- Peroxo derivatives of hydroxyapatite and calcium hydrophosphate
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Hydroxyapatite and calcium hydrophosphate peroxo solvates were synthesized and characterized by IR spectroscopy, powder X-ray diffraction, and TGA to be used as biocompatible and antibacterial medicaments in manufacturing calcium phosphate bioceramics for implantations in orthopedics and dentistry. A wide range of hydrogen peroxide percentages in stable mixtures of mCa 5(PO4)3(OH) + nCaHPO4 ? H 2O2 ? H2O (ranging from 0.5 to 18%) allows composites to be prepared with a tailored active oxygen content.
- Skogareva,Pilipenko,Shabalova,Tripol'Skaya
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- Di- tert-butylphosphate Derived Thermolabile Calcium Organophosphates: Precursors for Ca(H2PO4)2, Ca(HPO4), α-/β-Ca(PO3)2, and Nanocrystalline Ca10(PO4)6(OH)2
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Thermally and hydrolytically unstable di-tert-butyl phosphate (dtbp-H) has been used as synthon to prepare discrete and polymeric calcium phosphates that are convenient single-source precursors for a range of calcium phosphate ceramic biomaterials. The reactivity of dtbp-H toward two different calcium sources has been found to vary significantly, e.g., the reaction of Ca(OMe)2 with dtbp-H in a 1:6 molar ratio in petroleum ether forms a mononuclear calcium hexa-phosphate complex [Ca(dtbp)2(dtbp-H)4] (1), whereas the change of calcium source to CaH2, in a 1:2 molar ratio under otherwise similar reaction conditions, yields the calcium phosphate polymer, [Ca(μ-dtbp)2(H2O)2·H2O]n(2). Compounds 1 and 2 have been extensively characterized by various spectroscopic and analytical techniques. The solid-state structures of both 1 and 2 have been determined by single-crystal X-ray diffraction studies. In discrete molecule 1, the central calcium ion is surrounded by two anionic dtbp and four neutral dtbp-H ligands in an octahedral coordination environment. Compound 2 is a one-dimensional polymer in which adjacent calcium ions are connected through double dtbp bridges. Solid-state thermolysis of bulk 1 in air leads to the exclusive formation of calcium metaphosphate β-Ca(PO3)2 in the entire temperature range of 400-800 °C. Thermal decomposition of polymer 2, however, can be fine-tuned to produce either α-Ca(PO3)2 or β-Ca(PO3)2 depending on the thermolysis conditions employed. Although the sample sintered at 600 °C produces exclusively α-form of Ca(PO3)2, the sample annealed at 800 °C or above produces β-form. Both α- and β-forms can also be successively formed one after other by a slow heating of a freshly prepared 2 on the powder diffractometer sample holder. Additional forms of ceramic phosphates have been prepared by solvothermal conditions because of the highly labile nature of the tert-butoxy groups of dtbp in 1 and 2. Solution decomposition of either 1 or 2 in boiling toluene at 140 °C in a sealed tube produces calcium dihydrogen phosphate [Ca(H2PO4)2·H2O] as the only product in the form of single crystals. Solution thermolysis of 2 in protic solvents such as water and methanol can be biased to produce other calcium phosphate biomaterials such as hydroxyapatite [Ca10(PO4)6(OH)2]and calcium monohydrogen phosphate [Ca(HPO4)] in the presence of additional calcium precursors such as CaO and Ca(OMe)2, respectively.
- Murugavel, Ramaswamy,Verma, Sonam
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- Biocompatibility of apatite-containing implant materials
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Thermochemical decomposition of hydroxyapatite in phosphoric acid was studied with the aim of producing polymineral gradient-resorptivity composites. The procedure was tested on the BAK-1000 glass-apatite composite. The results indicate an enhancement of resorptivity, without changes in the performance parameters or crystal structure, thereby suggesting a new approach to controlling the bioactivity of apatite-containing bioceramics.
