Journal articles: 'Phosphates de calcium amorphes'

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Dorozhkin, Sergey V. "Amorphous Calcium Phosphates." Journal of Biomimetics, Biomaterials and Tissue Engineering 7 (October 2010): 27–53. http://dx.doi.org/10.4028/www.scientific.net/jbbte.7.27.

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Amorphous calcium phosphates (ACPs) represent a unique class of biomedically relevant calcium orthophosphate salts, in which there are neither translational nor orientational long-range orders of the atomic positions. Nevertheless, the constancy in their chemical composition over a relatively wide range of preparation conditions suggests the presence of a well-defined local structural unit, presumably, with the structure of Ca9(PO4)6 – so-called Posner’s cluster. ACPs have variable chemical but rather identical glass-like physicochemical properties. Furthermore, all ACPs are thermodynamically unstable compounds and, unless stored in dry conditions or doped by stabilizers, spontaneously they tend to transform to crystalline calcium orthophosphates. Although some order within general disorder is the most distinguishing feature of ACPs, the solution instability of ACPs and their easy transformation to crystalline phases might be of a great biological relevance. Namely, the initiating role ACPs play in matrix vesicle biomineralization raises the importance of this phase from a mere laboratory curiosity to that of a key intermediate in skeletal calcification. Furthermore, ACPs are very promising candidates to manufacture artificial bone grafts.

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Vecbiskena, Linda, Luigi de Nardo, and Roberto Chiesa. "Nanostructured Calcium Phosphates for Biomedical Applications." Key Engineering Materials 604 (March 2014): 212–15. http://dx.doi.org/10.4028/www.scientific.net/kem.604.212.

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This work is focused on the phase transformation from amorphous calcium phosphate (ACP) to nanostructured hydroxyapatite (HA) or tricalcium phosphate (TCP). Amorphous calcium phosphates with Ca/P molar ratio near 1.67 and 1.5 were synthesized by wet-chemical precipitation method and treated with ethanol. Upon thermal treatment, ACP clusters about 50 nm create a nanostructured HA or TCP. The highlights of this research: The precipitate treatment with ethanol provided a pure α-TCP that was found to be stable up to 1000 °C. HA is obtained from the ACP precursor synthesized using also ammonium dihydrogen phosphate.

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Dorozhkin, Sergey V. "Amorphous calcium (ortho)phosphates." Acta Biomaterialia 6, no. 12 (December 2010): 4457–75. http://dx.doi.org/10.1016/j.actbio.2010.06.031.

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Holt, Carl, Mathea J. J. M. van Kemenade, Lowell S. Nelson, Lindsay Sawyer, John E. Harries, Raymond T. Bailey, and David W. L. Hukins. "Composition and structure of micellar calcium phosphate." Journal of Dairy Research 56, no. 3 (May 1989): 411–16. http://dx.doi.org/10.1017/s0022029900028880.

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SummaryMicellar calcium phosphate has the chemical composition and physicochemical properties that are consistent with it being a complex of the phosphate centres of casein with an acidic amorphous calcium phosphate. Similar acidic amorphous calcium phosphates have been prepared in the laboratory and for these, as well as for micellar calcium phosphate, the most appropriate crystalline model compound from which the short-range structure may be derived is brushite, CaHPO4.2H2O. The predicted secondary structures around sites of phosphorylation in the Ca2+-sensitive caseins often comprise an α-hclix-loop-α-helix motif with the sites of phosphorylation in the loop region. This motif may be important in linking the colloidal calcium phosphate with casein in native casein micelles.

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Gross, Kārlis. "Towards Biotechnological Processing of Calcium Phosphates." Advanced Materials Research 1117 (July 2015): 193–200. http://dx.doi.org/10.4028/www.scientific.net/amr.1117.193.

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Transient or metastable phases offer an intermediate phase with additional flexibility for creating the end product. The processing pathway remains unknown when the final product is viewed. Biological processes frequently employ the amorphous phase as the transition phase. This is shown in mineralized tissues: invertebrates, pathological calcified deposits and murine fetal teeth. After a fast transition from an amorphous calcium phosphate to crystalline material, smaller changes occur over time. For an appreciation of the transition state, crystallinity is defined and measurement methods outlined. Biotechnology using transition material states offers fast, low temperature access to nanosized high temperature phases. Alfa tricalcium phosphate and apatite is made by a phase transition, but peroxyapatite requires long-range diffusion within the same structure. Tetracalcium phosphate is also possible, but this requires multiple transition states and phase decomposition. The pathway via the amorphous state offers an alternative route to biologically important materials.

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Brangule, Agnese, Līga Avotiņa, Artūrs Zariņš, Mihails Haļitovs, Kārlis Agris Gross, and Gunta Ķizāne. "Thermokinetic Investigation of the Drying Conditions on Amorphous Calcium Phosphate." Key Engineering Materials 758 (November 2017): 204–9. http://dx.doi.org/10.4028/www.scientific.net/kem.758.204.

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The present work investigated dried calcium phosphate powders which still retain an amorphous or poorly crystalline structure under a variety of conditions. In previous studies, freeze-drying was found to be the optimum drying condition. However, several publications, as well as our previous studies, have shown that calcium phosphate amorphous, or a poorly crystalline structure, can retain their structure even if the samples are dried immediately after synthesis up to 200°C. In our study, we used the thermokinetic studies FTIR and XRD and showed that the samples are amorphous, or poorly crystalline, but were unable to answer the questions: Is there a difference between the differently dried amorphous calcium phosphates? What are the optimum drying conditions under which the amorphous calcium phosphate (ACP) structure loses the physically bounded water, but still retains the chemically bounded water?

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Tas, A. Cuneyt. "Calcium metal to synthesize amorphous or cryptocrystalline calcium phosphates." Materials Science and Engineering: C 32, no. 5 (July 2012): 1097–106. http://dx.doi.org/10.1016/j.msec.2012.01.024.

