Study of the toxicity of ZnO nanoparticles to Chlorella sorokiniana under the influence of phosphate: spectroscopic quantification, photosynthetic efficiency and gene expression analysis
Study of the toxicity of ZnO nanoparticles to Chlorella sorokiniana under the influence of phosphate: spectroscopic quantification, photosynthetic efficiency and gene expression analysis
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磷酸盐影响下ZnO纳米颗粒对小球藻的毒性研究：光谱定量、光合效率和基因表达分析
DOI：
10.1039/c9en01464k
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Qing Huang
中科院分区：
文献类型：
--
作者：
Hong Zhang;Zhu Chen;Qing Huang
氧化锌纳米颗粒（ZnO NPs）是纳米技术为基础的工业中应用最广泛的纳米材料之一，最近的研究继续强调其潜在的生态毒性，特别是对水生环境。当它们进入水环境时，它们的物理化学转化可能会产生基本上未知的最终产品，并引起额外的潜在毒性。虽然以前的研究已经记录了ZnO纳米颗粒的转化，仍然缺乏深入的了解，相应的原始和转化的ZnO纳米颗粒对水生生物的毒性变化，特别是需要的物理化学转化的定量分析，以区分其在毒性评估中的贡献。因此，为了这个目的，我们开始研究在含磷酸盐的水中转化的ZnO NP对模型水生微生物的毒性，即，小球藻sorokiniana，借助光谱工具的表征和量化的物理化学转化，我们仔细研究了不同的P/Zn摩尔比转化的ZnO纳米颗粒的毒性变化。对可能的毒性机制进行了探讨，特别是与影响藻细胞光合作用效率有关的机制。结果发现，在磷酸盐水中转化的ZnO纳米颗粒对绿色藻类的毒性低于原始ZnO纳米颗粒。利用XRD和拉曼光谱等光谱工具，我们对ZnO纳米颗粒的物理化学变化进行了定性和定量评估，并揭示了对于原始ZnO纳米颗粒组，毒性主要源于原始ZnO纳米颗粒中锌离子的释放，而在磷酸盐存在下，纳米颗粒的新形成起着关键作用，由于转化的化合物中毒性较小的无定形磷酸锌（AZP）和磷酸锌（Zn 3（PO 4）2·4 H2O），导致总体毒性降低。此外，还对磷酸盐毒性诱导ZnO纳米颗粒向C. sorokiniana也通过光合作用相关基因表达的分析得到了验证。结果表明，未经处理的ZnO纳米颗粒抑制了光合作用相关基因的表达，而未经处理的ZnO纳米颗粒和未经处理的AZP纳米颗粒则上调了光合作用相关基因的表达，表明可溶性磷酸盐对藻类光合作用有显著影响，从而影响了ZnO纳米颗粒在水环境中的藻类毒性。这些新获得的结果肯定会阐述我们的知识的命运和影响的ZnO NP转化在水生环境中。
Zinc oxide nanoparticles (ZnO NPs) are one of the most abundantly applied nanomaterials in nanotechnology-based industries, and recent research continues to highlight their potential eco-toxicity especially to aquatic environments. When they enter into a water environment, their physicochemical transformations may result in largely unknown end products and induce additional potential toxicity. Although previous studies have documented the transformation of ZnO NPs, there is still a lack of the in-depth understanding of the corresponding variant toxicities of the pristine and transformed ZnO NPs to aquatic organisms, particularly demanding the quantitative analysis of the physicochemical transformations to distinguish their contributions in the toxicity assessment. For this purpose, therefore, we initiated a study of the toxicity of transformed ZnO NPs in phosphate containing water to a model aquatic microalga, i.e., Chlorella sorokiniana, with the aid of spectroscopic tools for characterization and quantification of the physicochemical transformations, and we scrutinized the toxicity variations of ZnO NPs transformed in different P/Zn molar ratios. The possible toxicity mechanisms were investigated, especially those related to the influence of photosynthesis efficiency of the algae cells. As a result, we found that the toxicity of transformed ZnO NPs in phosphate water to the green algae was lower than that of the pristine ZnO NPs. With spectroscopic tools such as XRD and Raman spectroscopy, we made both qualitative and quantitative assessments of the physicochemical changes of the ZnO NPs and revealed that for the pristine ZnO NP group, the toxicity stemmed mainly from the release of zinc ions from the pristine ZnO NPs, while in the presence of phosphate, the neoformation of the nanoparticles played a critical role, leading to the overall reduced toxicity due to the less toxic amorphous zinc phosphate (AZP) and hopeite (Zn3(PO4)2·4H2O) in the transformed compounds. Besides, the mechanism of the toxicity of phosphate induced transformations of ZnO NPs to C. sorokiniana was also verified by the analysis of gene expression involved in photosynthesis. Our results showed that the expressions of the photosynthesis associated genes were depressed by the treatment of pristine ZnO NPs, while the expressions of the related genes were up-regulated in the groups of hopeite and AZP, indicating that the soluble phosphate had profound effects on algal photosynthesis, and thus affected the algal toxicity of ZnO NPs in the aqueous environment. These newly acquired results will certainly elaborate our knowledge on the fate and effects of ZnO NP transformation in aquatic environments.