The Dual Role of Fibrinogen as Inhibitor and Nucleator of Calcium Phosphate Phases: The Importance of Structure.

Constant composition and free drift methods have been used to investigate the abilities of human serum albumin (HSA) and fibrinogen to influence calcium phosphate precipitation. Both molecules inhibit hydroxyapatite (HAP) crystal growth when present in the solution phase. Fibrinogen, when immobilized at hydrophobicized germanium or silica surfaces, is able to nucleate calcium phosphate phases; at clean germanium or silica surfaces, it appears to be inactive. The apparent configuration of fibrinogen molecules at germanium or silica surfaces on which octadecyltrichlorosilane (OTS) was deposited probably exposes more negative sites for participation in nucleation.