Main content area

Dual impact of dissolved organic matter on cytotoxicity of PVP-Ag NPs to Escherichia coli: Mitigation and intensification

Zhang, Weicheng, Huang, Jiaolong, Liang, Lei, Yao, Lunguang, Fang, Tao
Chemosphere 2019 v.214 pp. 754-763
Danio rerio, Escherichia coli, bioassays, cytotoxicity, dissolved organic matter, embryo (animal), fulvic acids, humic acids, ions, models, nanosilver, risk assessment, silver, viability
Cytotoxicity of silver nanoparticles (Ag NPs) is attributed to silver internalization, which can be depressed by dissolved organic matter (DOM) to form Ag-DOM. Ag-DOM are bioavailable and then silver internalization could be increased. Herein, 3 and 48-h Escherichia coli viability bioassays were employed to evaluate effect of fulvic acid and humic acid (10 mg L−1) on cytotoxicity of 30 and 100 nm PVP-Ag NPs. Moreover, zebrafish embryos were used as reference model to understand silver internalization routes. Ag ions or Ag-DOM internalization varied in routes to Escherichia coli and zebrafish embryos. Cytotoxicity mechanisms of PVP-Ag NPs are dynamic. In 3-h bioassays, cytotoxicity of PVP-Ag NPs mainly involves Ag particle-related toxicity. DOM significantly mitigated cytotoxicity of PVP-Ag NPs (p < 0.05) through adhering on surface of PVP-Ag NPs. Ag ions or Ag-DOM were hardly internalized into Escherichia coli cells during 3-h exposures duration. In 48-h bioassays, cytotoxicity of PVP-Ag NPs is dependent on Ag ion-related and particle-related toxicity. Silver was internalized into Escherichia coli via Ag-DOM consumption as an indirect route. Thus, DOM promoted silver internalization into Escherichia coli but not into zebrafish embryos, significantly intensifying cytotoxicity (p < 0.05). The results suggested DOM has a dual impact on cytotoxicity of PVP-Ag NPs: mitigation and intensification. For risk assessment, it should be considered that cytotoxicity mechanisms of PVP-Ag NPs are dynamic and threats can be intensified by DOM during prolonged exposure.