Interaction of acid glycosaminoglycans (mucopolysaccharides) with hydroxyapatite

Selected acidic glycosaminoglycans (GAG) have been used as a model series to study some binding properties of hydroxyapatite. The order of binding was heparin, heparin sulfate, dermatan sulfage/chondroitin-4-sulfate/chondroitin-6-sulfate (all similar) and hyaluronic acid, indicating that the negative charge on the molecules is a major determinant in the binding process. Both calcium and saliva pretreatment led to an increase in uptake of selected GAG whereas fluoride even at 1 and 3 parts/106 levels led to a graded reduction in uptake. The clinical significance of these findings may be related to the presence of certain GAG in the dental integuments and to the interaction of a chemically defined group of compounds at a specific solid surface. Such findings may also have an application in studies on endogenous mineralization. The results are in accord with the generally held view that polyanions may interact electrostatically with calcium sites present in the crystal lattice of the hydroxyapatite.