Nanosilver and the microbiological activity of the particulate solids versus the leached soluble silver

Abstract

Nanosilver (Ag NPs) is currently one of the most commercialized antimicrobial nanoparticles with as yet, still unresolved cytotoxicity origins. To date, research efforts have mostly described the antimicrobial contribution from the leaching of soluble silver, while the undissolved solid Ag particulates are often considered as being microbiologically inert, serving only as source of the cytotoxic Ag ions. Here, we show the rapid stimulation of lethal cellular oxidative stress in bacteria by the presence of the undissolved Ag particulates. The cytotoxicity characteristics are distinct from those arising from the leached soluble Ag, the latter being locked in organic complexes. The work also highlights the unique oxidative stress-independent bacterial toxicity of silver salt. Taken together, the findings advocate that future enquiries on the antimicrobial potency and also importantly, the environmental and clinical impact of Ag NPs use, should pay attention to the potential bacterial toxicological responses to the undissolved Ag particulates, rather than just to the leaching of soluble silver. The findings also put into question the common use of silver salt as model material for evaluating bacterial toxicity of Ag NPs.

NonToxic Silver/Poly-1-Vinyl-1,2,4-Triazole Nanocomposite Materials with Antibacterial Activity

“…In turn, it is a common knowledge that silver (in the form of ions or nanoparticles) is capable of effectively exerting the antimicrobial properties when directly contacting to a microbial cell [ 23 , 24 , 25 , 26 ]. In our certain case, the silver nanoparticles in a polymeric matrix either should be transported by this polymer to a microbe with subsequent release on a cell surface (for example, in the result of biodegradation–bio-utilization of polymer by the microbe) or the silver ions, which are in equilibrium with a metal skeleton of the nanoparticles, should migrate from the nanocomposite and also reach the microbial cell [ 27 ].…”

Antibacterial Activity of Reduced Graphene Oxide

“…The indiscriminate use of antibiotics has led to the emergence of many drug-resistant bacteria, urging the need to explore for alternative antimicrobial agents. A range of nonconventional materials, such as metallic and metal oxide nanoparticles, and more recently, the carbon-based materials, such as nanotubes and graphene, have been studied [1][2][3][4][5]. When compared to other antimicrobials, graphene, a two-dimensional singleatom thick sheet of sp 2 conjugated carbon atoms (arranged in hexagonal honeycomb lattices, the basal plane) [2,6], is more cost effective to synthesize [1,7,8].…”

Experimental Evolution ofPseudomonas putidaunder Silver Ion versus Nanoparticle Stress

“…Indeed, oxic conditions, which lead to dissolution of AgNPs, are required for the manifestation of any differences due to the way in which Ag + is delivered to the cells. For example, the concentration of free silver ions, added to cultures at the start, will decline as they bind to the cells and media components, an effect that will depend critically on cell density and environmental chemistry (Dong et al, 2017;Faiz et al, 2018). In contrast, AgNPs will continuously release new Ag + and the nanoparticle-specific kinetics of Ag + release and delivery can potentially alter the way in which cells are affected (Dong et al, 2017).…”