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Lapeyrie, F., J. Ranger, and D. Vairelles. "Phosphate-solubilizing activity of ectomycorrhizal fungi in vitro." Canadian Journal of Botany 69, no. 2 (February 1, 1991): 342–46. http://dx.doi.org/10.1139/b91-046.

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An easy to use method is presented here to compare and study the mineral phosphate-solubilizing activity of ectomycorrhizal fungi. This technique can discriminate between strains with differing phosphate-solubilizing activities. Synthetic mineral phosphates, crystalline or amorphous, were differentially solubilized by 10 ectomycorrhizal fungi. Natural crystalline phosphates studied do not seem to be solubilized by fungi under similar experimental conditions. Paxillus involutus 1 appears to be able to solubilize calcium phosphates using either ammonium or nitrate nitrogen, but the other isolates were able to effectively solubilize phosphate only in the presence of ammonium. This has implications regarding the possible mechanism used to solubilize phosphate by these isolates. Recrystallization can be seen in the culture medium if calcium ions are present. The type of crystals depends on the phosphate source and on the fungal strain. This technique is suitable for screening a large number of ectomycorrhizal strains. The significance of phosphate-solubilizing activity to plant growth stimulation needs to be determined by field trials. Key words: ectomycorrhizal fungus, phosphate, solubilization.

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9

Xu, J. L., Khiam Aik Khor, R. Kumar, and P. Cheang. "RF Induction Plasma Synthesized Calcium Phosphate Nanoparticles." Key Engineering Materials 309-311 (May 2006): 511–14. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.511.

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It was a normal phenomena that hydroxyapatite (HA) decomposes into tricalcium phosphate (TCP), tetracalcium phosphate (TTCP), calcium oxide (CaO) and amorphous calcium phosphate (ACP) during the plasma processing step. The present study characterized the phase evolution of calcium phosphates (CaPs) in the nanoparticles synthesized using a radio frequency (RF) induction plasma processing technique. The morphology and microstructure of the CaP nanoparticles were investigated by XRD, SEM, TEM, Raman spectroscopy, FTIR spectroscopy and thermal analysis. It was found that ACP, α-TCP, TTCP and CaO were the main decomposed phases in the nanoparticle. After heat treatment at dicalcium pyrophosphate (β-Ca2P2O7) due to the extreme decomposition of the starting HA during the RF plasma processing step which rapidly solidified into amorphous phase.

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LeGeros, Racquel Z., Dindo Q. Mijares, J. Park, X. F. Chang, I. Khairoun, Regina Kijkowska, Renata Dias, and John P. LeGeros. "Amorphous Calcium Phosphates (ACP): Formation and Stability." Key Engineering Materials 284-286 (April 2005): 7–10. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.7.

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Our earlier studies showed that several ions inhibit the crystal growth of apatite and promote the formation of amorphous calcium phosphates (ACP). These ions include: magnesium (Mg), zinc (Zn), stannous (Sn), ferrous (Fe), carbonate (CO3), pyrophosphate (P2O7). The purpose of this study was to investigate the effect of combination of these ions (e.g., Mg & CO3, Mg & P2O7, Mg & Zn, etc) on the formation and stability of ACP. ACP compounds containing the different ions were prepared at 25 and 37oC according to the method we previously described. Chemical stability was investigated by suspending the different ACP preparations in solutions with or without inhibitory ions. Thermal stability was determined by sintering the ACP at different temperatures. Dissolution properties were determined in acidic buffer. The ACP before and after chemical or thermal treatment were analyzed using X-ray diffraction, infrared spectroscopy, and thermogravimetry. Results showed synergistic effects of inhibitory ions on the formation of ACP. ACP materials, regardless of their composition, remained amorphous even after heat treatment at 400oC. Transformation of ACP to other calcium phosphate phases depended on the pH and on the solution composition.

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Kalnina, Daina, Karlis Agris Gross, Pavels Onufrijevs, Edvins Dauksta, Vizma Nikolajeva, Zivile Stankeviciute, and Aivaras Kareiva. "The Antimicrobial Action of Silver Halides in Calcium Phosphate." Key Engineering Materials 631 (November 2014): 384–89. http://dx.doi.org/10.4028/www.scientific.net/kem.631.384.

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Silver halides represent a yet unexplored avenue for imparting antimicrobial activity in calcium phosphates. Silver halide colloids were added to calcium phosphate. Concurrent melting of silver halides and crystallization of carbonated apatite was achieved by heating to increase the silver halide surface area available to bacteria.Pseudomonas aeruginosa were more sensitive to silver iodide and silver bromide than Staphylococcus aureus. Silver iodide demonstrated greater activity than silver bromide. Silver chloride did not produce an antibacterial response. Both amorphous calcium phosphate and carbonated apatite displayed similar antibacterial activity when accompanied by silver halides. It is thought that amorphous calcium phosphate dissolves more readily and increases the bioavailability of the silver halide particles. Silver iodide displays a greater antibacterial response of all silver halides, with a response that is improved in a more resorbable matrix.

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12

Sinyaev, V. A., R. Z. Le Geros, L. V. Levchenko, E. S. Shustikova, and R. A. Karzhaubaeva. "State of water in amorphous calcium and calcium-magnesium phosphates." Russian Journal of General Chemistry 78, no. 5 (May 2008): 864–67. http://dx.doi.org/10.1134/s1070363208050046.

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13

WENG, WENJIAN, YANBO GAO, LILI PAN, YANBAO LI, PIYI DU, GE SHEN, and GAORONG HAN. "PREPARATION AND MORPHOLOGY OF POROUS NANOCALCIUM PHOSPHATE/POLY(L-LACTIC ACID) COMPOSITES." International Journal of Nanoscience 04, no. 04 (August 2005): 517–23. http://dx.doi.org/10.1142/s0219581x05003553.

