纳米银在牡蛎幼体内累积和形态转化的机制与影响因素

Myriad production and application of silver nanoparticles (AgNPs) has attracted a great deal of concerns over their potential risk to environment and human health. A few studies have shown that silver nanoparticles could be ingested and accumulated by marine bivalves in the estuary area. AgNPs may enter the digestive gland after filtration through the gill of the bivalves, and undergo complex biotransformation. Mechanisms underlying the uptake, transformation and distribution of AgNPs in bivalves are unclear. In addition, there is still a lack of studies on the effect of multiple influencing factors on transformations of AgNPs in bivalves, which may limit the accurate understanding of the bioavailability and toxic mechanisms. In this proposal, oyster larvae will be used as testing organism. Traditional biological dynamic method combined with dual stable isotope tracing, aggregation-induced emission technique, and super-resolution imaging techniques will be employed to study the differential uptake and accumulation of AgNPs and dissolved Ag, and to trace and analyze the source and speciation distribution of Ag in bivalves. The effect of particle size, surface coating, salinity and exposure routes on the accumulation and transformation of AgNPs in the organism will be comprehensively studied. The mechanisms underlying the physicochemical transformation of AgNPs in marine organism and even cells will be elucidated. The outcomes of this project will shed new light on the understanding of the bioavailability and toxicity of nanoparticles, and provide data for environmental risk assessment of nanoparticles.

纳米银的大量生产与应用使得人们极为关注其对环境及人类健康的危害。已有研究表明纳米银能被河口区的海洋双壳类生物吸收累积。纳米银可能经双壳类生物的鳃过滤进入消化腺后发生复杂的生化反应而产生形态转化。目前对纳米银在双壳类生物体内的迁移、形态分布及转化机制不清，更缺乏不同因素影响其在体内迁移转化的针对性研究，这在很大程度上限制了对纳米银生物有效性和毒性机制的准确认识。因此本项目拟以牡蛎幼体为测试生物，采用传统的动力学方法与双重稳定同位素示踪技术、聚集诱导发光技术及先进的超分辨显微成像技术结合，研究其对纳米银及溶解态银不同的吸收累积过程，追溯并分析体内Ag的来源及形态分布，系统研究粒径、表面修饰、盐度及暴露方式对纳米银在生物体内累积及迁移转化过程的影响，最终阐明纳米银在生物体及细胞内的形态转化机制，研究结果将有助于加深对纳米颗粒生物有效性及毒性机制的认识，并为纳米材料的环境风险评估提供科学依据。

随着大量生产和使用，纳米银（AgNPs）不可避免会进入水体，对生生生物造成一定的威胁。为准确评估AgNPs的毒性，了解其在生物体内的分布及转化尤为重要。已有研究表明AgNPs能被海洋双壳类生物吸收累积。因此，本项目以葡萄牙牡蛎（Crassostrea angulata）幼体为研究对象，通过传统的电感耦合等离子体质谱法（ICP-MS）结合先进的聚集诱导发光（AIE）技术，监测AgNPs在牡蛎幼体内的积累及溶解等过程，评估了AgNPs在体内的溶解转化对AgNPs毒性的贡献；采用纳米二次离子质谱（NanoSIMS）等超分辨显微成像技术研究AgNPs暴露后牡蛎幼体不同组织或器官内Ag亚细胞水平的原位分布，揭示AgNPs在牡蛎幼体内的迁移转化及可能的解毒机制。.研究发现牡蛎幼体可直接摄入AgNPs颗粒，堆积在胃腔中，并会继续溶解释放Ag+。AgNPs对牡蛎幼体的毒性不完全是由AgNPs在体外溶解的Ag+引起的。牡蛎幼体内的Ag主要源于溶解态Ag，尤其是AgNPs被摄入后在体内溶解释放的Ag+。AgNPs吸附到细胞膜上会继续释放Ag+，在细胞外主要形成无机Ag-S复合物，而内化的Ag则会与细胞溶质中的富含S的分子（如金属硫蛋白等）形成有机硫复合物，并被隔离于面盘、食道和胃细胞的溶酶体以及消化细胞的消化泡中，这可能是牡蛎幼体对AgNPs的解毒机制。只有少量Ag分布在磷酸盐颗粒、粗面内质网和线粒体中。研究结果将加深对AgNPs的毒性效应及生物有效性的认识，为评估AgNPs的环境风险提供科学数据。在本项目支持下，共发表2篇标注SCI论文，培养3名硕士研究生。