THERMAL-BEHAVIOR OF AQUEOUS-SOLUTIONS OF SODIUM HYALURONATE FROM DIFFERENT COMMERCIAL SOURCES

The thermal behaviour of some commercial sodium hyaluronate solutions used in ophthalmology has been studied by DSC after cooling to -100 de grees C. During the rewarming, the endothermic effect that appears at around -22 degrees C is associated with the molecular weight (MW) of t he fractions of sodium hyaluronate: the higher the MW, the higher the endotherm temperature. At high temperatures, the dehydration temperatu res of the samples (onset at around 110 degrees C) are in a sequence t hat is the inverse of that obtained at low temperatures. Both effects, low-temperature phase transition and dehydration, have been related t o intramolecular and intermolecular hydrogen bonding capabilities and to hydration and crosslinking effects.