Hybrid silver-gold nanoparticles supress drug resistant polymicrobial biofilm formation and intracellular infection
Over decades bacteria have evolved multiple mechanisms to fight antibiotics. Biofilm formation by bacteria is one such mechanism as it forms a barrier and creates an acidic environment that reduces the efficiency of antimicrobials. Bacteria have also developed the ability to persist intracellularly within mammalian cells causing recurrent infections. Many antibiotics are rendered ineffective due to poor penetration across biofilms and within mammalian cells. In this study, silver-gold hybrid nanoparticles were developed as anti-microbial agents to combat biofilm formation and intracellular infections. Biogenic hybrid silver gold nanoparticles were developed in a organic solvent free single reaction mixture using quercetin, a flavonoid as the reducing and stabilizing agent. Silver-Gold nanoparticles of 40±10 nm diameter, were effective against broad spectrum of bacteria with minimum bactericidal concentration of 10 µg/ml and 20 µg/ml for gram negative and gram-positive organisms respectively. These nanoparticles were also effective against mixed infections at 20 µg/ml. Their mode of action involves generating intracellular oxidative stress in both gram negative and gram-positive bacteria that causes damage to cell wall. Polymicrobial biofilm formation was suppressed and intracellular infection was reduced by 70% to 90% in fibroblast and monocyte cell lines. These results indicate that hybrid silver gold nanoparticles are promising agents to suppress biofilm formation and tackle intracellular infections.