Strontium Hydrogen Phosphate Research Articles

SrHPO4-coated Mg alloy implant attenuates postoperative pain by suppressing osteoclast-induced sensory innervation in osteoporotic fractures

Osteoporotic fractures have become a common public health problem and are usually accompanied by chronic pain. Mg and Mg-based alloys are considered the next-generation orthopedic implants for their excellent osteogenic inductivity, biocompatibility, and biodegradability. However, Mg-based alloy can initiate aberrant activation of osteoclasts and modulate sensory innervation into bone callus resulting in postoperative pain at the sequential stage of osteoporotic fracture healing. Its mechanism is going to be investigated. Strontium hydrogen phosphate (SrHPO4) coating to delay the Mg-based alloy degradation, can reduce the osteoclast formation and inhibit the growth of sensory nerves into bone callus, dorsal root ganglion hyperexcitability, and pain hypersensitivity at the early stage. Liquid chromatography-mass spectrometry (LC-MS) metabolomics analysis of bone marrow-derived macrophages (BMMs) treated with SrHPO4-coated Mg alloy extracts shows the potential effect of increased metabolite levels of AICAR (an activator of the AMPK pathway). We demonstrate a possible modulated secretion of AICAR and osteoclast differentiation from BMMs, which inhibits sensory innervation and postoperative pain through the AMPK/mTORc1/S6K pathway. Importantly, supplementing with AICAR in Mg-activated osteoclasts attenuates postoperative pain. These results suggest that Mg-induced postoperative pain is related to the osteoclastogenesis and sensory innervation at the early stage in the osteoporotic fractures and the SrHPO4 coating on Mg-based alloys can reduce the pain by upregulating AICAR secretion from BMMs or preosteoclasts.

Accelerating bone regeneration in cranial defects using an injectable organic-inorganic composite hydrogel.

Bone tissue engineering, as an important and attractive multidisciplinary field, affords a feasible strategy for large bone defects which are difficult to heal without clinical intervention. However, the complicated requirements of bone regeneration result in the imperfect performance of many current materials. Inspired by the composite nature of bone tissues, we proposed an organic-inorganic composite strategy. Specifically, we loaded a bone regeneration drug (simvastatin, SIM) and an inorganic component (strontium hydrogen phosphate (SrHPO4)/beta-tricalcium phosphate (β-TCP)) to a thermogel, constituted by poly(ε-caprolactone-co-D,L-lactide)-poly(ethylene glycol)-poly(ε-caprolactone-co-D,L-lactide) (PCLA-PEG-PCLA), with a thermo-induced sol-gel transition, to prepare an injectable composite for bone regeneration in cranial defects. The SIM/(Sr/β-TCP)/PCLA-PEG-PCLA composite was able to be conveniently injected and it spontaneously filled the defect. The appropriate mechanical strength obtained by thermogelation under the stimuli of the body temperature provided the necessary support while the capacity of loading drugs and bioceramics offered bioactivity and osteoinduction. In vitro drug release experiments demonstrated a gentle and sustained release of SIM for as long as 2 months, benefitting bone regeneration. The excellent capacity of promoting the formation of osteocytes was proved by cell differentiation assays. Furthermore, the enhanced bone regeneration capacity was verified by the micro-CT results of rat cranial defects with implantation time. Based on our results, the organic-inorganic composite integrates the advantages of each component and is far beyond, thus it might serve as a promising material candidate for bone regeneration.

