Polysaccharide Film-Coating Process for Freely Swellable Hydrogels

Abstract

ABSTRACTIn order to control the drug release from coated hydrogels by preventing membrane fractures, an intramembrane freely swellable matrix device was designed by enclosing a void space between a crosslinkedpoly(vinyl alcohol) (PVA) matrix and a calcium alginate membrane. The highly swellable PVA matrix loaded with diltiazem hydrochloride was obtained by means of a simplified procedure of the polymer crosslinking reaction using glutaraldehyde in solution with ammonium persulfate. The undried swollen matrix was coated with a calcium alginate membrane employing 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 resulting calcium alginate membrane, which was uniform and compact in the structure, increased in thickness according to the coating time. Coating times exceeding 5 min allowed 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. Owing to the pH-dependent behavior of the membrane, most of the drug was delivered in intestinal fluid. Therefore, the device proposed could be advantageously used for drug targeting to the small intestine.