Calcium phosphate clusters

Kanzaki, Noriko; Treboux, Gabin; Onuma, Kazuo; Tsutsumi, Sadao; Ito, Atsuo

doi:10.1016/s0142-9612(01)00039-4

Cited by 92 publications

(107 citation statements)

References 15 publications

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“…OCP is not directly formed from the ions in the aqueous solution, but rather via several precursor phases, such as amorphous calcium phosphate (ACP; at least six forms) through solid-solid phase conversion instead of a dissolution-precipitation reaction [12][13][14][15][16][17][18][19][20]. Therefore, it is suggested that the property of the precursor, in this case the physicality of ACP, strongly affects the formation of OCP.…”

Section: Discussionmentioning

confidence: 99%

Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Sugiura

Ishikawa

2018

Crystals

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Octacalcium phosphate (OCP) has attracted much attention as an artificial bone substitute because of its excellent osteoconductive and bone replacement properties. Although numerous studies have investigated OCP powder fabrication, there are only a few studies on OCP block fabrication. Therefore, in this study, the feasibility of optimizing dicalcium hydrogen phosphate dihydrate (DCPD) blocks, as a precursor for OCP block fabrication, under a pH 6 adjusted acetate buffer solution at 70 • C for 2 days was investigated. When a DCPD block was immersed in acetate buffer, the block was partially converted to OCP, with a large amount of dicalcium hydrogen phosphate anhydrate (DCPA), and its macroscopic structure was maintained. When the DCPD block was immersed in a Ca-containing solution, it was converted to mainly hydroxyapatite (HAp) with DCPA. On the other hand, when the DCPD block was immersed in a PO 4 -containing solution, the block was converted to OCP, and its macroscopic structure was maintained. In other words, the PO 4 -induced calcium phosphate with a Ca/P molar ratio lower than 1.0 may represent an intermediate phase during the compositional transformation from a DCPD block to an OCP block through the dissolution-precipitation reaction.

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Section: Discussionmentioning

confidence: 99%

Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Sugiura

Ishikawa

2018

Crystals

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“…Namely, the crystal structure of HA is well described elsewhere (Elliott 1994;White and Dong 2003;Mathew and Takagi 2001), the detailed analysis of the electronic structure, bonding, charge transfer, optical and elastic properties is also available Rulis et al 2004;Snyders et al 2007;Ching et al 2009), while the readers interested in Posner's clusters are referred to still other papers (Treboux et al 2000;Kanzaki et al 2001). A shell model was developed to study the lattice dynamics of HA (Calderin et al 2005), while a cluster growth model was created to illustrate its growth (Onuma and Ito 1998).…”

Section: Ha (Or Hap or Ohap)mentioning

confidence: 99%

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

Dorozhkin¹

2017

Morphologie

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“…The transformation proceeds via direct conversion of an amorphous structure into crystalline ones. This kinetics is attributed to a common cluster unit present in both the amorphous and crystalline phases [11][12][13][14][15]. Posner's cluster [11] and its symmetric isomers [16] were proposed for this common cluster, and then more complex structures of clusters were found through experimental and computational investigations [17,18].…”

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confidence: 94%

Metastable Intermediate Phase during Phase Transformation of Calcium Phosphates

Onuma¹,

Sugiura²

2015

J Biotechnol Biomater

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Phase transformation of calcium phosphates from amorphous to crystalline phases around neutral pH proceeds via direct structure conversion using non-ionic elementary units. This transformation inevitably forms metastable intermediate-structured phase(s) between the two end phases. In addition to conventional calcium phosphate phases appearing in the transformation, new unknown phases were observed. They did not correspond to simply poor crystalline materials of conventional phases and instead had particular structures. One was pseudo-OCP, which lacked the HPO 4 -OH layers in the conventional OCP structure.Keywords: Phase transformation; Amorphous phase; Intermediate phase; OCP; HAP Calcium phosphates have been energetically investigated for more than half a century because of their important role not only in forming hard tissues such as bone and teeth but also being a frequent cause of calculus and arteriosclerosis [1,2]. One factor hindering a sound understanding of their formation mechanism is that they appear in several forms at room to body temperatures [3,4]. For example, amorphous calcium phosphate (ACP), dicalcium phosphate dihydrate (DCPD), β-tricalcium phosphate (β-TCP), octacalcium phosphate (OCP), and hydroxyapatite (HAP) form in weak acidic to weak basic calcium phosphate solutions. They precipitate and stably exist or transform into other more stable phases depending on the solution conditions. Transformation between each calcium phosphate [5][6][7] is of particular interest because the control of this process results in obtaining a desirable phase that can contribute to the design of calciumphosphate-based biomaterials with novel functions.Two phase-transformation mechanisms have been proposed. One is solvent-mediated transformation, which is the simple dissolution and growth of materials depending on the difference in solubility. A representative example for calcium phosphate is the hydrolysis of DCPD and subsequent growth of OCP [8]. The other is structural conversion from metastable to stable phases as was revealed in situ using a light scattering technique [9,10]. If the concentrations of calcium and phosphate ions in the solution are sufficiently high, ACP first forms in the solution and transforms into other phases such as OCP and HAP. The transformation proceeds via direct conversion of an amorphous structure into crystalline ones. This kinetics is attributed to a common cluster unit present in both the amorphous and crystalline phases [11][12][13][14][15]. Posner's cluster [11] and its symmetric isomers [16] were proposed for this common cluster, and then more complex structures of clusters were found through experimental and computational investigations [17,18]. That the clusters can be decomposed into smaller ion pairs as the minimum unit was also proposed [19], indicating the need for more careful investigation of the elemental unit in the phase transformation of calcium phosphates.Leaving aside the question about the structure of the minimum unit, we note that it is well accepte...

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Calcium phosphate clusters

Cited by 92 publications

References 15 publications

Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

Metastable Intermediate Phase during Phase Transformation of Calcium Phosphates

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