organisms, so it can be recommended as an indicator for early monitoring in freshwater environment.