| Background:Nanotechnology is supposed to be the new industrial revolution which will bring human large advantages in our daily life and manufacture. Many fields have shared the potential benefits of nanotechnology.As the building blocks of nanotechnology, manufactured nanomaterials have many interesting and unexpected properties. Zinc oxide nanoparticles is an important engineered nanomaterial which is currently used in products including rubber, paints, Personal Care Products, etc. In their production, application, aging process and treatment, ZnO nanoparticles might be released directly into the environment and cause adverse effect on the environmnet and human health. In this study, a series of behavioral and toxicological tests on ZnO nanoparticles were designed and conducted to assess systematically the potential ecotoxicological impact of ZnO nanoparticles.Results:(1)ZnO nanoparticles undergo considerable aggregation in aqueous systems and form agglomerates of variable sizes from a few hundred nanometers to several microns in diameter. Concentration of nanoscale ZnO particles is very low (about3%). Comparative aggregation and dissolution of ZnO nanoparticles in ultrapure water (UPW) and cultivation water (CW) suggested that more particles aggregated and lower solubility in CW. Besides, higher ZnO nanoparticles concentration made a higher percentage of big aggregation. After24hrs incubation, concentration of nanoscale particles fall below1%.(2) The effect of ZnO nanoparticles and their bulk counterparts and ZnCl2in goldfish were studied. It was found that although the size distribution of ZnO nanoparticles was similar to that of the bulk particles in suspension,5mg/L ZnO nanoparticles inhibited the growth of goldfish as compared with control after14days exposure.In liver and brain, zinc concentration significantly increased (p<0.05). Consumption of GSH reduced GSH/GSSG ratio. The MT content significantly increased in liver of NPs treatment and brain of all treatments as compared with control (p<0.05). Toxicity experiments revealed ZnO nanoparticles are more likely to enter into body and toxicity for ZnO nanoparticles is attributed to nanoscale particles.(3) The toxicity effect of ZnO nanoparticles on goldfish were concentration-dependent. The low exposure concentration (1,5,12.5mg/L) of ZnO nanoparticles induced locomotor hyperactivity. However, higher concentration (25,50mg/L) reduced locomotor activity and growth, and increased body mucus secretion. We observed a decrease of the zinc concentrations in the organs respect the following order:intestine> eye> gill> liver> brain> gonad>muscle. In every organs, zinc bioaccumulation showed high correlation with concentration of ZnO nanoparticles. Besides, testis had a lower zinc concentration than ovary in the same treatment. It suggested female fish might expose to higher toxicity risk of ZnO nanoparticles. The physiochemical indexes such as MDA and MT in the tissue of liver and brain were investigated after21days exposure. As compared with control, ZnO nanoparticles obviously caused lipid peroxidation in both of liver and brain. However, MDA content decreased with the concentration of ZnO nanoparticles increase. Moreover, MT content had a similar tendency to change with MDA. These results revealed excessive zinc could protect from oxidave stress induced by ZnO nanoparticles.Conclusion:The toxicity effect of ZnO nanoparticles is mainly caused by nanoscale particles. Besides, the effect may be related to sex. In aquatic environment, it remains possible that environmental behavior reduce the concentration of nanoscale particles. As a result, aggregation and dissolution will diminish the toxicity risk. |
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