- Malysheva,Beletskii
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- Effect of phase transformations during synthesis on the chemical composition and structure of calcium-deficient hydroxyapatite
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The chemical and phase changes during the precipitation of calcium-deficient hydroxyapatite from a solution of natural chalk in a mixture of phosphoric and nitric acids, with the use of aqueous ammonia as the precipitant, have been studied by potentiometric titration and physicochemical analysis. The initial solution concentration and precipitation time are shown to have a significant effect on the composition and structure of the precipitate. The processes in the solution and precipitate are interpreted in terms of thedegree of protonation of phosphate ions under various conditions.
- Kitikova,Shashkova,Zonov,Sycheva,Rat'ko
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- Analysis of the effects of thermal treatments on CaHPO4 by 31P NMR spectroscopy
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The compound CaHPO4 was obtained by slow evaporation at room temperature. The sample was characterised by X-ray diffraction, differential scanning calorimetry and 31P MAS NMR spectroscopy at different annealing temperature. At room temperature, the observed values of the 31P NMR chemical shift for the title compound are found to be -1.6, -0.4 and 1.4 ppm with the proportions 1/4, 1/2 and 1/4, respectively, revealing the presence of three non-equivalent phosphorus sites in the structure. The 31P NMR investigation at different annealing temperatures points to a conversion of (HPO42-) into (P2O 74-) at high temperature.
- Louati,Hlel,Guidara,Gargouri
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- Insight into shape control mechanism of calcium phosphate nanoparticles in reverse micelles solution
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The present experiment demonstrates a systematic morphosynthesis of calcium phosphate crystals with controlled morphology in reverse micelles solution of CTAB/n-pentanol/ water/cyclohexane. Well-defined morphologies of calcium phosphate particles, such as nanowires, tablets, brushlike particles, and fiber bundles, can be prepared. The microstructural characteristics of the CTAB/n-pentanol/water/cyclohexane reverse micelles solution has been investigated by FTIR spectroscopic, 31P NMR, and UV-visible absorption spectra techniques, demonstrating that the molar ratio of water to surfactant (Wo) and n-pentanol to surfactant (Po) showed significant effects on the morphology of the resulting particles. At lower Wo and Po, CTAB played a role in guiding the growth direction. With increasing Wo and Po, crystal growth lost the direction-guiding capability of CTAB. However, as crystal growth modifiers, water and cosurfactants follow different mechanisms. The solubility of water causes a decrease in bound water layer, resulting in a decrease in interactions between CTA+ and PO43- which invalidates the shape control of surfactant molecules. The loading of cosurfactant (n-pentanol) results in decreasing the rigidity of the reverse micelles interface. This in turn favors the shape fluctuations of reverse micelles, inducing crystal development. Copyright
- Lai, Chen,Tang, Shaoqiu,Wang, Yingjun,Wei, Kun,Zhang, Shiyin
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- Chemical processing of CaHPO4·2H2O: Its conversion to hydroxyapatite
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The aim of this paper is to develop a robust chemical process to synthesize Na- and K-doped brushite (DCPD: dicalcium phosphate dihydrate, CaHPO 4·2H2O), a potential starting material for bone substitutes. The powders were synthesized by using sodium phosphate and potassium phosphate and aqueous solutions containing calcium chloride at room temperature, followed by drying at 37°C. DCPD powders thus formed were found to contain 460 ppm K and 945 ppm Na. On calcination in air, these powders readily transformed into monetite (DCPA: dicalcium phosphate anhydrous, CaHPO4) first, and then into Ca2P2O7 (calcium pyrophosphate). Na- and K-doped DCPD powders were shown to completely transform, in less than 1 week, into poorly crystalline carbonated apatite on immersion in an acellular simulated/synthetic body fluid (SBF) solution at 37°C. The Tris (i.e., tris(hydroxymethyl)aminomethane) buffered SBF solution used in this study had a carbonate ion concentration of 27 mM equal to that of human plasma. DCPD powders of this study displayed a notable apatite-inducing ability. This finding suggests the use of these DCPD powders as the starting materials for potential bone substitutes, which can be easily manufactured in aqueous solutions friendly to living tissues, at temperatures between room temperature and 37°C.
