Interaction of green silver nanoparticles, determined by surface characterization techniques, with Staphylococcus aureus and Escherichia coli

FERREYRA MAILLARD, ANIKE PV; GONÇALVES, SÓNIA; SANTOS, NUNO; LÓPEZ DE MISHIMA, BEATRIZ A.; DALMASSO, PABLO R; HOLLMANN AXEL

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofisica; 2019

Sociedad Argentina de Biofisica

The nanoparticles have unique physical, chemical and biological properties and different from the bulk material they come from. In particular, 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 (GAgNPs), is attracting great attention in scientific research.Recently, we showed that membrane interactions seem to be involved in the antibacterial activity of AgNPs obtained via a green chemical synthesis using the aqueous leaf extract of chicory (Cichorium intybus L.). Furthermore, we observed that these G-AgNPs exhibited higher antibacterial activity than those obtained by chemical synthesis.Although the antibacterial activity of AgNPs in gramnegative and grampositive bacteria has been evidenced, its mechanism of action is not fully elucidated. The objective of this work was to study the antibacterial activity of green AgNPs against Escherichia coli and Staphylococcus aureus to characterize its mode of action and determine its cellular target.The effect of the G-AgNPs on the bacterial surface was first evaluated by zeta potential measurements and correlated with direct plate count agar method. Zeta potential of both tested bacteria become more negative after being incubated with increasing concentrations of G-AgNPs, but this effect becomes more noticeable in E. coli. This behavior matches with higher diminution of CFU obtained in E. coli. These results allow confirming a strong correlation of zeta potential variation with bacterial damage.Afterward, atomic force microscopy was applied to directly unravel the effects of these G-AgNPs on bacterial envelopes observing several damages in both bacteria. Overall, the data obtained in this study seems correlated with a multi-step mechanism by which electrostatic interactions is the first step prior to membrane disruption, resulting in antibacterial activity.