Parameters of Embryogenesis in Zebrafish Danio rerio as Indicators of the Ecological Toxicity of Zinc Oxide Nanoparticles

Abstract

The hazard of zinc oxide nanoparticles (NPs) with particles sizes of Δ₅₀ = 10–12 nm has been assessed by the toxicity of an aqueous disperse suspension system (DS) applying the biotesting technique using Zebrafish Danio rerio embryos. The DS of ZnO NPs at concentrations of 0.01, 0.1, 1.0, 5.0, 10.0, 20.0, 30.0, 40.0, and 50.0 mg/dm³ negatively affects Danio rerio embryogenesis. Impaired activity of the cardiovascular system is observed in the first 24 h of exposure. A statistically significant increase in the heartbeat rate is noted within the diapason of low concentrations (0.1–1.0 mg/dm³). At the same time of exposure, the mortality of embryos caused by coagulation is the highest (21.4 ± 4.0% at concentration of 10.0 mg/dm³). The extent of ZnO NPs effects on the somatogenesis is insufficient and is expressed as a decrease in the time of formation of somites only at high concentrations. The “number of hatched embryos” integral parameter reflecting the success of the whole process of embryogenesis is most sensitive to the presence of ZnO NPs in the exposure media. The retardation of hatching the embryos by 50% (EC₅₀) by 72 h of exposure occurs at a concentration of ZnO NPs of 0.012 ± 0.001 mg/dm³, which is 2600 times less than the concentration causing 50% mortality in the embryos. The contamination of aquatic environment with ZnO NPs even at low concentrations may result in a considerable decrease in ecosystem biodiversity.