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Biodegradable porous materials can serve as a scaffold in tissue engineering. In this work, highly porous nano-calcium phosphate (NCP)/poly(L-lactic acid)(PLLA) composites were prepared by a thermally induced phase separation technique. Five calcium phosphates with different biodegradation rate were selected, i.e. amorphous calcium phosphate, α-tricalcium phosphate, β-tricalcium phosphate and biphasic α/β-tricalcium phosphate. The results showed that the NCP particles could be homogenously incorporated into pore walls; the composites had a porosity of ~90%, and a pore size of ~200 μm. From the point of view of materials science, the obtained porous NCP/PLLA composites demonstrate to have a capability of applying in bone tissue engineering.

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Sinyayev, V. A., E. S. Shustikova, D. Griggs, and D. V. Dorofeev. "The Nature of P-O Bonds in the Precipitated Amorphous Calcium Phosphates and Calcium Magnesium Phosphates." Glass Physics and Chemistry 31, no. 5 (September 2005): 671–75. http://dx.doi.org/10.1007/s10720-005-0112-y.

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Brangule, Agnese, and Kārlis Gross. "Effect on Drying Conditions on Amorphous Calcium Phosphate." Key Engineering Materials 631 (November 2014): 99–103. http://dx.doi.org/10.4028/www.scientific.net/kem.631.99.

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Amorphous calcium phosphate (ACP) plays an important role in the body and can be used as an intermediate phase for forming calcium phosphates. All ACPs are thermodynamically unstable compounds, unless stored in dry conditions or at low temperature (-18oC), and spontaneously undergo transformation to crystalline calcium phosphates (CaP). This work will investigate the influence of drying on the stability of ACP. ACPs powders were prepared by wet synthesis; mixing solution made of Ca (NO3)2∙4H2O and 30% ammonia with (NH4)2HPO4 and (NH4)2CO3 solution at room temperature. The suspension was stirred, filtered and washed several times with deionized water containing ammonia. ACP samples were dried at different conditions and with different drying agents (DA). XRD and FTIR spectra showed poorly crystallinity powders after drying. Some FTIR spectra indicated residual organic compounds from drying. The Rietveld’s method and Schrrer’s relationship estimated the particle size (0.5 – 20 nm) of ACP. Thermogravimetry (TG) revealed that the moisture (7% – 25%) is released upon drying, and the drying agents have no significant effect on. The drying methods are ordered to show which the most effective for removing moisture. By changing the drying conditions, it is a possible to obtain poorly crystalline ACPs with different particle size and moisture content.

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Medvecky, L., T. Sopcak, V. Girman, and J. Briancin. "Amorphous calcium phosphates synthesized by precipitation from calcium D-gluconate solutions." Colloids and Surfaces A: Physicochemical and Engineering Aspects 417 (January 2013): 191–200. http://dx.doi.org/10.1016/j.colsurfa.2012.11.015.

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17

Aimanova, O. J., Racquel Z. LeGeros, and V. A. Sinyayev. "Antimicrobiologic Property Hydrated Amorphous Calcium Phosphates Containing Silver." Key Engineering Materials 284-286 (April 2005): 439–44. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.439.

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The purpose of this study was to determine the microbiologic effect silver (Ag) when incorporated in amorphous calcium phosphate (ACP) prepared from solutions containing calcium, phosphate and pyrophosphate ions. The preparations were obtained from solutions with phosphate/pyrophosphate ratio, P/P2 = 7/3, and characterized as ACP using X-ray diffraction, infrared spectroscopy, nuclear magnetic resonance and differential thermal analysis. The microbes tested were cultures of E. Coli, St. aureus, Ps aerogunosa, C. diphteroides and C. albicans in media alone (control), with ACP without Ag and with ACP containing different Ag concentrations. Results demonstrated the following: (1) Ag in ACP inhibited the growth of microorganisms in all five cultures, with ACP containing 3-6% Ag giving the greatest antimicrobial effect; (2) sensitivity to the antimicrobial action of Ag differed among the bacteria.

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Crutchik, D., and J. M. Garrido. "Struvite crystallization versus amorphous magnesium and calcium phosphate precipitation during the treatment of a saline industrial wastewater." Water Science and Technology 64, no. 12 (December 1, 2011): 2460–67. http://dx.doi.org/10.2166/wst.2011.836.

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Struvite crystallization (MgNH4PO4·6H2O, MAP) could be an alternative for the sustainable and economical recovery of phosphorus from concentrated wastewater streams. Struvite precipitation is recommended for those wastewaters which have high orthophosphate concentration. However the presence of a cheap magnesium source is required in order to make the process feasible. For those wastewater treatment plants (WWTP) located near the seashore magnesium could be economically obtained using seawater. However seawater contains calcium ions that could interfere in the process, by promoting the precipitation of amorphous magnesium and calcium phosphates. Precipitates composition was affected by the NH4+/PO43− molar ratio used. Struvite or magnesium and calcium phosphates were obtained when NH4+/PO43− was fixed at 4.7 or 1.0, respectively. This study demonstrates that by manipulating the NH4+/PO43− it is possible to obtain pure struvite crystals, instead of precipitates of amorphous magnesium and calcium phosphates. This was easily performed by using either raw or secondary treated wastewater with different ammonium concentrations.

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Julien, Marion, Ibrahim Khairoun, Racquel Z. LeGeros, Severine Delplace, Paul Pilet, Pierre Weiss, Guy Daculsi, Jean Michel Bouler, and Jerome Guicheux. "Physico-chemical–mechanical and in vitro biological properties of calcium phosphate cements with doped amorphous calcium phosphates." Biomaterials 28, no. 6 (February 2007): 956–65. http://dx.doi.org/10.1016/j.biomaterials.2006.10.018.

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LeGeros, Racquel Z., and John P. LeGeros. "In Situ Characterization of Degradation Behavior of Plasma-Sprayed Coatings on Orthopedic and Dental Implants." Advances in Science and Technology 49 (October 2006): 203–11. http://dx.doi.org/10.4028/www.scientific.net/ast.49.203.

