Disinfection of various bacterial pathogens using novel silver nanoparticle-decorated magnetic hybrid colloids

Silver nanoparticles (AgNPs) have long been considered a powerful disinfectant for controlling pathogenic microorganisms. However, AgNPs might have adverse effects on both human health and our ecosystems due to their potential cytotoxicity and the difficulty in recovering them after their release into the environment. In this study, we characterized the antimicrobial efficacy caused by a novel micrometer-sized magnetic hybrid colloid (MHC) containing 7, 15, or 30nm sized monodispersed AgNPs (AgNP-MHCs), which can be re-collected from the environment using simple procedures, such as a magnet or centrifugation. We evaluated the antibacterial capabilities of AgNP-MHCs against target bacteria (Legionella pneumophila, Bacillus subtilis, Escherichia coli, and Clostridium perfringens) and compared them with the inactivation efficacy of AgNPs ~30nm in diameter (nAg30s). Among the different AgNP-MHCs composites evaluated, Ag30-MHCs had the greatest antibacterial effect. After 1h of exposure, more than a 4-log₁₀ reduction of L. pneumophila and 6-log₁₀ reduction of B. subtilis was achieved by 4.6×10⁹particles/mL of Ag30-MHCs and Ag30-MHC-Ls. In addition, Ag30-MHC-Ls maintained their strong antibacterial capabilities under anaerobic conditions. Our results indicate that AgNP-MHCs can be considered excellent tools for controlling waterborne bacterial pathogens, with a minimal risk of release into the environment.