Conversion of Nastrophites to Fibrous Strontium Apatites and Their Crystallographic Characterization

Strontium apatite has attracted considerable attention from researchers in various disciplines, including the medical field, owing to its excellent biocompatibility and beneficial effects on enhanced bone regeneration. In addition to their chemical characteristics, morphological aspects of apatite crystals are of great importance because they can exert a significant influence on various biological functions. In this study, a versatile method for the synthesis of fibrous strontium apatite is developed for the first time. Highly crystalline strontium apatite nanofibers were prepared by alkaline hydrolysis of strontium hydrogen phosphate (SrHPO4) at ambient temperature via nastrophite (NaSrPO4) intermediates. Some strontium ions in the crystal lattice of strontium hydrogen phosphate were substituted with barium (Ba) ions with various molar ratios up to Ba/Sr = 5/5, and their molar ratios were retained in the final products of the substituted fibrous apatites. The products, including hydrogen phosphates, nastrophites, and apatite nanofibers, were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), wavelength dispersive X-ray fluorescence (WDX) analysis, and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). These analyses verified the integrity of the speculated structures of the fibrous apatites. The lattice parameters of apatites and other intermediates were calculated using a newly developed calculation process based on the least-squares method and the results were compared to those of EXPO2014.

The formation of strontium apatites through alkaline hydrolysis of strontium hydrogen phosphate and their crystallographic characterization

Pure and carbonate- or silicate-substituted strontium apatites (i.e., SrHAP, SrCAP and SrSiP) were synthesized via alkaline hydrolysis of strontium hydrogen phosphate using sodium hydroxide, carbonate, and metasilicate, respectively. Zinc substitution in SrSiP was performed by an ion exchange reaction to yield SrZnSiP. Characterization of these strontium apatites was carried out by powder XRD, Fourier-transform infrared (FTIR) spectroscopy, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), SEM- Energy dispersive X-ray spectroscopy (EDS), FE-SEM and TEM- Selected Area Electron Diffraction (SAED). From elemental analyses, the Sr/P ratios of all samples were found to be around 1.5, suggesting that these are strontium-deficient apatites. From FTIR analysis, presence of both the structural OH group and the HPO4 group could not be confirmed. Crystal morphology strongly depends on the pH during sample preparation. At high pH, bundles of spindle-like nanocrystalline SrHAP, SrSiP and SrZnSiP were produced, whereas at lower pH, cubical crystallite of SrCAP with increased crystallinity was formed. Powder XRD analysis revealed the effects of these substituents on the hexagonal lattice parameters which agreed well with the known dependence for the corresponding substituted hydroxyapatite. The relationship between the lattice parameters a and c for calcium to barium hydroxyapatite groups collected from various studies together with our data, showed a universal linear relationship represented by the following equation, c = 1.1348a −3.8043 with a coefficient of determination (R2) of 0.9982. Dissolution behavior of SrZnSiP in pure water was investigated by the surface coating on β-TCP disc. For over 24 days, Sr, Si and Zn ions were released constantly within moderate concentration ranges.

Heat treatment effect on the structure and morphology of strontium monoacid orthophosphate thin films

Abstract Highly crystalline β-type strontium hydrogen phosphate (β-SrHPO4) thin films were prepared by a simple electrodeposition method. Their composition and morphology were investigated via X-ray diffraction (XRD) and a scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy system (EDX). It was found that both the structure and the morphology of the thin films were changed as a reason of a heat treatment at 600 °C.

Crystallization process and growth mechanism for hexagonal prism of strontium hydroxyapatite by urea hydrolysis

Strontium hydroxyapatite (SrHAp) is not only used as drug carrier material for bone disease treatment, but also has application prospect in bone tissue engineering. But SrHAp is prepared with by-products strontium hydrogen phosphate (SrHP) and strontium phosphate (TSrP), which requires accurate process optimizations and adjustments to circumvent the undesirable morphology products. The integral hexagonal prism crystals of SrHAp were successfully synthesized by urea hydrolysis at ambient pressure and without any strong acids and bases. Similarly, variable by-products are classified and investigated for their effects on crystallization process of strontium hydroxyapatite via monitoring the urea hydrolysis time-dependent products. The crystallization process of SrHAp can be divided into four stages based on the crystallographic results for the samples acquired by XRD and SEM studies during the entire synthesis processes. In the first stage, SrHP is formed (0–0.17 h); secondly, SrHP is converted into SrHAp (0.17–4 h); TSrP is obtained (4–8 h) at the third stage; and at last, TSrP is transformed into SrHAp (8–24 h), especially the amount of SrHAp obtained at 24 h was the sum of the second and fourth stages. Simultaneously, the growth mechanism of SrHAp crystals was proposed, considered of the formation energy of Gibbs-Thomson crystal plane and Born-Lande lattice energy. By calculating the interfacial energy γ(h k l) of different crystal planes, the γ(1 0 0) of hexagonal prism plane family m{1 0 0} is 1.3 × 10−5U0, the γ(0 0 1) of parallel double-plane family c{0 0 1} is 7.5 × 10−6U0, the normal growth rate of Ic{0 0 1} ≫ Im{1 0 0}. Accordingly, the growth mechanism for the preferential c axis growth maintaining the hexagonal prism shape is derived.

