Abstract
In this study, the conditions and mechanism of antibacterial activity of hydrophilic polymer coated silver nanoparticles (AgNPs) against E. coli O157:H7 (CMCC44828) as model pathogen was studied. The AgNPs were coated with amphiphilic polymer that introduced carboxyl groups on the surface to make it water-soluble. The AgNPs were exposed to various treatment conditions of pH and temperature before these were combined with the E. coli. The mechanism of the antibacterial activity was studied through the formation of reactive oxygen species (ROS) that was later suppressed with antioxidant to establish correlation with the AgNPs antimicrobial activity. Studies were carried out at both anaerobic and aerobic conditions. The results indicated that 5 mg/L AgNPs inhibited ~50% of the growth of 106 colony forming units per milliliter (cfu/mL) E. coli cells in liquid Luria–Bertani (LB) medium. This dose-dependent antimicrobial activity was higher at increased temperature (37°C) but was lower when the AgNPs were treated with acid at pH 2 before exposure to the bacteria. It was also established that the conditions of higher antimicrobial effect generated more ROS that was dependent on the presence of oxygen. The antibacterial activity was suppressed in the presence of an antioxidant.
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Acknowledgments
This study was partly supported by a grant from “Cultivating the Excellent PhD Thesis of Jiangxi Province (YBP08A03)” of the Education Department of Jiangxi Province, China. The authors would like to thank Mr. Benjamin Jones and Mr. John Dixon for the AgNPs purification.
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Hengyi Xu and Feng Qu contributed equally to this study.
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Xu, H., Qu, F., Xu, H. et al. Role of reactive oxygen species in the antibacterial mechanism of silver nanoparticles on Escherichia coli O157:H7. Biometals 25, 45–53 (2012). https://doi.org/10.1007/s10534-011-9482-x
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DOI: https://doi.org/10.1007/s10534-011-9482-x