Calcium Sodium Phosphate Research Articles

31P NMR characterisation of phosphate fragments during dissolution of calcium sodium phosphate glasses.

Phosphate glasses in the system P2O5-CaO-Na2O dissolve in aqueous solutions, and their solubility can be varied by changing the glass composition. This makes them of interest for use as controlled release materials, e.g. as degradable implants, devices for the release of trace elements or as fertilizers, but in order to tailor glass solubility to meet specific requirements, we need to further our understanding of their dissolution behaviour and mechanism. The structure of P2O5-CaO-Na2O glasses (P2O5 between 55 and 35 mol%; glass structure analysed by 31P MAS NMR) changed from a network (55 mol% P2O5) to short chains (35 mol%) with decreasing phosphate content. Solubility in Tris buffer showed significant differences with phosphate content and glass structure; dissolution varied between 90% (50 mol% P2O5) and 15% (35 mol%) at 24 h. Glasses with high phosphate contents significantly lowered the pH of the solution, while glasses with low phosphate contents did not. Glasses consisting of a phosphate network dissolved by a mechanism involving P-O-P bond hydrolysis, as no Q3 groups but increasing concentrations of Q0 (orthophosphate) were found in solution by solution 31P NMR. Glasses consisting of chains, by contrast, can dissolve by hydration of entire chains, but hydrolysis also occurred, resulting in formation of Q0 and small ring structures. This occurrence of hydrolysis (and thus formation of P-OH groups, which can be deprotonated) caused the pH decrease and explains the variation in solution pH with structure.

Microwave‐Assisted Production of Amorphous Calcium Magnesium Phosphate: Study From Co‐Precipitation to Sintered Products

Under microwave irradiation, agglomerates of nanospherical amorphous calcium magnesium phosphate (ACMP) particles were precipitated from a source solution with Ca2+, Mg2+, and PO43−. These precipitates were achieved when Mg2+ was added no less than three times concentrated of Ca2+. Otherwise, the as‐precipitated powder would only be a mixture of brushite (DCPD) and calcium sodium phosphate (CNP) with poor Mg2+ substitution. As compared to the mixture of DCPD and CNP, the as‐formed ACMP presented great densification during sintering. Moreover, the as‐sintered products were bioactive with final composition of magnesium pyrophosphate (MPP), β‐tricalcium phosphate (β‐TCP), and calcium pyrophosphate (CPP).

Pilot-test of the calcium sodium phosphate (CNP) process for the stabilization/solidification of various mercury-contaminated wastes

A pilot-scale calcium sodium phosphate (CNP) plant was designed and manufactured to examine the performance of recently developed stabilization/solidification (S/S) technology. Hg-contaminated wastes samples generated via various industrial processes in Korea, including municipal, industrial, and medical waste incineration, wastewater treatment, and lime production, were collected and treated using the pilot-scale CNP plant. S/S samples were fabricated according to various operating conditions, including waste type, the dose of the stabilization reagent (Na2S), and the waste loading ratio. Although the performances (Hg leaching value and compressive strength) were reduced as the waste loading ratio increased, most of the S/S samples exhibited Hg leaching values that were below the universal treatment standard limit of 25μgL−1 and compressive strengths that exceeded the criterion of 3.45MPa.

Stabilization/solidification of mercury-contaminated waste ash using calcium sodium phosphate (CNP) and magnesium potassium phosphate (MKP) processes

This study examined the stabilization and solidification (S/S) of mercury (Hg)-contaminated waste ash generated from an industrial waste incinerator using chemically bonded phosphate ceramic (CBPC) technology. A magnesium potassium phosphate (MKP; MgKPO4·6H2O) ceramic, fabricated from MgO and KH2PO4, and a calcium sodium phosphate (CNP; CaNaPO4) ceramic, fabricated from CaO and Na2HPO4, were used as solidification binders in the CBPC process, and Na2S or FeS was added to each solidification binder to stabilize the Hg-contaminated waste ash. The S/S processes were conducted under various operating conditions (based on the solidification binder and stabilization reagent, stabilization reagent dosage, and waste loading ratio), and the performance characteristics of the S/S sample under each operating condition were compared, including the Hg leaching value and compressive strength. The Hg leaching value of untreated Hg-contaminated waste ash was 231.3μg/L, whereas the S/S samples treated using the MKP and CNP processes exhibited Hg leaching values below the universal treatment standard (UTS) limit (25μg/L). Although the compressive strengths of the S/S samples decreased as the sulfide dosage and waste loading ratio were increased, most of the S/S samples fabricated by the MKP and CNP processes exhibited good mechanical properties.