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Plasma-sprayed ‘HA’ coatings on commercial orthopedic and dental implants were developed to combine the strength of the metal (Ti or Ti alloy) and the bioactivity of the hydroxyapatite (HA). Several studies have shown that ‘HA’-coated implants provided greater amount of bone attachment, higher bone-implant interfacial strength and accelerated skeletal attachment. However, some reports on implant failures have been attributed to coating delamination and coating early resorption of the plasma sprayed ‘HA’ coating. This paper reviews studies on characterization and degradation of plasma-sprayed ‘HA’ coatings on orthopedic and dental implants and offers alternatives to plasma-spray method of providing calcium phosphate coating. X-ray diffraction analyses showed that plasma-sprayed HA coating consists principally of HA and amorphous calcium phosphate (ACP) with minor amounts of other resorbable calcium phosphates (α- or β-tricalcium phosphates, tetracalcium phosphate), sometimes calcium oxide. The HA/ACP ratios were found to range from 20HA/80ACP to 70HA/30ACP in coated implants from different manufacturers. In vitro initial dissolution rates in acidic buffer (pH 6, 37oC) increased with decreasing HA/ACP ratios in the coating because of the preferential dissolution of the ACP phase. These results suggest that coating with very low HA/ACP ratio may result in the premature resorption of the coating before the bone can attach to the implant thus causing loosening and eventual failure of the implant. Alternatives to plasma-sprayed ‘HA’ are implant surface modifications and low temperature calcium phosphate coatings using electrochemical deposition method or precipitation method.

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Drouet, Christophe, C. Largeot, G. Raimbeaux, Claude Estournès, Gérard Dechambre, Christèle Combes, and Christian Rey. "Bioceramics: Spark Plasma Sintering (SPS) of Calcium Phosphates." Advances in Science and Technology 49 (October 2006): 45–50. http://dx.doi.org/10.4028/www.scientific.net/ast.49.45.

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Calcium phosphates (Ca-P) are major constituents of calcified tissues, and are also extensively used for the elaboration of biomaterials. However, the usual high-temperature sintering processes generally lead to strong alterations of their chemical, physical and biological properties. Spark plasma sintering (SPS) is a non-conventional sintering technique based on the use of pulsed current, enabling fast heating and cooling rates, and lower sintering temperatures are often observed. The sintering of several orthophosphates (DCPD, amorphous TCP, beta-TCP, OCP, HA and biomimetic nanocrystalline apatites) by SPS was investigated in order to track potential advantages of this technique over usual Ca-P sintering methods. Special attention was given to the SPS consolidation of highly bioactive nanocrystalline apatites.

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Brangule, Agnese, Kārlis Gross, Laura Komarovska, and Arturs Viksna. "Exploring Zinc Apatites through Different Synthesis Routes." Key Engineering Materials 587 (November 2013): 171–76. http://dx.doi.org/10.4028/www.scientific.net/kem.587.171.

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nclusion of zinc in apatites is not completely understood due to complexes in solution preventing the incorporation or the inclusion of defects. Some work has shown zinc addition by alternative synthesis routes, but the level of incorporation has not been reassessed. This work uses a newly developed approach whereby zinc is included in an amorphous phase and subsequently crystallized. Different phosphate reactants (ammonium, sodium or potassium phosphates) were mixed together with calcium salts (calcium nitrate or calcium acetate) and the pH level adjusted (with ammonia or KOH) to investigate the ease of forming an amorphous phase and the inclusion of zinc. X-ray diffraction revealed that all reactants showed a tendency to form an amorphous phase, supporting the requirement of a high pH to prevent crystallization. X-ray fluorescence showed higher inclusion in the absence of ammonia. Potassium phosphate led to the highest zinc incorporation, accompanied by simultaneous inclusion of potassium. Crystallization at 700 °C indicated that zinc levels close to 20% replacement of calcium were the highest possible before the onset of tricalcium phosphate formation. FTIR-DRIFT showed a change in bonding conditions at higher zinc concentrations. This work shows the importance of reactants for including zinc, the larger zinc inclusion accompanied by potassium and zinc levels that can maintain the apatite structure.

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Borilo, Lyudmila P., Ekaterina S. Lyutova, and Larisa N. Spivakova. "Рroperties of Bioactive Thin-Films Based on System SiO₂-P₂O₅-CаO and SiO₂-P₂O₅-СаO-Na₂O Obtained by Sol-Gel Method." Key Engineering Materials 683 (February 2016): 306–11. http://dx.doi.org/10.4028/www.scientific.net/kem.683.306.

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Thin films were synthesized from alcohol film-forming solutions based on tethraethoxysilane, phosphoric acid, calcium chloride and sodium chloride using sol-gel method. Thin films were produced on the single-crystal silicon substrates (model substrate) by extraction at a velocity of 5 mm/s following by heat treatment at a temperature of 60°С for 20 minutes and at a temperature of 600°С for 1 hour. During the experiment it was established that film-forming solutions are usable only for 2 to 7 days from the moment of preparation. Using thermal and infra-red – spectroscopic analysis main stages of oxide system formation were retraced. According to data from x-ray phase analysis phases CaClH2PO4∙H2O, Ca (H2PO4)2∙H2O, CaHPO4∙2H2O, Ca2SiO4∙H2O, Ca5(PO4)3Cl и CaSiO3,NaCl, CaCl2, H2PO4·H2O, Ca5(PO4)3Cl, SiO2 are being registered in the sample. Biological activity of the received material was evaluated in SBF environment. Presence of the sodium oxide in the system leads to the increase in the bioactivity of the material. Such material intensively exchanges with solution in calcium ions and phosphate-ions; silanol groups fix calcium ions, furthering the formation of the layer of amorphous calcium phosphates gradually crystallizing in hydroxyapatite, and other calcium phosphates.

