Transformation of dicalcium phosphate dihydrate into octacalcium phosphate with incorporated dicarboxylate ions

Abstract

Octacalcium phosphate (OCP) has a layered structure consisting of apatitic and hydrated layers. The hydrogen phosphate ions in the hydrated layer can be replaced by dicarboxylate ions resulting in the formation of OCP with incorporated dicarboxylate ions. We herein report the transformation behaviour of dicalcium phosphate dihydrate (DCPD), which is used as starting material for the synthesis of OCP in acetic acid (Ace), succinic acid (Suc), suberic acid (Sub), and isophthalic acid (Isp) solutions at a pH of approximately 5.5 at 60°C. We found that DCPD with a small crystal size (specific surface area: 4.9 m 2 •g ¹1) completely transformed into OCP within 1 h in Ace solution, whereas DCPD with a large crystal size (specific surface area: 0.62 m 2 •g ¹1) did not form the OCP phase even when treated for 3 h. OCP incorporating Suc and Isp was formed from DCPD with a small crystal size in solutions of these dicarboxylic acids. On the other hand, Sub was not incorporated into OCP although Sub is a typical dicarboxylic acid that could be incorporated into the OCP structure. We concluded that although the dicarboxylic acids that are adaptable to these experimental conditions are limited, DCPD can be used as a starting material for OCP with incorporated dicarboxylate ions.

Effect of orotic acid addition on hydrolysis conversion of α‐tricalcium phosphate to hydroxyapatite

“…Namely, carboxylate ions are assumed to form the bonding with calcium phosphate precursor via interaction between Ca 2+ and carboxylate ions in the solution. Moreover, in the case of the dicarboxylic acid ion (e.g., succinate ion) coexists instead of Ort under the synthetic condition of this study, a hybrid of OCP and succinate ion is formed at the reaction time of 3 h. 20 As shown in Figure 2A, the production amount of OCP or HA is small in the absence of carboxylic acid ions at the reaction time of 3 h (e.g., Ort-0-3). These results suggest that the presence of dicarboxylate ions promotes the formation of OCP structure.…”

Incorporation of tetracarboxylate ions into octacalcium phosphate for the development of next-generation biofriendly materials

“…Synthesis of DCPD as a precursor of OCP. We synthesised DCPD as a precursor of OCP using the following process developed by our research group 40 . A solution of calcium nitrate (100 cm 3 , 200 mol m −3 ) was stirred at 30°C at 500 rpm in a glass beaker using a magnetic stirrer.…”

“…Synthesis of OCP with incorporated pyromellitate ions. We synthesised OCP with incorporated pyromellitate ions by the hydrolysis of DCPD in an acetate buffer solution containing pyromellitic acid, based on the method developed by our research group with appropriate modifications 40 . To evaluate the effects of the pyromellitic acid concentrations, synthesised DCPD (1.38 g) was added to an acetate buffer solution (100 cm 3 , 200 mol m −3 ) containing 0-100 mol m −3 pyromellitic acid at 60°C under vigorous stirring.…”

The development of novel calcium phosphate–polymer composite biomaterials with macro- to nano-level controlled hierarchical structures

“…As is imaginable, since DCPD is formed as an intermediate phase, it should be possible to synthesize OCP incorporated with dicarboxylate ions from DCPD as a starting material. 54) In addition, OCP with incorporated dicarboxylate ions can also be synthesized by homogeneous precipitation methods. 55) Studying the interlayer expansion behavior of OCP through the incorporation of dicarboxylate ions is attractive in terms of the materials chemistry of layered compounds.…”