1. Negligible Particle-SpecificAntibacterial Activityof Silver Nanoparticles.
- Author
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Xiu, Zong-ming, Zhang, Qing-bo, Puppala, Hema L., Colvin, Vicki L., and Alvarez, Pedro J. J.
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ANTIBACTERIAL agents , *NANOSTRUCTURED materials synthesis , *SILVER nanoparticles , *REACTION mechanisms (Chemistry) , *SILVER ions , *OXIDATION , *SURFACE coatings - Abstract
For nearly a decade, researchers have debated the mechanismsbywhich AgNPs exert toxicity to bacteria and other organisms. The mostelusive question has been whether the AgNPs exert direct “particle-specific”effects beyond the known antimicrobial activity of released silverions (Ag+). Here, we infer that Ag+is the definitivemolecular toxicant. We rule out direct particle-specific biologicaleffects by showing the lack of toxicity of AgNPs when synthesizedand tested under strictly anaerobic conditions that preclude Ag(0)oxidation and Ag+release. Furthermore, we demonstratethat the toxicity of various AgNPs (PEG- or PVP- coated, of threedifferent sizes each) accurately follows the dose–responsepattern of E. coliexposed to Ag+(addedas AgNO3). Surprisingly, E. colisurvivalwas stimulated by relatively low (sublethal) concentration of alltested AgNPs and AgNO3(at 3–8 μg/L Ag+, or 12–31% of the minimum lethal concentration (MLC)),suggesting a hormetic response that would be counterproductive toantimicrobial applications. Overall, this work suggests that AgNPmorphological properties known to affect antimicrobial activity areindirect effectors that primarily influence Ag+release.Accordingly, antibacterial activity could be controlled (and environmentalimpacts could be mitigated) by modulating Ag+release,possibly through manipulation of oxygen availability, particle size,shape, and/or type of coating. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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