Diabetes mellitus, a chronic metabolic disease in which blood glucose levels are increased, has become an important public health problem in Brazil and worldwide. It is estimated that the global diabetic population will increase from 200 million in 2012 to 336 million in 2030. Oral hypoglycemics are used to treat DM-II, whereas daily subcutaneous administration of insulin is the treatment basis for the DM-I type. However, type II diabetic people may with time require exogenous insulin for adequate control of blood glucose. The parenteral route of drug administration, although convenient in terms of bioavailability, often leads to decrease patient compliance, since it is invasive and causes discomfort. Accordingly, different strategies have been developed in order to achieve an alternative route for insulin administration and the oral route is considered the most convenient, because it is safe, natural and provides the first-pass metabolism to insulin, which will mimic its natural secretion by the islets of Langerhans. However, insulin is a peptide and the challenge here is to protect it against enzymatic attack in the upper portions of the GI tract. Thus, colon specific drug delivery may be regarded as promising, because colon provides a more pleasant environment and can be achieved by coating solid dosage forms with biodegradable polymers, such as resistant starch type 3, obtained by the retrogradation process. Although resistant to the action digestive enzymes, this polysaccharide can be fermented and eroded by the colonic microflora. Pectin plays a major role in this type of delivery, since it is resistant to proteases and amylases. Furthermore, the low absorption rate of proteins and peptides, due to their high hydrophilicity and molecular weight, can be overcome by using bioadhesive polymers, such as gellan gum, which immobilizes the drug in the target organ and prolongs the contact time between drug and mucosa. Therefore, the aim of this project is to prepare and analyze gellan gum microcapsules coated with resistant starch/pectin films in relation to their morphological (surface aspect, shape and size), thermal stability (DSC), and to assess their release properties (swelling, mechanisms of "in vitro" drug release and "ex vivo" bioadhesion) and their effectiveness in lowering blood glucose levels.
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