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Gross, Kārlis, Daina Kalnina, Zivile Stankeviciute, and Vizma Nikolajeva. "Charge State of Silver Halide Colloids Determines the Antibacterial Activity in Amorphous Calcium Phosphate." Key Engineering Materials 587 (November 2013): 74–79. http://dx.doi.org/10.4028/www.scientific.net/kem.587.74.

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Removal of bacteria is important not only at implantation, but after long-term implant/prosthesis use. This requires strategies that employ different approaches for combating bacteria. Halides have the potential of an additional mechanism, and together with silver may provide a more powerful antibacterial strategy. Silver iodide was synthesized as colloids with a positive and negative charge and incorporated into an amorphous calcium phosphate (ACP) to provide a possible greater antibacterial action. Colloids were characterized by FTIR spectroscopy and the charge measured by zeta potential. Phase analysis by X-ray diffraction patterns confirmed the formation of b-AgI nanoparticles. Minimum inhibitory concentrations (MIC) for preventing the growth ofStaphylococcus aureusandPseudomonas aeruginosawere lower for ACP containing negatively charged silver halides. Amorphous calcium phosphates with silver iodide exhibited good inhibition capacity. Solubility was determined by the increase in pH and the release of silver after 48 hours. The minimum bactericidal concentration (MBC) was also determined. This work has shown the effect of AgI charge in amorphous calcium phosphate for providing antibacterial action.

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Olesen, P. T., T. Steenberg, E. Christensen, and N. J. Bjerrum. "Electrolytic deposition of amorphous and crystalline zinc–calcium phosphates." Journal of Materials Science 33, no. 12 (June 1998): 3059–63. http://dx.doi.org/10.1023/a:1004379319348.

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Holt, C., M. J. J. M. Van Kemenade, L. S. Nelson, D. W. L. Hukins, R. T. Bailey, J. E. Harries, S. S. Hasnain, and P. L. De Bruyn. "Amorphous calcium phosphates prepared at pH 6.5 and 6.0." Materials Research Bulletin 24, no. 1 (January 1989): 55–62. http://dx.doi.org/10.1016/0025-5408(89)90008-1.

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Combes, C., and C. Rey. "Amorphous calcium phosphates: Synthesis, properties and uses in biomaterials." Acta Biomaterialia 6, no. 9 (September 2010): 3362–78. http://dx.doi.org/10.1016/j.actbio.2010.02.017.

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Li, Yanbao, Fanzhi Kong, and Wenjian Weng. "Preparation and characterization of novel biphasic calcium phosphate powders (α-TCP/HA) derived from carbonated amorphous calcium phosphates." Journal of Biomedical Materials Research Part B: Applied Biomaterials 89B, no. 2 (May 2009): 508–17. http://dx.doi.org/10.1002/jbm.b.31242.

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Vecstaudza, Jana, and Janis Locs. "Effect of Synthesis Temperature and Ca/P Ratios on Specific Surface Area of Amorphous Calcium Phosphate." Key Engineering Materials 721 (December 2016): 172–76. http://dx.doi.org/10.4028/www.scientific.net/kem.721.172.

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Amorphous and low crystalline calcium phosphates are prospective candidates for bone implant manufacturing. Amorphous calcium phosphate (ACP) preparation technologies could be improved in terms of specific surface area (SSA) of obtained products. Current study is dedicated to the effect of synthesis temperature and Ca and P molar ratios (Ca/P) on SSA of ACP. Higher SSA can improve bioactivity of biomaterials. ACP was characterized by XRD, FT-IR, SEM and BET N2 adsorption techniques. Spherical nanoparticles (<45 nm in size) were obtained independently of initial Ca/P ratio and synthesis temperature. For the first time comparison of SSA was shown for ACP obtained at different temperatures (0 °C and 20 °C) and Ca/P molar ratios (1.5, 1.67 and 2.2).

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Arsenijevic, Natalija, Dragica Selakovic, Jelena S. Katanic Stankovic, Vladimir Mihailovic, Slobodanka Mitrovic, Jovana Milenkovic, Pavle Milanovic, et al. "The Beneficial Role of Filipendula ulmaria Extract in Prevention of Prodepressant Effect and Cognitive Impairment Induced by Nanoparticles of Calcium Phosphates in Rats." Oxidative Medicine and Cellular Longevity 2021 (February 12, 2021): 1–12. http://dx.doi.org/10.1155/2021/6670135.

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Mineral components of dental composites are used in many medical and dental applications, including preventive, restorative, and regenerative dentistry. To evaluate the behavioural alterations induced by nanosized particles of novel dental composites, by means of depressive level and cognitive functions, experimental groups of rats were chronically administered with nanosized hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) with or without simultaneous application of Filipendula ulmaria L. (FU) methanolic extract. The significant prodepressant action was observed in groups solely treated with HA and ACP. Besides, prolonged treatment with ACP also resulted in a significant decline in cognitive functions estimated in the novel object recognition test. The adverse impact of calcium phosphates on estimated behavioural functions was accompanied by increased oxidative damage and apoptotic markers in the prefrontal cortex, as well as diminished specific neurotrophin (BDNF) and gabaergic expression. The results of our investigation showed that simultaneous antioxidant supplementation with FU extract prevented calcium phosphate-induced behavioural disturbances, as well as prooxidative and apoptotic actions, with the simultaneous restoration of BDNF and GABA-A receptors in the prefrontal cortex. These findings suggest that FU may be useful in the prevention of prodepressant impact and cognitive decline as early as the manifestation of calcium phosphate-induced neurotoxicity.

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Jabłońska, Mariola, Janusz Janeczek, and Beata Smieja-Król. "The Impact of Ambient Atmospheric Mineral-Dust Particles on the Calcification of Lungs." Minerals 11, no. 2 (January 27, 2021): 125. http://dx.doi.org/10.3390/min11020125.

