Journal
CHEMOSPHERE
Volume 144, Issue -, Pages 1682-1689Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2015.10.066
Keywords
Aging; Carboxymethyl cellulose; Colloidal stability; Escherichia coli; Nanoscale zero-valent iron; Toxicity
Categories
Funding
- Fundamental Research Funds for the Central Universities [531107040788]
- National Natural Science Foundation of China [51409100, 51521006, 51378190]
- Program for Changjiang Scholars and Innovative Research Team in University [IRT-13R17]
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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 (Ca2+) 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 Ca2+ 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 to the less toxic or non-toxic iron oxides, as indicated by the XRD analysis. (C) 2015 Elsevier Ltd. All rights reserved.
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