The properties of gelatin–poly (γ-glutamic acid) hydrogels as biological glues

The influence of the molecular weight and the type of gelatin (A or B), as well as the molecular weight of poly (γ-glutamic acid) (γ-PGA), on the properties of gelatin/γ-PGA mixed bioadhesives were studied. The gelation of the system was enhanced by a crosslinker, 1-(3-dimethylaminopropyl)-3-(ethylcarbodiimide) hydrochloride (EDC). The gelation time of the bioadhesives was analyzed using rheological measurements. The results indicated that the type of gelatin was a critical factor in determining the gelation time of the biological glues. The mixed glues had greater bonding strength and smaller gelation times as the molecular weight of γ-PGA or gelatin increased. The swelling ratio decreased and the denaturation temperature increased upon raising the EDC concentration, indicating a greater degree of crosslinking at higher EDC concentrations. The mixed glues crosslinked with various concentrations of EDC (1.7–2.5%) showed no cytotoxicity to fibroblasts. In addition, no significant inflammatory response was observed in the rat subcutaneous implantation. The bioadhesives based on gelatin/γ-PGA remained at the site for 7 days while the fibrin glue had almost completely degraded. By choosing the appropriate gelatin type and higher molecular weight γ-PGA in the mixtures, the gelatin/γ-PGA biological glues could serve as soft tissue adhesives. Rheological characterization was essential in the evaluation of biological glues.