Antibacterial action of green silver nanoparticles with Staphylococcus aureus and Escherichia coli: membrane interaction

FERREYRA MAILLARD ANIKE PV; DALMASSO, PABLO R.; HOLLMANN, AXEL

Online

Congreso; Biofísica en tiempos de COVID-19; 2020

Sociedad Argentina de Biofisica

Silver nanoparticles (AgNPs) has proven to be an alternative for the development of new antibacterial agents. The possibility to generate AgNPs coated with novel capping agents, such as phytomolecules obtained via a green synthesis (G-AgNPs), is interesant.Recently we showed that membrane interactions are involved in the antibacterial activity of AgNPs obtained via green synthesis using aqueous leaf extract of chicory (Cichorium intybus L.). However, the mechanism of antibacterial action has not yet been fully elucidated. The data obtained suggest a multi-step mechanism by electrostatic interactions, membrane disruption and subsequent bacterial death.The objective of this work was to continue with characterization of the antibacterial action of G-AgNPs against Escherichia coli and Staphylococcus aureus and determine its celular target.In order to evaluate the inhibitory effect as a function of time growth curve of G-AgNPs and the kill index after 1 h of incubation with different AgNPs concentrations were obtained. Membrane permeabilization vs. concentration of AgNPs and the kinetics of the membrane disruption on E. coli and S. aureus was also analyzed. Finally, the antioxidant effect of GSH on bacterial strains was tested.The results obtained show that both bacteria exhibit the same MIC but a higher effect on E. coli was observed in short incubation times. The AgNPs induce damage in the outer membrane of E. coli and plasmatic membrane of S. aureus. This does not appear to be capable of directly inducing bacterial death. Oxidative stress induced by Ag ions was also postulated as a way of action of several nanoparticles. When AgNPs were incubated with bacteria in the presence of GSH no lethal effects were observed neither in E. coli or S. aureus. Further in presence of GSH, the ability of AgNPs to damage the bacterial membrane disappears. This could be due to direct effects of GSH on AgNPs, or due to a protective effect on bacteria. The result of the pretreatment of the bacteria with GSH showed that GHS seems to directly affect the AgNPs, inducing changes on the nanoparticle that inhibit its antibacterial activity.