A novel pH-sensitive hydrogel based on dual crosslinked alginate/N-α-glutaric acid chitosan for oral delivery of protein

A novel pH-sensitive hydrogel based on dual crosslinked alginate/N-α-glutaric acid chitosan (GAC) was prepared. The homogeneous alginate/GAC solution was dropped into calcium chloride solution and crosslinked by Ca2+ ions. Sequentially, the crosslinked beads were suspended in sodium sulfate solution for forming dual crosslinked beads. The swelling behaviors of dual crosslinked beads were investigated in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and simulated colonic fluid (SCF). Bovine serum albumin (BSA) was loaded in beads with the high loading efficiency. The sustained release profiles of BSA loaded beads were studied at different pH environment for simulating gastrointestinal condition. The amount of BSA released from the beads at pH 1.2 was relatively low (below 18%), while almost 100% of BSA could be released at pH 7.4. The preliminary results clearly suggested that the dual crosslinked alginate/GAC hydrogel may be a potential polymeric carrier for oral delivery of protein drugs.