Antimicrobial activity of silver and copper nanoparticles: Variation in sensitivity across various strains of bacteria and fungi

Abstract

The antimicrobial activity of silver and copper nanoparticles is widely reported and is linked with ions that leach out from these nanoparticles. The activity is further enhanced due to their small size and high surface area to volume ratio which allows them to interact closely with microbial membranes. Most studies on antibacterial effects have been limited to one or a few strains and comparison across studies becomes difficult due to differences in the size and other characteristics of the nanoparticles and due to differences in the protocols followed in the various studies. The sensitivity in response to silver nanoparticles is seen to vary widely across various strains of Escherichia coli and Staphylococcus aureus. Most strains typically show greater sensitivity to silver compared to copper nanoparticles. Antifungal activity of silver nanoparticles has been found to be comparable to commercially available antifungal agents. Nanoparticles embedded/immobilized on supports may be better utilized for applications such as water disinfection. Such systems can promote a continuous release of Ag+ and Cu2+ ions in solution and thus promote disinfection while ensuring a low enough concentration to avoid deleterious effect on humans and other organisms in the ecosystem.