HYDRATION OF HYALURONIC-ACID AS A FUNCTION OF THE COUNTERION TYPE ANDRELATIVE-HUMIDITY

The form of water associated with different ionic and physical forms o f hyaluronic acid was investigated primarily using differential scanni ng calorimetry. The amount of non-freezable water associated with the polysaccharide was about 0.7 g H2O/g dry solids which corresponded to 15 water molecules per disaccharide unit. This value depended slightly on the physical form of the material (powder, film or freeze-dried ma terial) and also on the ionic form. The physical properties of a hyalu ronic acid film showed a transition around a relative humidity of 88% when freezable water starts to be observed.