One step synthesis of antimicrobial peptide protected silver nanoparticles: The core-shell mutual enhancement of antibacterial activity.

Over the past few decades, the overuse of antibiotics has led to the emergence of resistant bacteria and environmental issues. Both silver nanoparticles (AgNPs) and antimicrobial peptides (AMPs) hold potential to replace antibiotics. Combining both AMPs and AgNPs into a composite material may create novel properties such as enhanced antibacterial activity, lower cytotoxicity and favorable stability in aqueous solution. We designed a 13 amino acid peptide (in short, P-13) with two functional regions: one is for antibacterial activity, and the other for reducing and stabilizing AgNPs with containing cysteine (C) residues in its C-terminus. With a single step reaction, we have successfully synthesized P-13 protected AgNPs (P-13@AgNPs) with a hydrodynamic diameter of about 11 nm. In the preliminary antibacterial activity assay, the minimum inhibitory concentrations (MICs) of P-13@AgNPs were up to 7.8 μg/mL against E. coli, S. aureus and B. pumilus, and 15.6 μg/mL against P. aeruginosa. Moreover, Flow cytometry analysis of E. coli, S. aureus, P. aeruginosa and B. pumilus show that the mortality of the strains reached 96 %, 96 %, 91 % and 90 %, respectively. The cytotoxicity of AgNPs was reduced dramatically after protected by P-13, and P-13 was favorable for the stability of the AgNPs solution. We believe this work could set up an example to make the best use of the individual material's properties to produce novel nanocomposites with better antibacterial activity.