Sublethal toxicity of selenium nanoparticles in zebrafish early life stages: biochemical and behavioral responses

Selenium nanoparticles (SeNPs) are used in diverse sectors, but their sublethal effects on aquatic vertebrates remain incompletely characterized. Zebrafish (Danio rerio) early life stages were exposed to 0.010-0.050 mg L^-1 nominal total Se associated with a chemically synthesized polysorbate 20-stabilized SeNP dispersion (predominantly spherical; primary diameter 67 ± 11 nm; stock dispersion hydrodynamic diameter ~52.7 ± 0.2 nm) for 120 hpf. No statistically detectable treatment-related differences were identified in final hatching success, cumulative mortality, the developmental endpoints, total swimming distance, or outer-zone distance percentage during the short behavioral assay. In contrast, catalase activity was higher at several nominal concentrations, selenium-dependent glutathione peroxidase activity was lower at 0.019-0.050 mg L^-1, CYP3A-like activity was lower at 0.012-0.025 mg L^-1, and TBARS expressed as MDA equivalents were higher at several concentrations. No overall group differences were detected in total glutathione peroxidase and CYP1A-like or acetylcholinesterase activities. Several biochemical responses did not follow monotonic patterns. Under the present design, the measured biochemical endpoints were more responsive than the assessed apical and short-window behavioral endpoints. Because exposure medium concentrations and particle behavior were not verified, these findings are specific to the tested formulation and nominal exposure conditions.