Allium cepa root tip assay in assessment of toxicity of magnesium oxide nanoparticles and microparticles.

Allium cepa bioassay had been used from decades for the assessment of toxicants and their harmful effects on environment as well as human health. Magnesium oxide (MgO) particles are being utilized in different fields. However, reports on the adverse effects of MgO nanoparticles on the environment and mankind are scarce. Hence, the toxicity of MgO particles is of concern because of their increased utilization. In the current study, A. cepa was used as an indicator to assess the toxicological efficiency of MgO nano- and microparticles (NPs and MPs) at a range of exposure concentrations (12.5, 25, 50, and 100µg/mL). The toxicity was evaluated by using various bioassays on A. cepa root tip cells such as comet assay, oxidative stress and their uptake/internalization profile. Results indicated a dose dependent increase in chromosomal aberrations and decrease in mitotic index (MI) when compared to control cells and the effect was more significant for NPs than MPs (at p<0.05). Comet analysis revealed that the Deoxyribonucleic acid (DNA) damage in terms of percent tail DNA ranged from 6.8-30.1 over 12.5-100µg/mL concentrations of MgO NPs and was found to be significant at the exposed concentrations. A significant increase in generation of hydrogen peroxide and superoxide radicals was observed in accordance with the lipid peroxidation profile in both MgO NPs and MPs treated plants when compared with control. In conclusion, this investigation revealed that MgO NPs exposure exhibited greater toxicity on A. cepa than MPs.

Toxicity of internalized laser generated pure silver nanoparticles to the isolated rat hippocampus cells.

Silver nanoparticles (AgNPs) are the most commonly used nanoparticles (NPs) in medicine, industry and cosmetics. They are generally considered as biocompatible. However, contradictory reports on their biosafety render them difficult to accept as 'safe'. In this study, we evaluated the neurotoxicity of direct AgNP treatment in rat hippocampal slices. We produced pure uncoated AgNPs by a pulsed laser ablation method. NP characterization was performed by Ultraviolet (UV) visible spectrophotometer, scanning electron microscope, transmission electron microscope (TEM) and energy-dispersive X-ray spectroscopy. Rat hippocampal slices were treated with AgNPs for an hour. AgNP exposure of hippocampal tissue resulted in a significant decrease in cell survival in a dose-dependent manner. Our TEM results showed that AgNPs were distributed in the extracellular matrix and were taken into the cytoplasm of the neurons. Moreover, we found that only larger AgNPs were taken into the neurons via phagocytosis. This study showed that the pure AgNPs produced by laser ablation are toxic to the neural tissue. We also found that neurons internalized only the large NPs by phagocytosis which seems to be the major mechanism in AgNP neurotoxicity.