Dual antimicrobial actions on modified fabric leads to inactivation of drug-resistant bacteria

We report a strategy to prepare an antimicrobial fabric coated with two layers of antibiotic agents, each with different antimicrobial mechanisms. The bottom layer is ε-polylysine which uses its positive charge to disrupt bacterial membrane, but shows only limited antimicrobial efficacy. The second layer is a photosensitizer (zinc phthalocyanine) which uses a photodynamic antimicrobial mechanism and can inactivate microorganisms by singlet oxygen or redox oxygen species. The surface-modified fabric was shown to be stable, durable, and washable. We found that such composite fabric demonstrates potent antimicrobial property to both Gram-positive and -negative bacterial strains, reducing the survival of E. coli or S. aureus by 99% and 98%, respectively. Importantly, the fabric also kills drug resistant bacterial strain (MRSA). At molecular level, we found that conjugated photosensitizer exists in both monomeric and aggregate forms, the former accounts for its antimicrobial efficacy while the latter is responsible for the photo stability of the fabric. Thus, this strategy of using antimicrobial agents with two orthogonal mechanisms can be used to develop antimicrobial materials.