| Summary: | 碩士 === 元培科技大學 === 食品科學研究所 === 99 === Nowadays the estimated prevalence of diabetes mellitus, a worldwide chronic metabolic disease, is nearly one tenth among the population over 40s in Taiwan. For the past few years, diabetes mellitus has been the fifth or fourth major leading cause of death for people in Taiwan. Clinically, for normalizing the excessively high blood sugar, anti-hyperglycaemic medicines are often orally given, or recombinant insulin intravenously or subcutaneously in diabetes patients. However, in addition to the fear of pain and inconvenience, it has been reported that some skin allergic reaction such as local erythema and swelling could be elicited at the injection site. Furthermore, continuous injection of insulin at the same site causes lipohypertrophy, a lump under the skin caused by accumulation of extra fat. Without the proper sterilization of needle before injection, patient would be at the risk of bacterial infection by Staphylococcus aureus, Mycobacterium chelonae or M. kansasii.
Orally administration, which is pain-free and low risk of infection, is one of the best routes for insulin delivery. However, like most of oral medicines, the bioavailability of orally delivered insulin is low due to acidic environment and several gastric enzymes which digest peptide-like materials such as insulin. Numerous studies have focus on the encapsulation of insulin by either non-digestible polysaccharides or biopolymers that encapsulate the insulin against acidic environment and digestive enzymes. However expensive cost and organic solvents required during encapsulation preparation are the main obstacles for the development of oral insulin delivery. The aim of the study is attempt to develop a novel fluidic type carrier for oral insulin delivery using non-digestible polysaccharide which forms gelation in response to acidic pH.
Two types of fluidic-like carriers, acid-induced gelation N3 hydrogel and non acid-induced gelation nN3 hydrogel that formulated various polysaccharides were designed for protection of insulin from attack of acidic and enzymatic digestion. Bovine serum albumin (BSA) was used as the testing protein and encapsulated by the designed carriers. In addition, activity of α-amylase encapsulated with the designed hydrogels was determined after treatment of stimulated gastric fluid (SGF) for different periods of time, evaluating the protective efficacy of the gels under gastric environment. Finally, streptozotocin-induced diabetic Sprague Dawley rats were fed with insulin-loaded hydrogels and the plasma glucose was monitored for evaluating the anti-hyperglycaemic efficiency in vivo.
Our results indicated the loading efficiency of N3 hydrogel for BSA is about 96 %. Furthermore, BSA was slowly released from the hydrogels under neutralized solution. nN3 hydrogel, on the other hand, has ability to protect BSA from acid and enzymatic digestion, which is proportional to the concentration of G in the nN3 gel.Moreover, nN3-G20 prevented BSA from the destructive hydrolysis by pepsin and acid, as shown in a clear protein band of SDS-PAGE following coomassie blue staining. In vivo experimental results showed that insulin-loaded N3 hydrogel only reduced 19.91±11.93% plasma glucose level within 8 hours after orally administration. Nevertheless, insulin-loaded nN3 hydrogel could significantly reduce plasma glucose level to the extent of 63.38±16.34% after orally administration. A significant decrease of plasma glucose in rats was observed 4 hours after feeding diabetic rats with insulin-loaded nN3-G10, and it reduced to the extent of 64.27±11.39% within 8 hours. In conclusion, our results indicated that N3 and nN3-G carriers function differently. The former is pH-responsive and able to encapsulate protein effectively in acidic environment. The latter, however, can directly protect insulin from acidic and enzymatic attack. It is highly potential for nN3-G developed as an effective carrier for oral insulin delivery.
|
|---|
