In vitro Evaluation of Arabinoxylan Gels as an Oral Delivery System for Insulin
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In vitro Evaluation of Arabinoxylan Gels as an Oral Delivery System for Insulin E. Carvajal-Millan1, C. Berlanga-Reyes1, A. Rascón-Chu2, A. L. Martínez-López2, J. A. Márquez-Escalante1, A. C. Campa-Mada1, K. G. Martínez-Robinson1 1 CTAOA, Laboratory of Biopolymers, 2CTAOV. Research Center for Food and Development, CIAD, A.C. Carretera a La Victoria Km. 0.6, Hermosillo, Sonora, 83000 Mexico. ABSTRACT Arabinoxylan gels are receiving increasing attention as oral delivery systems of biomolecules for therapeutic purposes. The aim of this research was to evaluate arabinoxylan gels as an oral delivery system for insulin, representing a painless therapy for diabetics. Gels at two concentrations of arabinoxylan were prepared (2.5 and 3.5 % w/v). One concentration of insulin (0.05 % w/v) entrapped in the arabinoxylan gels was investigated. At the end of gelation elasticity (G’) values were 11 and 20 for gels at 2.5 and 3.5% (w/v) in arabinoxylan, respectively. The presence of insulin in the gels did not affect the values of G’. The apparent diffusion coefficient for insulin decreased from 1.30 x 10-7 to 1.09 x 10-7 cm2/s when the concentration of arabinoxylan in the gel increased from 2.5 to 3.5% (w/v). The percentage of proteolysis for insulin entrapped in the gels at 2.5 and 3.5% in arabinoxylan (w/v) were 35 and 17%, respectively, in relation to 100% hydrolysis of insulin in solution. Results indicate that arabinoxylan gels could be potential candidates as oral delivery systems for insulin. INTRODUCTION In oral administration, gels can deliver drugs to four major sites: mouth, stomach, small intestine and colon. The gastrointestinal (GI) tract is the most popular route of drug delivery because of the facility of administration and its large surface area for systemic absorption. However, it is also the most complex route, so that the design of gel-based devices is needed to deliver drugs in specific sites in the GI tract [1]. Research on the controlled release of peptides and proteins is expanding as they are becoming an increasingly important class of therapeutic agents. Nevertheless, oral delivery of peptides and proteins to GI tract is complicated because of protein inactivation by digestive enzymes in the GI tract and poor epithelial permeability of these drugs. The colonic region, due to its lower proteolytic activity in comparison to that in the small intestine, has been considered as a possible absorption site for orally administrated peptides and proteins [2]. Polysaccharides like dextran, amidated pectin and arabinoxylans, which form gels resistant to enzymatic digestion but degraded in the presence of colonic enzymes or microflora, are potential devices for colon-specific drug delivery [3-4]. Thus, oral administrated polysaccharide gels loaded with peptide or protein therapeutic agents can protect the drug while passing through stomach and small intestine, being further released in the colon during gel degradation. Arabinoxylans (AX) are polysaccharides constituted by a linear backbone of xylose units containing a
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