Β-calcium Pyrophosphate Research Articles

The reactivity of α-tricalcium phosphate powders is affected by minute amounts of β-calcium pyrophosphate and by the synthesis temperature

α-tricalcium phosphate (α-TCP) is the most widespread raw material for hydraulic calcium phosphate cements (CPCs). CPCs are widely used in bone repair due to their injectability, setting ability, and osteoconductivity. This study investigated the reactivity of α-TCP powders, focusing on the impact of minor phase impurities, β-calcium pyrophosphate and hydroxyapatite, and the synthesis temperature. The α-TCP powders were synthesized via a solid-state reaction of calcium carbonate and anhydrous dicalcium phosphate, with varying Ca/P molar ratios (1.4850–1.5075) and synthesis temperatures (1175°C–1350 °C). Powders produced with a Ca/P molar ratio below 1.50 and synthesized at a temperature above the melting point of β-CPP (1296 °C) had a broader size distribution and a two to fourfold lower hydraulic reactivity. Conversely, a higher Ca/P molar ratio improved reactivity. The study underscores the importance of precise control over synthesis parameters to enhance the performance of α-TCP-based CPCs, offering insights for optimizing material design in biomedical applications.

Synthesis and Characterization of Calcium Phosphate Using Two Stages of Process

Calcium phosphate, a naturally occurring biomaterial found in human and animal bones and teeth, possesses desirable properties such as strength, biocompatibility, and the ability to stimulate tissue growth. This study investigates the synthesis of calcium phosphate through a precipitation method without calcination. The process involves dissolving raw materials in phosphoric acid, followed by precipitation using KOH as the precipitating agent. The resulting precipitate was then calcined for 3 hours. The calcium phosphate product was characterized using XRF, XRD, and SEM-EDX techniques. The results indicate a Ca-P molar ratio ranging from 1.855 to 2.302, with the predominant phase identified as β-calcium pyrophosphate. SEM analysis reveals a plate-like morphology with agglomerated particles ranging in size from 888 nm to 7.79 μm. The synthesized calcium phosphate holds potential for various biomedical applications due to its unique properties and composition.

Ceramic Materials in Na2O-CaO-P2O5 System, Obtained via Heat Treatment of Cement-Salt Stone Based on Powder Mixture of Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and NaH2PO4

Ceramic materials in Na2O-CaO-P2O5 system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca3(C6H5O7)2∙4H2O, monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2∙H2O and/or sodium dihydrogen phosphate NaH2PO4. The phase composition of the obtained samples of cement-salt stone after adding water, hardening and drying included brushite CaHPO4∙2H2O, monetite CaHPO4 and also unreacted Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and/or NaH2PO4. The phase composition of ceramics in Na2O-CaO-P2O5 system obtained by firing cement-salt stone was formed due to thermal conversion of hydrated salt and heterophase reactions between components presented in samples during firing. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O and Ca(H2PO4)2∙H2O after firing at 900 °C included β-calcium pyrophosphate (CPP) β-Ca2P2O7. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, and NaH2PO4 after firing at 900 °C included β-sodium rhenanite β-CaNaPO4. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and NaH2PO4 after firing at 900 °C included β-Ca2P2O7, β-CaNaPO4, double calcium-sodium pyrophosphate Na2CaP2O7, and Na-substituted tricalcium phosphate Сa10Na(PO4)7. Obtained ceramic materials in Na2O-CaO-P2O5 system including biocompatible and biodegradable phases could be important for treatments of bone tissue defects by means of approaches of regenerative medicine.

Simultaneous extraction of calcium phosphates and proteins from fish bones. Innovative valorisation of food by-products

By-products of the fish industry can be a source of valuable molecules, with different technological applications. Fish bones contain both organic and inorganic phases (collagen/other proteins and calcium phosphate minerals respectively), with several uses and among them in cosmetics and medicine. Using the common extraction protocols, only one of the two phases can be extracted, while the other one is degraded. In the present work a method of extraction which allows the obtainment of both proteins and calcium phosphates was developed. Bones from two different species (salmon and sea bream) were tested. Saline solutions based on (NH4)HCO3/(NH4)2HPO4 or (NH4)HCO3 were employed for the protein extraction. Analysis of the organic phase showed that the main extracted proteins were collagen in its different forms (especially α-1); some differences were observed between salmon and sea bream and between the methods of extraction. As for the mineral phase, after calcination at 700 °C, single phase hydroxyapatite was obtained with (NH4)HCO3 solution, while the use of (NH4)HCO3/(NH4)2HPO4 led to a biphasic material of β-tricalcium phosphate and β-calcium pyrophosphate. Biocompatibility tests performed on both organic and inorganic extracts (with fibroblast and osteoblast-like cellular lines) showed their non-toxicity and, hence, their potential suitability for cosmetic or biomedical applications. This work shows that it is possible to obtain a more complete valorisation of the fish bones, with the simultaneous extraction of organic and inorganic valuable compounds. The principles of this process could be applied also to bones of other species, with a positive impact on the environment for the reduction of the wastes and a better use of all available resources.

