Polysaccharide film-coating process for freely swellable hydrogels

The highly swellable PVA matrix loaded with diltiazem hydrochloride was obtained by means a procedure of the polymer crosslinking reaction using glutaraldehyde in solution with ammonium persulfate. The undried swollen matrix was coated with a calcium alginate membrane employng an ionotropic gelation of sodium alginate induced by calcium ions. The subsequent drying process generated a void space separating the inner core from the membrane. The system presented a modification of the drug release profile providing, after a short burst period, sustained and constant rate phases in both simulated gastric fluid and simulated intestinal fluid. Because the inner hydrogel expanded freely inside the device, the unstressed and intact membrane could act as the rate-controlling factor in the drug release process.