Glucose-responsive composite microparticles based on chitosan, concanavalin A and dextran for insulin delivery.

Glucose-responsive systems are very useful for self-regulated insulin delivery. In this study, glucose-responsive composite microparticles based on chitosan, concanavalin A and dextran were prepared by first fabricating chitosan microparticles subsequently coupling concanavalin A via Schiff-base reaction and dextran layer via specific affinity. SEM, fluorescence microscope, XPS and TGA were used to characterize the morphology and composition of the microparticles. SEM results indicated that the microparticles could exist individually and in a spherelike shape. The fluorescence image showed that the microparticles were well dispersed with an average diameter of 2.5 microm. The XPS and TGA data confirmed the composite layers of the microparticles. Insulin could be loaded into the microparticles due to electrostatic and intermolecular interaction with high entrapment efficiency of 92.2% and loading capacity of 9.1%. The release profiles of insulin revealed that the insulin release was in response to the glucose concentration in the medium and the glucose sensitivity was reversible. The released insulin was proved to remain active through the whole process. The results suggest that this composite microparticle may be a promising system for self-regulated insulin delivery.