納米銀在環境水樣和實驗介質中的理化性質和毒性效應

納米銀在自然環境中的理化性質可能嚴重影響其環境效應，本文的目的是為了比較納米銀在自然水樣和實驗介質條件下的理化性質和毒性效應。實驗表徵了粒徑4 nm表面包裹物為油胺的納米銀，在不同介質條件下的粒徑和團聚性，並進一步研究了不同環境介質條件下納米銀暴露對枯草芽孢桿菌的毒性效應。透射電鏡照片顯示油胺包裹的4 nm納米銀在環境介質中發生明顯團聚。油胺包裹的4 nm納米銀暴露會抑制培養基中細菌的生長速率，降低生理鹽水溶液中細菌的存活率。納米銀在實驗條件下對細菌的毒性呈一定劑量效應關係，但是在環境水樣中劑量效應關係不明顯。低濃度納米銀在環境水樣中的毒性比其在實驗介質中弱。納米銀的透析袋暴露實驗中，細菌的存活率有顯著提升，揭示納米銀與細菌的直接相互作用對毒性效應有重要作用。與實驗條件的培養基和生理鹽水介質相比，環境水樣中的納米銀更趨向以團聚形式存在，與細菌的相互作用幾率減小，因此納米銀在環境介質中對細菌的毒性會降低。
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. Copyright © 2017 中國科學院生態環境研究中心.