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New hydrogels obtained by a crosslinking reaction between the polycarboxylated derivative of scleroglucan (sclerox) and 1, 6-hexanedibromide have been prepared and characterized. Different ratios between the alkane dihalide and sclerox yielded products with appreciably different properties. Water uptake by the hydrogel with a low degree of crosslinking was remarkably affected by ionic strength. The diffusion of a model molecule (theophylline) through the swelled crosslinked polymers was studied and the theoretical analysis leading to the calculation of permeability coefficients in different environmental conditions is reported. Tablets prepared with one of the new hydrogels behaved as swellable monolithic systems suitable for sustained drug release.

Swelling and diffusion experiments, performed in vitro with tablets prepared with scleroglucan and several hydrophilic and hydrophobic additives, indicate that it is possible to modulate drug delivery from the matrix by appropriate choice of the nature and amount of the additive. The additives in the formulations may affect the mechanisms (zero order, diffusion, erosion) involved in the release of drugs from the dosage forms.

Four carboxylated derivatives of scleroglucan have been obtained by oxidation, to different extents, of the glucopyranose side chains of the natural polysaccharide. The diffusion of model molecules through aqueous solutions of these new products was measured at various pH values. The reversible pH induced sol-gel transition of some of the polyelectrolyte solutions tested effects a remarkable variation in the diffusion rate of the permeating species; in this sense the most interesting polysaccharide appears to be the product with 70% oxidized glucopyranose moieties. The behaviour of scleroglucan and its derivatives has been compared with that of carboxymethylcellulose and the mechanism involved in drug permeation and release discussed. The possible application of one of the new products in controlled release formulations for oral use is also reported.

Experiments performed in vitro with tablets and capsules indicate that the fungal polysaccharide scleroglucan is suitable for the formulation of sustained-release, oral dosage forms. Delivery of model drugs from the non-disintegrating matrix was studied in solutions buffered at different pH values. The effect on drug release of drug concentration, the physico-chemical properties of the drug, and the compression force used in the preparation of the matrix are reported, and the possible mechanisms of release are discussed.