Search

The model anti-inflammatory drug prednisolone (PS) was retained in chitosan (CS) gel beads, which were prepared in a 10% aqueous amino acid solution (pH 9.0). Sustained release of PS from the CS gel beads was observed. Carrageenan solution was injected into air pouches (AP), which were prepared subcutaneously on the dorsal surface of mice, in order to induce local inflammation. CS gel beads retaining PS were then implanted into the AP to investigate the therapeutic efficacy of sustained PS release against local inflammation. In vivo PS release from CS gel beads was governed by both diffusion of the drug and degradation of the gel matrix. Sustained drug release by CS gel beads allowed the supply of the minimum effective dose and facilitated prolonged periods of local drug presence. Inflammation indexes were significantly reduced after implantation of CS gel beads when compared with injection of PS suspension. Thus, extension of the duration of drug activity by CS gel beads resulted in improved therapeutic efficacy. These observations indicate that CS gel beads are a promising biocompatible and biodegradable vehicle for treatment of local inflammation.

Alginate gel bead containing chitosan salt was prepared and the function was investigated. When the bead was placed in bile acid solution it rapidly took bile acid into itself. The uptake amount of taurocholate was about 25 μmol per 0.2 g dried gel beads. This phenomenon was observed on the case of the beads incorporating colestyramine instead of chitosan. Therefore, it seems that the ion-exchange reaction accompanying the insoluble complex-formation between chitosan salt and bile acid occurs in calcium alginate gel matrix.

Chitosan-reinforced alginate gel beads were prepared and the release patterns of coloring matter (Brilliant Blue G, BB) held within them were investigated. The release rates of BB from the gel beads were much slower after an initial lag time when they were incubated with chitosan compared with the original intact gels prepared without chitosan. These differences were observed irrespective of the β- d -mannuronic acid/α- l -guluronic acid (M/G) ratio of the alginate used and an additive effect on the release rate was observed when two species of alginates were combined. The initial release rates were reduced gradually in proportion to the increases in the chitosan concentration and/or incubation times used when preparing the gel beads. Furthermore, erosion of the gel beads was suppressed by chitosan treatment. The release of phenytoin from alginate gel beads showed the same characteristics as that of BB.

Chitosan (CS) gel beads were prepared with chelated copper (II) ions as a vehicle for the delivery of peptide and protein drugs. Insulin, which is a model of peptide and protein drugs, was scarcely released from the CS gel beads in vitro, presumably due to the nature of interactions occurring between insulin, CS and the copper (II) ions. The efficacy of insulin released from the CS gel beads was confirmed by implantation into diabetic mice. A consistent reduction in blood glucose level was observed in vivo due to insulin release as the CS gel beads were degraded. Control over insulin release was achieved by altering the properties of the CS. Thus, CS gel beads are promising as a biocompatible and biodegradable vehicle by which peptide and protein drugs can be delivered.