The Difference Of Cytotoxicity And Genotoxicity Of Pristine And Transformed Zinc Oxide Nanoparticles

With the rapid development of nano-technology and the increasing application of nanomaterials in food, pharmacy and cosmetic industries, the amount of nanoparticles released into the environment rises as well. Various transformation of nanoparticles in their physichemical properties and bio-availabilitiesmay occurred in the environment, and their threat to human health and ecosystem can no longer be ignored. Therefor, more and more concern has been focused on the transformation of nanoparticles in their physichemicalproperties and their potential toxicity in the environment.As one of the most frequently used nano-material in industry and daily life, zinc oxide nanoparticles (ZnO-NPs) excels in products related to sun-screening, growth improvement, antibioticsand photocatalysis and so on. The mass production promoted the amount of zinc oxide nanoparticles released in the environment and the interaction between the material and the environment media, causing transformation in their physi-chemical properties and turning the "pristine" nano-materials to "transformed" nano-materials, along with possible change in their toxicity. Up to now, a thorough and systematic study on the difference of toxicity caused by pristine and transformed zinc oxide nanoparticles is still lacking. This thesis focuses mainly on the physi-chemical property change of zinc oxide nanoparticles occurred in the aquatic environment after aging, and the subsequent toxicological effects on human-hamster hybrid (AL) cells.In this study, we have found the physi-chemical properties were changing after aging, probably related to the dissolution of zinc oxide nanoparticles in water. Furthermore, transformed zinc oxide nanoparticles caused less cytotoxicity and less actived caspase-3 expression (a key protein in the signaling pathway related to cell apoptosis) compared to their fresh counterpart. By contrast, the genotoxicity results showing that transformed zinc oxide nanoparticles caused higher DNA double-strand break level and less gene deletion of CD59 (with other correlated genes). We also found transformed zinc oxide nanoparticles induced higher production of ROS (reactive oxygen species) level. Meanwhile, the insoluble titanium dioxide nanoparticles (TiO2-NPs) nanoparticles shows no apparent transformation (only agglomeration in water) in physi-chemical property during aging, and the difference of toxicity between pristine and transformed titanium dioxide nanoparticles nanoparticles is negligible.This study demonstrates that the difference of cytotoxicity and genotoxicity induced by pristine and transformed zinc oxide nanoparticles is attributed to the transformation of their physi-chemical properties. Also, whether nanoparticles are soluble or not may be the reason why zinc oxide nanoparticles and titanium dioxide nanoparticles showing different response to aging.Our result provides basis for further study on the toxicity of zinc oxide nanoparticles on mammalian cells, which is also important for environment risk assessment of nano-materials.