Hygroscopicity modulation of hydrogels based on carboxymethyl chitosan/Alginate polyelectrolyte complexes and its application as pH-sensitive delivery system

Polyelectrolyte complex (PECs) hydrogels with high hygroscopicity modulation ability were successfully prepared based on carboxymethyl chitosan (CMCS)/alginate. The swelling ratio of the hydrogels could be tuned from 1 to 450 simply by changing the weight ratio of CMCS to alginate, and superabsorbent hydrogels were obtained when the weight ratio of CMCS to alginate was below 1/1. Also, the swelling kinetics and water diffusion mechanism in the hydrogels were discussed. In vitro cytotoxicity results indicated that hydrogels had excellent cytocompatibility. The swelling ratio of the hydrogel as well as its BSA releasing profile was notably pH dependent. Compared with the values at pH 1.2, the swelling ratio of hydrogels (CMCS/alginate weight ratio of 1/2) at pH 7.4 was about 34 times higher, and the amount of BSA released at pH 7.4 was also significantly higher. The as-prepared CMCS/alginate PECs hydrogels hold great potential for oral delivery of protein drugs through the intestinal tract.