Strontium doping stimulates the phase composition and evolution of β-tricalcium phosphate prepared by wet chemical method

In this study, Sr-doping β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP) nanoparticles were synthesized by the wet chemical method. And the effect of Sr2+ doping concentration on the phase composition and evolution of β-TCP was researched. In the synthesis process, the precursor calcium deficient hydroxyapatite (CDHA) was fully converted into β-TCP after being sintered at 850 ​°C for 2 ​h. With the Sr2+ addition, the degree of agglomeration of CDHA was reduced, and the corresponding β-TCP particle size became smaller. Besides, the phase composition showed that the hydroxyapatite (Ca10(PO4)6(OH)2, HA) and β-calcium pyrophosphate (β-Ca2P2O7, β-CPP) impurities in the β-TCP changed with the increasing of Sr2+ doping concentration. In addition, the impurity of β-CPP in the β-TCP revealed a discontinuity at Sr/(Sr ​+ ​Ca) molar ratio of 2 and 5 ​at.%. According to the above results, the formation mechanisms of Sr-doping CDHA into Sr-doping β-TCP was discussed.

Formation of octacalcium phosphate in the interaction of calcium carbonate and monocalcium phosphate monohydrate under galvanostatic conditions

The calcium phosphate composite octacalcium phosphate / calcite was obtained at pH 5–7 from the CaCO3/Ca(H2PO4)2 aqueous suspension in a galvanostatic mode at a current density of 20 mA/cm2 for 20 min. Drying at 80 °C without the precipitate maturation stage led to a powder formation consisting of brushite, calcite and a small amount of octacalcium phosphate. Prolonged maturation in air for 2 months led to the hydrolytic transformation of brushite into octacalcium phosphate stabilized by calcite. The use of electric current made it possible to increase the amount of octacalcium phosphate in the composite powder with the morphology of lamellar rosettes. Calcination at 800 °C of the composite powders led to the formation of α/β-tricalcium phosphate, β-calcium pyrophosphate, hydroxyapatite, and calcium oxide.

Bioactive calcium phosphate foam ceramics modified by biomimetic apatite

By combining the method of replication of polyurethane foam matrices at 1200 °C and modification in model SBF (Simulated Body Fluid) solutions of various compositions, open-pore calcium phosphate foam ceramics with a porosity of 53-60 % was obtained. The architecture and morphology of the calcium phosphate foam ceramics surface was formed by using polyurethane foam matrices («Granufoam», «STR») with different porosity and quantity of open pores. Modification of the calcium phosphate foam ceramics in SBF solutions of various compositions leads to a slight decrease in porosity to 3 %, which indicates the formation of an ultrathin apatite layer. The calcium phosphate-modified foam ceramics consisted of β-tricalcium phosphate, β-calcium pyrophosphate, α-tricalcium phosphate, and biomimetic apatite. In the standard SBF solution, the formation of apatite on calcium phosphate foam ceramics occurs slowly (14-56 days) and the strength increases by a factor of 2 as compared to the initial one. Soaking of calcium phosphate foam ceramics in SBF without HCO3- leads to the formation of biomimetic apatite with inclusions of calcium chloride dihydrophosphate in spherulites. Modification in a 5-fold concentrated SBF solution for 3-5 days at 37 °C makes it possible to form 6-10 times more biomimetic apatite compared to standard SBF with a 2.5-fold increase in static strength to 0.05 MPa. It has been established that at 800 °C biomimetic apatite crystallizes into β- tricalcium phosphate.

Bioceramics Based on β-Calcium Pyrophosphate.

