Preparation Of Core-Shell Hydrogel Beads Loaded With Polyphenols

Polyphenol compounds and their metabolic derivatives are widely found in all kinds of plants in nature,such as citrus,grape,tea and microalgae,and most of them exist in the form of flavanones and flavonols.Phenolic hydroxyl and ketone groups in their structures play an important role in the antioxidant and modification of substances.Studies have shown that polyphenols are related to antiinflammatory,antibacterial,antiviral,immune enhancement,anti-tumor and neuroprotection.Therefore,more and more people begin to pay attention to the intake of citrus fruits.Between 2009 and 2010,global production of citrus fruits increased dramatically to about 82milliontons,with oranges accounting for more than 60 percent of the total,and the commercial value increased.Colitis is a chronic bowel disease that is prone to recurring episodes due to damage to the mucus layer of the intestine,which leads to inflammation caused by bacterial invasion.Because the colon is basically located at the very end of digestion,there are fewer nerves,so it is not easy to detect the early stage of the disease,and the treatment after discovery is more complicated,and it is easy to develop into colon cancer.And commonly used such as 5-aminosalicylic acid and other drugs in the treatment at the same time easy to cause complications and recurrence,so the need fora more convenient and no side effects of food to prevent the occurrence of ulcerative colitis.In the current research field,more colon targeting delivery systems have been developed,such as liposomes,microcapsules,nanoparticles,etc.But they also have different shortcomings.On the basis of previous studies,this study improved their shortcomings,using chitosan and alginate saltwater gel to wrap polyphenols,in order to target delivery of hesperetin and improve bioavailability and prolong the protection of polyphenols as goals,using polyphenol ketone group（-C=O）and chitosan amid o（-NH3）for Schiff base reaction,to generate imine（-C=N）,increase the binding strength.Compared with the system prepared by predecessors,the encapsulation rate of polyphenols was improved,and an outer layer of alginate was used to reduce the damage of digestive fluid to the inclusions.The positively charged surface of chitosan is cross-linked with the negative l y charged surface formed by MUC2 protein in the intestinal mucus layer to prolong the residence time of the loaded substances,so that nutrients can be released and play a role in the colon as much as possible.Then the parameters in the preparation process were adjusted and optimized,and the effects of hydrogel microbeads were verified by in vitro simulated digestion and fermentation tests.The optimal parameter ratio was determined by orthogonal design,and a core-shell structure hydrogel microbeads were prepared.The research results are as follows:1.Through the determination of particle size,potential,FTIR and SEM,the changes of chemical bonds and the binding principle during the preparation and binding of polyphenols and hydrogels were explored,and the retention of DMSO organic reagents was studied.The results show that polyphenols react with amino groups in chitosan to form imine bonds by reaction with amino groups in chitosan under the action of ketone groups under the action of organic reagents,which realizes the firm combination of polyphenols and chitosan,and improves the retention efficiency of polyphenols.Chitosan and sodium alginate are connected by Ca²⁺as the medium,which makes alginate compact and easy to be decomposed in the digestive juice.The addition of DMSO is beneficial to improve the dispersion of HP in CS colloidal solution,while rotary evaporation can completely remove DMSO organic reagents present in colloidal solution,excluding the possible toxic effects.The core-shell structure particles act in diameter at 0.6um and have a low swelling rate,so they can be present in a certain number in the digestive tract.2.The encapsulation efficiency,targeted delivery and sustained release effects of hydrogel microspheres under different parameters were studied by orthogonal optimization design,and characterized by in vitro simulated digestion test and in vitro fermentation test,the results showed that ALG crosslinking time and DMSO concentration had the greatest influence on improving the HP encapsulation effect,Ca²⁺was the smallest,and the optimal parameter combination was ALG crosslinking time of 40min,Ca²⁺crosslinking time of 0min,and DMSO concentration of 0.8%;Microgel beads have good digestive stability,can tolerate the digestion of gastrointestinal juice during digestion,and delay the release of HP;Within 0-48 h of anaerobic fermentation,HP is gradually released completely,which achieves the effect of prolonging the residence time of HP in the colon,and can play a sustained role in the growth of bacteria in it.3.In this study,the universality of the delivery system was also determined,and the encapsulation results of naringenin proved that the delivery system had a good encapsulation effect on other polyphenols containing ketone groups.The results showed that the microgel beads dried overnight at 45°C could achieve uniform shrinkage,complete structure,stable morphology,small diameter and low swelling rate,which could achieve a certain capacity of retention in the digestive tract,and had good edibility and realism.Conclusion:This study overcomes the shortcomings of other delivery systems such as complex preparation process,long time period and difficult preservation.Hesperidin is used as the supported substance,chitosan and alginate saline gel as the complex,and the preparation of cored shell structure hydrogel delivery system is realized.