DNA damage induced by ZnO and CuO nanoparticles: a comparative study against bulk materials

As nanoparticles are increasingly incorporated into consumer products and specialized areas, the need to study their toxicity and the importance of caution in their use are becoming more evident. The use of these novel materials in the automotive industry is causing increased nanoparticle emissions into the atmosphere, sparking concerns due to recent toxicology reports. Detecting and characterizing nanostructured atmospheric pollutants represent a complex task that alternative methods like genotoxic bioindicators may overcome. Ricinus communis was selected as a model plant to describe the genotoxic effect of air-dispersed nanostructured materials, using comet assay to evaluate the DNA damage by exposure to ZnO and CuO nanoparticles (ZnO-NPs, CuO-NPs), and total chlorophyll was determined to correlate the results. The plants were exposed for 1.25 h by nebulizing dispersions of the nanoparticles, and their effects were evaluated at 24 h and 5 days after exposure. Time was essential in demonstrating the DNA damage induced by lower levels of CuO-NPs and ZnO-NPs, which showed more significant damage after 5 days than bulk materials. In both compounds (CuO and ZnO), significant differences were observed in the comparison of their nanoscale and their bulk form, which confirms that the lower size of the nanoparticles presents a more significant genotoxic potential. In the scanning electron microscopy (SEM) micrographs, the accumulation of nanoparticles was observed near the stomata. The study demonstrated the viability of the comet assay as a sensitive tool both to assess DNA damage from ZnO-NPs and CuO-NPs on R. communis as a bioindicator and to investigate the potential risks of emerging nanomaterials, emphasizing the need for caution in their use.