scholarly journals Phase transformation of calcium phosphates in the presence of glutamic acid

2011 ◽  
Vol 89 (7) ◽  
pp. 885-891 ◽  
Author(s):  
Tim W. T. Tsai ◽  
Wei-Ya Chen ◽  
Yao-Hung Tseng ◽  
Jerry C. C. Chan
Keyword(s):  
Phase Transformation ◽  
Calcium Phosphate ◽  
Glutamic Acid ◽  
Crystal Surface ◽  
Calcium Phosphates ◽  
Water Layer ◽  
Octacalcium Phosphate ◽  
Growth Direction ◽  
Transformation Kinetics ◽  
Transformation Pathway

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.

Effects of citrate and NaCl on size, morphology, crystallinity and microstructure of calcium phosphates obtained from aqueous solutions at acidic or near-neutral pH

2012 ◽  
Vol 79 (2) ◽  
pp. 238-248 ◽  
Author(s):  
Omar Mekmene ◽  
Thierry Rouillon ◽  
Sophie Quillard ◽  
Paul Pilet ◽  
Jean-Michel Bouler ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Inhibitory Effect ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Phosphate Dihydrate ◽  
Constant Ph ◽  
Starting Solutions ◽  
Calcium Phosphate Precipitation

Precipitation of calcium phosphates occurs in dairy products and depending on pH and ionic environment, several salts with different crystallinity can form. The present study aimed to investigate the effects of NaCl and citrate on the characteristics of precipitates obtained from model solutions of calcium phosphate at pH 6·70 maintained constant or left to drift. The ion speciation calculations showed that all the starting solutions were supersaturated with respect to dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP) in the order HAP>OCP>DCPD. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses of the precipitates showed that DCPD was formed at drifting pH (acidic final pH) whereas poor crystallised calcium deficient apatite was mainly formed at constant pH (6·70). Laser light scattering measurements and electron microscopy observations showed that citrate had a pronounced inhibitory effect on the crystallisation of calcium phosphates both at drifting and constant pH. This resulted in the decrease of the particle sizes and the modification of the morphology and the microstructure of the precipitates. The inhibitory effect of citrate mainly acted by the adsorption of the citrate molecules onto the surfaces of newly formed nuclei of calcium phosphate, thereby changing the morphology of the growing particles. These findings are relevant for the understanding of calcium phosphate precipitation from dairy byproducts that contain large amounts of NaCl and citrate.

Development of Bisphosphonate-Calcium Phosphate Composites and Drug Release Characteristic

2012 ◽  
Vol 1418 ◽  
Author(s):  
Hidekuni Kameda ◽  
Tomohiko Yoshioka ◽  
Toshiyuki Ikoma ◽  
Junzo Tanaka
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphates ◽  
Drug Carrier ◽  
Phosphate Buffer Solution ◽  
Octacalcium Phosphate ◽  
Acetate Buffer Solution ◽  
Unit Weight ◽  
Unit Surface Area ◽  
Acetate Solution ◽  
Buffer Solution

ABSTRACTBisphosphonate (Bp) was adsorbed on the surface of crystalline calcium phosphates (CP); hydroxyapatite (HAp), octacalcium phosphate (OCP) and Dicalcium phosphate dehydrate (DCPD). The amount of Bp adsorbed was the largest for DCPD per unit surface area, while the amount was the largest for HAp per unit weight. The composites of Bp and amorphous calcium phosphate (ACP) were synthesized by titrating calcium acetate solution into phosphate buffer solution containing Bp. The amount of Bp doped in the composites was 366 μg / mg and was approximately 7 times larger than those of Bp adsorbed on the crystalline Calcium phosphates. TG-DTA measurements of a Bp-calcium and the composite indicated exothermic peaks due to Bp combustion, of which temperature were shifted to higher temperature for the composite. Bp in the composites was gradually released into phosphate buffered saline, while Bp was rapidly released into acetate buffer solution accompanied with the dissolution of ACP. This result suggests that the composite of Bp and ACP has potential for a drug-carrier releasing Bp in response to the condition of osteoclastic bone resorption.

