Preparation of Polyion Complex Capsule and Fiber of Chitosan and Gellan-Sulfate at Aqueous Interface

The electrostatic interaction between polysaccharides has been studied. Different characteristic surface structures, such as true spheres and fibrous forms, are made from gellan-sulfate (GS) and chitosan via polyion complex (PIC) formation. When a chitosan solution is added dropwise into a GS solution, spherical droplets form in the GS solution. The procedure makes true spherical capsules with various diameters, which are stable enough for finger pinching or magnetic stirring in distilled water. The soft droplet capsule is acid resistant, alkali resistant, and stable in boiling water. When an aqueous GS solution is added into an aqueous chitosan solution without mixing, a film of PIC is formed at the interface. When this PIC film is withdrawn from the interface, a fiber line forms in the wet states. After the intact wet fiber is dried in air, a strong fiber forms. The tensile strength of the strongest fiber created is 196 MPa. The swelling degree of the capsules and the strength of the fibers depend on the degree of sulfation of gellan.