Properties and degradation of selected polysaccharides: hyaluronan and chitosan

The main techniques proposed for characterisation of two important polysaccharides, chitosan and hyaluronan, which may have great importance as biomaterials, are described. The main properties obtained in aqueous phase are described for each of them; it is pointed out that they behave as semirigid polymer giving good films and good thickening effect. They are rich in -OH groups allowing chemical modifications to modify their physical properties. They are polyelectrolytes and can form electrostatic complexes; especially hyaluronan/chitosan complexes are recognised to be promising systems (also allowing multilayer capsule formation) for biomedical applications and drug release. The different causes of degradation are exposed in relation with their biodegradability and their susceptibility to sterilisation.