Abstract:In this paper, two different methods of ion cross-linking and sulfhydrylization were used to modify chitosan to prepare chitosan hydrogel with active protein. Through infrared spectroscopy, particle size/zeta potential analysis, transmission electron microscopy, scanning electron microscopy, and simulated digestion experiments, the microstructure and controlled release performance were discussed. The experimental results found that due to intermolecular hydrogen bonding, pH value, CS:TPP mass ratio, and BSA concentration had significant effects on the protein loading rate of cross-linked chitosan hydrogels, and the introduction of sulfhydryl groups made the sulfhydryl chitosan polymerized. Sugar hydrogel had a smaller particle size (average 409.61 nm) and a lower surface potential (average -0.67 mV) in an acidic environment. The changes in the microstructure of chitosan-based materials further affected the controlled release properties of their hydrogels. The simulated digestion experiment showed that the cross-linked chitosan hydrogel had a sudden release phenomenon in the simulated gastric juice. Before being transported to the colon, 44.76% of the active protein had been released, while the sulfhydryl chitosan hydrogel simulated the environment of the upper digestive tract. The medium release rate was slow, only 8.42% of the active protein was released. When it runs to the simulated colon, the release rate of the active protein gradually increases, showing a sustained release effect. About 30% of BSA is gradually released in the colon. Therefore, sulfhydryl chitosan-based hydrogels have better controlled release performance, which plays an important role in improving the bioavailability of active proteins.
