Toxicity of microwave-assisted biosynthesized zinc nanoparticles in mice: a preliminary study

This study was designed to describe the oral acute and subacute toxicities and underlying toxicological mechanisms of biogenic Zn NPs in mice. The Zn NPs were prepared by a green microwave-assisted synthesis method in the presence of Lavandula vera leaf extract. Determination of median lethal dose (LD₅₀) of Zn NPs and the subacute toxicity after 14 days of exposure was performed as a measurement of substance toxicity through general toxicological, hematological, serum, and histopathological investigations. The western blotting was used to determine the cleaved-caspase-3 expression in the sampled tissues. Flame atomic absorption spectrophotometer (AAS) was applied to estimate the Zn levels in tissues. The SEM analyses revealed that the biogenic Zn NPs were spherical-shaped with the size range of 30-80 nm. The LD₅₀ value above 5 g/kg indicated that biogenic Zn NPs could be classified as non-toxic chemicals. In subacute toxicity, no significant differences were found in the body weight as well as hematological and oxidative stress (OS) biomarkers after exposure to Zn NPs at the dose of 1 g/kg in comparison to the control. The AAS results indicated that Zn NPs were mainly distributed in the testis, liver, and brain. The findings of histology images of Zn NPs at the dose of 1 g/kg were similar to those of the control. Furthermore, no significant differences were observed in cleaved-caspase-3 expression after exposure to Zn NPs at the dose of 5 g/kg. The results demonstrated that changes in the OS were not related to caspase pathway and the no-observed-adverse-effect level (NOAEL) dose of biogenic Zn NPs in 14-days subacute toxicity study was lower than 1 g/kg.