Abstract: The chitosan microspheres were prepared by emulsion cross-linking method, and vanillin was used as a cross-linking agent in the water-in-oil (W/O) emulsion composed of chitosan aqueous solution and liquid paraffin. According to the results of IR and XRD, two main mechanisms lead to the formation of cross-linked chitosan microspheres: one was the Schiff base reaction and hydrogen bond formation, the other was the acetalization. It was also discussed that the reduction of cross-linked chitosan’s crystallinity was resulted from the lack of enough rearrangement of chitosan molecular linkages and the decline of regularity of crosslinked chitosan molecular with complex structure. Using berberine hydrochloride as the model drug, the drug-loaded chitosan microspheres were observed by SEM, and the results indicate that these microspheres showed dense surface and excellent sphere-forming ability, and the sizes of microspheres are in the range of 5—15 μm. In addition, the drug loading ratio and efficiency as well as drug releasing curves were also investigated in vitro, and the results show that chitosan microspheres displayed an excellent drug-controlled release.

Key words: Chitosan microsphere, Cross-linking, Vanillin, Drug-loaded, Mechanism