Radiation-induced cross-linking of gelatin by using γ-rays:: Insoluble gelatin hydrogel formation

Gelatin hydrogels with various concentrations were cross-linked by the irradiation with Co-60 gamma-rays, and we investigated the radiation-induced cross-linking of gelatin hydrogels by estimating the physical properties of irradiated hydrogels. In case of the 1, 5, and 10% (w/v) gelatin solutions, the specific water content of the irradiated hydrogels, the index showing the extent of cross-linking depended on the absorbed dose, and that of the irradiated gelatin hydrogels with the lower concentration decreased drastically. The breaking strength correlated to the absorbed dose, irrespective of the initial gelatin concentration. More than 8 kGy irradiation induced insolubility due to the cross-linking of the gelatin hydrogels. Besides, gamma-ray irradiation to gelatin with free amino acids revealed that amino acids, which have side chains of hydrocarbon groups that are more than two carbon atoms, obstructed the cross-linking of gelatin hydrogels. It is thought that the hydrocarbon groups, such as an alkyl or a phenyl group of the side chains, are the cross-linking sites of gelatin hydrogels.