A two-step reaction to prepare a fast-hardening strontium-calcium phosphate scaffold in room temperature

Objective To evaluate a fast-hardening strontium-calcium phosphate scaffold using a two-step reaction in room temperature. Methods The original powder phase consisted of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and strontium hydrogen phosphate (DSPA). The liquid phase consisted of 20wt% citric acid and 12wt% polyvinylpyrrolidone K-30. Groups were designed as Sr-0, Sr-5, Sr-10, and Sr-20, according to the molar ratios of Sr/(Sr+Ca) being 0, 5%, 10%, and 20% in the powder phase, respectively. The ratio 0.5 mL/g in the liquid to solid phase was used for mixing. After the scaffold was prepared, its setting time, compression strength, phase composition and structural morphology, ions release and pH value of the substrates were analyzed. Results Addition of citric acid accelerated the setting reaction. Acceptable setting time was achieved by optimizing composition of the original powder and liquid phases. On the other hand, the compression strength, phase composition and structural morphology were not affected by addition of strontium. In addition, calcium and strontium ions were detected in the substrates, without any significant change in the pH value. Conclusion This two-step reaction can be used to prepare a fast hardening strontium-calcium phosphate scaffold in room temperature. Key words: Strontium; Calcium phosphates; Hydroxyapatites; Setting time

Facile Synthesis of β-SrHPO4 with Wide Applications in the Effective Removal of Pb2+ and Methyl Blue

A facile synthesis routine of β-type strontium hydrogen phosphate (β-SrHPO4) nanosheets was provided by the method of solution growing at temperatures below 80 °C. β-SrHPO4 was utilized for removing lead ions (Pb2+) and adsorbing methyl blue. Within the pH values from 2.0 to 6.0 of lead solutions, the adsorption capacity of β-SrHPO4 could reach above 1000 mg·g–1. The maximum removal capacity was 1409 mg·g–1 for Pb2+ within 15 min at pH = 4.5 and remained stable with the increase of temperatures. Different cations (Zn2+, Cr3+, Cd2+, and Co2+) affected slightly on the adsorption of Pb2+. It is revealed that the adsorption mechanism of Pb2+ was based on dissolution–precipitation theory. The maximum adsorption capacity was 335.68 mg·g–1 for methyl blue. The adsorption data of methyl blue accorded with the Langmuir isotherm model with R2 = 0.994 and the pseudo-second-order kinetic model with R2 = 0.99996, showing that the removal of methyl blue was dominated by a chemical sorption process. The thermodynamic st...

Synthesis of 1,4-Diazabicyclo [2,2,2] Octane with Alkaline Earth Phosphate Catalysts

Here we report on the discovery and development of a new catalyst based on strontium hydrogen phosphate for efficient production of DABCO, 1,4-diazabicyclo [2,2,2] octane. It was brought from initial lab scale discovery to commercial use in less than 1 year. It provides significant value for production of DABCO via much higher selectivity and nearly double the productivity of the silica–alumina material used as the previous commercial catalyst. The value is not only in higher observed productivity but also in large savings in feedstock costs derived from the improved reaction selectivity and also a much longer effective useful lifetime than the previous silica–alumina.

Do Textiles Impact DXA Bone Density/Body Composition Results?

