Hydroxyapatite Mineralization in the Presence of Anionic Polymers

In biological systems, hydroxyapatite (HAP) mineralization is directed by macromolecules with anionic functional domains. This study investigates the effect of four anionic polymers with varying functional groups with respect to their inhibition of HAP growth. The anionic polymers include naturally occurring alginate and heparin as well as synthesized phosphorylated alginate and poly(3-sulfopropyl acrylate) (PSPA), thus investigating the three anionic functional groups of carboxylate, phosphate, and sulfate. Crystal growth inhibition was studied through the determination of the rates of HAP crystal growth while maintaining a constant composition of the supernatant as well as by investigations of the morphology of crystals grown in the presence of the anionic polymers. It was found that neither alginate nor PSPA had a large effect on crystal growth, phosphorylated alginate showed strong nonspecific binding, and heparin displayed preferential binding to the 002 face of the crystal.