- Tas, A. Cuneyt,Bhaduri, Sarit B.
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- A Comparative study of the synthesis of calcium, strontium, barium, cadmium, and lead apatites in aqueous solution
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The aqueous syntheses of the hydroxy and halo apatites of calcium, strontium, barium, lead, and cadmium were explored. Because these cations represent the main group s- and p-fillers and a transition metal, they present different synthetic challenges. The alkaline earth cations and lead form hydrogen phosphates at slightly acidic and slightly basic conditions, the alkaline earths form the fluorides (MF2) in the preparation of the fluoroapatites with excess fluoride, and ammonia is required for the preparation of the cadmium apatites through decomplexation. A variety of reagents were utilized with most of the derivatives, but, in general, the source of the cation was its nitrate or halide, and the phosphate is best provided as ammonium hydrogen phosphate. The requirements for pH, heating, and reaction time were also explored. A number of literature syntheses for pure phase apatites could not be reproduced: calcium iodoapatite, strontium fluoroapatite, and cadmium hydroxyapatite. Several apatites were prepared for the first time in aqueous solution: barium fluoroapatite, lead bromoapatite, and cadmium chloroapatite. The relative ease of formation of the compounds is rationalized with arguments based upon lattice and hydration energies.
- Flora, Natalie J.,Hamilton, Keith W.,Schaeffer, Richard W.,Yoder, Claude H.
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- Synthesis and thermal characterization of copper and calcium mixed phosphates
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A series of compounds with composition of Ca1-xCu xHPO4, where x varied from 0.05 to 0.5 were synthesized by precipitation method. The compounds were characterized by elemental analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and thermogravimetry. The chemical stabilities of solids were investigated at several pH. Elemental analysis of copper, calcium and phosphorus are in agreement with the proposed composition. The formation of lamellar phosphates was evidenced. The stability of the set of compounds was better for samples with high copper content. Springer-Verlag 2007.
- Da Silva Filho,Da Silva, Oberto G.,Da Fonseca, Maria G.,Arakaki, Luiza N. H.,Airoldi
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- Transformation of Brushite (CaHPO4·2H2O) to Whitlockite (Ca9Mg(HPO4)(PO4)6) or Other CaPs in Physiologically Relevant Solutions
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Brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) and whitlockite [WH, Ca9Mg(HPO4)(PO4)6] are usually found in the mammalian metabolism in the form of diverse pathological calcifi
- Tas, A. Cuneyt
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- Low-temperature biomimetic synthesis of β-tricalcium phosphate by altering pH
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Biomimetic synthesis of β-tricalcium phosphate (β-TCP) in polyvinyl alcohol is done at a much lower temperature of 450°C compared with conventional synthesis. By varying the pH of the reaction in a patented process for hydroxyapatite synthesis, the authors synthesized β-TCP with controlled particle morphology at a very low temperature. The synthesized powder has been structurally characterized and cell studies with mesenchymal stem cells shows good adhesion.
- Guha, Avijit,Nayar, Suprabha
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- Synthesis of Monetite from Calcium Hydroxyapatite and Monocalcium Phosphate Monohydrate under Mechanical Activation Conditions
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Abstract: A powder of monetite СаНРО4 with a particle size of 100–300 nm was synthesized from monocalcium phosphate monohydrate Ca(H2PO4)2 ? H2O and calcium hydroxyapatite Ca10(PO4)6(OH)2 in an acetone medium upon mechanical activation in a planetary mill. According to X-ray powder diffraction data, after heat treatment in the range 900–1100°С, the phase composition of the samples was represented by calcium β-pyrophosphate β-Ca2P2O7. The synthesized powder can be used for producing resorbable calcium phosphate ceramic materials.
