Silver nanoparticle antibacterial effect: negligible particle specific antibacterial activity and silver ions migration into E. Coli bacteria cells

Abstract

Antimicrobial effects of silver salts and silver nanoparticles are well known and are used in wide range of applications, but its antimicrobial mechanism(s) is not yet fully understood. In this publication we compare silver ions (Ag+) and silver nanoparticles (collargol & silver proteinate) antimicrobial activity by measuring Ag+ concentration in nanoparticle suspensions and their impact on membrane potential of E. Coli KMY as a model of gram-negative bacteria via tetraphenylphosphonium (TPP+) selective electrodes. In our experiments we conclude that silver nanoparticles antibacterial effects mainly are, if not only, a result of Ag+ released by silver nanoparticles and thus are not particle specific. Furthermore, by measuring Ag+ migration into E. Coli KMY bacteria with selective Ag+ electrode, we show that silver ions enter cells in a manner similar to facilitated diffusion.