Effects of Engineered Zinc Oxide Nanoparticles on Freshwater Fish, Labeo rohita: Characterization of ZnO Nanoparticles, Acute Toxicity and Oxidative Stress

Concerns regarding zinc oxide nanoparticles (ZnO-NPs) have gained much attention due to their unique properties and widespread applications in cosmetics, electronics and medicinal industry that may induce an adverse impact not only on specific ecosystem but also on human health. ZnO-NPs were synthesized by co-precipitation method and characterization was done by Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) analysis. SEM showed the hexagonal wurtzite crystal structure of particles. From XRD pattern, average particle size, lattice parameters (a and c), X-ray density and volume of unit cell of zinc oxide nanoparticles were 52.22 nm, (a =3.25 Å and c=5.21 Å), 5.0 g/cm3 and 54.82 Å3, respectively. FT-IR confirmed the attached compound of synthesized nanoparticles. The acute toxicity of ZnO-NPs was determined by using fish, Labeo rohita as a genetic model during this study. The mean 96-h LC50 and lethal concentration were measured as 31.15 and 57.84 mg/L, respectively. Oxidative stress in terms of catalase, lipid peroxidation and superoxide dismutase was also determined in fish gills, muscle, liver and heart after chronic exposure of ZnO-NPs for 80 days and sampling were done on 20, 40, 60 and 80 days. Significantly decreased catalase and superoxide dismutase activity was determined in selected fish organs. However, level of lipid peroxidation was significantly increased in the fish organs as compared to control group. The overall results indicated that induced toxicity mechanism of ZnO-NPs in aquatic ecosystem was oxidative stress