Preparation of PEG-grafted chitosan nanoparticles as peptide drug carriers

It has recently become very important to develop drug delivery systems for water-soluble natural macromolecules, such as peptides, proteins and polynu cleotides. We have found that poly(ethylene glycol)-grafted chitosan, PEG-g -chitosan, formed nanoparticles through intermolecular hydrogen bonding in an aqueous solution. PEG-g-chitosan nanoparticles can be expected to incorp orate water-soluble, polar or anionic molecules, which can then interact wi th chitosan by hydrogen bonds or electrostatiscally. We therefore decided t o investigate the incorporation of a peptide hormone, insulin, as a model p eptide drug into PEG-g-chitosan nanoparticles. PEG-g-chitosan nanoparticles incorporated a certain quantity of insulin molecules spontaneously but thi s depended on the degree of introduction of PEG chain on chitosan. The rele ase rate also depended on the degree of introduction of PEG chain on chitos an. The sustained release of insulin from nanoparticles was also observed. PEG-g-chitosan nanoparticles are can be expected to be applied as delivery vehicles for peptide drugs.