Heightened Reactive Oxygen Species Generation in the Antimicrobial Activity of a Three Component Iodinated Chitosan−Silver Nanoparticle Composite

Abstract

Herein we report synergy in antimicrobial activity of a chitosan-silver nanoparticle (CS-Ag NP) composite in the presence of molecular iodine. Green fluorescent protein (GFP) expressing recombinant Escherichia coli bacteria have been used to test the efficacy and establish the mechanism of action. Experimental evidence indicate significantly high bactericidal activity of the nanocomposite in the presence of iodine than either due to the composite, chitosan, Ag NP or iodine only. Transmission electron microscopy measurements revealed attachment of bacteria to the composite. In addition, flow cytometry results supported definite occurrence of cell wall damage of the bacteria treated with the composite in the presence of iodine. Further, the nanocomposite and iodine combination was found to exert reactive oxygen species (ROS) generated oxidative stress in the cytoplasm of bacterial cells, leading to cell death. Elucidation of the mechanism of synergy due to three potential antibacterial components suggested that on the surface of Ag NPs molecular iodine possibly generated iodine atom thus contributing toward free radical induced oxidative stress, whereas chitosan and Ag NPs facilitated the process of cell killing and thus collectively enhanced the potency of antimicrobial effect at the lowest concentrations of individual components.

Antibacterial activity of silver nanoparticles: A surface science insight

“…For instance, nanoparticles can be prepared using ligands or compounds that possess themselves an antibacterial activity (chitosan [72], surfactants [73], etc.). The antibacterial effect is then at least partly attributable to this extra component.…”

Natural reducing agents for electroless nanoparticle deposition: Mild synthesis of metal/carbon nanostructured microspheres

“…Also silver nanoparticles have numerous applications, e.g. in fuel cells [11][12][13], optical sensors and biological applications [14][15][16][17][18]. However, many of these applications rely on the ability to control nanoparticle aggregation and consequent loss of function, while at the same time preserving their chemical, optical and/or catalytic properties.…”

The Effect of Silver Nanoparticles Size, Produced Using Plant Extract from Arbutus Unedo, on Their Antibacterial Efficacy

“…In fact, scanning electron microscopy in time samples of liquid cultures of E.coli, the least sensitive among the species tested, and in the presence of AgNP1, revealed that co-incubation of 5 h disrupted the integrity of the bacterial membrane and cell wall. It is known that AgNPs action largely relies on releasing silver ions that damage membranes and affect several biochemical processes but especially interact with thiol and amino groups of proteins and induce the release of reactive oxygen species (ROS), forming free radicals with strong bactericidal action [2,20].…”