Oxidative stress in juvenile common carp ( Cyprinus carpio ) exposed to TiO 2 nanoparticles

Acute toxicity and oxidative stress caused by exposure of titanium dioxide nanoparticles (TiO 2 -NPs) in juvenile common carp ( Cyprinus carpio ) were investigated. TiO 2 -NPs solution was prepared using deionized water and dispersed by sonication. Juvenile carp were exposed to different concentrations (5, 10, 20, 40, and 80 mg/L) of TiO 2 -NPs. TiO 2 -NP characteristics (particle morphology, size distribution, and zetapotential) were analyzed using transmission electron microscopy (TEM) and dynamic light scattering (DLS). Different tissue samples (skin, liver, brain, and gill) of fish were dissected, and the biochemical responses (catalase [CAT] and glutathione S-transferase [GST] activities) were measured. The results showed that acute exposure to TiO 2 -NPs induced GST and CAT levels to vary in all observed organs. The effective concentration of TiO 2 -NPs was 20 mg/L in the liver and brain and 40 mg/L in the gill. Histopathological changes were as follows: (1) skin: hypertrophy and increased number of mucous cells and thickening of the epidermal layer; (2) gill: hypertrophy of chloride cells, degeneration of mucous cells, and increased acidification of mucous cells; and (3) liver: hyperplasia and cytoplasm vacuolation of hepatic cells. No lethal effects were observed during the acute test. Our results show that there is a potential risk of TiO 2 -NP exposure to aquatic organisms in the environment.