MOE Key Laboratory of Environmental Remediation & Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China.
Environ Sci Technol. 2010 Jul 1;44(13):4981-7. doi: 10.1021/es100507p.
Chitosan, a natural polysaccharide, is widely regarded as a biocompatible and potential carrier for controlled-release drug formulations. However, the potential effect of chitosan on the environmental behavior of contaminants is poorly understood, especially on chiral chemicals. In this study, the changes in bioavailability of the chiral herbicide dichlorprop to Chlorella pyrenoidosa by chitosan were investigated. The dissipation of (S)-enantiomer in Chlorella pyrenoidosa culture media without chitosan was faster than that of the herbicidally active (R)-enantiomer, whereas it was inversed to (R)-enantiomer being faster than (S)-enantiomer when chitosan was added into the media. In the absence of chitosan, the toxicity of (R)-enantiomer to Chlorella pyrenoidosa was more potent than that of the (S)-enantiomer. On the contrary, in the presence of chitosan, (R)-enantiomer was less toxic than (S)-enantiomer. These observations clearly suggest that chitosan changed the enantioselective bioavailability of dichlorprop. Fluorescence spectroscopic analysis showed that the interaction between chitosan and dichlorprop enantiomers depended greatly on the steric structure of dichlorprop, which offers a possible explanation as to why the addition of chitosan changed the enantioselective dissipation of dichlorprop by Chlorella pyrenoidosa. This work suggests that the enantioselective behaviors of chiral compounds in the environment might be shifted when interactions with other chiral receptors coexist.
壳聚糖是一种天然多糖，被广泛认为是一种具有生物相容性和潜在的控释药物制剂载体。然而，壳聚糖对污染物环境行为的潜在影响，尤其是对手性化学物质的影响，还了解甚少。在这项研究中，研究了壳聚糖对小球藻生物可利用性的变化二氯丙酸。在没有壳聚糖的小球藻培养基中，（S）-对映体的消解速度比具有除草活性的（R）-对映体快，而当向培养基中加入壳聚糖时，（R）-对映体的消解速度比（S）-对映体快。在没有壳聚糖的情况下，（R）-对映体对小球藻的毒性比（S）-对映体更强。相反，在存在壳聚糖的情况下，（R）-对映体的毒性比（S）-对映体小。这些观察结果清楚地表明，壳聚糖改变了二氯丙酸的对映体选择性生物可利用性。荧光光谱分析表明，壳聚糖与二氯丙酸对映体之间的相互作用在很大程度上取决于二氯丙酸的立体结构，这为为什么添加壳聚糖会改变小球藻对二氯丙酸的对映体选择性消解提供了一个可能的解释。这项工作表明，当与其他手性受体相互作用共存时，环境中手性化合物的对映体行为可能会发生变化。
