环境老化过程和细胞膜通透性对纳米金属氧化物植物吸收的影响研究

Understanding plant uptake and translocation of nanoparticles has been one of the top-priority issues in environmental science research. Environmental processes are known to alter the properties and bioavailability of nanoparticles, thereby influencing their plant uptake. Environmental aging is therefore an important factor affecting plant uptake of nanoparticles in the natural environment. Endocytosis is shown to be the principal transmembrane pathway of nanoparticles in plant, which is closely related to the permeability of cell membrane. Variation in the permeability of plant cell membrane arising from metal oxide nanoparticles and hence the accumulation of reactive oxygen species is therefore expected to influence their distribution in plant. As such, this project is designed based on environmental aging process and the permeability of cell membrane as the center stage to explore plant uptake and distribution of nanoparticles, in relation to the state of nanoparticles in environmental media as affected by environmental aging, and the variation in membrane fatty acid profiles. Arabidopsis will be used as the model plant, and CuO and TiO2 nanoparticles as the model metal oxide nanoparticles. The proposed work includes the variation in CuO and TiO2 nanoparticle state in nutrient solution as influenced by environmental aging, the uptake and distribution of CuO and TiO2 nanoparticles subjected to different degrees of aging, as well as membrane fatty acid profiles in tissues of Arabidopsis. The results will be used to elucidate the role of environmental aging and cell membrane permeability in plant uptake and distribution of nanoparticles. The successful implementation of this project is expected to not only advance our knowledge of nanoparticle plant uptake, but also provide a scientific foundation for rational ecological risk assessment of nanoparticles, both theoretically and practically.

研究纳米颗粒植物吸收是评估纳米颗粒生态风险的关键之一。环境行为能改变纳米颗粒的性质和生物可利用性，从而影响植物吸收，因此环境老化过程是影响纳米颗粒植物吸收的重要因素。内吞作用是纳米颗粒主要跨膜运输途径，与细胞膜通透性密切相关，纳米金属氧化物因活性氧自由基积累造成的植物细胞膜通透性变化，会影响其植物分布。本课题据此立项，以环境老化过程和细胞膜通透性为中心，以拟南芥为模式植物，以纳米CuO和TiO2为代表性纳米颗粒，测定营养液中纳米CuO和TiO2存在状态随环境老化的变化、拟南芥对不同老化程度纳米CuO和TiO2的吸收与分布、及植物各部分细胞膜脂肪酸饱和度，探索纳米颗粒存在状态、脂肪酸饱和度变化与纳米颗粒植物吸收与分布之间的关系，从而阐明环境老化过程、细胞膜通透性在纳米颗粒植物吸收中的作用及影响规律。本研究将是纳米颗粒植物吸收理论的重要拓展，并为合理评估纳米颗粒生态风险提供理论和现实依据。

本项目围绕纳米颗粒（NPs）的环境老化过程和行为以及NPs的植物吸收和效应展开研究，取得了预期的成果。实验用NPs为nCuO、nZnO、nSiO2和nAu，植物为拟南芥和麦苗。采用吸光度动态分析、动态光散射及电泳淌度等技术，研究了NPs的团聚、沉降和溶解规律。通过植物水培吸收实验，测定了暴露于不同老化程度NPs及相应对照组植株中的金属离子总量及分布含量、脂肪酸饱和度，研究了环境老化过程及其细胞膜流动性和通透性对NPs植物吸收和分布的影响，探讨了环境老化过程在NPs植物吸收和分布中的作用、以及细胞膜流动性对NPs植物分布的影响规律。NPs在水环境中的团聚、沉降和溶解不但取决于水化学因素，同时取决于NPs自身的化学性质。nCuO的团聚与沉降主要受NOM与表面Cu2+的螯合作用主导，其溶解释放Cu2+受无机盐和NOM共同影响，颗粒对费氏狐菌直接产生毒性。nZnO的团聚与沉降主要受IS控制，其溶解释放Zn2+主要受NOM决定，主要由Zn2+对费氏狐菌产生毒性。nSiO2对NOM吸附能力低且Hamaker常数较小，其团聚与沉降并不取决于水环境条件，但溶解受无机盐影响。暴露于nZnO的小麦苗对Zn具有明显的累积，导致根部和茎叶部细胞膜流动性下降，但并不存在真正的纳米效应，其累积过程及其产生的植物毒性主要通过吸收溶出Zn2+作为主要作用机制。暴露于nCuO的拟南芥能显著累积Cu，细胞中发现CuO固体的存在，根细胞膜流动性下降主要由nCuO引起，而茎叶细胞膜流动性下降主要由Cu2+造成，累积过程和毒性作用中表现出明显的纳米效应。重新暴露于无Cu污染水中，拟南芥释放出Cu，细胞膜流动性恢复正常，表现出很好的可逆性。nCuO暴露造成的细胞膜流动性下降降低对nAu的吸收和转运。因此，可以通过改变细胞膜流动性来调控植物对纳米颗粒的吸收，为有效控制纳米颗粒的生态风险提供了很好的技术思路和手段。发表两篇论文、在投两篇，另一篇稿件在撰写中，共计可产生五篇论文。授权和申请发明专利两件。参加国际学术会议两人次、国内会议两人次。培养了一名本科、一名硕士，两名博士研究生即将毕业。