硫化物纳米颗粒对大肠杆菌的光致毒性及机理研究

The wide application of sulfide nanoparticles (NPs) in the fields of optics, electronics, and magnetism leads to their potential risk toward ecosystem and human health. This project intends to prepare sulfide NPs (cadmium sulfide, zinc sulfide, copper sulfide, manganese sulfide, and lead sulfide) by the hydrothermal synthesis method. The Escherichia coli cells (E. coli) ubiquitous in aqueous environment have been selected as model organism to investigate the effect of sulfide NPs on bacterial activity, protein contents, enzyme activity, and morphological change of E. coli cells under different light irradiation conditions (xenon lamp, mercury lamp, and solar). The ROS types, concentrations, and mechanism photogenerated by NPs and the effect of ROS scavengers on bacterial activity will be investigated to elucidate the mechanism of oxidative stress on photoinduced toxicity of NPs toward E. coli cells. To elucidate the effect mechanism of toxic ions released by NPs on their photoinduced toxicity toward E. coli cells, the quantitative relationship between the concentrations of released ions and the survival rates of bacteria will be established. The mechanism of NP size effect on bacterial activity will be investigated by the influence of initial NP size and hydrodynamic size change induced by light on survival rates of bacteria. The unknown toxic mechanism of sulfide NPs toward bacteria and the difference and relationship between each mechanism of NPs on bacteria could be elucidated. The implementation of this project will provide foundation data and theoretical basis for understanding and reducing the risk of sulfide NPs toward ecosystem and human health.

金属硫化物纳米颗粒（NPs）在光、电和磁学等方面广泛应用的同时，对生态系统和人类健康构成了潜在的危害。本项目拟采用水热合成法制备典型金属硫化物NPs（硫化镉、硫化锌、硫化铜、硫化锰和硫化铅），以水中普遍存在的大肠杆菌为模型生物，研究不同光源照射下（氙灯、汞灯和太阳光）金属硫化物NPs对细菌活性、蛋白质含量、酶活性和表面形态的影响，考察每种NPs光致活性氧自由基（ROS）的种类、浓度和机理，结合ROS淬灭剂加入后NPs对细菌活性的影响，阐明氧化应激效应对细菌光致毒性的作用机理，建立NPs释放金属离子的浓度与其对细菌光致毒性的定量关系，研究NPs的粒径和光致NPs水力学直径的变化对细菌毒性的影响机理，揭示尚不明确的金属硫化物NPs对细菌光致毒性的作用机理，并识别每种机理对细菌毒性作用的区别和联系。本项目的实施，能够为深入了解和减轻金属硫化物NPs对生态系统和人类健康的危害提供基础数据和理论依据

金属硫化物纳米颗粒(NPs)在光、电和磁学等方面广泛应用的同时，对生态系统和人类健康构成了潜在的危害。本项目以典型金属硫化物NPs (硫化镉CdS、硫化钼MoS2和硫化钨WS2)为目标，研究紫外光照下金属硫化物NPs对大肠杆菌(E. coli)活性、表面形态和核酸释放量的影响，考察NPs光致活性氧自由基(ROS)和释放毒性金属离子的浓度和机理，结合ROS淬灭剂或金属离子加入后细菌活性的变化，阐明氧化应激效应和毒性金属离子释放对细菌光致毒性的作用机理，探讨天然水体中广泛存在的有机质(NOM)对三种纳米颗粒光致毒性的影响。本项目取得了以下三个方面的重要结果：(1) 在相同浓度下，三种NPs对细菌的毒性遵循如下顺序：CdS > MoS2 > WS2。暴露于50 mg/L CdS、MoS2和WS2 NPs的细菌死亡率分别为96.7％、38.5％和31.2％。透射电子显微镜和激光共聚焦显微镜照片显示，暴露在三种NPs的细菌细胞壁被破坏，细胞内成分释放出来。与MoS2和WS2 纳米颗粒相比，CdS处理后的细菌细胞膜的变形更显著。(2) 在紫外光照射下，WS2和MoS2 纳米颗粒产生超氧自由基(O2•−)、单线态氧(1O2)和羟基自由基(•OH)，而CdS只产生O2•−和1O2。NOM可以过滤紫外线或作为抗氧化剂减少WS2和MoS2产生三种ROS的浓度。HA/NPs混合体系中HA较高的吸光度和HA与ROS较快的反应速度导致HA对WS2和MoS2产生O2•−和•OH的抑制作用高于FA。HA和FA能够彻底抑制WS2和MoS2产生1O2。NOM可以向CdS传递电子促进其产生O2•−。无论有无NOM，CdS均未产生•OH。由于FA和1O2之间的反应速率较高，FA对CdS产生1O2的抑制作用高于HA。CdS和WS2在紫外光照射下能够释放金属离子，而MoS2不能释放金属离子。HA对CdS和WS2溶解的抑制作用高于FA。(3) ROS产生和毒性离子的释放共同导致了CdS和WS2 对细菌的毒性。ROS产生是MoS2对细菌的主要毒性机制。HA和FA对CdS抗菌活性的影响很小，但由于降低了WS2和MoS2 产生ROS和/或溶解浓度，抑制了WS2和MoS2对细菌的毒性。本项目的实施，有助于了解纳米颗粒进入天然水体后的环境行为，能够为了解和减轻纳米颗粒对生态系统和人类健康的危害提供基础数据和理论依据。