Reduction in wound bioburden using a silver-loaded dissolvable microfilm construct

Silver is a widely used antimicrobial agent, yet, when impregnated in macroscopic dressings, it stains wounds, can lead to tissue toxicity, and can inhibit healing. Recently, polymeric nanofilms containing silver nanoparticles were reported to exhibit antimicrobial activity at loadings and release rates of silver that are 100× lower than conventional dressings. Here, fabrication of composite microfilm constructs that provide a facile way to transfer the silver-loaded polymeric nanofilms onto wounds in vivo is reported. The construct is fabricated from a silver nanoparticle-loaded polymeric nanofilm that is laminated with a micrometer-thick-soluble film of polyvinylalcohol (PVA). When placed on a moist wound, the PVA dissolves, leaving the silver-loaded nanofilm immobilized on the wound-bed. In vitro, the immobilized nanofilms release <1 μg cm^-2 d^-1 of silver over 30 d from skin dermis and they kill 5 log₁₀ CFUs of Staphylococcus aureus in 24 h. In mice, wounds inoculated with 10⁵ CFU S. aureus presented up to 3 log₁₀ less bacterial burden when treated with silver/nanofilms for 3 d, as compared to unmodified wounds. In uncontaminated wounds, silver/nanofilms allow normal and complete wound closure by re-epithelialization. Dissolvable microfilm constructs may overcome key limitations associated with current uses of silver in wound healing.