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For the first time, it is shown that inhaled ambient air-dust particles settled in the human lower respiratory tract induce lung calcification. Chemical and mineral compositions of pulmonary calcium precipitates in the lung right lower-lobe (RLL) tissues of 12 individuals who lived in the Upper Silesia conurbation in Poland and who had died from causes not related to a lung disorder were determined by transmission and scanning electron microscopy. Whereas calcium salts in lungs are usually reported as phosphates, calcium salts precipitated in the studied RLL tissue were almost exclusively carbonates, specifically Mg-calcite and calcite. These constituted 37% of the 1652 mineral particles examined. Mg-calcite predominated in the submicrometer size range, with a MgCO3 content up to 50 mol %. Magnesium plays a significant role in lung mineralization, a fact so far overlooked. The calcium phosphate (hydroxyapatite) content in the studied RLL tissue was negligible. The predominance of carbonates is explained by the increased CO2 fugacity in the RLL. Carbonates enveloped inhaled mineral-dust particles, including uranium-bearing oxides, quartz, aluminosilicates, and metal sulfides. Three possible pathways for the carbonates precipitation on the dust particles are postulated: (1) precipitation of amorphous calcium carbonate (ACC), followed by its transformation to calcite; (2) precipitation of Mg-ACC, followed by its transformation to Mg-calcite; (3) precipitation of Mg-free ACC, causing a localized relative enrichment in Mg ions and subsequent heterogeneous nucleation and crystal growth of Mg-calcite. The actual number of inhaled dust particles may be significantly greater than was observed because of the masking effect of the carbonate coatings. There is no simple correlation between smoking habit and lung calcification.

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Sharkeev, Yu P., M. B. Sedelnikova, T. V. Tolkacheva, N. A. Shcheglova, A. A. Panchenko, I. B. Krasovsky, М. V. Solomatina, et al. "Micro-Arc Zn- and Ag-Containing Coatings for Implants with Complex Porous Architecture Obtained by 3D Printing Method from Titanium Alloy." Traumatology and Orthopedics of Russia 26, no. 2 (July 9, 2020): 109–19. http://dx.doi.org/10.21823/2311-2905-2020-26-2-109-119.

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Relevance. The creation of porous three-dimensional materials for bone defects compensation and its subsequent regeneration is an important direction of medical materials science. The key issue in the interaction of an implant and bone tissue is the surface properties of the implant.The purpose of the study is to evaluate the physicochemical properties and compatibility of tissues of a living organism and porous implants with calcium phosphate Zn- and Ag-containing formed by microarc oxidation.Materials and Methods. Implants with various types of porous structure were made by direct laser sintering of titanium alloy Ti-6Al-4V powders. The calcium phosphate coatings, including Zn- and Ag-containing, were formed on the implants surface by microarc oxidation.Results. Coatings, deposited in electrolytes of various compositions, were uniformly distributed over the implants mesh structure. The phase composition of Zn-containing coatings, deposited in the acidic electrolyte, was represented by amorphous calcium phosphates. Ag-containing coatings, deposited in the alkaline electrolyte, had an amorphous-crystalline structure, the crystalline phase of which was identified as tricalcium phosphate in the α and β modifications. The samples of extracts of calcium phosphate Zn and Ag-containing coatings were co-cultured with pFb line of the human postnatal fibroblasts for 48 hours at 37°C in 5% CO2 atmosphere. The MTT test revealed a high metabolic activity of the co-cultured fibroblasts in comparison with the fibroblasts of control.Conclusion. The pFb line of the human postnatal fibroblasts retained their viability for 48 hours of co-culturing with calcium-phosphate Zn- and Ag-containing coatings. The tested product and its components did not negatively affect the cellular respiration. However, further studies are needed to determine the rate of bioresorption and the degree of antibacterial activity of calcium-phosphate Zn- and Ag-containing coatings.

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Gross, Karlis Agris, and Elina Rozite. "Synthesis of Tetracalcium Phosphate at Reduced Temperatures." Key Engineering Materials 631 (November 2014): 93–98. http://dx.doi.org/10.4028/www.scientific.net/kem.631.93.

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Tetracalcium phosphate (TTCP) requires the highest synthesis temperatures of all the calcium phosphates, but now a new process is available at 400 °C lower than previously, at 900 °C. Instead of ball-milling reactants for a homogeneous mix, the reactants were included in an amorphous phase. Heating produced hydroxyapatite, oxyapatite and then TTCP. Amorphous nanoparticles were synthesized and heated in air or in vacuum. The sequence of solid-state reactions were tracked with X-ray diffraction and Fourier transform infra-red spectroscopy. Heating in air stabilized the carbonate containing apatite, thereby requiring higher temperatures for decomposition, as per previous studies. Heating in vacuum promoted oxyapatite; a critical step for reaction with calcium oxide to generate TTCP. This faster process enables production at a lower temperature and reduces the use of ball milling for producing fine TTCP powders.

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Luginina, Marina, Roberto Orru, Giacomo Cao, David Grossin, Fabien Brouillet, Geoffroy Chevallier, Carole Thouron, and Christophe Drouet. "First successful stabilization of consolidated amorphous calcium phosphate (ACP) by cold sintering: toward highly-resorbable reactive bioceramics." Journal of Materials Chemistry B 8, no. 4 (2020): 629–35. http://dx.doi.org/10.1039/c9tb02121c.

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An adequate tuning of amorphous calcium phosphates ionic composition and cold sintering conditions allowed the first successful stabilization of these bioactive compounds. These results show promise for the setup of highly-resorbable bone substitutes.

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Ressler, Antonia, Maja Antunović, Matija Cvetnić, Marica Ivanković, and Hrvoje Ivanković. "Selenite Substituted Calcium Phosphates: Preparation, Characterization, and Cytotoxic Activity." Materials 14, no. 12 (June 21, 2021): 3436. http://dx.doi.org/10.3390/ma14123436.