Electrochemical Hydroxyapatite Coatings on Nitinol Stents for the Reduction of Metal Ions Elution

2014 ◽  
Vol 1626 ◽  
Author(s):  
Daisuke Kondo ◽  
Tomohiko Yoshioka ◽  
Toshiyuki Ikoma ◽  
Kensuke Takamatsu ◽  
Kunihiro Ohta ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Metal Ions ◽  
Calcium Phosphates ◽  
Toxic Metal ◽  
Octacalcium Phosphate ◽  
Electrolytic Deposition ◽  
Nickel Ions ◽  
Nitinol Stent ◽  
Hydroxyapatite Coatings ◽  
Nitinol Stents

ABSTRACTNitinol was coated with biocompatible calcium phosphate materials by pulsed electrolytic deposition (ELD) to reduce toxic metal-ions elution. The pulse ELD for the stents was carried out with changing the current off-periods (toff) of the pulse wave. The pulse ELD suppressed the generation of H2 gas due to the electrolysis of water on a calcium phosphate layer and improved the adhesiveness of the coating layer on nitinol compared with a conventional DC-ELD. The coating layers were identified to be octacalcium phosphate (OCP) at lower toff, while they were transformed to dicalcium phosphate anhydraous (DCPA) with an increase of toff. The layers of OCP or DCPA on the nitinol surface were subjected to a NaOH treatment at 60°C for 3days to transform them into hydroxyapatite (HAp). From results of a metal-ions elution test, the deposited calcium phosphates suppressed nickel ions elution at one quarter compared with the bare nitinol stent. These results indicate that the pulse ELD of biocompatible calcium phosphate materials on the nitinol stent was one of the best techniques to create firmly attached coating on it and reduce toxic nickel ions elution.

scholarly journals Release Profiles of Dyes and Proteins from Calcium Phosphate Microspheres with Different Crystalline Phases

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 291-301
Author(s):  
Toshiki Miyazaki ◽  
Koudai Masuda ◽  
Kazuki Sakamoto
Keyword(s):  
Calcium Phosphate ◽  
Anticancer Agents ◽  
Bone Repair ◽  
Calcium Phosphates ◽  
Molecular Size ◽  
Octacalcium Phosphate ◽  
Release Behavior ◽  
Crystalline Phases ◽  
Adsorption And Release ◽  
Ph Decrease

Calcium phosphate is attracting attention as a bone repair material and a controlled-release carrier of various drugs such as bone disease therapeutic agents and anticancer agents. Compared with some bioabsorbable polymers, calcium phosphates have the advantage of preventing a pH decrease in the surrounding body fluid. However, there are few studies comparing the effect of supporting substances with different physicochemical properties on the production of calcium phosphate microspheres with different crystalline phases. In this study, we investigated conditions for obtaining low crystallinity apatite and octacalcium phosphate (OCP) microspheres from calcium carbonate microspheres with different crystalline structures using a simple phosphoric acid treatment. Furthermore, we investigated the adsorption and release behavior of different dyes and proteins from the apatite and OCP microspheres. Overall, the factors governing the adsorption and release behavior are different depending on the molecular size and surface charge of the dye and protein adsorbates.

Electrochemically Deposited Calcium Phosphate Coating on Titanium Alloy Substrates

2005 ◽  
Vol 284-286 ◽  
pp. 247-250 ◽  
Author(s):  
John P. LeGeros ◽  
Shu Jie Lin ◽  
Dindo Q. Mijares ◽  
Fred Dimaano ◽  
Racquel Z. LeGeros
Keyword(s):  
Calcium Phosphate ◽  
Electric Fields ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Calcium Phosphate Coating ◽  
Pulse Time ◽  
Uniform Coating ◽  
Spray Method ◽  
Electrochemically Deposited ◽  
Plasma Sprayed

Plasma-sprayed HA coating combines the strength of the metal and the bioactivity of the HA. However, this method has several disadvantages. Alternatives to the plasma-spray method such as electrochemical deposition (ECD) and biomimetic or precipitation methods are being explored. The purpose of this study was to develop an ECD method for coating Ti alloy substrate with different calcium phosphates (octacalcium phosphate, calcium deficient apatite, carbonatesubstituted apatite, fluoride-substituted apatite). Pairs of Ti6Al4V plates that have been mechanically polished, ultrasonically cleaned, acid etched, rinsed and dried were used as anodes and cathodes. ECD was carried out using programmed pulse time electric fields. Results showed that uniform coating with only the desired calcium phosphate can be obtained using metastable calcium phosphate solutions at different pH and temperature conditions and different electrolyte concentrations. Coating thickness varied with the duration of coating deposition. Crystal size varied with other ECD conditions (e.g., pulse time, current density). This method can be used to obtain uniform coating of the desired calcium phosphate composition at low temperatures (25 to 80oC) on substrates of any type of geometry.

