title: Silver nanoparticle enhanced silver ion stress response in Escherichia coli K12.
abstract: This study investigated the dissolution-based toxicity mechanism for silver nanoparticles to Escherichia coli K12. The silver nanoparticles, synthesised in the vapour phase, are effective anti-bacterial agents against the Gram-negative bacterium, E. coli K12. The nanoparticles associate with the bacterial cell wall, appearing to interact with the outer and inner membranes, and then dissolve to release Ag(+) into the cell and affect a transcriptional response. The dissolution of these nanoparticles in a modified LB medium was measured by inductively coupled plasma mass spectrometry (ICP-MS) and has been shown to follow a simple first-order dissolution process proportional to the decreasing surface area of the nanoparticles. However, the resulting solution phase concentration of Ag(+), demonstrated by the ICP-MS data, is not sufficient to cause the observed effects, including inhibition of bacterial growth and the differential expression of Cu(+) stress response genes. These data indicate that dissolution at the cell membrane is the primary mechanism of action of silver nanoparticles, and the Ag(+) concentration released into the bulk solution phase has only limited anti-bacterial efficacy.
authors: Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors: Jonathan S
authors: JS
authors: McQuillan
authors: Heidi Groenaga
authors: HG
authors: Infante
authors: Emma
authors: E
authors: Stokes
authors: Andrew M
authors: AM
authors: Shaw
mesh_terms: D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D013058:Mass Spectrometry; D053768:Metal Nanoparticles / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D018384:Oxidative Stress / Q000187:drug effects*; D060888:Real-Time Polymerase Chain Reaction; D012834:Silver / Q000737:chemistry*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D012834:Silver