Zinc oxide nanoparticles at environmentally relevant concentrations cause cytotoxic and chromosomal damage to Allium cepa root cells
Although environmental toxicity of high concentrations of nanoparticles (NP) is well reported in the literature, information about their effects on biological systems at environmentally relevant concentrations remains scarce. We investigated whether low ZnO-NP concentrations influence the dynamics of cell division processes, cause nuclear abnormalities and induce changes in the genomic DNA using Allium cepa root cells. Healthy A. cepa bulbs were exposed to environmentally relevant concentrations of ZnO-NP for 48 hours under four different environmental conditions, namely: optimistic, median, pessimistic and known toxic. Mitotic index (MI), chromosomal abnormalities (CAs) and genomic stability based on DNA markers were estimated. ZnO-NPs induced significant changes in MI and CAs, with clear dose-response effects, even at very low concentrations and short exposure times. This outcome is clear evidence of negative effects. In addition, we evidenced instability in the repair mechanism of DNA mutated due to low concentrations of ZnO NPs based on RAPD-PCR results. Therefore, even short-term exposure of eukaryotic cells to low concentrations of ZnO-NP can damage cells and, consequently, negatively affect their biological functioning.