Asymmetric chitosan membranes prepared by dry/wet phase separation: A new type of wound dressing for controlled antibacterial release

An AgSD-incorporated chitosan membrane with sustained antimicrobial capability has been developed by a dry/wet phase separation method to overcome current limitations in silver sulfadiazine (AgSD) cream for treating acute burn wounds. The asymmetric chitosan membrane consists of a dense skin and sponge-like porous layer, which can fit the requirements (oxygen permeability, controlled water vapor evaporation and the drainage of wound exudates) for this membrane to be used as a wound dressing. AgSD cream is a traditionally-used antibacterial for the prevention of wound infection; however, it has raised concern of potential silver toxicity. The asymmetric chitosan membrane acts as a rate-controlling wound dressing to incorporate AgSD, and release sulfadiazine and silver ions in a sustained way. The release mechanism depends on the mass-transfer resistance for the release of sulfadiazine and silver ions from the dense and sponge-like porous layers, and the chemical resistance for the interaction of silver ions with chitosan polymeric chains, respectively. The bacteria-cultures (Pseudomonas aeruginosa and Staphylococcus aureus) and cell-culture (3T3 fibroblasts) assay of the AgSD-incorporated asymmetric chitosan membrane showed prolonged antibacterial activity and decreased potential silver toxicity. The results in this study indicate that the new type of chitosan wound dressing incorporated with AgSD may be effective in the treatment of infected wounds.