- Safronova,Sadilov,Chaikun,Shatalova,Filippov, Ya. Yu.
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- Intriguing structural chemistry of neutral and anionic layered monoalkylphosphates: Single-source precursors for high-yield ceramic phosphates
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Building up on an available synthetic methodology, phosphate monoesters ROPO3H2 have been synthesized in good yields. The synthetic procedure employed features acetic anhydride mediated activation of phosphoric acid in the presence of alcohols, leading to the formation of phosphate monoesters. The products have been isolated as their cyclohexyl amine salts, [CyNH3]2[(MeO)PO3]·3H2O (1) and [CyNH3][(RO)PO3H] (Cy = cyclohexyl; R = Et (2), iPr (3), or tBu (4)). Neutralization of 1-4 by readily available inexpensive ion exchange resin Amberlite produces monoalkylphosphates (RO)P(O)(OH)2 (R = Me (5), Et (6), iPr (7), or tBu (8)). Thermally labile 1-4 and 7 have been structurally characterized by single crystal X-ray diffraction studies. Due to their intrinsic thermal instability due to β-H elimination, these compounds can be used as ligands for the preparation of single-source precursors for ceramic phosphates by reacting them with suitable metals ions. It is also possible to isolate co-crystals of the anionic and neutral forms of these phosphates as it has been demonstrated in the isolation and structural characterization of [(iPrO)PO3H2]·{[CyNH3][(iPrO)PO3H]} (9). To demonstrate the utility of these monoalkylphosphates in the low-temperature synthesis of metal phosphate bioceramics, isopropyl phosphate 7 has been employed to prepare calcium phosphate [{Ca((iPrO)PO3)(OH2)}·H2O]n (10), which undergoes neat thermal decomposition in two stages to lose water and propene to yield β-Ca2P2O7 at low temperatures (280 °C).
- Bhat, Gulzar A.,Kalita, Alok Ch.,Murugavel, Ramaswamy
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p. 5390 - 5401
(2017/09/26)
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- Core particle for pharmaceutical preparation
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The present invention provides a core particle for a pharmaceutical preparation which features the requisite properties of a core particle, and which has enough chemical stability, and in which reactivity with the drug (an active pharmaceutical ingredient) is limited or prevented. More specifically, the present invention relates to a core particle wherein a film containing an active pharmaceutical ingredient can be formed on the surface thereof, and (1) the core particle comprises a pharmaceutically acceptable inorganic material, (2) the inorganic material is poorly soluble in water, and (3) pH of a solution of the inorganic material is 5 to 8.
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- Porous calcium phosphate bone material
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Porous calcium phosphate implant compositions that approximate the chemical composition of natural bone mineral are provided. In addition to calcium phosphate, the compositions include an effervescent agent to promote the formation of interconnected pores and a cohesiveness agent to maintain the shape and hardness of the hardened composition. When introduced at an implant site, the calcium phosphate compositions are remodeled into bone. Methods for using the calcium phosphate compositions, e.g., to repair or replace bone, are also provided.
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(2008/06/13)
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- Purification of sphene concentrate to remove phosphorus impurity with dilute mineral acids
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Methods of crystal-optic, X-ray phase, chemical, and IR spectroscopic analyses were used to study the interaction of sphene and fluorapatite concentrates with dilute mineral acid solutions. The conditions under which the sphene concentrate can be purified
- Nikolaev,Petrov,Pleshakov,Bychenya,Kadyrova
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p. 860 - 863
(2008/03/11)
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- Osteoinductive bone material
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Osteogenic bone implant compositions that approximate the chemical composition of natural bone are provided. The organic component of these implant compositions is osteoinductive despite the presence of the inorganic component and, further, is present in an amount sufficient to maximize the regenerative capabilities of the implant without compromising its formability and mechanical strength. The composition may be an osteoinductive powder, including demineralized bone matrix (DBM) particles, a calcium phosphate powder, and, optionally, a biocompatible cohesiveness agent. The powder may be combined with a physiologically-acceptable fluid to produce a formable, osteoinductive paste that self-hardens to form a poorly crystalline apatitic (PCA) calcium phosphate having significant compressive strength. The bone implant materials retain their cohesiveness when introduced at an implant site and are remodeled into bone in vivo. Methods for using these implant materials to repair damaged bone and a method of assaying the content of DBM particles, by weight, in a bone implant material are also provided.