Changes in structure and thermal properties with phosphate content of ternary calcium sodium phosphate glasses

Phosphate glasses in the system P2O5–CaO–Na2O dissolve in aqueous solutions, making them of interest for use as controlled release materials, e.g. as degradable implants or fertilisers. However, glasses showing slow dissolution tend to be in the poly- or pyrophosphate range and thus have high tendencies to crystallise, making the processing of these glasses challenging. This study therefore aims at systematically investigating how structural changes in the glass affect thermal properties and crystallisation. P2O5–CaO–Na2O glasses with phosphate contents between 55 and 35mol% were prepared by a melt-quench route. Glass density increased and molar volume decreased with increasing modifier content, owing to a more densely packed glass structure. Raman and 31P magic angle spinning nuclear magnetic resonance spectroscopy showed that the glass structure changed from a network (55mol% P2O5) to short chains (35mol%) with decreasing phosphate content. The increasing concentration of non-bridging oxygens with increasing modifier content resulted in a pronounced increase in glass transition temperature and a smaller processing window, making processing, such as sintering, challenging.

Development of a novel calcium phosphate cement composed mainly of calcium sodium phosphate with high osteoconductivity

Two novel calcium phosphate cements (CPC) have been developed using calcium sodium phosphate (CSP) as the main ingredient. The first of these cements, labeled CAC, contained CSP, α-tricalcium phosphate (TCP), and anhydrous citric acid, whereas the second, labeled CABC, contained CSP, α-TCP, β-TCP, and anhydrous citric acid. Biopex(®)-R (PENTAX, Tokyo, Japan), which is a commercially available CPC (Com-CPC), and OSferion(®) (Olympus Terumo Biomaterials Corp., Tokyo, Japan), which is a commercially available porous β-TCP, were used as reference controls for analysis. In vitro analysis showed that CABC set in 5.7 ± 0.3 min at 22 °C and had a compressive strength of 86.0 ± 9.7 MPa after 5 days. Furthermore, this material had a compressive strength of 26.7 ± 3.7 MPa after 2 h in physiologic saline. CAC showed a statistically significantly lower compressive strength in the presence of physiologic saline and statistically significantly longer setting times than those of CABC. CABC and CAC exhibited apatite-forming abilities in simulated body fluid that were faster than that of Com-CPC. Samples of the materials were implanted into the femoral condyles of rabbits for in vivo analysis, and subsequent histological examinations revealed that CABC exhibited superior osteoconductivity and equivalent bioresorbability compared with Com-CPC, as well as superior osteoconductivity and bioresorbability compared with CAC. CABC could therefore be used as an alternative bone substitute material.

Characterization and In Vitro Bioactivity of Calcium and Phosphorous Containing Titania Layer on Ti6Al4V Alloy

Calcium and phosphorous containing titania layers on Ti6Al4V biomedical alloy were formed by micro arc oxidation (MAO) in an electrolyte containing calcium acetate and sodium phosphate, and then subjected to hydrothermal treatment (HT) in order to achieve improved biocompability with modified titania layer. Samples were hydrothermally treated in water solution whose pH was adjusted to 11.0-11.5 by adding NaOH, at 230 °C for 10 h and cooled in the autoclave . Surface morphology, microstructure, and phase com position of titania layer were investigated systematically before and after HT. Their biomimetic apatite inducing ability in a simulated body fluid (SBF) was investigated. The bioactivity tests of modified MAO surface on Ti6Al4V alloy showed a considerable improvement compared to the unmodified MAO surface. Abstract: Ti6Al4V biomedikal titanyum alasimi uzerinde kalsiyum asetat ve sodyum fosfat iceren elektrolit icinde gerceklestirilen mikro ark oksidasyon islemi ile kalsiyum ve fosfor iceren titanyum oksit tabakasi olusturulmustur. Olusturulan oksit tabakasinin biyomimetik apatit olusturma ozelligini iyilestirmek amaciyla numuneler 10 saat sureyle 230 °C'de sodyum hidroksit iceren sulu cozelti icerisinde hidrotermal isleme maruz birakilmistir. Numunelerin yu zey morfolojileri, oksit tabakalarin mikroyapisi ve faz kompozisyonlari hidrotermal islem oncesi ve sonrasinda incelenmistir. Numunelerin biyomimetik apatit olusum karakteristigi incelemesi yapay vucut sivisi icinde gerceklestirilmistir. Mikro ark oksidasy on islemini takiben uygulanan hidrotermal islem sonucunda Ti6Al4V numunenin yuzeyinde biyomimetik apatit olusumunun iyilestigi gozlemlenmistir.

