Exposure Pathways, Dissolution Kinetics, and Fate of Nano-Silver in the Environment

摘要提案1057547目的：本项目的重点是暴露途径，命运，和风险的纳米银在自然环境中。 该提案的目的是解决两个假设：（1）纳米银可以通过动力学限制氧化过程在环境中进行完全反应性溶解。纳米银在含有溶解氧的环境隔室中以颗粒形式将是非持久性的，但在缺氧隔室或含有还原剂的生物基质中是持久性的。(2)反应性溶解速率将显示出对nAg颗粒尺寸、表面状态（配体、涂层）和介质组成的显著依赖性，需要在复杂介质和生物组织中进行详细的实验，以便为生命周期风险评估做出有用的预测。该项目将分四项任务进行：（1）开发环境中纳米银的来源和材料流的第一代模型，解释动态溶解行为，（2）纳米银溶解的详细动力学和机制，解释附着于颗粒表面的稳定配体、涂层、近颗粒环境的组成和表面氧化态的影响，（3）银在生物区室中的分布和纳米颗粒持久性，通过使用生物体非洲爪蟾的实验，非洲爪蟾是一种两栖动物，用作水生系统中的模式哨兵物种，非常容易受到环境污染物的影响，非常适合研究纳米银的生物分布和持久性，以及（4）综合模型开发和分析不同的纳米风险。智力优点：该提案将找到一些毒性问题的解决方案，这些问题是由于含纳米银的产品被洗涤、磨损或丢弃，银可以作为纳米颗粒、纳米颗粒聚集体或可溶性离子进入环境。 据报道，银对某些水生生物具有高毒性，并且作为抗生素也可能破坏或改变环境中的有益微生物群落。银还已知会在浮游植物和一些海洋无脊椎动物中生物积累，并且已被证明对斑马鱼胚胎具有高度毒性。更广泛的影响这个项目解决了当前市场上产量最高的纳米技术产品之一：纳米银的潜在环境影响。该项目的主要成果将是纳米银暴露途径的概念模型，从而可以估计各种环境分区中银的位置、形式和浓度。这项工作将提供与政策相关的信息，以帮助定义“差异纳米风险”，定义为纳米银在多大程度上有可能造成环境风险，超出了从源条件和以往经验和传统银形式的数据容易估计的范围。这是一个关键的监管问题，决定了nAg是否需要作为纳米风险进行特殊考虑，或者可以作为常规的Ag离子释放进行处理。最后，深入了解Ag+释放动力学和机制将有助于开发控释制剂，优化nAg的使用，避免材料浪费和真核细胞毒性作为抗菌医疗产品的副作用。

AbstractProposal 1057547Objective:This project focuses on the exposure pathways, fate, and risk of nano-silver in the natural environment. The objective of this proposal is to address two hypothesis: (1) nano-silver can undergo complete reactive dissolution in the environment through kinetically limited oxidation processes. Nano-silver will be non persistent in particle form in environmental compartments containing dissolved oxygen, but persistent in anoxic compartments or in biological matrices containing reducing agents. (2) Reactive dissolution rates will show significant dependence on nAg particle size, surface state (ligands, coatings) and media composition, requiring detailed experimentation in complex media and biological tissue to make useful predictions for life-cycle risk assessment. The project will proceed in four tasks: (1) development of a first generation model of sources and materials flows of nano-silver in the environment accounting for dynamic dissolution behavior, (2) detailed kinetics and mechanisms of nanosilver dissolution, accounting for the effects of stabilizing ligands attached to the particle surfaces, coatings, composition of the near-particle environment, and surface oxidation state, (3) silver distribution and nanoparticle persistence in biological compartments, through experiments using the organism Xenopus laevis, an amphibian used as a model sentinel species in aquatic systems that is highly vulnerable to environmental pollutants and well suited to the study of nanosilver biodistribution and persistence, and (4) integrated model development and analysis to differential nano-risk. Intellectual merit: This proposal will find solutions to some of the toxicity issues as a result of nano-silver-containing products are washed, abraded, or discarded, silver can enter the environment either as nanoparticles, nanoparticle aggregates, or soluble ions. Silver is reported to be highly toxic to some aquatic organisms, and as an antibiotic may also damage or alter beneficial microbial communities in the environment. Silver is also known to bioaccumulate in phytoplankton and some marine invertebrates and has been shown to be highly toxic to zebrafish embryos. Broader Impacts This project addresses the potential environmental impacts of one of the highest production volume nanotechnology products on the current market: nano-silver. The main result of this project will be a conceptual model of nano-silver exposure pathways, allowing estimation of the location, forms, and concentrations of silver in a variety of environmental compartments. The work will provide policy-relevant information to help define the "differential nano-risk" defined as the extent to which nano-silver has the potential to pose environmental risks beyond those easily estimable from source terms and prior experience and data on conventional silver forms. This is a key regulatory issue that governs whether nAg requires special consideration as a nano-risk or can be treated as a conventional Ag ion release. Finally, insight into Ag+ release kinetics and mechanisms will and aid in the development of controlled release formulations that optimize the use of nAg and avoid material waste and eukaryotic toxicity as a side effect of antibacterial medical products.