University of Kentucky , Department of Plant and Soil Sciences, Lexington Kentucky 40546, United States.
Environ Sci Technol. 2014 Jan 21;48(2):1280-9. doi: 10.1021/es404503c. Epub 2014 Jan 8.
The objective of this study was to investigate the role of the CeO2 nanoparticle (NP) surface charge and the presence of natural organic matter (NOM) in determining bioavailability and toxicity to the model soil organism Caenorhabditis elegans. We synthesized CeO2-NPs functionalized with positively charged, negatively charged, and neutral coatings. The positively charged CeO2-NPs were significantly more toxic to C. elegans and bioaccumulated to a greater extent than the neutral and negatively charged CeO2-NPs. Surface charge also affected the oxidation state of Ce in C. elegans tissues after uptake. Greater reduction of Ce from Ce (IV) to Ce (III) was found in C. elegans, when exposed to the neutral and negatively charged relative to positively charged CeO2-NPs. The addition of humic acid (HA) to the exposure media significantly decreased the toxicity of CeO2-NPs, and the ratio of CeO2-NPs to HA influenced Ce bioaccumulation. When the concentration of HA was higher than the CeO2-NP concentration, Ce bioaccumulation decreased. These results suggest that the nature of the pristine coatings as a determinant of hazard may be greatly reduced once CeO2-NPs enter the environment and are coated with NOM.
本研究旨在探讨 CeO2 纳米颗粒（NP）表面电荷和天然有机物（NOM）的存在在确定模型土壤生物秀丽隐杆线虫的生物可利用性和毒性方面的作用。我们合成了带有正电荷、负电荷和中性涂层的 CeO2-NP。带正电荷的 CeO2-NP 对秀丽隐杆线虫的毒性明显更大，并且比中性和负电荷的 CeO2-NP 更易生物积累。表面电荷也影响了 Ce 在秀丽隐杆线虫组织中的氧化态在摄取后的状态。与带正电荷的 CeO2-NP 相比，当暴露于中性和带负电荷的 CeO2-NP 时，在秀丽隐杆线虫中发现 Ce 从 Ce(IV)还原为 Ce(III)的程度更大。在暴露介质中添加腐殖酸（HA）显著降低了 CeO2-NP 的毒性，并且 CeO2-NP 与 HA 的比例影响了 Ce 的生物积累。当 HA 的浓度高于 CeO2-NP 的浓度时，Ce 的生物积累减少。这些结果表明，一旦 CeO2-NP 进入环境并被 NOM 覆盖，原始涂层的性质作为危害决定因素的可能性可能会大大降低。
