title: 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.
authors.affiliation: Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam, Hong Kong, China.
authors.forename: Chun-Nam
authors.initials: CN
authors.lastname: Lok
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Ho
authors.forename: Rong
authors.initials: R
authors.lastname: Chen
authors.forename: Qing-Yu
authors.initials: QY
authors.lastname: He
authors.forename: Wing-Yiu
authors.initials: WY
authors.lastname: Yu
authors.forename: Hongzhe
authors.initials: H
authors.lastname: Sun
authors.forename: Paul Kwong-Hang
authors.initials: PK
authors.lastname: Tam
authors.forename: Jen-Fu
authors.initials: JF
authors.lastname: Chiu
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Che
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis; D002462:Cell Membrane / Q000502:physiology*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D019084:Fluorescent Antibody Technique, Indirect; D015151:Immunoblotting; D008163:Luminescent Measurements; D013058:Mass Spectrometry; D008564:Membrane Potentials / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures; D010539:Permeability; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods*; D011522:Protons; D012834:Silver / Q000737:chemistry* / Q000493:pharmacokinetics*; D012996:Solutions; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D011522:Protons; D012996:Solutions; D012834:Silver