Effects of realistic concentrations of TiO2 and ZnO nanoparticles in Prochilodus lineatus juvenile fish

Abstract

The impact of nanoparticles on fish health is still a matter of debate, since nanotechnology is quite recent. In this study, freshwater benthonic juvenile fish Prochilodus lineatus were exposed through water to three concentrations of TiO2 (0.1, 1, and 10 μg l(-1)) and ZnO (7, 70, and 700 μg l(-1)) nanoparticles, as well as to a mixture of both (TiO2 1 μg l(-1) + ZnO 70 μg l(-1)) for 5 and 30 days. Nanoparticle characterization revealed an increase of aggregate size in the function of concentration, but suspensions were generally stable. Fish mortality was high at subchronic exposure to 70 and 700 μg l(-1) of ZnO. Nanoparticle exposure led to decreased acetylcholinesterase activity either in the muscle or in the brain, depending on particle composition (muscle-TiO2 10 μg l(-1); brain-ZnO 7 and 700 μg l(-1)), and protein oxidative damage increased in the brain (ZnO 70 μg l(-1)) and gills (ZnO 70 μg l(-1) and mixture) but not in the liver. Exposed fish had more frequent alterations in the liver (necrosis, vascular congestion, leukocyte infiltration, and basophilic foci) and gills (hyperplasia and epithelial damages, e.g., epithelial disorganization and epithelial loss) than the control fish. Thus, predicted concentrations of TiO2 and ZnO nanoparticles caused detectable effects on P. lineatus that may have important consequences to fish health. But, these effects are much more subtle than those usually reported in the scientific literature for high concentrations or doses of metal nanoparticles.

Overview of the toxic effects of titanium dioxide nanoparticles in blood, liver, muscles, and brain of a Neotropical detritivorous fish

“…Acute exposure to TiO 2 ‐NP decreased AChE levels in P. lineatus , although no changes in fish locomotor behavior were observed during the experiments. A similar result was found in the same fish species exposed to very low TiO 2 ‐NP concentrations, indicating that muscular tissue might be especially sensitive in this species. Other studies on other fish have reported neurotoxic effects of metals such as mercury, lead, and cadmium through inhibition of esterases, yet the way metals could inhibit AChE is still under debate .…”

“…Hypertrophy, in turn, displaces hepatocyte's nucleus to the periphery of the cell, later causing degenerative morphological alterations, such as complete degeneration of cellular components and focal necrosis . Necrotic cells with condensed nuclei and appearance of apoptotic bodies in hepatic tissue are common in fish exposed to TiO 2 ‐NP, as well as to copper and zinc; it is associated with oxidative stress, and the degree of impairment of liver function depends on the xenobiotic concentration . In this study, the low frequency of morphological damage, which was likely prevented by increased production of antioxidants, indicates that the TiO 2 ‐NP concentrations used were not high enough to cause liver function impairment.…”

Investigations of the nervous system biomarkers in the brain and muscle of freshwater fish ( Oreochromis niloticus ) following accumulation of nanoparticles in the tissues

“…They also found significant decreases in the Na,K-ATPase activity in the brain of trout, though this was not the case for tilapia in the present study. Studies of Miranda et al (2016) also accorded with the present study. The authors exposed freshwater juvenile fish (Prochilodus lineatus) to low concentrations of TiO 2 and ZnO NPs for up to 30 days and found that there were significant decreases in AChE activity in either the muscle or the brain.…”

Toxicity of metallic nanoparticles in the central nervous system

“…Lowering of Na + /K + -ATPase activity in the brain was also observed in juvenile rainbow trout after waterborne exposure to Cu NPs [115]. NPs-dependent decrease in activity of AChE and increased protein oxidative damage in brain was also observed in juvenile fish Prochilodus lineatus exposured to TiO 2 NPs and ZnO NPs [139]. In line Xia et al showed that 1 mg/l of TiO 2 NPs in water increased the level of AChE activity in gills (after day 5) and in digestive gland (after day 12) in the scallop (Chlamys farreri) [140].…”