Swelling behavior and mechanical properties of chemically cross-linked gelatin gels for biomedical use

Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or as devices for sustained drug release. As these applications involve surgical insertion of gels, the effect of cross-linking on mechanical properties is relevant. The effect of cross-linking on the gel water uptake is also relevant for the kinetics of drug release. Equally important is the influence of initial amounts of gelatin in the gelling solutions. We investigated the influence of cross-linking (with glutaraldehyde) and of gelatin content upon the equilibrium water content and tensile properties of resulting gels. A range of gels was prepared with gelatin contents of 10 to 40% wt, and cross-linked with 2.5 to 50% wt glutaraldehyde. The increase in gelatin content and degree of cross-linking reduced the water uptake of gels from about 60-65% wt to about 50% wt. The tensile characteristics were differentially affected. While the increase of cross-linking induced a decrease of toughness and elasticity and an increase of stiffness, it did not affect the ultimate strength of gels. On the contrary, the increase of gelatin content induced a definite increase of the ultimate strength but did not significantly affect the other properties.