Preparation and characterization of chitosan-gellan hybrid capsules formed by self-assembly at an aqueous solution interface

True spherical capsules are formed by electrostatic polysaccharide interaction between chitosan and gellan gum via polyion complex (PIC) formation in aqueous solutions. Dropwise addition of a chitosan solution into the gellan solution gave spherical capsules whose outside surface was gellan and whose inside was chitosan (chitosan(in)-gellan(out) capsule). Conversely, the addition of gellan into chitosan in yields chitosan(out)-gellan(in) capsules. SEM observation revealed a fibrous network spreading along the capsule membrane of the chitosan(in)-gellan(out) capsule. The releasing properties of the capsules were examined using low molecular weight substances and high molecular weight proteins. For low molecular weight substances, the releasing kinetics were affected by the attractive and repulsive interactions between the substances and the inside component of the capsule. The molecular weight of the encapsulated substances also affects the releasing kinetics. These results, together with a simple preparation procedure, indicate the applicability of chitosangellan capsules as drug-carrier materials having a controlling release mechanism. As an application example, preparation of an actually eatable artificial roe was also described.