Acute exposure to tenorite nanoparticles induces phenotypic and behavior alterations in zebrafish larvae

Abstract

Tenorite or copper oxide nanoparticles (CuO NPs) are extensively used in biomedical fields due to their unique physicochemical properties. Increased usage of these NPs leads to release in the environment, affecting varied ecosystems and the biota within them, including humans. The effect of these NPs can be evaluated with zebrafish, an excellent complementary model for nanotoxicity studies. Previous reports focusing on CuO NPs-induced teratogenicity in zebrafish development have not elucidated the phenotypical changes in detail. In most of the studies, embryos at 3 hpf with a protective chorion layer were exposed to CuO NPs, and their effect on the overall developmental process is studied. Hence, in this study, we focused on the effect of acute exposure to CuO NPs (96-120 hpf) and its impact on zebrafish larvae. Larvae were exposed to commercially available CuO NPs (<50 nm) at various concentrations to obtain the LC₅₀ value (52.556 ppm). Based on the LC₅₀, three groups (10, 20, and 40 ppm) were taken for further analysis. Upon treatment, bradycardia, and impaired swim bladder (reduced/absence of inflation) were found in the treated groups along with alterations in the erythrocyte levels. Also, the angles and distance between the cartilages varied in the treated larvae affecting their craniofacial structures. There was a significant behavior change, as evidenced by the reduced touch escape response and locomotion (speed, distance, time mobile, time frozen, and absolute turn angle). Further, the acetylcholinesterase activity was reduced. Overall, our results suggest that acute exposure to CuO NPs elicits morphological defects in zebrafish larvae.

Keywords: Behavior alterations; Copper oxide nanoparticles; Nanotoxicity; Swim bladder defects; Teratogenicity; Zebrafish.