Genipin-cross-linked chitosan microspheres prepared by a water-in-oil emulsion solvent diffusion method for protein delivery

Genipin-cross-linked chitosan microspheres containing model protein were prepared by a water-in-oil emulsion solvent diffusion method. Aqueous chitosan solution and ethyl acetate were used as water and oil phases, respectively. Bovine serum albumin (BSA) was used as a model protein. Chitosan solution was cross-linked with genipin before dissolving BSA and microsphere formation. Effects of BSA ratio and genipin-cross-linking on chitosan microsphere and BSA release characteristics were determined. BSA-loaded chitosan microspheres were spherical in shape. All BSA encapsulation efficiencies after rinsing the coated BSA were approximately 50-60%. The rinsing of coated BSA on the microspheres can reduce initial burst release effect. The cumulative release of BSA decreased as the BSA ratio decreased, and the genipin ratio and cross-linking time increased. This data indicated that protein release rate can be controlled by adjusting the protein ratio and the genipin-cross-linking.