Gamma-poly glutamate/gelatin composite hydrogels crosslinked by proanthocyanidins for wound healing

A novel multifunctional poly(gamma-glutamic acid) (gamma-PGA)/gelatin hydrogel has been developed and used as a wound dressing. An ideal wound dressing should effectively provide a moist environment, absorb wound exudates and protect the wound from foreign microbes. Water soluble gamma-PGA salts of sodium and calcium forms were chosen for their good biocompatibility, biodegradability and water absorption capacity. Oligomeric proanthocyanidins (OPCs), naturally occurring plant metabolites and potent antioxidants, were investigated as a nontoxic crosslinking agent in this study. The effects of hydrogels on the degree of crosslinking, swelling, in vitro degradation, mechanical properties and radical scavenging activity were systemically evaluated. A cell viability assay demonstrated that these OPCs crosslinked gamma-PGA/gelatin (PGO) hydrogels were not cytotoxic to L929 fibroblasts. Dermal irritation and skin sensitization tests were examined using a guinea pig model; the hydrogels were considered to be neither allergic nor a dermal sensitizer in guinea pigs. Lastly, an in vivo wound healing model in rats was used to study the effects of the hydrogels on wound healing for 21 days. PGO hydrogels formed by both Na and Ca salts could accelerate wound contraction and re-epithelialization, in which Na-PGO hydrogel was significantly better than the untreated control group. The findings suggest that PGO hydrogels are promising wound dressing materials for the treatment for wound healing.