Research Grant Report
Synthesis of Calcium Apatite Particles using the Enzyme Reaction
2008 Volume 16 Pages 63-67
Details
2008 Volume 16 Pages 63-67
Layered calcium phenyl phosphate (Ca(C6H5PO4)0.92(HPO4)0.08Ca・1.3H2O: CaPP), which is composed of a multilayer alternating bimolecular layer of phenyl groups and amorphous calcium phosphate phase, was treated in aqueous media including an enzyme such as alkaline phosphatase (ALP) at pH ＝9.6 and 37℃ for 1 - 48 h. The CaPP was transformed into amorphous calcium phosphate with the same Ca/P molar ratio of calcium hydroxyapatite (Ca10(PO4)6(OH)2: Hap) by treating for 1 h. The formed amorphous material possessed no phenyl groups. Furthermore, the plate-like CaPP particles were vanished and the rod-like particles due to amorphous calcium phosphate with ca. 43nm in length and ca. 8nm in width were generated. These facts suggested that all the phenyl phosphates in CaPP were hydrolyzed to generate inorganic phosphate species such as PO43-. The low crystalline Hap nano-particles with irregular shape were produced at 3 h. Then, the molar ratio Ca/P of the product was 1.68, almost corresponding to 1.67 of the theoretical ratio of Hap. The crystallinity of Hap was increased by elongating the treating period up to 6 h and then almost constant. The yielded Hap was rod-like particles with ca. 100nm in length and ca. 10nm in width. On the other hand, when the CaPP particles were treated in aqueous media in the absence of ALP, the CaPP was dissolved and the formation of Hap was not recognized. From these results, it can be presumed that the layered CaPP was dissolved, hydrolyzed and recrystallized to Hap nano-particles by using the ALP. This phase transformation of CaPP in Hap with ALP resembled to the formation mechanism of Hap in animal organism.
