Antibacterial activity of chitosan-alginate sponges incorporating silver sulfadiazine: Effect of ladder-loop transition of interpolyelectrolyte complex and ionic crosslinking on the antibiotic release

Hydrogel membranes prepared from polyelectrolyte complex (PEC) have been used for repair of wounds and controlled antibacterial release. A simple method, based on homogenizing interpolyelectrolyte complex, has been developed to prepare a chitosan-alginate sponge with high stability. The spongelike chitosan-alginate hydrogel can be used as a wound dressing for the sustained release of silver sulfadiazine (AgSD) in a controlled way. In this study, we evaluated the effect of electrolyteic properties of chitosan and alginate on the characteristics of the prepared chitosan-alginate PEC. All types of the spongelike chitosan-alginate hydrogels exhibited superabsorbent properties. However, only the chitosan-alginate hydrogel prepared by the interpolyelectrolyte complex of alginate with low pH of chitosan, and that prepared by the interpolyelectrolyte complex of chitosan with high pH of alginate, can keep their stability after swelling in PBS solution. FTIR analysis suggests that the protonated amino groups on chitosan and the ionized carboxylic groups on alginate should be responsible for the formation of a stable ladder-type of chitosan-alginate PEC. Ionic crosslinking is helpful to increase the stability of the loop-type of chitosan-alginate PEC. The release of AgSD from chitosan-alginate PEC sponges could be controlled by the variation of ladder-loop structural transition of chitosan-alginate PEC and the ionic crosslinking of the chitosan-alginate complex. The antibacterial ability of AgSD-incorporated PEC sponges was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. The result suggests that the PEC sponges containing antimicrobial agents should effectively suppress bacterial proliferation to protect the wound from bacterial invasion.