Dong Haoran, Xie Yankai, Zeng Guangming, Tang Lin, Liang Jie, He Qi, Zhao Feng, Zeng Yalan, Wu Yanan
College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan 410082, China.
College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan 410082, China.
Chemosphere. 2016 Feb;144:1682-9. doi: 10.1016/j.chemosphere.2015.10.066. Epub 2015 Nov 11.
Nanoscale zero-valent iron (NZVI) particles are usually modified with surface coating to mitigate the particle stability in water during the environmental application. However, the surface coating may not only influence the particle stabilization but also the particle cytotoxicity. In this study, we investigated the dual effects of carboxymethyl cellulose (CMC) on the colloidal stability and cytotoxicity of NZVI towards gram-negative Escherichia coli (E. coli) and discussed the interrelation between particle stability and cytotoxicity. The effect of CMC concentration, ionic strength (Ca(2+)) and aging treatment on the particle cytotoxicity were also examined. Specifically, the aqueous stability of NZVI suspensions with CMC ratio dose-dependently strengthened within 1 h. The inactivation of E. coli by bare NZVI was significant and concentration- and time-dependent. On the contrary, an increasing reduction in cytotoxicity of NZVI with CMC ratio increasing was observed, even though the particles became more dispersed. TEM analysis demonstrates the membrane disruption and the cellular internalization of nanoparticles after exposure of E. coli to NZVI. However, in the case of CMC-modified NZVI (CNZVI), the bacterial cell wall displays an outer shell of a layer of nanoparticles attached around the outer membrane, but the cell membrane was kept intact. The presence of Ca(2+) can either increase or decrease the cytotoxicity of NZVI and CNZVI, depending on the concentration. The aged NZVI and CNZVI particles did not seem to present obvious bactericidal effect due to the transformation of Fe(0) to the less toxic or non-toxic iron oxides, as indicated by the XRD analysis.
纳米零价铁（NZVI）颗粒通常通过表面包覆进行改性，以减轻其在环境应用过程中在水中的颗粒稳定性。然而，表面包覆不仅可能影响颗粒的稳定性，还可能影响颗粒的细胞毒性。在本研究中，我们研究了羧甲基纤维素（CMC）对NZVI对革兰氏阴性大肠杆菌（E. coli）的胶体稳定性和细胞毒性的双重影响，并讨论了颗粒稳定性与细胞毒性之间的相互关系。还考察了CMC浓度、离子强度（Ca(2+)）和老化处理对颗粒细胞毒性的影响。具体而言，NZVI悬浮液与CMC比例的水稳定性在1小时内呈剂量依赖性增强。裸露的NZVI对大肠杆菌的灭活作用显著，且具有浓度和时间依赖性。相反，尽管颗粒变得更加分散，但随着CMC比例增加，观察到NZVI的细胞毒性呈逐渐降低的趋势。透射电镜分析表明，大肠杆菌暴露于NZVI后，纳米颗粒会破坏细胞膜并被细胞内化。然而，在CMC改性的NZVI（CNZVI）的情况下，细菌细胞壁在外膜周围显示出一层附着的纳米颗粒外壳，但细胞膜保持完整。Ca(2+)的存在可根据浓度增加或降低NZVI和CNZVI的细胞毒性。如X射线衍射分析所示，老化的NZVI和CNZVI颗粒似乎没有呈现明显的杀菌作用，这是由于Fe(0)转化为毒性较小或无毒的铁氧化物所致。
