Dynamic Cytotoxicity Of ZnO Nanoparticles And Bulk Particles To Escherichia Coli

ZnO nanoparticles(ZnO NPs),as a kind of nano material,not only has unique antibacterial,optical and electrical properties,but also has good surface,volume and size effects.ZnO NPs have been widely used in our production and life,and they will inevitably enter and accumulate in the aquatic environment.After entering the aquatic environment,ZnO NPs undergo a range of migrations and transformations by physical(dissolution,adsorption and sedimentation),chemistry(oxidation,reduction and photochemical transformation)and biological(bioconcentration,biodegradation)effects.This in turn has an incalculable impact on humans and the ecosystem.Research indicated that the toxicity of ZnO NPs derived from ZnO NPs particles or free Zn²⁺.The ZnO NPs particles and Zn²⁺with mixture concentration ratio is dynamical in the aquatic environment.However,current studies have not compared the toxic contributions of the two components,and the underlying toxicity mechanisms have not been fully understood.Therefore,it is important to investigate the potential toxic effects of ZnO nanoparticles.In this research,Escherichia coli Top10 was selected as a model organism to investigate the toxicity effects of ZnO NPs and ZnO bulk particles(ZnO BPs).The effects of environmental factors on unfix ratio of ZnO particles and Zn²⁺were determined,as well as revealed their toxicity machanisms.The specific analysis results are as follows:1.The dissolution of ZnO NPs and ZnO BPs is different under the action of different environmental factors.Na⁺did not significantly promote the release of Zn²⁺,but Fe³⁺,HA,temperature and mixed environmental factors(Na⁺,Fe³⁺and HA)all promoted the release of Zn²⁺.Fe³⁺could promote Zn²⁺release,due to its oxidation capability;HA facilitated the release of Zn²⁺,due to the formation of HA-Zn complexes,temperature and mixed environmental factors facilitated the release of Zn²⁺,owing to the energy of the system and stability of the system.2.Due to changes in environmental factors,the accumulation of Zn by E.coli Top10shows different trends.Na⁺,Fe³⁺,temperature and mixed environmental factors all inhibited the accumulation of Zn by E.coli Top10;but the low concentration of HA had no significant effect(p>0.05).3.The cytotoxicity of ZnO NPs and ZnO BPs is comparable,but with different mechanisms of effect.ZnO NPs cytotoxicity arises mainly from ZnO particles for 3h and from Zn²⁺afterwards(8?48 h).The cytotoxicity of ZnO BPs depends predominantly on ZnO particles for 12 h and on Zn²⁺from 24 to 48 h.The cytotoxicity of ZnO NPs and ZnO BPs is partially attributable to Zn.In addition,under the effect of different environmental factors,the linear regressions of acute toxicity for ZnO NPs,ZnO BPs and Zn²⁺yielded excellent r²(0.9994 and 0.9998)from literature data and good r²(?0.714).This research aims to provide necessary data support and scientific basis for the safety assessment of ZnO NPs and ZnO BPs on the ecological environment and human health.