Osteoporotic patients treated with strontium ranelate show relatively large increases in bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) due to the replacement of some of the calcium atoms in bone by strontium. A study published by Pors Nielsen and colleagues reported that replacement of 1% of calcium atoms by strontium causes a 10% increase in BMD. We refer to the ratio of the percentage increase in BMD to the molar percentage of strontium in bone as the strontium ratio. Theoretically it is expected that the strontium ratio should vary between different manufacturers' DXA equipment depending on the effective photon energy of the device, an effect that arises because of the proximity of the X-ray energies produced by lower energy devices to the strontium K-edge at 16 keV. In this study we report theoretical estimates of the strontium ratio for two axial DXA systems and two peripheral DXA devices based on their broad spectrum X-ray emission. The theoretical figures were verified in an experimental study in which the strontium ratio for each device was measured using phantoms containing mixtures of hydroxyapatite and strontium hydrogen-phosphate. The theoretical values of the strontium ratio were 11.0 for the Hologic Discovery, 9.9 for the GE-Lunar Prodigy, 9.1 for the Demetech Calscan, and 8.5 for the Osteometer Dexacare G4. Experimental results were 11.2 for the Discovery, 9.9 for the Prodigy, 8.6 for the Calscan and 6.3 for the Dexacare G4. The results confirm both theoretically and experimentally that the effect of bone strontium on BMD measurements is different for different DXA systems. In the future it might be possible to exploit this effect to make a non-invasive estimate of average bone strontium content in groups of patients receiving strontium medication for osteoporosis.

Synthesis of β-type Strontium Hydrogen Phosphate Nanosheets and Its Immobilization of Pb2+ in Acidic Aqueous Solution

Highly crystalline β-type strontium hydrogen phosphate (β-SrHPO4) nanosheets were prepared by a hydrothermal method and used for the immobilization of lead ions (Pb2+) from acidic aqueous solution. The effects of various parameters on the immobilization process, including solution pH value, contact time, initial ion concentrations, and coexistent competing cations, were studied to optimize the conditions for maximum immobilization. The β-SrHPO4 nanosheets exhibited a capacity of (1,120 ± 22) mg/g toward Pb2+ in acidic solution (pH value is 3.0), and the equilibrium was achieved within 8 min. The competing cations such as Cu2+, Zn2+, Cd2+, and Co2+ affected slightly on the selective immobilization of Pb2+. The results revealed that the removal mechanism of Pb2+ by the β-SrHPO4 nanosheets was the dissolution/precipitation process in the acidic solution.

Inserting of strontium during coating of hydroxyapatite compound on titanium substrate

For the first time, strontium hydrogen phosphate, SrHPO4 (SrHP) with or without brushite (dicalcium phosphate dihydrate CaHPO4.2H2O) is electrocrystallised on titanium substrate by electrochemical deposition technique. SrHP is converted to strontiumapatite, Sr10(PO4)6(OH)2. Different Ca substitution percentages by Sr were applied ranged from 0% to 100%. The electrolyte was 0.167 M CaCl2, 0.167 M SrCl2 and 0.1 M NH4H2PO4. The results showed that at all Sr substitution percentages (0%–100%) and at coating time of one hour, the coating layer is brushite or strontium hydrogen phosphate at 100% Ca substitution by Sr. Furthermore, with increasing Ca substitution by Sr percentages from 0% to 100%, the coating thickness is significantly decreased. Moreover, with increasing Ca substitution by Sr percentages (0%–100%), the morphology and composition are changed. Thickness and weight gain are decreased with sodium hydroxide treatment.

