A novel hydrogel system (HD) composed of soybean (SB) protein and chitosan(CS) blended with naturally non-toxic genipin was developed for controlling theophylline delivery. Additionally

the release profile of a model drug (theophylline) from test hydrogels was investigated in simulated gastric and intestinal fluid as well as pH7.4 buffer. The surface morphology and structure of composite chitosan-based hydrogels were characterized by infrared spectrophotometry and scanning electron microscopy as well as 1H NMR spectra. These results showed obvious crosslinking systems for soybean protein and chitosan by genipin in the composite hydrogels. These composite hydrogels had retained compact sheets. All hydrogels swelled in the simulated gastric and intestinal solution as well as pH7.4 buffer

but the swelling ratio of the hydrogels in the simulated gastric medium was low. In addition

the amount of theophylline released in the simulated gastric medium (pH1.2) was lower than that in intestinal fluid (pH6.8) and pH7.4 buffer. These composite hydrogels were found to be pH-sensitive. The controlled release of theophylline was realized in 120 h. Therefore

the genipin-corsslinked composite hydrogel could be a suitable carrier for site-specific drug delivery in the intestine.