The Experts below are selected from a list of 94824 Experts worldwide ranked by ideXlab platform
Franz Schinner - One of the best experts on this subject based on the ideXlab platform.
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Solubilization of inorganic Calcium Phosphates—Solubilization mechanisms
Soil Biology & Biochemistry, 1995Co-Authors: Paul Illmer, Franz SchinnerAbstract:Abstract Two species [Penicillium aurantiogriseum and Pseudomonas sp. ( PI18 89 )] having high abilities in solubilizing inorganic Phosphates (hydroxylapatite and brushite) were used to examine solubilization mechanisms. No direct contact between microorganisms and Calcium Phosphates (Ca-Ps) were necessary for effective solubilization. The P-concentration in solution did not increase according to a sigmoid curve type. Therefore, sampling time is of particular importance for estimating P mobilization. The widespread theory that solubilization is always caused by the release of organic acids may prove wrong for our two organisms. In our opinion the most probable reason for solubilization without acid production is the release of protons accompanying respiration or NH4+ assimilation. It was shown that solubilization of Ca-Ps with two different solubility products may lead to a short-term increase of the amount of at least one CaP. Precipitation and subsequent resolubilization of different organic or inorganic Phosphates result in hardly predictable P-concentrations in culture solution.
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solubilization of inorganic Calcium Phosphates solubilization mechanisms
Soil Biology & Biochemistry, 1995Co-Authors: Paul Illmer, Franz SchinnerAbstract:Abstract Two species [Penicillium aurantiogriseum and Pseudomonas sp. ( PI18 89 )] having high abilities in solubilizing inorganic Phosphates (hydroxylapatite and brushite) were used to examine solubilization mechanisms. No direct contact between microorganisms and Calcium Phosphates (Ca-Ps) were necessary for effective solubilization. The P-concentration in solution did not increase according to a sigmoid curve type. Therefore, sampling time is of particular importance for estimating P mobilization. The widespread theory that solubilization is always caused by the release of organic acids may prove wrong for our two organisms. In our opinion the most probable reason for solubilization without acid production is the release of protons accompanying respiration or NH4+ assimilation. It was shown that solubilization of Ca-Ps with two different solubility products may lead to a short-term increase of the amount of at least one CaP. Precipitation and subsequent resolubilization of different organic or inorganic Phosphates result in hardly predictable P-concentrations in culture solution.
Jerome L Ackerman - One of the best experts on this subject based on the ideXlab platform.
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multinuclear solid state three dimensional mri of bone and synthetic Calcium Phosphates
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: David A Chesler, Melvin J Glimcher, Leoncio Garrido, Jinxi Wang, Hong J Jiang, Jerome L AckermanAbstract:Multinuclear three-dimensional solid-state MRI of bone, tooth, and synthetic Calcium Phosphates is demonstrated in vitro and in vivo with a projection reconstruction technique based on acquisition of free induction decays in the presence of fixed amplitude magnetic field gradients. Phosphorus-31 solid-state MRI provides direct images of the Calcium phosphate constituents of bone substance and is a quantitative measurement of the true volumetric bone mineral density of the bone. Proton solid-state MRI shows the density of bone matrix including its organic constituents, which consist principally of collagen. These solid-state MRI methods promise to yield a biological picture of bone richer in information concerning the bone composition and short range-crystalline order than the fluid-state images provided by conventional proton MRI or the density images produced by radiologic imaging techniques. Three-dimensional solid-state projection reconstruction MRI should be readily adaptable to both human clinical use and nonmedical applications for a variety of solids in materials science.
Paul Illmer - One of the best experts on this subject based on the ideXlab platform.
