Layer-by-layer adsorption of biopolyelectrolytes as a universal approach to fabrication of protein-loaded microparticles

This study was aimed at examination of microparticles formed via the layer-by-layer adsorption of dextran sulfate and chitosan onto the insoluble complexes of various proteins with polyanions. Microparticles with all tested proteins were stable at pH values of 1–5. At pH > 6 the mucoadhesivity of the microparticles changed and the encapsulated proteins were released. Microparticles were able to protect the proteins from proteases. Proteinous protease inhibitors encapsulated as well (2–3%) completely prevented protein proteolysis. The pharmacological effect of microencapsulated insulin was studied in vivo using the model of chronic diabetes in rats, which were treated by oral administration.