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The aim of this study was to prepare a biomimetic selenium substituted calcium phosphate system for potential application in osteosarcoma therapy. Calcium phosphate (CaP) systems substituted with selenite ions were prepared by the wet precipitation method, using biogenic CaCO3 (derived from cuttlefish bone), CO(NH2)2-H3PO4, and Na2SeO3·5H2O as reagents. Starting reaction mixtures were prepared based on the formula for selenite-substituted hydroxyapatite, Ca10(PO4)6-x(SeO3)x(OH)2, with Ca/(P + Se) molar ratio of 1.67 and Se/(P + Se) molar ratio of: 0, 0.01, 0.05, and 0.10, respectively. The prepared CaP powders were characterized by Fourier transform infrared spectrometry, elemental analysis, scanning electron microscopy, X-ray powder diffraction analysis and Rietveld refinement studies. Phase transformation and ion release were analyzed during 7 days of incubation in simulated body fluid at 37 °C. The metabolic activity of healthy and osteosarcoma cell lines was assessed by cell cytotoxicity and viability test. The as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP). Along with the selenite substitution, the presence of Sr2+, Na+, and Mg2+ was detected as a result of using cuttlefish bone as a precursor for Ca2+ ions. Inductively coupled plasma mass spectrometry analysis showed that the Se/(P + Se) molar ratios of selenite substituted powders are lower than the nominal ratios. Heat treated powders were composed of HAp, α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). Doping CaP structure with selenite ions improves the thermal stability of HAp. The powder with the Se/(P + Se) molar ratio of 0.007 showed selective toxicity to cancer cells.

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Tsai, Tim W. T., Wei-Ya Chen, Yao-Hung Tseng, and Jerry C. C. Chan. "Phase transformation of calcium phosphates in the presence of glutamic acid." Canadian Journal of Chemistry 89, no. 7 (July 2011): 885–91. http://dx.doi.org/10.1139/v11-032.

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This work describes a phase-transformation pathway of calcium phosphate in the presence of glutamic acid. The route follows the order starting from amorphous calcium phosphate and brushite, then octacalcium phosphate (OCP), and finally hydroxyapatite (HAp). The preferred growth direction of the intermediate OCP and the final HAp phases lies along the c axis. On the basis of our scanning electron microscopy, X-ray powder diffraction, and 31P solid-state NMR data, we suggest that the transformation is via the dissolution–reprecipitation process, which is facilitated in the presence of glutamic acid. The effect on the transformation kinetics is rationalized by the disruption of the water layer bound on the crystal surface.

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Engin, Arzu, and İsmail Girgin. "Synthesis of hydroxyapatite by using calcium carbonate and phosphoric acid in various water-ethanol solvent systems." Open Chemistry 7, no. 4 (December 1, 2009): 745–51. http://dx.doi.org/10.2478/s11532-009-0063-6.

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AbstractThe purpose of the present study is to synthesize hydroxyapatite by using CaCO3 and H3PO4 in various water-ethanol solvent systems. It was observed from experiments that formation of ammonium phosphate compounds hindered the formation of calcium phosphates in ethanol medium. Although the reactivity was better in aqueous medium, the carbonate contents of the products obtained were above 8.5%. Best results with a carbonate content as low as 3.82% was obtained in 50% ethanol containing mixed-aqueous medium at 80°C and the FTIR analysis showed that the product was a carbonated apatite with a calculated composition of 14CaO·4.2P2O5·CO3·7.2H2O. The amorphous and porous phosphate compound obtained with a BET surface area of 106.6 m2 g−1 seems to be useful as adsorbent in wastewater treatment. Upon sintering of the amorphous product at 750°C, crystalline hydroxyapatite with a BET surface area of 25.9 m2 g−1 is obtained that may be used in biomedical applications.

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Maciejewski, Marek, Tobias J. Brunner, Stefan F. Loher, Wendelin J. Stark, and Alfons Baiker. "Phase transitions in amorphous calcium phosphates with different Ca/P ratios." Thermochimica Acta 468, no. 1-2 (February 2008): 75–80. http://dx.doi.org/10.1016/j.tca.2007.11.022.

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Nelson, L. S., C. Holt, J. E. Harries, and D. W. L. Hukins. "Amorphous calcium phosphates of different composition give very similar EXAFS spectra." Physica B: Condensed Matter 158, no. 1-3 (June 1989): 105–6. http://dx.doi.org/10.1016/0921-4526(89)90216-0.

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Skrtic, D., J. M. Antonucci, E. D. Eanes, and N. Eidelman. "Dental composites based on hybrid and surface-modified amorphous calcium phosphates." Biomaterials 25, no. 7-8 (March 2004): 1141–50. http://dx.doi.org/10.1016/j.biomaterials.2003.08.001.

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Scepanovic, Radomir, Dragica Selakovic, Jelena S. Katanic Stankovic, Natalija Arsenijevic, Marija Andjelkovic, Jovana Milenkovic, Pavle Milanovic, Miroslav Vasovic, Nemanja Jovicic, and Gvozden Rosic. "The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats." Oxidative Medicine and Cellular Longevity 2021 (August 17, 2021): 1–16. http://dx.doi.org/10.1155/2021/8207283.

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The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

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Borilo, Lyudmila P., Ekaterina S. Lyutova, and Larisa N. Spivakova. "Synthesis and Biological Properties of Thin-Film Materials on the Basis of SiO₂–P₂O₅–СаO–Na₂O System." Key Engineering Materials 670 (October 2015): 196–201. http://dx.doi.org/10.4028/www.scientific.net/kem.670.196.

