Phosphorus Research Bulletin

Editorial Board

2021 年 37 巻 p. i-
発行日: 2021年
公開日: 2021/05/08

DOIhttps://doi.org/10.3363/prb.37.i

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AMORPHOUS-PRECURSOR MEDIATED FORMATION OF MAGNESIUM-FREE WHITLOCKITE

Toshiisa Konishi, Sadayuki Watanabe

2021 年 37 巻 p. 1-10
発行日: 2021年
公開日: 2021/05/08

DOIhttps://doi.org/10.3363/prb.37.1

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Calcium phosphates (CPs) were widely used as synthetic bone graft substitutes. However, the control of particle size and morphology of CP materials have not been achieved substantially, even though these factors would influence the physicochemical properties. Recent studies revealed that a uniform nanostructured Mg-free whitlockite (WH), which was structurally similar to a high temperature polymorph of β-tricalcium phosphate, was synthesized by precipitation in organic solvents of N,N-dimethylformamide (DMF) and ethylene glycol (EG). The present study therefore aims to synthesize WH particles in the DMF-EG binary solvents by a solvothermal reaction to investigate the formation mechanism of the WH particles. The nucleation of the amorphous precursor, which occurred at 3 h, was dominated by the slow hydrolysis of organophosphate, which retarded reaching critical supersaturation and hindered the fast nucleation. The investigation on the effect of reaction time on WH formation revealed that the amorphous-precursor mediated WH formation via a solid-solid phase transformation occurred

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LOW-TEMPERATURE SYNTHESIS OF TRICALCIUM PHOSPHATE AND RELATED MATERIALS

Toshiisa Konishi

2021 年 37 巻 p. 11-20
発行日: 2021年
公開日: 2021/05/08

DOIhttps://doi.org/10.3363/prb.37.11

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Calcium phosphate-based ceramics, in particular, biodegradable β- and α-tricalcium phosphate (TCP), have received much attention as synthetic bone substitutes. Although there is a consensus that β- and α-TCP are both high temperature polymorphs, in which the β phase transforms to the α phase at above ~1125 °C, recent extensive studies reported novel synthetic methods for TCP and related materials such as magnesium- or magnesium-free whitlockite at temperatures below 800 °C. While several synthesis methods for TCP and related materials have been reported, few have focused on the low-temperature synthesis of TCP and related materials, but rather on conventional methods. Therefore, the focus of this short review is upon the low-temperature synthesis of TCP and related materials. In addition, future strategies to synthesize three-dimensional shapes of TCP and related materials at low temperature are discussed.

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HYDROTHERMAL TRANSFORMATION OF CALCIUM HYDROGEN PHOSPHATE DIHYDRATE INTO MAGNESIUM WHITLOCKITE

Toshiisa Konishi, Sadayuki Watanabe

2021 年 37 巻 p. 21-25
発行日: 2021年
公開日: 2021/11/23

DOIhttps://doi.org/10.3363/prb.37.21

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We here report a single-step, rapid synthesis method for magnesium whitlockite (MgWH). The hydrothermal synthesis of MgWH by transformation of calcium hydrogen phosphate dihydrate (DCPD) in formic acid solution was investigated. The fraction of MgWH increased with increasing Mg²⁺ ion concentration. Single-phase MgWH with monodisperse, hexahedral-shaped particles was obtained when the reaction was conducted in the presence of 15 mmol/L Mg²⁺ ions and at 220 °C for more than 3 h. The results also indicated that the hydrothermal transformation into MgWH in the presence of Mg²⁺ ions was not pH-dependent precipitation but thermodynamically stable precipitation. Local structure analysis by ¹H and ³¹P nuclear magnetic resonance confirmed the presence of protonated phosphate (HPO₄^2-) and showed three distinct phosphate peaks corresponding to the MgWH structure, which were consistent with the crystal structure of conventional MgWH.

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EFFECT OF ORGANOPHOSPHATES ON THE FORMATION OF MAGNESIUM-FREE WHITLOCKITE

Toshiisa Konishi, Sadayuki Watanabe

2021 年 37 巻 p. 26-31
発行日: 2021年
公開日: 2021/11/23

DOIhttps://doi.org/10.3363/prb.37.26

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Objective of the present study was to synthesize Mg-free whitlockite (WH) particles using organophosphates with different alkyl chain lengths via a solvothermal reaction. The effects of the organophosphates and their Ca/P molar ratio on the formation of WH were investigated. With increasing alkyl chain length of the organophosphate and increasing Ca/P molar ratio, the dominant phase changed from WH to hydroxyapatite (HA). This result suggests that the organophosphates exhibited different hydrolysis rates. With all of the organophosphates, WHs were obtained only at a Ca/P molar ratio of 0.25. In addition, an analysis of the local structure using ¹H and ³¹P nuclear magnetic resonance spectroscopy indicated that the WH contained protonated phosphate (HPO₄^2-) and trace amount of HA subphase.

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FABRICATION OF POROUS β-TRICALCIUM PHOSPHATE SCAFFOLDS USING FOAM REPLICA WITH 3D TECHNOLOGY

Kakeru Tsuchiya, Shohei Nakata, Masahiro Ohno, Shigetaka Tamagawa, Hir ...

2021 年 37 巻 p. 32-38
発行日: 2021年
公開日: 2021/12/06

DOIhttps://doi.org/10.3363/prb.37.32

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The present work is based on prior research into the synthesis of porous β-tricalcium phosphate (β-TCP) with continuous pores by applying a β-TCP suspension onto a porous polyurethane foam by spray coating followed by pyrolysis of the foam. In the work reported herein, the three-dimensional (3D) pore structure of a polyurethane foam specimen was scanned using X-ray computerized tomography after which a porous acrylic foam with an optimized pore structure was fabricated using a 3D printer based on this scan. The pore size and pillar diameter of the porous printed material could be modified simply by changing the brightness value of the image data in the processing software. Specifically, the pillar diameter was increased while the pore size became smaller as the brightness was increased. β-TCP with interconnecting pores could be easily fabricated by spray coating these printed molds. The physical properties and porous structure of the product could also be tuned by modifying the pore structure of the foam and the amount of spray coating. The porous β-TCP obtained in this study had sufficient physical properties to be used as a scaffold material, suggesting the possibility of applying this scanning process to other porous materials, including living bones.

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