Lethal photosensitisation of bacteria using a tin chlorin e6-glutathione-gold nanoparticle conjugate

Because of the increasing resistance of bacteria to antibiotics there is considerable interest in light-activated antimicrobial agents (LAAAs) as alternatives to antibiotics for treating localized infections. In this paper we report that covalently coupling the LAAA tin-chlorin e6 to a gold nanoparticle via glutathione results in a potent antimicrobial agent when activated by white light. On a molar basis, the tin chlorin e6-nanogold conjugate was a hundred times more effective at killing Staphylococcus aureus than free tin chlorin e6. The conjugate also displayed antibacterial activity against methicillin-resistant S. aureus and Streptococcus pyogenes. This potent new LAAA may be useful for the treatment of topical infections or could be incorporated into coatings that could be used to reduce the microbial load in sensitive environments such as hospitals and food processing facilities.