Kinetics of phosphate absorption in lactating dairy cows after enteral administration of sodium phosphate or calcium phosphate salts

Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7 h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration–time curves of P and acetaminophen after administration of 1M-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment.

Effect of Camphor Addition on Mechanical Properties and Bioactivity of P2O5-CaO-Na2O Bioactive Glass

In this work, we have studied the effects of camphor addition on the properties of porous ceramics of P2O5-CaO-Na2O glass for biomedical applications. Mixed powders were formed into pellets and subsequently sintered at the temperatures ranging between 550 and 650°C. The sintered ceramics were investigated in terms of pore characteristics, phase formation, and in vitro bioactivity. The pore sizes of the structures were observed by SEM to be in the range of 150–400 μm. XRD results revealed that calcium phosphate and sodium phosphate phases were formed in the porous ceramics. In vitro bioactivity was assessed in SBF solution and the results confirm the formation of apatite like cells on the surface of all glass ceramic compositions.

Osteoconductivity of New Sodium Calcium Phosphate Pastes

We are developing a new bone paste (CaNaP paste), consists of calcium sodium phosphate (CaNaPO4), alpha-TCP, beta-TCP and citrate. It has improved handling and mechanical property with decreased setting time. For in vivo analysis using a rabbit model, four kinds of materials (Material 1: CaNaPO4 + alpha, beta-TCP + citrate, Material 2: commercially available CaP paste, Material 3: CaNaPO4 + alpha-TCP + citrate, and Material 4: commercially available porous beta-TCP) were prepared, and they were implanted into the rabbit femoral condyles (n=8). After 4 weeks and 12 weeks, histo-morphometrical analyses were performed, and bone-material contact index, bone area in the material, bone area ratio around the material, degree of bone penetration into the material, and material absorptivity were calculated. Results showed that Material 1 (newly developed CaNaP pasted containing beta-TCP) is more osteoconductive than Material 2 and Material 3 (CaNaP paste without beta-TCP), and can be expected as an attractive alternative for the bone substitute material.

Multiphase ceramics based on powders synthesized from sodium pyrophosphate and soluble calcium salts using mechanical activation

A multiphase ceramics has been obtained from calcium phosphate powders synthesized by mechanical activation from sodium pyrophosphate and soluble calcium salts (acetate, nitrate, chloride). After synthesis from sodium pyrophosphate and calcium acetate or calcium nitrate the powders comprised a mixture of double calcium-sodium phosphate, unreacted calcium salt and reaction byproduct (NaNO3 or NaCH3COO). After synthesis from sodium pyrophosphate and calcium chloride the powders comprised a mixture of amorphous calcium phosphate and byproduct NaCl. After heat-treatment the phase composition of the samples depended on the firing temperature and the composition of the initial powders. After firing Ca2P2O7, Na2CaP2O7, NaCaPO4 and Ca3(PO4)2 were present in the samples.

Fabrication of P2O5–CaO–Na2O glasses doped with magnesium oxide for artificial bone applications

Effects of MgO doping on properties of P2O5–CaO–Na2O glass system were investigated. The glass samples were prepared by conventional glass melting technique at 1000 °C for 1 h. Thermal parameter of each glass sample were studied by differential thermal analysis (DTA). The glass samples were annealed at crystallization temperature to form glass ceramics. The glass ceramics were investigated in terms of phase formations by XRD, microstructure by SEM and in vitro bioactivity. The phases formed in all glass ceramics are calcium phosphate (Ca2P2O7 file no. 09-0346), sodium phosphate (NaPO3 file no. 11-0650) and sodium calcium phosphate (Na1.8Ca1.1P6O17 file no. 47-0863) as detected by XRD. The 5–10 mol% MgO glass ceramics having well separated two crystallization peaks (Tx1 and Tx2) within the temperature range of 557–590 °C contained additional sodium magnesium phosphate (NaMg(PO3)3 file no. 72-2341). Large porosity was found in all glass ceramics due to free volume and void formation during the crystallized phase. The in vitro study revealed that all glass ceramic samples exhibited apatite cell growth at the surface after immersed in simulated body fluid (SBF) for 7 days. The results suggested that these glass ceramics were appropriate for biomedical application.