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- Phase equilibria among acid calcium phosphates
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The stable ternary system H3PO4-Ca(OH)2-H2O has been established further by determining the equilibria among the acidic calcium phosphates. In particular, equilibria involving CaHPO4·2H2O, CaHPO4, Ca(H2PO4)2·H2O, and Ca(H2PO4)2·H2O have been established. In contrast to earlier opinions, Ca(H2PO4)2 is not a stable phase in this system at any temperature below 100°C. Ca(H2PO4)2 can be made only in boiling H3PO4 liquors at 130°C or by dehydration of Ca(H2PO4)2·H2O. Ca(H2PO4)2 converts to Ca(H2PO4)2·H2O upon equilibration in calcium phosphate solutions. A liquid region seems to exist between H3PO4 and Ca(H2PO4)2·H2O. Therefore, the related invariant point between H3PO4 and Ca(H2PO4)2·H2O does not exist at 25°C. The most soluble point lies between Ca(H2PO4)2·H2O and H3PO4. The invariant point involving the solids Ca(H2PO4)2·H2O and CaHPO4 is outside its compatibility triangle, and Ca(H2PO4)2·H2O dissolves incongruently. Furthermore, the compatibility line between H2O and Ca(H2PO4)2·H2O intersects the solubility curve of hydroxyapatite, suggesting Ca(H2PO4)2·H2O dissolution can form hydroxyapatite initially. The dissolution of Ca(H2PO4)2·H2O in deionized water forms CaHPO4·2H2O, having a very-thin-plate morphology below 55°C, and CaHPO4, having a rectangular-block morphology above 55°C. Over time CaHPO4·2H2O converts to CaHPO4 at temperatures above 36°C. The data obtained in this study have been combined with published data to construct a more complete H3PO4-Ca(OH)2-H2O diagram at 25°C.
- Martin,Brown
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p. 1263 - 1266
(2008/10/08)
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- Conversions of Calcium Phosphates in Water and H3PO4 Solutions
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The behavior of CaH2P2O7 in water and in H3PO4 solutions was studied under different conditions [S : L = (1 : 1.5)-(1 : 19)]; pH 1.38-1.83; T= 25-200°C; acid concentration, 0-40% P2O5; and contact time. 1 min to 10 days. Chemical analysis, X-ray diffraction, and paper chromatography methods were used. Depending on the experimental conditions, both individual monocalcium and dicalcium phosphates and their mixtures may form. The conditions under which CaHPO4, Ca(H2PO4)2 · H2O, and Ca3(HP2O7)2 · 4H2O exist in the form of individual compounds were determined.
- Golubina,Komissarova,Pushkina
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p. 359 - 364
(2008/10/08)
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- Reaction Characteristics of Hydroxyapatite with F- and PO3F2- Ions Chemical States of Fluorine in Hydroxyapatite
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The reactions of F- and PO3F2- ions with hydroxyapatite (HAP) are of interest owing to their dental application.The mechanism of the anti-caries effect of the fluorides, however, is still not clearly understood.In the present study t
- Tanizawa, Yoshiaki,Tsuchikane, Hideo,Sawamura, Kunio,Suzuki, Takashi
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p. 2235 - 2240
(2007/10/02)
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