Cationic Silver Nanoclusters as Potent Antimicrobials against Multidrug-Resistant Bacteria

[Image: see text] Bacterial multidrug resistance (MDR) is a serious healthcare issue caused by the long-term subtherapeutic clinical treatment of infectious diseases. Nanoscale engineering of metal nanoparticles has great potential to address this issue by tuning the nano–bio interface to target bacteria. Herein, we report the use of branched polyethylenimine-functionalized silver nanoclusters (bPEI–Ag NCs) to selectively kill MDR pathogenic bacteria by combining the antimicrobial activity of silver with the selective toxicity of bPEI toward bacteria. The minimum inhibitory concentration of bPEI–Ag NCs was determined against 12 uropathogenic MDR strains and found to be 10- to 15-fold lower than that of PEI and 2- to 3-fold lower than that of AgNO(3) alone. Cell viability and hemolysis assays demonstrated the biocompatibility of bPEI–Ag NCs with human fibroblasts and red blood cells, with selective toxicity against MDR bacteria.