Fabrication And Characterization Of Insulin Loaded Microcapsules With Controlled Release Properties

Oral insulin spray is a new, noninjectable method of insulin delivery. The goal of oral insulin delivery devices is to protect the sensitive drug from proteolytic degradation in the stomach and upper portion of the small intestine. The incorporation of insulin into microcapsules fabricated by layer-by-layer adsorption of oppositely charged polyelectrolytes (dextran sulfate and protamine/Fe3+) on insulin microaggregates was studied. Microaggregates with insulin were prepared by two different techniques: 1) formation of insoluble polyelectrolyte complex consisting of insulin and dextran sulfate, or 2) salting out of insulin from solution by sodium chloride. Morphology of the microcapsules was studied by laser confocal scanning electron microscopy and Zeta-potential analyzer. Regulation of insulin release from the microcapsules of both types by varying the pH of the medium was demonstrated. Insulin not bound to polyelectrolytes was released from the microcapsules at pH values of about 7, which corresponds to the pH of the human small intestine and ileum.