Enhanced oxidative stress and physiological damage in daphnia magna by copper in the presence of Nano-TiO ₂

This study examines the potential hazard of an individual nanomaterial on the Cu biotoxicity to aquatic organisms. Daphnia magna in the absence or presence of nano-TiO ₂ was exposed to Cu. Maintaining nano-TiO ₂ at a safe concentration cannot eliminate its potential hazard. The biomarkers superoxide dismutase, catalase, and Na ⁺/K ⁺-ATPase in D. magna were measured. Cu in the presence of nano-TiO ₂ induced higher levels of oxidative stress and physiological damage because of the sorption of Cu. Nano-TiO ₂ also caused Na ⁺/K ⁺-ATPase inhibition possibly by impeding the Na ⁺/K ⁺ transfer channel. The correlations among the biomarkers, mortality, and accumulation further showed that the overloading reactive oxygen species generation caused by nano-TiO ₂ contributed to deeper oxidative stress and physiological regulation, thereby causing greater toxic injury.