Preparation of alginate coated chitosan hydrogel beads by thermosensitive internal gelation technique

Chitosan hydrogel beads were successfully prepared by the method of thermosensitive internal gelation technique. The prepared beads were spherical, smooth-surfaced and non-aggregated with a diameter of 1.7–2.1 mm. The diameters of beads can be controlled and have a correlation with the initial drop size, the concentration of CaCl₂, alginate and the time of solidification. The bead is comprised of three parts, which are chitosan/glycerophosphate (CS/GP) hydrogel core, chitosan-alginate (CS/SA) gel layer in the middle and calcium-alginate gelatin capsules in outer layer. Swelling studies indicate that the beads can be stable in simulated gastric fluid. But the beads shrink sharply when removed to simulated intestinal fluid. Drug release behavior showed that release of ornidazole in the beads is much slower than in the CS/GP hydrogel.