Influence of the acid type on the physical and drug liberation properties of chitosan–gelatin sponges

The influence of acid type used to dissolve chitosan on the resulting sponge physical properties, and their consequent effect on the drug liberation were investigated. Chitosan was dissolved in different acid solutions and chitosan–gelatin sponges were produced by frothing up the polymer solution and then freeze-drying the foam. Prednisolone was used as a model drug. Using tartaric or citric acid resulted in instable, soft, elastic and disintegrating sponges with fast drug release. Elastic but harder sponges from stable foams were obtained when hydrochloric or lactic acid were used. The use of acetic or formic acid enabled the production of stable foams, soft and elastic sponges and a slow drug release. The rate of drug release was decreased by crosslinking the polymers with glutaraldehyde, but only if acetic, formic or acetic acid were used. Therefore, it is possible to manipulate the mechanical properties and the drug liberation rate by using different acids to dissolve chitosan.