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Solubilization of inorganic Calcium Phosphates—Solubilization mechanisms
Soil Biology & Biochemistry, 1995Co-Authors: Paul Illmer, Franz SchinnerAbstract:Abstract Two species [Penicillium aurantiogriseum and Pseudomonas sp. ( PI18 89 )] having high abilities in solubilizing inorganic Phosphates (hydroxylapatite and brushite) were used to examine solubilization mechanisms. No direct contact between microorganisms and Calcium Phosphates (Ca-Ps) were necessary for effective solubilization. The P-concentration in solution did not increase according to a sigmoid curve type. Therefore, sampling time is of particular importance for estimating P mobilization. The widespread theory that solubilization is always caused by the release of organic acids may prove wrong for our two organisms. In our opinion the most probable reason for solubilization without acid production is the release of protons accompanying respiration or NH4+ assimilation. It was shown that solubilization of Ca-Ps with two different solubility products may lead to a short-term increase of the amount of at least one CaP. Precipitation and subsequent resolubilization of different organic or inorganic Phosphates result in hardly predictable P-concentrations in culture solution.
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solubilization of inorganic Calcium Phosphates solubilization mechanisms
Soil Biology & Biochemistry, 1995Co-Authors: Paul Illmer, Franz SchinnerAbstract:Abstract Two species [Penicillium aurantiogriseum and Pseudomonas sp. ( PI18 89 )] having high abilities in solubilizing inorganic Phosphates (hydroxylapatite and brushite) were used to examine solubilization mechanisms. No direct contact between microorganisms and Calcium Phosphates (Ca-Ps) were necessary for effective solubilization. The P-concentration in solution did not increase according to a sigmoid curve type. Therefore, sampling time is of particular importance for estimating P mobilization. The widespread theory that solubilization is always caused by the release of organic acids may prove wrong for our two organisms. In our opinion the most probable reason for solubilization without acid production is the release of protons accompanying respiration or NH4+ assimilation. It was shown that solubilization of Ca-Ps with two different solubility products may lead to a short-term increase of the amount of at least one CaP. Precipitation and subsequent resolubilization of different organic or inorganic Phosphates result in hardly predictable P-concentrations in culture solution.
David A Chesler - One of the best experts on this subject based on the ideXlab platform.
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multinuclear solid state three dimensional mri of bone and synthetic Calcium Phosphates
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: David A Chesler, Melvin J Glimcher, Leoncio Garrido, Jinxi Wang, Hong J Jiang, Jerome L AckermanAbstract:Multinuclear three-dimensional solid-state MRI of bone, tooth, and synthetic Calcium Phosphates is demonstrated in vitro and in vivo with a projection reconstruction technique based on acquisition of free induction decays in the presence of fixed amplitude magnetic field gradients. Phosphorus-31 solid-state MRI provides direct images of the Calcium phosphate constituents of bone substance and is a quantitative measurement of the true volumetric bone mineral density of the bone. Proton solid-state MRI shows the density of bone matrix including its organic constituents, which consist principally of collagen. These solid-state MRI methods promise to yield a biological picture of bone richer in information concerning the bone composition and short range-crystalline order than the fluid-state images provided by conventional proton MRI or the density images produced by radiologic imaging techniques. Three-dimensional solid-state projection reconstruction MRI should be readily adaptable to both human clinical use and nonmedical applications for a variety of solids in materials science.
Christian Rey - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Calcium Phosphates Using Vibrational Spectroscopies
Advances in Calcium Phosphate Biomaterials, 2014Co-Authors: Christian Rey, David Grossin, Olivier Marsan, Christophe Drouet, Christele Combes, Stéphanie SardaAbstract:Vibrational spectroscopies are extensively used for the characterization of Calcium Phosphates either as natural biological minerals (bone, teeth, ectopic calcifications) or as biomaterials (bioceramics, coatings, composites). The present review begins with a theoretical description of expected spectra for the main Calcium phosphate phases (i.e., brushite, monetite, octaCalcium phosphate, triCalcium Phosphates, apatites, amorphous Calcium phosphate) followed by the analysis of real spectra, line positions and assignments, and observed anomalies. In the second part, the spectra of complex well-crystallized ion-substituted apatites and other Calcium Phosphates, as well as solid solutions, are investigated, and the information gained regarding the substitution types and ion distributions are derived. Finally, we will examine and interpret the spectra of nanocrystalline apatites considering the ion substitution effects and the existence of a surface hydrated layer. Quantification processes and spectra treatments are briefly presented and discussed. Examples of the use of vibrational spectroscopies for biomaterials and biominerals characterization will be detailed for coating evaluations, including spectroscopic imaging, following up on mineral cement setting reactions, adsorption studies, near infrared investigations of surface water, residual strains determinations in bone, orientation of apatite crystals in biological tissues, and crystallinity and maturity of bone mineral.
