Effects of solution chemistry on antimicrobial activities of silver nanoparticles against Gordonia sp

摘要

Silver nanoparticles (NPs) are the largest and fastest growing category of nanotechnology-based medicines and consumer products. Silver can have great toxicity to some aquatic organisms and, as a biocidal agent, may also damage or alter the most abundant and vulnerable beneficial microorganisms in the environment, such as Gordonia sp. However, considering the complex chemical background of natural waters, silver NPs can have complicated interactions with background chemicals such as chloride, surfactants, and dissolved natural organic matters (NOM). The results of this study show that the average particle size and dispersivity of silver NPs and the surface characteristics play an important role in the toxicity of silver NPs. Aggregation was enhanced for silver NPs in 10 mM NaNO_3, but not much in 10 mM NaCl due to reactions with chloride. However, the presence of 3 mM sodium dodecyl sulfate (SDS) or 8 mgC/L Suwannee River (SR) NOM appeared to reduce the aggregation of silver NPs. Regarding the bactericidal effect of silver NPs, solubility analysis suggests silver NPs inactivate Gordonia sp. differently from Ag~+ and/or a slow release of Ag~+ from silver NPs. When the silver NP concentration was raised from 73 to 29.2 mg/L in DI water, the log inactivation rate of Gordonia sp. increased from 0.16 ± 0.04 to 0.45 ± 0.13. However, with 292 mg/L silver NPs the log inactivation rate reached 1.40 ± 026 in 3 mM SDS. The presence of SRNOM mitigated the bactericidal efficacy of silver NPs due to surface coating/adsorption. On the other hand, 10 mM NaCl reduced the log inactivation rate to 0.07 ± 0.07 due to the formation of likely less toxic silver chloride species, such as AgCl, AgCl_2~-, AgCl_3~(2-), and AgCl_4~(3-).