CHITOSAN POLYETHYLENE-GLYCOL ALGINATE MICROCAPSULES FOR ORAL DELIVERYOF HIRUDIN

A mild chitosan/calcium alginate microencapsulation process, as applie d to encapsulation of biological macromolecules such as albumin and hi rudin, was investigated. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form microcapsu les with a polyelectrolyte complex membrane. Hirudin-entrapped alginat e beads were further surface coated with polyethylene glycol (PEG) via glutaraldehyde functionalities. It was observed that approximately 70 % of the content is being released into Tris-HCl buffer, pH 7.4 within the initial 6 h and about 35% release of hirudin was also observed du ring treatment with 0.1 M HCl, pH 1.2 for 4 h. But acid-treated capsul es had released almost all the entrapped hirudin into Tris-HCl, pH 7.4 media within 6 h. From scanning electron microscopic and swelling stu dies, it appears that the chitosan and PEG have modified the alginate microcapsules and subsequently the protein release. The microcapsules were also prepared by adding dropwise albumin-containing sodium algina te mixture into a PEG- CaCl2 system. Increasing the PEG concentration resulted in a decrease rate of albumin release. The results indicate t he possibility of modifying the formulation to obtain the desired cont rolled release of bioactive peptides (hirudin), for a convenient gastr ointestinal tract delivery system. (C) 1998 John Wiley & Sons, Inc.