a School of Biosciences , Institute of Microbiology and Infection, University of Birmingham , Birmingham , UK.
b School of Geography, Earth and Environmental Sciences , University of Birmingham , Birmingham , UK.
Nanotoxicology. 2017 Jun;11(5):637-646. doi: 10.1080/17435390.2017.1342010.
It is still unclear whether the toxicity of silver nanoparticles (AgNPs) can be attributed solely to the release of Ag or whether dissolved and nanoparticulate Ag act in parallel; this is due to the difficulty in distinguishing Ag- from AgNP-effects. Also, AgNPs undergo changes during toxicity tests. This is the first study to investigate the influence of AgNP dissolution over time on viable counts at high time resolution and low cell density, avoiding the apparently reduced toxicity at higher cell densities identified in our study. Uncapped AgNPs were synthesized to avoid any interference from surface coatings. The transformations of AgNPs during storage were reduced. Lowering the concentration of AgNPs reduced their aggregation in Davis minimal medium (DMM). Also, AgNPs dissolved more slowly in DMM than in water. The minimum inhibitory concentrations (MICs) of Ag and AgNPs increased with cell density according to a power law, suggesting that binding to cells decreased effective concentrations. However, AgNPs acted as a reservoir of Ag, releasing new Ag to maintain the Ag stress. The toxicity of AgNPs was dominated by dissolved Ag. Combining controlled conditions, high time-resolution and low cell density, we could demonstrate different roles of ionic and nano Ag in bacterial death caused by AgNPs.
目前尚不清楚银纳米粒子（AgNPs）的毒性是否仅归因于 Ag 的释放，还是溶解态和纳米态的 Ag 同时起作用；这是因为难以区分 Ag 和 AgNP 的作用。此外，AgNPs 在毒性测试过程中会发生变化。本研究首次调查了 AgNP 溶解随时间变化对高时间分辨率和低细胞密度下活菌计数的影响，避免了我们研究中发现的较高细胞密度下毒性明显降低的问题。合成无壳 AgNPs 以避免表面涂层的任何干扰。储存过程中 AgNPs 的转化减少了。降低 AgNPs 的浓度可降低其在 Davis 最小培养基（DMM）中的聚集。此外，AgNPs 在 DMM 中的溶解速度比在水中慢。Ag 和 AgNPs 的最小抑菌浓度（MIC）随细胞密度按幂律增加，表明与细胞的结合降低了有效浓度。然而，AgNPs 充当 Ag 的储库，释放新的 Ag 以维持 Ag 胁迫。AgNPs 的毒性主要由溶解的 Ag 决定。结合控制条件、高时间分辨率和低细胞密度，我们可以证明在 AgNPs 引起的细菌死亡中，离子态和纳米态 Ag 发挥了不同的作用。
