Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China.
Environ Int. 2011 Aug;37(6):1098-104. doi: 10.1016/j.envint.2011.01.008. Epub 2011 Mar 13.
The extensive use of nanoparticles (NPs) in a variety of applications has raised great concerns about their environmental fate and biological effects. This study examined the impact of dissolved organic matter (DOM) and salts on ZnO NP dispersion/solubility and toxicity to the earthworm Eisenia fetida. To be able to better evaluate the toxicity of NPs, exposure in agar and on filter paper was proposed for enabling a comparison of the importance of different uptake routes. A dose-related increase in mortality was observed in earthworms exposed in agar with almost 100% mortality after 96 h exposure to the highest concentration (1000 mg ZnO/kg agar). Scanning electron microscopy (SEM) showed that the addition of salts enhanced the aggregation of ZnO NPs in agar and consequently affected the dissolution behavior and biological availability of the particles. On filter paper, mortality was the highest at the lowest exposure concentration (50 mg ZnO/L) and seemed to decrease with increasing exposure levels. TEM images of ZnO showed that the solubility and morphology of NPs were changed dramatically upon the addition of humic acids (HA). The subcellular distribution pattern of Zn in earthworms after 96 h exposure in agar and on filter paper showed that the Zn taken up via dietary ZnO particles (from agar) was mainly found in organelles and the cytosol while the Zn accumulated as soluble Zn from filter paper was mainly distributed in cell membranes and tissues. Antioxidant enzymatic activities (SOD, CAT, and GSH-px) were investigated in the worms surviving the toxicity tests. A slight increase of SOD activities was observed at the lowest exposure dose of ZnO (50mg/kg), followed by a decrease at 100mg/kg in the agar cubes. Activities of both CAT and GSH-Px enzymes were not significantly influenced in the worms exposed to agar, although a slight decrease at 500 and 1000 mg ZnO/kg agar was observed. A similar change trend of SOD activities was observed for the earthworms on filter paper, but a significant decrease began at a higher ZnO NP concentration of 500 mg ZnO/L. The use of soil extracts instead of deionized water (DW) to simulate a realistic exposure system significantly reduced the toxicity of the ZnO NPs on filter paper, which increases the predictive power of filter paper toxicity tests for the environmental risk assessment of NPs.
纳米颗粒（NPs）在各种应用中的广泛使用引起了人们对其环境归宿和生物效应的极大关注。本研究考察了溶解有机物（DOM）和盐对 ZnO NPs 分散/溶解度以及对蚯蚓赤子爱胜蚓毒性的影响。为了能够更好地评估 NPs 的毒性，提出了在琼脂和滤纸上暴露的方法，以便能够比较不同摄取途径的重要性。在琼脂中暴露的蚯蚓死亡率呈剂量相关性增加，在最高浓度（1000mg ZnO/kg 琼脂）暴露 96 小时后，几乎 100%的蚯蚓死亡。扫描电子显微镜（SEM）显示，盐的添加增强了 ZnO NPs 在琼脂中的聚集，从而影响了颗粒的溶解行为和生物可利用性。在滤纸上，最低暴露浓度（50mg ZnO/L）时死亡率最高，随着暴露水平的增加似乎有所下降。TEM 图像显示，腐殖酸（HA）的添加极大地改变了 ZnO 的溶解度和形态。在琼脂和滤纸上暴露 96 小时后，蚯蚓体内 Zn 的亚细胞分布模式表明，通过饮食摄入的 ZnO 颗粒（来自琼脂）中的 Zn 主要存在于细胞器和细胞质中，而从滤纸上积累的可溶性 Zn 主要分布在细胞膜和组织中。在幸存的毒性试验的蚯蚓中，研究了抗氧化酶活性（SOD、CAT 和 GSH-px）。在 ZnO 的最低暴露剂量（50mg/kg）下观察到 SOD 活性略有增加，随后在琼脂立方体中 100mg/kg 时活性降低。暴露于琼脂的蚯蚓中 CAT 和 GSH-Px 酶的活性没有明显受到影响，尽管在琼脂中观察到 500 和 1000mg/kg ZnO 时略有下降。在滤纸上的蚯蚓中观察到 SOD 活性的相似变化趋势，但在 500mg ZnO/L 更高的 ZnO NP 浓度下，活性开始显著下降。使用土壤提取物而不是去离子水（DW）来模拟实际暴露系统，显著降低了滤纸上 ZnO NPs 的毒性，从而提高了滤纸上毒性试验对 NPs 环境风险评估的预测能力。