Ceramic samples based on β-calcium pyrophosphate β-Ca2P2O7 were prepared from powders of γ-calcium pyrophosphate γ-Ca2P2O7 with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(C3H5O3)2⋅5H2O and monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate Ca2P2O7). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-Ca2P2O7 according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(H2PO4)2·H2O (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-Ca2P2O7) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t melt = 984 °C), formed from monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-Ca2P2O7 were biocompatible and could maintain bone cells proliferation.

Формирование биомиметического апатита на кальцийфосфатной пенокерамике в концентрированной модельной среде

By firing polyurethane foam templates (“STR” brand, 12 pores per cm, China) with a porosity of ~ 65 % at 1200 °С, an open-pore calcium phosphate foam ceramics was obtained using a highly concentrated suspension based on synthetic hydroxyapatite, heat-treated at 800 °С, monocalcium phosphate monohydrate and 0.8 % polyvinyl alcohol. The resulting calcium phosphate foam ceramics after modification in the SBF (Simulated Body Fluid) solution concentrated 5 times (SBF×5) consisted of β-tricalcium phosphate, β-calcium pyrophosphate and biomimetic apatite, had a porosity of 53 – 59 % and a static strength of ~ 0.05 MPa. The formed biomimetic apatite, consisting of amorphous calcium phosphate Ca9(PO4)6 and apatite tricalcium phosphate Ca9HPO4(PO4)5OH, crystallizes into β-tricalcium phosphate at 1200 °С. Calcium phosphate foam ceramics modified with biomimetic apatite, after soaking in 5 % hydroxyapatite gel and SBF×5, which simulating a bone defect in vitro, in parallel with the formation of biomimetic apatite, is partially destroyed, which confirmed its high bioactivity and degradation.

Synthesis and Characterization of Porous β-Calcium Pyrophosphate Bone Scaffold Derived from Avian Eggshell

Synthesis and Characterization of Porous β-Calcium Pyrophosphate Bone Scaffold Derived from Avian Eggshell

Effect of minor amounts of β-calcium pyrophosphate and hydroxyapatite on the physico-chemical properties and osteoclastic resorption of β-tricalcium phosphate cylinders

β-Tricalcium Phosphate (β-TCP), one of the most used bone graft substitutes, may contain up to 5 wt% foreign phase according to standards. Typical foreign phases include β-calcium pyrophosphate (β-CPP) and hydroxyapatite (HA). Currently, the effect of small amounts of impurities on β-TCP resorption is unknown. This is surprising since pyrophosphate is a very potent osteoclast inhibitor. The main aim of this study was to assess the effect of small β-CPP fractions (<1 wt%) on the in vitro osteoclastic resorption of β-TCP. A minor aim was to examine the effect of β-CPP and HA impurities on the physico-chemical properties of β-TCP powders and sintered cylinders. Twenty-six batches of β-TCP powder were produced with a Ca/P molar ratio varying between 1.440 and 1.550. Fifteen were further processed to obtain dense and polished β-TCP cylinders. Finally, six of them, with a Ca/P molar ratio varying between 1.496 (1 wt% β-CPP) and 1.502 (1 wt% HA), were incubated in the presence of osteoclasts. Resorption was quantified by white-light interferometry. Osteoclastic resorption was significantly inhibited by β-CPP fraction in a linear manner. The presence of 1% β-CPP reduced β-TCP resorption by 40%, which underlines the importance of controlling β-CPP content when assessing β-TCP biological performance.

Calcium Phosphate Powder for Obtaining of Composite Bioceramics

Calcium phosphate powder were synthesized from aqueous solutions of calcium lactate Ca(C3H5O3)2 and ammonium hydrophosphate (NH4)2HPO4 at a Ca/P = 1 molar ratio. According to the XRD data, the phase composition of as-synthesized powder consisted of brushite CaHPO4 ⋅ 2H2O and hydroxyapatite Ca10(PO4)6(OH)2. After heat treatment at 350–600°C, the powder was colored dark brown owing to the destruction of the by-product of the reaction. The composition of the powder heat-treated at 350°C included monetite CaHPO4 and hydroxyapatite Ca10(PO4)6(OH)2, and the powder heat-treated at 600°C consists of hydroxyapatite Ca10(PO4)6(OH)2 and γ-calcium pyrophosphate γ-Ca2P2O7. The phase composition of ceramic obtained from the synthesized powder after sintering at 1100°C consisted of β-calcium pyrophosphate β-Ca2P2O7 and β‑tricalcium phosphate β-Ca3(PO4)2. The colored after the heat treatment in a range of 350–600°C powders can be used as a starting for the molding of porous biocompatible calcium phosphate composite materials with the given geometry of the porous space by stereolithographic printing. The synthesized powder can be recommended for the development of biocompatible and biodegradable both ceramic composite materials and composites with polymer or inorganic matrix for bone implants.