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Controlled adsorption and release onto Calcium Phosphates materials and drug delivery applications
MATEC Web of Conferences, 2013Co-Authors: Allal Barroug, Stéphanie Sarda, Sophie Cazalbou, Christele Combes, Christian Rey, Hassan Noukrati, Farid Errassifi, Melvin J GlimcherAbstract:The adsorptive properties of synthetic Calcium Phosphates analogous to bone mineral were examined with respect to cisplatin and risedronate, two biological active drugs; the uptake and release experiments were carried out under various conditions in order to understand the basic mechanism of interaction. The effect of temperature and solution composition were highlighted and discussed. The adsorption results obtained for the therapeutic agents demonstrated that, depending on the conditions investigated (nature of the sorbent, concentration range, ionic composition, temperature. . . ), the shape of the isotherms is of Freundlich or Langmuir type. The adsorption is described as an ion-exchange process in dilute solutions, while the interaction appears to be reactive for concentrated solutions (dissolution of mineral ions from the apatite substrate and formation of soluble Calcium complex and/or precipitation of Calcium salts involving sorbate molecules). The information gained on the surface reactivity of Calcium phosphate were exploited to associate an antibiotic to Calcium phosphate cements for drug delivery applications. The specimens were obtained by combination of Calcium phosphate and Calcium carbonate powders upon mixing with water. The physicochemical properties of the paste were altered by the drug loading method (in the liquid or solid phase). Thus, a dose-dependent effect was noticed for the paste setting time, hardening and the release process.
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amorphous Calcium Phosphates synthesis properties and uses in biomaterials
Acta Biomaterialia, 2010Co-Authors: Christele Combes, Christian ReyAbstract:This review paper on amorphous Calcium Phosphates (ACPs) provides an update on several aspects of these compounds which have led to many studies and some controversy since the 1970s, particularly because of the lack of irrefutable proof of the occurrence of an ACP phase in mineralised tissues of vertebrates. The various synthesis routes of ACPs with different compositions are reported and the techniques used to characterise this phase are reviewed. We focus on the various physico-chemical properties of ACPs, especially the reactivity in aqueous media, which have been exploited to prepare bioactive bone substitutes, particularly in the form of coatings and cements for orthopaedic applications and composites for dental applications.
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Calcium Phosphates for medical applications
1998Co-Authors: Christian ReyAbstract:In the last decade, the biomedicai applications of Calcium phosphate have increased significantly.1-5 This success is mainly due to the biological properties of these materials and the total absence of toxicity of their constituents. Much progress has been made in recent years to facilitate their use. Several different types of Ca-P materials including resorbable and non-resorbable ceramics, prosthetic coatings, cements, injectable cements, composite materials, and drug carriers are proposed that are suited to a wide range of applications: bone defect filling, bone reconstruction (especially in maxilo-facial applications), bone replacement (especially small bones and middle ear bones), drug carrier (antibiotics, anticancerous drugs, growth factors), coatings of metal prostheses (hip and knee joints), and even nerve guide.6 Considering the large amounts of natural Ca-P materials of human or animal origin that are available, why is there a need for synthetic Calcium Phosphates? In addition to cultural and religious objections, there are also well founded medical reasons.
