纳米银在环境水样和实验介质中的理化性质和毒性效应

纳米银在自然环境中的理化性质可能严重影响其环境效应,本文的目的是为了比较纳米银在自然水样和实验介质条件下的理化性质和毒性效应.实验表征了粒径4 nm表面包裹物为油胺的纳米银,在不同介质条件下的粒径和团聚性,并进一步研究了不同环境介质条件下纳米银暴露对枯草芽孢杆菌的毒性效应.透射电镜照片显示油胺包裹的4 nm纳米银在环境介质中发生明显团聚.油胺包裹的4 nm纳米银暴露会抑制培养基中细菌的生长速率,降低生理盐水溶液中细菌的存活率.纳米银在实验条件下对细菌的毒性呈一定剂量效应关系,但是在环境水样中剂量效应关系不明显.低浓度纳米银在环境水样中的毒性比其在实验介质中弱.纳米银的透析袋暴露实验中,细菌的存活率有显著提升,揭示纳米银与细菌的直接相互作用对毒性效应有重要作用.与实验条件的培养基和生理盐水介质相比,环境水样中的纳米银更趋向以团聚形式存在,与细菌的相互作用几率减小,因此纳米银在环境介质中对细菌的毒性会降低.

Physicochemical Properties and Antibacterial Effect of Silver Nanoparticles: A Comparison of Environmental and Laboratorial Conditions

This study aimed to understand how the physicochemical properties of silver nanoparticles (AgNPs) affected its toxicity in the aquatic environment. The morphologies of oleylamine-coated AgNPs (4 nm) under environmental and laboratory water conditions were studied under transmission electron microscopy, and the results showed oleylamine-coated AgNPs formed big aggregates in the environmental water samples after 12 h equilibration. Dynamic light scattering results also showed that oleylamine-coated AgNPs had larger hydrodynamic size in all water samples as compared to its primary size (4 nm). Exposure to oleylamine-coated AgNPs inhibited the growth of Bacillus subtilis (B. subtilis) and reduced its cell viability in Luria-Bertani (LB) broth and 0.85% NaCl, respectively. A dose-dependent toxicity of AgNPs in B. subtilis was observed in laboratorial medium conditions but not in environmental water condition. Low concentration of AgNPs exhibited lower toxicity in environmental water samples as compared to that in laboratorial medium conditions. Separating AgNPs from bacterial suspension through a dialysis membrane enhanced the cell viability of B. subtilis significantly. In the environmental water samples, the AgNPs-bacteria interaction would be reduced with the formation of big aggregates by AgNPs, which consequently decreased its toxicity in aquatic environment.