Disentangling the “tip-effects” enhanced antibacterial mechanism of Ag nanoparticles

Abstract

: Silver nanoparticles (Ag NPs) exhibit strong antibacterial activity and are widely used in industries such as medical, food and cosmetics. In this study, Ag nanospheres and Ag nanotriangles are selected as antibacterial agents to reveal the distinct mechanism of tip effects towards their antibacterial performance. A series of antibacterial experiments were implemented, including in-situ monitoring as well as studying and determining of the evolution of the inhibition zone, minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) values, growth kinetics, bactericidal curve, bacterial morphologies and intracellular reactive oxygen species (ROS). Ag nanotriangles can eradicate E. coli and S. aureus at extremely low concentrations in comparison to Ag nanospheres, in particular under sunshine irradiation. The destroyed bacterial cell walls were examined by scanning electron microscopy. Through the investigation of ROS production, the generation efficiency of ROS is improved by the merit of sunshine irradiation thanks to the localized surface plasmon resonance (LSPR) property of Ag NPs. However, a more significant improvement of ROS generation efficiency occurred in the presence of Ag nanotriangles contributed by the pronounced “tip effects”. This study sheds light on the relationship of structure-performance for the rational design of antibacterial agents.