Role of lipid membrane on way of action of "green" silver nanoparticles as unconventional antibiotics.

FERREYRA MAILLARD, ANIKE PV; LÓPEZ DE MISHIMA, BEATRIZ A; DISALVO, E ANIBAL; DALMASSO, PABLO R; HOLLMANN, AXEL

San Miguel de Tucumán.

Congreso; IX IberoAmerican Congress of Biophysics.; 2016

Silver nanoparticles (AgNPs) are clusters of zero-valent silver with a size between 1 nm and 100 nm, which are intriguing for showing their great ability in terms of numerous functionalities.1 In this sense, there is a rising demand to develop ?green? synthetic strategies for AgNPs that provide biocompatible nanomaterials for pharmaceutical applications.2 Even, nowadays AgNPs are being considered as potential novel nanoantibiotics because of their outstanding antimicrobial activity1,3, however the exact mechanism of action remains to be elucidated.3 In a previous work, we demonstrated that green AgNPs were able to interact with lipid membranes, and a correlation was found between membranothropic behavior and antimicrobial activity. In this context, the aim of this work was contribute to a better understanding of the role of lipid membrane in the antimicrobial activity of these novel AgNPs. By using dynamic light scattering (DLS), we found a significant increase from 100 nm to around 220 nm on the average diameter of small unilamellar liposomes after be incubated with green AgNPs. This result allows us to indicate an interfacial adsorption of the AgNPs (with an average diameter of 45 nm) onto the liposomes. Furthermore, the ability of AgNPs to interact with bacterial membrane was studied by zeta potential using Escherichia coli as model. After be treated with green AgNPs, an increase in the net negative charge of the bacteria was determined confirming an interfacial adsorption. In addition, leakage experiments with carboxyfluorescein-loaded liposomes were conducted to evaluate if AgNPs were able to affect the membrane permeability. However, it is noteworthy that green AgNPs are not able to disrupt the lipid membrane. In conclusion, we could hypothesize that membranothropic properties of green AgNPs would allow to increase their local concentration at the membrane level enhancing the antibacterial effectiveness of them vía localized release of biologically active Ag+ ions. 1 Schröfel A et al., Acta Biomaterialia 10 (2014) 4023?4042. 2 Adil SF, et al., Dalton Transactions 44 (2015) 9709?9717.3 Durán N, et al., Nanomedicine 12 (2016) 789?799.