Structure of Clusters and Formation of Amorphous Calcium Phosphate and Hydroxyapatite: From the Perspective of Coordination Chemistry

Du, Lin-Wei; Bian, Sha; Gou, Bao-Di; Jiang, Yun; Huang, Jian; Gao, Yuxi; Zhao, Y. B.; Wen, Wen; Zhang, Tian‐Lan; Wang, Kui

doi:10.1021/cg400498j

Cited by 83 publications

(88 citation statements)

References 23 publications

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“…In general, amorphous HA can form as a precursor phase in a solution at sufficiently high supersaturation and pH. Subsequently, it transforms to the thermodynamically stable HA [Ca 10 (PO 4 ) 6 (HO) 2 ] [14]. The degradation rate of HA also depends on its particle size.…”

Section: Figure 2 (A)mentioning

confidence: 99%

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Physical and biological characteristics of nanohydroxyapatite and bioactive glasses used for bone tissue engineering

Yousefi

Oudadesse

Akbarzadeh

et al. 2014

Nanotechnology Reviews

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Critical-sized bone defects have, in many cases, posed challenges to the current gold standard treatments. Bioactive glasses are reported to be able to stimulate more bone regeneration than other bioactive ceramics; however, the difficulty in producing porous scaffolds made of bioactive glasses has limited their extensive use in bone regeneration. On the other hand, calcium phosphate ceramics such as synthetic hydroxyapatite and tricalcium phosphate are widely used in the clinic, but they stimulate less bone regeneration. This paper gives an overview of the recent developments in the field of bioactive nanoparticles, with a focus on nanohydroxyapatite and bioactive glasses for bone repair and regeneration. First, a brief overview of the chemical structure and common methods used to produce synthetic nanohydroxyapatite and bioactive glasses has been presented. The main body of the paper covers the physical and biological properties of these biomaterials, as well as their composites with biodegradable polymers used in bone regeneration. A summary of existing challenges and some recommendations for future directions have been brought in the concluding section of this paper.

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Section: Figure 2 (A)mentioning

confidence: 99%

“…The study included needle-shaped (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) , the stronger the toxicity (Figure 8) [80]. Most of the cytotoxicity was attributed to apoptosis rather than necrosis.…”

Section: Biological Propertiesmentioning

confidence: 99%

Physical and biological characteristics of nanohydroxyapatite and bioactive glasses used for bone tissue engineering

Yousefi

Oudadesse

Akbarzadeh

et al. 2014

Nanotechnology Reviews

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“…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.…”

Section: Introductionmentioning

confidence: 96%

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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“…42 However, due to the lack of long-range order and Rontgen amorphous character of the ACP phase, very little structural information is available about this phase. 43,44 In this context, it is important to note that ex situ XRD analysis shows the formation of CaHPO 4 ·2H 2 O after t = 10 min (Fig. S6B ‡), while in situ measurements locate this phase transition at t = 13 min.…”

Section: In Situ Luminescence Experimentsmentioning

confidence: 95%

In situ luminescence analysis: a new light on monitoring calcium phosphate phase transitions

Terraschke

Rothe

Tsirigoni

et al. 2017

Inorg. Chem. Front.

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In this work, in situ luminescence analysis was applied for the first time for monitoring the phase transitions of calcium phosphate (CaP) and confirmed by synchrotron in situ X-ray diffraction in addition to in situ infrared spectroscopy, with simultaneous measurements of pH and ion conductivity. Applying doped Ce 3+ and Eu 3+ as local coordination sensors, the high sensitivity of their emission spectra upon the changes in the coordination sphere of the doped cation sites enabled to detect the formation of amorphous calcium phosphate (ACP) and Ca 5 (PO 4 ) 3 OH, besides their subsequent transitions to CaHPO 4 ·2H 2 O and Ca 8 H 2 (PO 4 ) 6 ·5H 2 O under real reaction conditions. Calcium phosphates are widely present in mammals and understanding their phase transitions is important to comprehend the conversion between healthy and diseased tissues. In situ luminescence measurements are advantageous for allowing monitoring these phase transitions in a fast and sensitive fashion also in conventional laboratories, independent of synchrotron radiation.

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Structure of Clusters and Formation of Amorphous Calcium Phosphate and Hydroxyapatite: From the Perspective of Coordination Chemistry

Cited by 83 publications

References 23 publications

Physical and biological characteristics of nanohydroxyapatite and bioactive glasses used for bone tissue engineering

Physical and biological characteristics of nanohydroxyapatite and bioactive glasses used for bone tissue engineering

Metastable Intermediate Phase during Phase Transformation of Calcium Phosphates

In situ luminescence analysis: a new light on monitoring calcium phosphate phase transitions

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