Design of oral insulin delivery systems

The possibility of administering insulin orally in replacement of painful subcutaneous route has been investigated over years but with varying degree of success. Nanoparticles, microparticles, hydrogel, capsule, tablet, and film patch are designed to deliver insulin orally. They are largely formulated with polymeric adhesive, protease inhibitor, insulin aggregation inhibitor, and functional excipients to induce transcellular, paracellular, Peyer's patches, or receptor-mediated transport of insulin in gastrointestinal tract. Superporous matrix, intestinal patches, and charged-coupled micromagnet microparticles are recent formulation strategies to promote oral insulin absorption. The formulation emphasizes on assembly of insulin and excipients into a physical structure which provides an element of drug targeting to maintain stability and increase bioavailability of insulin. The overview of various strategies applied in oral insulin delivery system design denotes the significance of mucoadhesiveness whereby a prolonged retention of dosage form in intestinal tract translates to cumulative insulin release and absorption, overcoming the intestinal transport capacity limit. Synthesis and use of mucoadhesive excipients, chemical modification of insulin to promote its physicochemical and biological stability for encapsulation in dosage form with prolonged retention characteristics and identification of potential insulin adjuncts are efforts needed to accelerate the speed of obtaining a functional oral insulin delivery system.