Stabilization of the amorphous state of calcium carbonate-phosphates with phosphate ions

Abstract

Amorphous calcium carbonate-phosphate with a Ca/P ratio of 1.83 was precipitated from Ca²⁺, Ca²⁺, PO^3–₄, CO^2-₃  − containing solutions at pH 10 and stabilized by ethanol dehydration and followed by heating at 400 °C. The presence of PO^3–₄ ions in the structure of amorphous calcium carbonate-phosphate provides its increased resistance to transformation into crystalline phases. Aging in a Ca²⁺, PO^3–₄ , CO^2-₃  − containing mother solution at pH 10 for 4 days promotes the transformation of amorphous calcium carbonate-phosphate into amorphous calcium carbonate-phosphate / carbonated hydroxyapatite / calcite. The combined effect of PO^3–₄ и CO^2-₃  − ions in the aquatic environment on the crystallization of amorphous calcium carbonate-phosphate into carbonated hydroxyapatite contributes to a maximum stabilization of the amorphous state that provides a high extent of bioactivity.