Synthesis and characterization of pH-sensitive hydrogels of dextran

pH-sensitive dextran hydrogels were synthesized by photochemical cross-linking reaction of metacrylated dextran (DEX-MA) functionalized with acidic residues through reaction with anhydrides of different nature (succinic, glutaric and phthalic respectively). All the hydrogels were characterized by FT-IR spectra and swelling measurements. The swelling behavior, studied as a function of the pH of the medium, was related to the nature of the group in the side chain. In principle the hydrogels, showing the lowest swelling degree at acidic pH, could be employed as systems for the controlled release of drugs potentially dangerous for the gastric mucosa or in order to obtain a site-specific release in the colon. Ibuprofen ((S)-4-isobutyl-2-phenylpropionic acid) was loaded into the three systems. The analysis of the release profiles of the drug from the three networks shows that the derivative having phthalic residues in the side chain is the most suitable in order to retain ibuprofen during transit through the stomach and release it in a sustained way in the intestinal tract.