Chemically pure β-tricalcium phosphate powders: Evidence of two crystal structures

The question whether β‐tricalcium phosphate (β‐TCP) can form a solid solution with β-calcium pyrophosphate (β-CPP) and/or hydroxyapatite (HA) has still not been solved. For this reason, wet-chemically synthesized β-TCP powders with only 20 ppm Sr (among 43 tested elements) and with different HA and β-CPP contents, or in other words Ca/P molar ratios, were used. The graphical relationship between these various Ca/P molar ratios determined by X-ray diffraction and by inductively-coupled plasma mass spectrometry showed no discontinuity, indicating the absence of a solid solution between β‐TCP and β-CPP or HA. Analysis of the β‐TCP lattice parameters as a function of the Ca/P molar ratio revealed a discontinuity at a Ca/P molar ratio of 1.500 and a maximum microstrain. These results indicated that at least two β‐TCP structures co-existed, with variable mixing ratios depending on the Ca/P molar ratio, and with a distinct jump at a Ca/P molar ratio of 1.500.

Ca2P2O7–Ca(PO3)2 Ceramic Obtained by Firing β-Tricalcium Phosphate and Monocalcium Phosphate Monohydrate Based Cement Stone

Ceramic in the system Ca2P2O7–Ca(PO3)2 was obtained by firing cement stone fabricated from a powder mixture which included β-tricalcium phosphate β-Ca3(PO4)2 and monocalcium phosphate monohydrate Ca(H2PO4)2 ∙ H2O. The molar ratio Ca/P of the initial powder mixtures was set as Ca/P ≤ 1. X-ray phase analysis shows all ceramic samples after firing at 1000°C to include β-calcium pyrophosphate β-Ca2P2O7, and a sample of the ceramic made from a powder mixture with the maximum content of monocalcium phosphate monohydrate Ca(H2PO4)2 ∙ H2O also contained β-calcium polyphosphate β-Ca(PO3)2. The obtained calcium phosphate ceramic with reduced firing temperature can be used to develop a resorbable matrix for tissue engineering structures.

Ceramics Based on a Powder Mixture of Calcium Hydroxyapatite, Monocalcium Phosphate Monohydrate, and Sodium Hydrogen Phosphate Homogenized under Mechanical Activation Conditions

Calcium phosphate ceramics, with the phase composition represented by β-calcium pyrophosphate β-Ca2P2O7, was obtained from a powder mixture of calcium hydroxyapatite Ca10(PO4)6(OH)2, monocalcium phosphate monohydrate Ca(H2PO4)2 · H2O, and sodium hydrogen phosphate Na2HPO4. The powder mixture was preliminarily homogenized in acetone using a planetary mill. This treatment resulted in the chemical reaction between the starting components to form monetite, calcium hydrogen phosphate CaHPO4 (precursor of calcium pyrophosphate Ca2P2O7). According to the XRD data, sodium hydrogen phosphate Na2HPO4 when present in an amount of 5 wt % in the starting mixture had no effect on the phase composition of the powder after homogenization and of the ceramics after annealing. Sodium pyrophosphate Na4P2O7 formed from sodium hydrogen phosphate Na2HPO4 as a result of thermal conversion had a significant effect on sintering mechanism and the microstructure of the ceramics. A ceramics with a low sintering temperature based on β-calcium pyrophosphate β-Ca2P2O7 was obtained for the first time from a powder system, upon preparation of which under mechanical activation conditions homogenization of components and synthesis of the main crystal phase precursor were combined.

β-Tricalcium Phosphate for Bone Substitution: Synthesis and Properties

β tricalcium phosphate (β-TCP) is one the most used and potent synthetic bone graft substitute. It is not only osteoconductive, but also osteoinductive. These properties, combined with its cell-mediated resorption, allow full bone defects regeneration. Its clinical outcome is sometimes considered to be unpredictable, possibly due to a poor understanding of β-TCP physico-chemical properties: β-TCP crystallographic structure is not fully uncovered; recent results suggest that sintered β-TCP is coated with a Ca-rich alkaline phase; β-TCP apatite-forming ability and osteoinductivity may be enhanced by a hydrothermal treatment; β-TCP grain size and porosity are strongly modified by the presence of minute amounts of β-calcium pyrophosphate or hydroxyapatite impurities. The aim of the present article is to provide a critical, but still rather comprehensive review of the current state of knowledge on β-TCP, with a strong focus on its synthesis and physico-chemical properties, and their link to the in vivo response.

