Structural Formulas and Chemical Composition

Chondroitin sulfate and sodium hyaluronate share similar chemical and physical characteristics. They consist of repeating disaccharide sub-units sodium glucu- 

The binding of medication to the viscoelastic substance in the eye seems to be of secondary importance in the cases of Amvisc , Healon , and Viscoat . Viscoelastics, thus, have no absorptive mechanism influencing the effects of intraocular or topical therapeutics (McDermott 8c Edelhauser, 1989). 

Cellulose, a disaccharide of D-glucose, represents the basic molecule, stereo-chemically differing from dextrose in the bonds existing between the two monomers a )S-glycoside bond in cellulose and a a-glycoside bond in dextrose. To increase hydrophilic properties, methoxy- and hydroxypropyl- side-chains are replaced by hydroxy groups (Fig. 22). The molecule is uncharged. 

Within the sodium hyaluronate molecule, reduced flexibility at the glycoside bond causes a rotation of carbohydrate units along the molecule chain. As a consequence, the molecule shows a flexible, random coil conformation with a certain rigidity. Chondroitin sulfate, however, is a low-molecular-weight glycosaminogly-can and assumes a conformation between the coil described above and a rigid rod. 

Sodium hyaluronate contains no other carbohydrates or amino acids and shows no covalent intermolecular bonds (Balazs, 1983). In such solutions as water or aqueous, this rigid molecule takes on the form of a very flexible and long random coil. Small molecules can penetrate into and disperse inside the sodium hyaluronate molecule, while larger molecules, such as fibrinogen, collagen or proteoglycan, cannot (Balazs, 1983). Osmotic activity, as well as, the interaction of molecules in the intercellular matrix, have often been pointed out as the influence of this so-called steric exclusion of transport (Comper Laurent, 1978). 

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