Proteomic Analysis of the Mode of Antibacterial Action of Silver Nanoparticles

Abstract

Silver nanoparticles (nano-Ag) are potent and broad-spectrum antimicrobial agents. In this study, spherical nano-Ag (average diameter = 9.3 nm) particles were synthesized using a borohydride reduction method and the mode of their antibacterial action against E. coli was investigated by proteomic approaches (2-DE and MS identification), conducted in parallel to analyses involving solutions of Ag(+) ions. The proteomic data revealed that a short exposure of E. coli cells to antibacterial concentrations of nano-Ag resulted in an accumulation of envelope protein precursors, indicative of the dissipation of proton motive force. Consistent with these proteomic findings, nano-Ag were shown to destabilize the outer membrane, collapse the plasma membrane potential and deplete the levels of intracellular ATP. The mode of action of nano-Ag was also found to be similar to that of Ag(+) ions (e.g., Dibrov, P. et al, Antimicrob. Agents Chemother. 2002, 46, 2668-2670); however, the effective concentrations of nano-Ag and Ag(+) ions were at nanomolar and micromolar levels, respectively. Nano-Ag appear to be an efficient physicochemical system conferring antimicrobial silver activities.

Strain specificity in antimicrobial activity of silver and copper nanoparticles

“…Cho et al [15] reported that the surface of the cell walls of E. coli treated with silver nanoparticles were severely damaged compared to untreated E. coli. Cell wall rupture due to silver ions and silver nanoparticles was reported by Lok et al [33]. The attachment of both silver ions or nanoparticles to the cell wall caused accumulation of envelope protein precursors, which resulted in dissipation of the proton motive force.…”

“…The attachment of both silver ions or nanoparticles to the cell wall caused accumulation of envelope protein precursors, which resulted in dissipation of the proton motive force. Silver nanoparticles also exhibited destabilization of the outer membrane and rupture of the plasma membrane, thereby causing depletion of intracellular ATP [33]. The mode of action of both silver nanoparticles and silver ions were reported to be similar, although the nanoparticles were reported to be effective at significantly lower concentration than that of the ions.…”

“…For treatment with silver nitrate, a low molecular weight central region was formed within the cells as a defense mechanism, whereas for treatment with nanoparticles, no such phenomenon was observed, although the nanoparticles were found to penetrate through the cell wall. With a detailed study of DNA/protein migration profiles Gogoi et al [32] demonstrated that silver nanoparticles have no direct effect on either cellular DNA or protein, although the silver nanoparticles were more efficient bactericidal agent compared to the silver ions [33]. For E. coli (ATCC 10536) and S. aureus (ML 422), silver nanoparticles demonstrated greater bactericidal efficiency compared to penicillin [37].…”

Atmospheric pressure plasma deposition of antimicrobial coatings on non-woven textiles

“…Number of different mechanisms responsible for interaction of metal ions with microorganisms structure has been proposed [21,22], e.g., oxygen associated with silver can react with the sulfhydryl (-S-H) groups on cell wall to form R-S-S-R bonds thus, blocking respiration and causing death of cells. Lok et al [23] have found that the surface of the cell walls of E. coli treated with AgNPs were severely damaged compared to untreated E. coli leading to cell wall rupture due to silver ions. Difference in the mechanisms of antibacterial efficiency in between ZnO and Cu/Ag nanoparticles can explain observed here (see Figs.…”

Exposure of Staphylococcus aureus to silver(I) induces a short term protective response

“…Although the mechanism(s) by which silver kills cells is not fully understood (Lok et al 2006) there have been many suggestions regarding its mode of action. Ag(I) ions interact with thiol groups of the L-cysteine residue of proteins (Park et al 2009;Cortese-Krott et al 2009;Atiyeh et al 2007;Castellano et al 2007).…”