Crystallization of metastable and stable phases from hydrolyzed by rinsing precipitated amorphous calcium phosphates with a given Ca/P ratio of 1:1

Abstract Single-phase metastable α ¯ -calcium pyrophosphate, stable β-calcium pyrophosphate and their mixtures were prepared as nanopowders via procedures of the fast nitrate synthesis, rinse, lyophilization and subsequent heat treatment of the precipitates with a set Ca/P ratio of 1:1. It was revealed that rinsing under certain conditions (a high water/slurry value, relatively prolonged treatment and a high pH) resulted in hydrolysis and increase in the Ca/P ratio up to 1.5 in the precipitates. Single-phase metastable α ¯ - and stable β-tricalcium phosphates, mixtures with each other and the calcium pyrophosphates in a desired composition were processed by heat treatment of the hydrolyzed precipitates for producing prospective biomaterials.

Fish Bone as a Source of Raw Material for Synthesis of Calcium Phosphate

Fish bone is rich in calcium carbonate, which makes it an alternative source of low cost calcium carbonate for the synthesis of calcium phosphate bioceramic for use in bone regeneration. The calcium phosphate bioceramic was prepared by a wet precipitation method with acid and base reactions. The synthesized bioceramic was characterized in terms of X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTRI), average crystallite size and refinement by the Rietveld method for the quantification of crystalline phases. The results indicated the formation of a biphasic calcium phosphate bioceramic comprising 67.6 % of β-calcium pyrophosphate (β-CPP) and 32.1 % of β-tricalcium phosphate (β-TCP). This biphasic calcium phosphate bioceramic synthesized using fish bone waste presented nanostructured nature with an average crystallite size of 69.58 nm, which is very promising for biomedical applications.

Effect of reaction solvent on hydroxyapatite synthesis in sol-gel process.

Synthesis of hydroxyapatite (HA) through sol–gel process in different solvent systems is reported. Calcium nitrate tetrahydrate (CNTH) and diammonium hydrogen phosphate (DAHP) were used as calcium and phosphorus precursors, respectively. Three different synthesis reactions were carried out by changing the solvent media, while keeping all other process parameters constant. A measure of 0.5 M aqueous DAHP solution was used in all reactions while CNTH was dissolved in distilled water, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) at a concentration of 0.5 M. Ammonia solution (28–30%) was used to maintain the pH of the reaction mixtures in the 10–12 range. All reactions were carried out at 40 ± 2°C for 4 h. Upon completion of the reactions, products were filtered, washed and calcined at 500°C for 2 h. It was clearly demonstrated through various techniques that the dielectric constant and polarity of the solvent mixture strongly influence the chemical structure and morphological properties of calcium phosphate synthesized. Water-based reaction medium, with highest dielectric constant, mainly produced β-calcium pyrophosphate (β-CPF) with a minor amount of HA. DMF/water system yielded HA as the major phase with a very minor amount of β-CPF. THF/water solvent system with the lowest dielectric constant resulted in the formation of pure HA.

Synthesis of β-Calcium Pyrophosphate by sol-gel method

Beta calcium pyrophosphate [β-CPP, β-Ca2P2O7] can be used as bone graft extender in posterolateral lumbar fusion. In this research, β-CPP was synthesized by sol-gel method using phosphorus pentaoxide [P2O5] and calcium nitrate tetrahydrate [Ca(NO3)2.4H2O] as phosphorus and calcium precursors. The reaction was carried out in ethanol medium with Ca/P ratio of 1.67. After 21 hours of reaction and 20 hours of drying at 80°C, white powder of amorphous calcium phosphate (ACP) was produced. Transformation of ACP to β-CPP was undertaken by firring at 400-800°C for 8 hours. Transformations of amorphous to microcrystalline, semicrystalline and crystalline structures occur at 400, 600 and 800°C, respectively. The β-CPP with the crystallite size of 61.71 nm, Ca/P ratio of 0.89 and Ca/O ratio of 0.21 was achieved by firing at 800°C. Morphology changes due to firing in which irregular shape of β-CPP at 400° changed to regular cuboid at 600 °C and above.