Hollow chitosan microspheres prepared by an oil1-in-water-in-oil2 double emulsion method

Hollow chitosan microspheres with and without genipin-cross-linking were prepared by an oil1-in-water-in-oil2 emulsion solvent diffusion method without any surfactants and core templates. Aqueous chitosan solution and ethyl acetate were used as the water and oil phases, respectively. The effects of oil1/water ratio, oil2 volume, cross-linker ratio and cross-linking time on the characteristics of the chitosan microspheres were determined. Chitosan microspheres with spherical shape and hollow structure were obtained. The density of the chitosan microspheres decreased slightly as the oil1 ratio increased. The average particle size increased slightly as the oil2 volume decreased and the oil1 ratio, cross-linker ratio and cross-linking time increased.