Effects of surfactant and acid type on preparation of chitosan microcapsules

Abstract Chitosan microcapsules were prepared by a method involving emulsification and crosslinking. The effects of surfactants and acid type for dissolving chitosan on the characteristics of chitosan microcapsules were investigated. The results showed that the mixed surfactant consisting of Span80 and Tween60 had an obvious effect on reducing the size of the microcapsules. The two-surfactant complex, formed on the basis of hydrogen bonding, strengthened the interfacial membrane in the emulsion, thus decreasing not only the size of the microcapsules but also the coalescence of dispersed chitosan liquid drops. In the case of monoacid such as hydrochloric acid or acetic acid for dissolving chitosan, the chitosan microcapsules obtained were spherical in shape with smooth surfaces. For diacids or triacid, the chitosan microcapsules obtained were also spherical, but their surfaces were covered by folds and crinkles. The number of carboxyl groups in the acids used influenced the chemical crosslinking between chitosan and the crosslinker (glutaraldehyde) as well as the morphology of the particles. For diacids or triacid, physical crosslinking occured due to electrostatic force, accompanied by substantial decrease of covalent crosslinking, leading to decreased strength of the microcapsules as shown by the collapse of microcapsule walls and the formation of multiple folds and crinkles on their surfaces.