The influence of feed phosphates on the structural, mechanical and chemicalproperties of bone tissue in pigs

The aim of the study was to assess the influence of various feed phosphates on the structural and mechanical properties as well as on the chemical composition of femurs in adult pigs (weight approx. 110 kg). Three types of phosphates--monocalcium phosphate (MCP), dicalcium phosphate (n-DCP) and calcium-sodium phosphate (CSP)--were used alternatively in pigs fed with the standard feed mixture. The MCP and CSP phosphates were typical, imported products used traditionally in pig feeding. Dicalcium phosphate (n-DCP) was manufactured in Poland on the basis of phosphoric acid with the new pro-ecological method. The following parameters were determined: the mean physical density of the samples of the compact and spongy bone tissue, values of Young's modulus, strength and the energy of deformation, and Vickers microhardness (HV). Also the content of C, O, Na, Mg, Al, and Si, as well as Ca, P and Sr was determined. Significant differences in mean values of the mentioned parameters occurred between the studied groups. The best mechanical properties were shown by the bones from the n-DCP group, and the compact bone tissue (diaphysis) contained the most Ca, P, and Sr when compared to the MCP and CSP groups.

A Comparison of Alumino and Calcium Phosphate Sintering Aids for Consolidation of Halide Containing Wastes

ABSTRACTA process has been developed at AWE for the immobilisation of halide containing wastes arising from the reprocessing of plutonium. Initially, the wastes are calcined with a calcium phosphate to form a number of target host phases, β-tricalcium phosphate (β-TCP) and apatite for the immobilisation of actinides, and apatite and spodiosite for halide.These mineral phases are then mixed with a glass binder, cold pressed and sintered to form a monolithic waste form. Two glass binders GTI/168, a sodium alumino phosphate glass and GTI/206, a sodium calcium phosphate glass were compared to optimise the halide retention in the waste-form. Analysis from powder X-ray Diffraction (PXRD) and scanning electron microscopy (SEM) showed that neither glass stabilises spodiosite. However, GTI/206 glass retains 10 wt.% more apatite and results in a much smaller proportion of the non-chloride bearing whitlockite phase than GTI/168.In all compositions where GTI/168 glass was used as a sintering aid, the sodium deficient and calcium enriched glass was present as an amorphous matrix phase.

Facile route to obtain a highly bioactive SiO 2–CaO–Na 2O–P 2O 5 crystalline powder

This work describes a facile method to obtain highly bioactive crystalline powders of the SiO 2–CaO–Na 2O–P 2O 5 system using a simple route: solid state reaction. Success in obtaining the highly bioactive crystal phase of interest (sodium calcium silicate Na 2Ca 2Si 3O 9 containing phosphorus) involves heating the starting reactant powder mixture under an oxidizing atmosphere for 480 min in the temperature range 950–1000 °C. Despite a significant loss of phosphorus at heat treatment temperatures above 950 °C, the resulting Na 2Ca 2Si 3O 9 crystal phase is thermally stable up to 1100 °C. Longer treatment times favor the formation of a secondary phase (sodium calcium phosphate NaCaPO 4), which, according to recent studies, further increases the bioactivity of a similar material. Finally, in vitro bioactivity tests in acellular simulated body fluid (SBF) of a powder containing only the Na 2Ca 2Si 3O 9 phase has shown behavior similar to that of Biosilicate® — an ~ 99.5% crystalline glass–ceramic whose outstanding characteristics of interaction with living tissue have already been reported in the literature.

Magnetic properties of bioactive glass-ceramics containing nanocrystalline zinc ferrite

Glass-ceramics with finely dispersed zinc ferrite (ZnFe 2O 4) nanocrystallites were obtained by heat treatment of x(ZnO,Fe 2O 3)(65− x)SiO 220(CaO,P 2O 5)15Na 2O (6≤ x≤21 mole%) glasses. X-ray diffraction patterns of the glass-ceramic samples revealed the presence of calcium sodium phosphate [NaCaPO 4] and zinc ferrite [ZnFe 2O 4] as major crystalline phases. Zinc ferrite present in nanocrystalline form contributes to the magnetic properties of the glass-ceramic samples. Magnetic hysteresis cycles of the glass-ceramic samples were obtained with applied magnetic field sweeps of ±20 kOe and ±500 Oe, in order to evaluate the potential of these glass-ceramics for hyperthermia treatment of cancer. The evolution of magnetic properties in these samples, viz., from a partially paramagnetic to fully ferrimagnetic nature has been explored using magnetometry and X-ray diffraction studies.

