Silver Nanoparticles Templated by the M13 Phage Exhibit High Antibacterial Activity against Gram-Negative Pathogens and a Reduced Rate of Bacterial Resistance In Vitro

Silver and silver nanoparticles (AgNPs) are well-known for their antibacterial properties. However, their low potency and the emergence of resistance are major barriers to the use of AgNPs in systemic therapy. Biological products can be used to reduce and cap AgNPs during synthesis from silver salts, but the structure and properties of biotemplated AgNPs are not understood well. We observed that AgNPs templated by the <i>Escherichia coli</i> phage M13 showed unusually high potency as well as activity against multiple Gram-negative pathogens, including <i>E. coli</i>, <i>Pseudomonas aeruginosa</i>, and <i>Vibrio cholerae</i>. The increased antimicrobial activity was attributable to the structural properties of the AgNPs rather than to the contributions from the phage. Furthermore, M13-templated AgNPs elicited bacterial resistance >10-fold more slowly than commercially purchased AgNPs and exhibited good cytocompatibility above the concentrations needed for bacterial inhibition. The improvements in antimicrobial properties obtained through biotemplating move AgNPs toward becoming a viable candidate for future systemic applications.