Three cases are presented where modified chitins have been extensively administered to volunteers, as dressings for wounded soft and bone tissues, as anticholesterolemic dietary foods, and in the controlled delivery of anti-inflammatory drugs. The interactions of the modified chitins with human enzymes is critically examined. In the context of drug carrier resorption and wound healing, chitooligomers and monomers, generated by lysozyme, N-acetylglucosaminidase and human chitinase, activate macrophages and stimulate fibroblasts, respectively; the effects are production of smooth, vascularized and physiologically normal tissues. In the dietary food area, lipase, amylase, 3-hydroxy-3-methylglutaryl CoA reductase, glucokinase and the enzymes of prostaglandin synthesis are involved in the oral administration of chitosan: lipid adsorption is depressed mainly because of the physical form of the chitosan-lipid aggregates which are unsuitable as substrates. When chitosan is used as a drug carrier, chitosan-drug complxes are present. The uniqueness of chitosan among polysaccharides is underlined in terms of susceptibility to enzymatic depolymerization, cationicity, supply of cell-activating oligomers, and supply of N-acetylglucosamine for rebuilding of other biopolymers. Advances in molecular recognition and biocompatibility are also presented.

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