Synchrotron X-ray analyses demonstrate phosphate-bound gadolinium in skin in nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF) is an incurable, debilitating disease found exclusively in patients with decreased kidney function and comprises a fibrosing disorder of the skin and systemic tissues. The disease is associated with exposure to gadolinium (Gd)-based contrast agents (GBCA) used in magnetic resonance imaging (MRI). Tissue samples from many patients with NSF contain micron-sized insoluble Gd-containing deposits. However, the precise composition and chemical nature of these particles is unclear. To clarify the precise chemical structure of the Gd-containing deposits in NSF tissues. Autopsy skin tissues from a patient with NSF were examined in situ using synchrotron X-ray fluorescence (SXRF) microscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy and in correlation with light microscopy and the results of scanning electron microscopy /energy dispersive spectroscopy analyses. The insoluble Gd deposits were shown to contain Gd no longer coordinated by GBCA chelator molecules but rather in a sodium calcium phosphate material. SXRF microscopy shows a clear correlation between Gd, Ca and P. EXAFS spectroscopy shows a very different spectrum from the GBCAs, with Gd–P distances at 3·11 A and 3·11 A as well as Gd–Gd distances at an average of 4·05 A, consistent with a GdPO4 structure. This is the first direct evidence for the chemical release of Gd from GBCA in human tissue. This supports the physical–chemical, clinical and epidemiological data indicating a link between stability and dose of GBCA to the development of NSF.

Apatite-forming ability and magnetic properties of glass-ceramics containing zinc ferrite and calcium sodium phosphate phases

Fine particles of zinc ferrite (ZnFe 2O 4) and calcium sodium phosphate [NaCaPO 4] were crystallized in bulk x(ZnO, Fe 2O 3)(65− x)SiO 220(CaO, P 2O 5)15Na 2O (6 ≤ x ≤ 21 mol %) glassy matrix by heat treatment. Initial magnetization curves reveal that samples with x = 6 and 9 mol % zinc–iron oxide exhibit both ferrimagnetic and paramagnetic contributions, whereas, samples with x > 9 mol % zinc–iron oxide exhibit only ferrimagnetic contribution. This observation is supported by the disappearance of the electron paramagnetic resonance (EPR) absorption line centered at g ≈ 4.3 in samples with x > 9 mol % zinc–iron oxide. Apatite-forming ability of the glass-ceramic samples was investigated by examining apatite formation on the surface of the samples treated in simulated body fluid (SBF). Increase in apatite-forming ability was observed with an increase in zinc–iron oxide content. The results obtained have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass-ceramic composition. A good correlation has also been observed between the magnetic nature of the samples and their apatite-forming ability. These materials are expected to find application as thermo-seeds in hyperthermia treatment of bone cancer.

The effect of zinc and titanium on the structure of calcium–sodium phosphate based glass

An array of different structural probes has been used to define the effect of adding Zn and Ti to a sodium–calcium phosphate glass. X-ray absorption spectroscopy at the Zn K-edge suggests that the Zn atoms occupy mixed (4- and 6-fold) sites within the glass matrix. X-ray diffraction reveals a feature at 2.03 Å that develops with the addition of Zn and Ti and is consistent with Zn–O and Ti–O near-neighbour distances. Neutron diffraction is used to resolve two distinct P–O distances and highlights the decrease in P···P coordination number from 2.0 to 1.7 as the Ti metal concentration rises, which is attributed to the O/P fraction moving away from the metaphosphate value of 3.0 to 3.1 with the addition of Ti. Other correlations, such as those associated with CaO x and NaO x polyhedra, remain largely unaffected. These results suggest that the network forming P···P correlation is most disrupted, with the disorder parameter rising from 0.07 to 0.10 Å with the additional modifiers. Zn appears to be introduced into the network as a direct replacement for Ca and causes no structural variation over the composition range studied.

Titanium and Strontium-doped Phosphate Glasses as Vehicles for Strontium Ion Delivery to Cells

This study investigated the use of a Ti-containing quaternary phosphate glass system P(2)O(5)-Na(2)O-CaO-TiO(2) as a vehicle for strontium ion delivery to cells. Four glass compositions were manufactured: 0.5P(2)O(5)-0.15Na(2)O-0.05TiO(2)-(0.3 - x)CaO-xSrO (x = 0, 0.01, 0.03, and 0.05). Structural characterization revealed that sodium calcium phosphate is the dominant phase in all the glasses. Degradation studies demonstrated highly linear glass degradation, with Sr-containing glasses degrading at higher rates than the Sr-free glass. Biocompatibility studies using MG63 cells showed that the Sr-containing glasses possess excellent cell attachment and growth, particularly over short periods (~4 days).