Effect And Mechallism Of TiO₂and CuO Nano-Particles On Lemna Minor Growth

With the rapid development of nanotechnology, metal oxide nanoparticles are widely used in fields of electronics, optics, chemicals, ceramics, biology, medicine and environmental protection. Metal oxide nanoparticles can inevitablly enter into the aquatic environment in process of production, synthesis and usage. It is necessary for scientifically evaluating the potential toxic effect of nanomaterials. Most researches were focus on the effect of metal oxide nanoparticles (NPs) on mammals, the toxicity study of nanoparticles on growth of plant was still at the preliminary stage. The effect and the mechanism of two kinds of metal oxide NPs (TiO2NPs and CuO NPs) on the growth of Lemna minor were study in this paper through determination of growth index, activities of antioxidant enzymes, the changes of lipid oxidation and protein expression.The results showed that the TiO2NPs should promote the growth of Lemna minor when the concentration was lower than500mg/L. When the concentration was higher than500mg/L, TiO2NPs inhibited the growth of Lemna minor. The growth of Lemna minor was significantly inhibited by CuO NPs from the concentration of10mg/L in culture media.By determining the activities of antioxidant enzymes and the changes of lipid oxidation under the treatment of metal oxide NPs, it can be concluded that two kinds of metal oxides NPs can cause accumulation of oxygen radicals species. When the concentration of TiO2NPs was higher than the500mg/L, the SOD activity of Lemna minor decreased. The capacity of scavenging reactive oxygen species reduced, and eventually Malondialdelyde (MDA) content was enhanced. When the concentration of CuO was higher than50mg/L, excessive amounts of reactive oxygen species produced, Malondialdelyde (MDA) content was enhanced. Therefore, oxidative damage induced by metal oxide NPs might play a role in the phytotoxicity of NPs on plant. This may be one of mechanisms of NPs s inhibiting the growth of Lemna minor.Two kinds of metal oxides nanoparticles can cause protein expression changes of Lemna minor, and induced the expression of new protein, affected the synthesis and degradation of the original protein.The results of this reasearch showed that the toxic effects of TiO2NPs and CuO NPs were significantly higher than the effects of bulk-TiO2and bulk-CuO at the same concentration. The experiment compared with Cu2+whose concentration was twice as the content of Cu2+release from CuO NPs, the toxic effect of nano-CuO was higher than the toxic effect of Cu2+on Lemna minor.