School of Life Sciences, Gibbet Hill Campus, University of Warwick, Coventry CV4 7AL, United Kingdom..
Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7EQ, United Kingdom.
Sci Total Environ. 2020 Dec 10;747:141229. doi: 10.1016/j.scitotenv.2020.141229. Epub 2020 Jul 25.
Global demand for silver nanoparticles (AgNPs), and their inevitable release into the environment, is rapidly increasing. AgNPs display antimicrobial properties and have previously been recorded to exert adverse effects upon marine phytoplankton. However, ecotoxicological research is often compromised by the use of non-ecologically relevant conditions, and the mechanisms of AgNP toxicity under environmental conditions remains unclear. To examine the impact of AgNPs on natural marine communities, a natural assemblage was exposed to citrate-stabilised AgNPs. Here, investigation confirmed that the marine dominant cyanobacteria Prochlorococcus is particularly sensitive to AgNP exposure. Whilst Prochlorococcus represents the most abundant photosynthetic organism on Earth and contributes significantly to global primary productivity, little ecotoxicological research has been carried out on this cyanobacterium. To address this, Prochlorococcus was exposed to citrate-stabilised AgNPs, as well as silver in its ionic form (AgSO), under simulated natural conditions. Both AgNPs and ionic silver were observed to reduce Prochlorococcus populations by over 90% at concentrations ≥10 μg L, representing the upper limit of AgNP concentrations predicted in the environment (10 μg L). Longer-term assessment revealed this to be a perturbation which was irreversible. Through use of quenching agents for superoxide and hydrogen peroxide, alongside incubations with ionic silver, it was revealed that AgNP toxicity likely arises from synergistic effects of toxic superoxide species generation and leaching of ionic silver. The extent of toxicity was strongly dependent on cell density, and completely mitigated in more cell-dense cultures. Hence, the calculation and reporting of the particle-to-cell ratio reveals that this parameter is effective for standardisation of experimental work, and allows for direct comparison between studies where cell density may vary. Given the key role that marine cyanobacteria play in global primary production and biogeochemical cycling, their higher susceptibility to AgNP exposure is a concern in hotspots of pollution.
全球对银纳米粒子（AgNPs）的需求，以及它们不可避免地释放到环境中，正在迅速增加。AgNPs 具有抗菌特性，以前曾被记录对海洋浮游植物产生不利影响。然而，生态毒理学研究常常受到非生态相关条件的限制，并且在环境条件下 AgNP 毒性的机制仍不清楚。为了研究 AgNPs 对天然海洋群落的影响，将天然混合物暴露于柠檬酸稳定的 AgNPs 中。在这里，研究证实海洋优势蓝藻聚球藻对 AgNP 暴露特别敏感。虽然聚球藻是地球上最丰富的光合生物，对全球初级生产力有重大贡献，但对这种蓝藻的生态毒理学研究很少。为了解决这个问题，将聚球藻暴露于柠檬酸稳定的 AgNPs 以及离子银（AgSO）中，在模拟的自然条件下进行。在浓度≥10μg/L 时，AgNPs 和离子银都观察到聚球藻种群减少了 90%以上，这代表了环境中预测的 AgNP 浓度上限（10μg/L）。长期评估表明，这是一种不可逆转的干扰。通过使用超氧化物和过氧化氢的猝灭剂，以及与离子银的孵育，发现 AgNP 的毒性可能是由于有毒超氧化物的协同作用和离子银的浸出。毒性的程度强烈依赖于细胞密度，在更密集的细胞培养物中完全减轻。因此，颗粒与细胞的比例的计算和报告表明，该参数对于实验工作的标准化是有效的，并允许在细胞密度可能变化的研究之间进行直接比较。鉴于海洋蓝藻在全球初级生产和生物地球化学循环中发挥的关键作用，它们对 AgNP 暴露的更高敏感性是污染热点的一个关注点。
