Preparation Of Protein Cold-set Hydrogels And Its Controlled-release Characters

The consumption of nutraceutical molecules, whether in foods or as dietary supplements can not provide the excepted benefits if the molecules of interest lose their bioactivity. Therefore, it is very important to create a delivery decices which can maintain their bioactivity in the gastric and intestinal fluid. Over the past decade, systems based on including derivatives of polyacrylamide(PAM)and have been studied for delivering drugs.But they are not suitable for food manufacturing because of their high cost and toxicity. In this paper, preparation and properties of several new drug delivery devices were studied systemically by the traditional chemical cross-linking reaction and transglutaminase cross-linking reaction. Three delivery decices have been studied such as chitosan/gelatin-based hydrogels, SPI/gelatin composite cold-set hydrogels and SPI/κ-carrageenan composite cold-set hydrogels. Riboflavin and theophylline was chosen as the drug model. The main results are as follows:Chitosan/gelatin hydrogels were prepared through the reaction between natural chitosan and gelatin. Swelling ratios of the hydrogels in buffer solutions at different pH values were studied. The structure was confirmed by FTIR. The results showed that the hydrogels were strongly pH-sensitive and the swelling ratio of the hydrogels in acid medium was higher than that in alkaline medium. Furthermore, the largest swelling ratio was obtained in a pH 3.0 buffer solution and the smallest was obtained in a pH 9.0 buffer solution. The hydrogels had good swelling-contracting reversibility in the solution which pH value was alternately changed and the loading of drug in hydrogels was about 10%-13%.Cross-linking of microbial transglutaminase (MTGase) was applied during production of protein hydrogels via incubation and heating treatmen. The results showed that the elastic modulus of the gels were enhanced with the increaseing gelatin concentration. The structure of the hydrogels was dense network and the swelling ratio of the hydrogels in the gastric fluid (SGF)was low, while they were all digested in intestinal fluid(SIF). Furthermore, the relesse ratio of the hydrogels in the intestinal fluid was faster than that in the gastric fluid. all hydrogels types provided good protection of theophylline for at least 5 h. They should be of great interest to developers of innovative functional foods. The release of riboflavin from soy protein/κ-carrageenan mixed cold-set gels microstructure was investigated under gastric and intestinal conditions in the presence or absence of digestive proteases. Microscopic examination showed riboflavin arranged into crystals dispersed randomLy throughout the gels. The results showed that the elastic modulus of the gels were enhanced with the increaseingκ-carrageenan concentration. Rheological analysis revealed that the riboflavin load weakened the gel networks. Dissolution tests showed that riboflavin release was faster in SIF than in SIF. In the presence of pepsin at pH 1.2 and in the presence of pancreatin at pH7.5, soy protein/κ-carrageenan mixed cold-set gels provided good protection of riboflavin for at least 10 h. Release from three devices is slow during the pepsin step, reaching no more than 20%. This indicates that most of the riboflavin is released during the subsequent 8 h period in SIF under the action of pancreatin. These results suggest that soy protein/κ-carrageenan mixed cold-set gels might be useful for transporting bioactive molecules through the gastrointestinal tract and delivering them in the small intestine.The swelling of soy protein/κ-carrageenan mixed tablets and the release of riboflavin from two delivery devices were investigated under simulated gastroinestinal conditions in the presence or absence of digestive proteases. The mechanisms involved in swellling were diffusion and matrix degradation for both gels at pH 1.2 and pH 7.5. In the absence of digestive enzyme, Riboflavin release from soy protein/κ-carrageenan mixed tablets was slow, Riboflavin release from tablets in SGF was found to be Fickian in contrast with riboflavin release from tablets in SIF, which was anomalous(non-Fickian). Swelling was the principal mechanism of riboflavin release from tablets at pH 7.5, while drug-polymer interactions slowed this release at pH1.2. In the presence of pepsin at pH 1.2 and in the presence of pancreatin at pH7.5, riboflavin release from tablet-a and tablet-b in SGF reaching 34.26% and 54.27%, in SIF reaching 70.04% and 97.08%. Release from both devices is slow during the pepsin step, reaching no more than 10%, during the subsequent 9 h period in SIF riboflavin release from tablet-a and tablet-b reaching about 80% and 100%.