The use of chitosan gels as matrices for electrically-modulated drug delivery

This study evaluated and characterized the use of chitosan gels as matrices for electrically modulated drug delivery. Chitosan gels were prepared by a cetylation of chitosan and subsequently hydrated to facilitate further stud ies. After determining the degree of deacetylation, hydrated and unhydrated gel formulations were characterized for their microviscosity and compressi on strength. In the electrification studies, gel mass variation, surface pH changes, and later, release-time profiles for neutral (hydrocortisone), an ionic (benzoic acid), and cationic (lidocaine hydrochloride) drug molecules from hydrated chitosan gels were monitored in response to different millia mperages of current as a function of time. Hydrated gels had very similar m icroviscosity while exhibiting differences in the gel strength, results whi ch are not inconsistent as they pertain to different aspects of the gel. Th e cumulative gel mass loss and rate of gel mass loss increased with an incr ease in the milliamperage (mA) of the applied current. Gel syneresis - prin cipally involving electroosmosis and gel collapse - was pronounced, particu larly at higher mAs and for chitosan gels with lower degrees of acetylation . The surface pH values of the gels were lower at the anode and higher at t he cathode, in accordance with reports in the literature. The release of th e model drugs from the gel matrix was in the order benzoic acid>hydrocortis one>lidocaine, which is consistent with the electrokinetically competing fo rces that are involved in these gels. Adequate characterization of electric al effects on formulation matrices, such as chitosan gels, is critical to t he development of effective and reliable electrically modulated drug delive ry systems. (C) 2001 Elsevier Science B.V. All rights reserved.