Hydrogel based on an alginate-Ca2+/chondroitin sulfate matrix as a potential colon-specific drug delivery system

This work reports on the formation and characterization of a novel hydrogel based on the polysaccharide alginate physically crosslinked by calcium ions (Ca2+) in the presence of chondroitin sulfate (CS). Swelling data and morphological analysis showed that the alginate-Ca2+/CS hydrogel has a clear pH-dependent behavior. Compression tests revealed a gradual decrease in the elastic moduli (E) as the pH of hydrogel-immersed solution is raised but a pronounced decrease for the samples swelled at pH 8 was observed. This fact was attributed to a complete disruption of the polymer network. On the other hand, the hydrogel matrix remains stable when immersed in acidic media. In vitro drug release studies were performed in simulated gastric and intestinal fluids and the collected data showed that the hydrogels formed in this work respond to external stimuli (changes in pH) and, thus, present great potential to be applied in a colon-specific drug delivery system.