Form-Stable Hydrogel Carriers Based on Chitosan and Sodium Alginate for Sustained Drug Release

Abstract The possibility of obtaining hybrid hydrogels based on sodium alginate and chitosan that acquire form stability through interpolyelectrolyte complex formation was studied. The advantages of such hydrogels include the absence of chemical crosslinking agents, the combination of beneficial physiological properties, and the possibility of controlling the release rate of incorporated drugs by varying the ratio of the polymer components. Hybrid hydrogels were prepared by mixing 2% aqueous solutions of the polysaccharides. Conventional mixing produces a lumpy mass that cannot be molded. Mechanical treatment of the mixture of polysaccharide solutions in a rotor-pulsation apparatus for 4 s produced a hydrogel mass capable of assuming a specified shape after being held in special cells. The ability of the mixtures to form physical hydrogels was studied by rheological measurements and by measuring the physicomechanical properties of tablet-shaped samples using three compositions with chitosan : alginate molar ratios of 1 : 2, 1 : 1, and 2 : 1. Hydrogels with an equimolar ratio of the polyelectrolytes in the mixture were found to have the highest consistency coefficient and, accordingly, the lowest flow behavior index, as well as the highest uniaxial compressive strength. The highest resistance to syneresis was obtained at a chitosan : alginate ratio of 1 : 2. The cationic dye methylene blue and the anionic dye Reactive Brilliant Red 5CX were used as model compounds to evaluate the effect of the polyelectrolyte ratio in the hydrogels on the release rate of ionic drugs. The release rate of a model compound was found to decrease with an increase in the proportion of the oppositely charged polyelectrolyte in the polymer matrix.