International journal of pharmaceutics vol:172 issue:1-2 pages:127-135
Inulin hydrogels were developed as potential new carriers for colonic drug targeting. This work describes the dynamic and equilibrium swelling properties of the prepared inulin hydrogels. The influence of various parameters on these properties were assessed, in particular the degree of substitution and feed concentration of methacrylated inulin and varying concentrations of the initiators of the polymerisation reaction. As these hydrogels were developed as colon-specific drug delivery systems, also the effect of pH, ionic strength and esterases were investigated. The results suggest that the rate of water transport into the inulin hydrogels is quite high (mean swelling time < 1.2 h) and that the hydrogels exhibit anomalous dynamic swelling behaviour. The equilibrium swelling of the hydrogels is influenced by the degree of substitution and feed concentration of methacrylated inulin, by the initiator concentration, and by the ionic strength and an acidic pH of the swelling solvent. Esterase activity and pH values of the swelling solvent commonly encountered in the small intestine and the colon on the contrary do not affect equilibrium swelling. By means of differential scanning calorimetry, the glass transition temperature of dry methacrylated inulin hydrogel samples was determined. The mobility of the hydrogel chains seemed to be affected by both the degree of substitution and the feed concentration of methacrylated inulin.