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      Negligible particle-specific antibacterial activity of silver nanoparticles.

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          Abstract

          For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct "particle-specific" effects beyond the known antimicrobial activity of released silver ions (Ag(+)). Here, we infer that Ag(+) is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag(+) release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose-response pattern of E. coli exposed to Ag(+) (added as AgNO(3)). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO(3) (at 3-8 μg/L Ag(+), or 12-31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive to antimicrobial applications. Overall, this work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release. Accordingly, antibacterial activity could be controlled (and environmental impacts could be mitigated) by modulating Ag(+) release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.

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          Author and article information

          Journal
          Nano Lett
          Nano letters
          American Chemical Society (ACS)
          1530-6992
          1530-6984
          Aug 08 2012
          : 12
          : 8
          Affiliations
          [1 ] Department of Civil and Environmental Engineering, Rice University, Houston, Texas 77005, USA.
          Article
          10.1021/nl301934w
          22765771
          8b5ae93f-73d1-4c80-b6b5-869e13da821b
          History

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