Sustained insulin release with biodegradation of chitosan gel beads prepared by copper ions

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.