scholarly journals The Influence of Different Classes of Amino Acids on Calcium Phosphates Seeded Growth

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4798
Author(s):  
Tea Mihelj Josipović ◽  
Monika Kovačević ◽  
Sarah Mateša ◽  
Marina Kostešić ◽  
Nives Matijaković ◽  
...  
Keyword(s):  
Amino Acids ◽  
Calcium Phosphate ◽  
Control Systems ◽  
Aspartic Acid ◽  
Significant Influence ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Seeded Growth ◽  
Material Synthesis

Amino acids (AAs) attract attention for elucidating the role of proteins in biomineralization and the preparation of functionalized biomaterials. The influence that AAs exert on calcium phosphate (CaP) mineralization is still not completely understood, as contradictory results have been reported. In this paper, the influence of the addition of different classes of AAs, charged (L-aspartic acid, Asp; L-lysine, Lys), polar (L-asparagine, Asn; L-serine, Ser; L-tyrosine, Tyr), and non-polar (L-phenylalanine, Phe), on CaP growth in the presence of octacalcium phosphate (OCP) and calcium hydrogenphosphate dihydrate (DCPD) seeds was investigated. In control systems (without AAs), a calcium-deficient apatite (CaDHA) layer was formed on the surface of OCP, while a mixture of CaDHA and OCP in the form of spherical aggregates was formed on the surface of DCPD crystals. Charged and non-polar promoted, while polar AAs inhibited CaDHA formation on the OCP seeds. In the case of DCPD, Lys, Asp, and Phe promoted CaP formation, while the influence of other AAs was negligible. The most efficient promotor of precipitation in both cases was non-polar Phe. No significant influence of AAs on the composition and morphology of precipitates was observed. The obtained results are of interest for understanding biomineralization processes and additive controlled material synthesis.

Seeded Growth of Calcium Phosphates: Effect of Different Calcium Phosphate Seed Material

1976 ◽  
Vol 55 (4) ◽  
pp. 617-624 ◽  
Author(s):  
G.H. Nancollas ◽  
J.S. Wefel
Keyword(s):  
Calcium Phosphate ◽  
Tricalcium Phosphate ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Dicalcium Phosphate ◽  
Dicalcium Phosphate Dihydrate ◽  
Seeded Growth ◽  
Seed Crystals ◽  
Phosphate Dihydrate ◽  
Supersaturated Solutions

The growth of calcium phosphates on seed materials, dicalcium PhosPhate dihydrate (DCPD), tricalcium phosphate (TCP), octacalcium phosphate (OCP), and hydroxyapatite (HAP) in stable supersaturated solutions has been studied under conditions of pH and concentration for which the predominant phases are 1, DCPD, and II, HAP. All seed crystals are good nucleators for DCPD in system I, but, aside from HAP itself, only OCP will readily induce growth under condition II.

scholarly journals Solid state phase transformation kinetics in Zr-base alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. R. Massih ◽  
Lars O. Jernkvist
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Zirconium Alloys ◽  
Excess Oxygen ◽  
Transformation Kinetics ◽  
Fuel Cladding ◽  
Reactor Accident ◽  
Phase Transformation Kinetics ◽  
Solid State Phase Transformation ◽  
Water Reactors

AbstractWe present a kinetic model for solid state phase transformation ($$\alpha \rightleftharpoons \beta$$ α ⇌ β ) of common zirconium alloys used as fuel cladding material in light water reactors. The model computes the relative amounts of $$\beta$$ β or $$\alpha$$ α phase fraction as a function of time or temperature in the alloys. The model accounts for the influence of excess oxygen (due to oxidation) and hydrogen concentration (due to hydrogen pickup) on phase transformation kinetics. Two variants of the model denoted by A and B are presented. Model A is suitable for simulation of laboratory experiments in which the heating/cooling rate is constant and is prescribed. Model B is more generic. We compare the results of our model computations, for both A and B variants, with accessible experimental data reported in the literature covering heating/cooling rates of up to 100 K/s. The results of our comparison are satisfactory, especially for model A. Our model B is intended for implementation in fuel rod behavior computer programs, applicable to a reactor accident situation, in which the Zr-based fuel cladding may go through $$\alpha \rightleftharpoons \beta$$ α ⇌ β phase transformation.

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