Sodium Induces Octacalcium Phosphate Formation and Enhances Its Layer Structure by Affecting the Hydrous Layer Phosphate

Abstract

Octacalcium phosphate (OCP), a layered calcium phosphate compound, has attracted attention in areas such as biomaterial and pharmacy, as well as the environmental industry, because of its excellent biocompatibility and low environmental load. However, little is known about the effect of alkaline metal ions on OCP formation, even though the Na ion is always present as a pH neutralizing or ionic strength-adjusting agent. Therefore, in this study, we investigated the role of the Na ion in OCP formation from dicalcium phosphate dihydrate through hydrolysis by using solutions with various Na concentrations. When the Na concentration in the treatment solutions increased, the formation of hydroxyapatite as a residual material was inhibited and the purity of OCP was increased. Furthermore, at higher concentrations, OCP crystals evolved layer structures because Na affects the P5 PO4 in the OCP lattice and enhances the HPO4-OH layer structure, which significantly contributes to OCP crystallinity and crystal structure. Thermal stability measurements indicate that the thermal stability of OCP decreases with increasing Na content. This study suggests that Na incorporation into OCP crystals can induce OCP formation but simultaneously decreases the OCP stability.

Calcification Microstructure Reflects Breast Tissue Microenvironment

“…Therefore, benign cell, neutral pH environments promote ACP hydrolysis that is more likely to produce A/B carbonated apatites, whereas invasive cell environments, (favouring OCP hydrolysis), would result in predominantly B-type carbonate apatites. This is further supported by the observations that sodium incorporation into the HAp lattice induces OCP formation, and sodium substitution is highest in invasive calcifications [15, 39]. Hypoxia has also been shown to initiate osteogenic differentiation in other cell types, therefore may contribute to the differing formation mechanisms between benign, in-situ and invasive breast tissue pathologies [40].…”

Inorganic process for wet silica-doping of calcium phosphate

“…Several previous studies indicate that OCP was likely formed in PO 4 rich solutions. [21][22][23] This study suggests that silica also played a similar role of PO 4 for OCP formation. At further concentrated conditions, high alkalinity induced apatite formation.…”

Aesthetic Silver-Doped Octacalcium Phosphate Powders Exhibiting Both Contact Antibacterial Ability and Low Cytotoxicity

“…When OCP was fabricated in weak basic solutions containing Na + , the Na + substituted into the Ca 2+ sites conjugated to P 5 PO 4 , which is a root of the HPO 4 –OH layer; the relative intensity ratio of I (100) / I (200) associated with the layer structure of OCP then increased. 32 …”