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Thin films for the SiO2–P2O5–CaO–Na2O system are synthesized using sol-gel method. Content of the oxides in the system is 52-18-20-10 wt.% correspondingly. Thin films were produced from film-forming solutions on the single-crystal silicon substrates (model substrate) by extraction at a velocity of 5 mm/s following by heat treatment at a temperature of 60-80 °С for 20 minutes and at a temperature of 600 °С for 1 hour. During the experiment it was established that film-forming solutions are usable only for 2 to 7 days from the moment of preparation. Using thermal and infra-red – spectroscopic analysis main stages of oxide system formation were retraced. On the surface of the material NaCl, CaCl2, H2PO4·H2O, Ca5(PO4)3Cl, and SiO2 phases are being registered. Presence of the significant amount of pores leads to the essential increase in the specific surface area, creating optimal conditions for the new bone tissue formation. Biological activity of the received material was evaluated in SBF environment. Ca and P content on the surface of the material increased twofold in two weeks. Such material interchanges calcium ions and phosphate ions with solution; silanol groups fix calcium ions, furthering the formation of the layer of amorphous calcium phosphates gradually crystallizing in hydroxyapatite, and other calcium phosphates. Presence of magnesium and sodium on the surface of the samples after their immersion into SBF solution indicates the settling of SBF solution components on the film surface.

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Simkiss, K., and M. G. Taylor. "Calcium magnesium phosphate granules: atomistic simulations explaining cell death." Journal of Experimental Biology 190, no. 1 (May 1, 1994): 131–39. http://dx.doi.org/10.1242/jeb.190.1.131.

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1. A large number of invertebrates have cells that produce intracellular granules of amorphous calcium magnesium phosphates that are thought to act as ion stores or sites of metal detoxification. 2. The interatomic potentials and force constants have been calculated for these ions, and computer simulations of the crystal lattices have been used to determine the effects of ion substitutions on these lattice energies. 3. The results provide insights into the mechanisms of granule formation and the effects of ion substitutions on cell physiology.

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Ivan, Florina Daniela, Andreea Marian, Constantin Edi Tanase, Maria Butnaru, and Liliana Verestiuc. "Biomimetic Composites Based on Calcium Phosphates and Chitosan - Hyaluronic Acid with Potential Application in Bone Tissue Engineering." Key Engineering Materials 587 (November 2013): 191–96. http://dx.doi.org/10.4028/www.scientific.net/kem.587.191.

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Composites based on calcium phosphates (CP) and mixtures of biopolymers (chitosan and hyaluronic acid) have been prepared by a biomimetic co-precipitation method and tested as scaffolds for bone tissue engineering. The biomimetic strategy is inspired by natural mineralization processes, where the synthesized minerals are usually combined with proteins, polysaccharides or other mineral forms to form composite, in physiological conditions of temperature and pH. Fourier transformed infrared spectroscopy, scanning electron microscopy, X-ray diffraction and XPS analyses confirmed the porous morphology of the scaffolds and formation of various forms of calcium phosphates with amorphous nature. Thein vitrodegradation studies showed a slow degradation process for CP-biopolymers composites and limited swelling in simulated body fluids. The scaffolds compositions have no negative effect on osteoblasts cell, emphasizing a good biocompatibility.

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LI, Yan-Bao, Huai-Dong LI, Xin CHENG, Wen-Hao LIU, Dong-Xu LI, and Zhong-Zi XU. "Surface Modification of Amorphous Calcium Phosphates by Stearic Acid and Their Stability." Journal of Inorganic Materials 24, no. 4 (August 13, 2009): 707–11. http://dx.doi.org/10.3724/sp.j.1077.2009.00707.

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Brangule, Agnese, and Karlis Agris Gross. "Importance of FTIR Spectra Deconvolution for the Analysis of Amorphous Calcium Phosphates." IOP Conference Series: Materials Science and Engineering 77 (March 9, 2015): 012027. http://dx.doi.org/10.1088/1757-899x/77/1/012027.

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Ikawa, Nobuaki, Tatsuo Kimura, Yasunori Oumi, and Tsuneji Sano. "Amino acid containing amorphous calcium phosphates and the rapid transformation into apatite." Journal of Materials Chemistry 19, no. 28 (2009): 4906. http://dx.doi.org/10.1039/b815154g.

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Skrtic, Drago, Joseph M. Antonucci, Edward D. Eanes, Frederick C. Eichmiller, and Gary E. Schumacher. "Physicochemical evaluation of bioactive polymeric composites based on hybrid amorphous calcium phosphates." Journal of Biomedical Materials Research 53, no. 4 (2000): 381–91. http://dx.doi.org/10.1002/1097-4636(2000)53:4<381::aid-jbm12>3.0.co;2-h.

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Borovik, Paula, Víctor Oestreicher, Cristián Huck‐Iriart, and Matías Jobbágy. "Amorphous Calcium Phosphates: Solvent‐Controlled Growth and Stabilization through the Epoxide Route." Chemistry – A European Journal 27, no. 39 (June 4, 2021): 10077–86. http://dx.doi.org/10.1002/chem.202005483.

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Ma, Weiping, and Paul W. Brown. "Hydration of sodium phosphate-modified high alumina cement." Journal of Materials Research 9, no. 5 (May 1994): 1291–98. http://dx.doi.org/10.1557/jmr.1994.1291.

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High strength can be achieved in high alumina cement (HAC) through the incorporation of phosphate-based additions at levels of 10 and 20 wt. %. In order to establish the mechanism that results in higher strength, the effects of a variety of condensed sodium phosphates (NaPO3)n, (NaPO3)n · Na2O, Na5P3O10, and (NaPO3)3 were studied. The influence of these additions on the kinetics of hydration was studied using isothermal calorimetry. The phosphatic additions enhanced reactivity, but x-ray diffraction analyses did not reveal evidence of new crystalline phosphate-containing hydration products. Microstructural evolution was examined in real time using environmental SEM, and hydration products exhibiting distinct morphologies were observed. The features exhibited ranged from amorphic to polygonal shapes, plates, and fibers. These frequently formed between crystalline calcium aluminate hydrate grains and by doing so appear to provide a means to enhance the strengths of these cements. In spite of the morphological variations, companion energy dispersive x-ray analysis showed that the compositions of these products did not vary widely. Their ranges of compositions are 52-60 wt. % Al2O3, 20-26 wt. % P2O5, and 20-24 wt. % CaO.

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Journal articles on the topic 'Phosphates de calcium amorphes'

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