The effect of bone strontium on BMD is different for different manufacturers' DXA Systems

Osteoporotic patients treated with strontium ranelate show relatively large increases in bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) due to the replacement of some of the calcium atoms in bone by strontium. A study published by Pors Nielsen and colleagues reported that replacement of 1% of calcium atoms by strontium causes a 10% increase in BMD. We refer to the ratio of the percentage increase in BMD to the molar percentage of strontium in bone as the strontium ratio. Theoretically it is expected that the strontium ratio should vary between different manufacturers' DXA equipment depending on the effective photon energy of the device, an effect that arises because of the proximity of the X-ray energies produced by lower energy devices to the strontium K-edge at 16 keV. In this study we report theoretical estimates of the strontium ratio for two axial DXA systems and two peripheral DXA devices based on their broad spectrum X-ray emission. The theoretical figures were verified in an experimental study in which the strontium ratio for each device was measured using phantoms containing mixtures of hydroxyapatite and strontium hydrogen-phosphate. The theoretical values of the strontium ratio were 11.0 for the Hologic Discovery, 9.9 for the GE-Lunar Prodigy, 9.1 for the Demetech Calscan, and 8.5 for the Osteometer Dexacare G4. Experimental results were 11.2 for the Discovery, 9.9 for the Prodigy, 8.6 for the Calscan and 6.3 for the Dexacare G4. The results confirm both theoretically and experimentally that the effect of bone strontium on BMD measurements is different for different DXA systems. In the future it might be possible to exploit this effect to make a non-invasive estimate of average bone strontium content in groups of patients receiving strontium medication for osteoporosis.

Indium strontium hydrogen phosphate SrIn2[PO3(OH)]4: Synthesis and crystal structure

Indium strontium hydrogen nitrate SrIn2[PO3(OH)]4 was synthesized under mild hydrothermal conditions (T = 180 or 200°C) and characterized using IR spectroscopy, chemical analysis, and thermal analysis. A structure model obtained ab initio was refined by the Rietveld method: a= 9.6412(1) A, b = 13.763(1) A, c = 9.3579(1) A, Robs = 0.0183, Rp = 0.0493 (space group B2212, Z = 4). The acentricity of the structure was confirmed by SHG tests (I2ω/I2ω(SiO2) ≈ 2.0). In the SrIn2[PO3(OH)]4 structure, indium atoms reside in distorted InO6 octahedra and form, together with PO3(OH) tetrahedra, a mixed 3D structure {In2[PO3(OH)]4}3∞2− whose voids are occupied by Sr2+ cations (CN = 8). The block-dimer In2(HPO4)10 is the most informative unit of the framework. Blocks are condensed into infinite columns running in the [101] direction. The compound is thermally stable up to 400°C.

Preparation and Characterization of a New Type of Sr-Contained Hydroxyapatite Bone Cement

A novel route is developed to prepare a new type of Sr-contained hydroxyapatite bone cement. Tetracalcium phosphate, strontium hydrogen phosphate or anhydrous strontium chlorite, dicalcium phosphate, phosphoric and water are used as precursors. XRD, FTIR and EDXS are used to characterize the incorporation of 5% or 10% Sr2+ into the crystal lattice of hydroxyapatite. Results indicate that the Sr-contained CPC system of TTCP/DCPA/DSPA can set in 0.5M diluted phosphate acid with a final product of non-stoichiometric Sr-contained hydroxyapatite.

Development of a strontium-containing hydroxyapatite bone cement

A new route was developed to synthesis a new type of strontium-containing hydroxyapatite (Sr-HAP) bone cement with precursors of tetracalcium phosphate (TTCP), strontium hydrogen phosphate (DSPA), dicalcium phosphate (DCPA), phosphate acid and water. The processing parameters and fundamental properties including pH value, setting time, compressive strength of final hardened body and the cytotoxicity for serial extracts of each cements were investigated. The result shows that the final product of the cement after setting for 24 h is nonstoichiometic Sr-containing hydroxyapatite (Ca 10− m − x Sr x □ m (HPO 4) y (PO 4) 6− y (OH) 2−2 m □ 2 m , 0< x<1, nSr-HAP) and no other harmful impurities were detected. The pH value of Sr-containing cement pastes approaches to 7.0–7.6 when they are mixed with a ratio of 1:1 of powder to liquid ( P/L) in weight. The setting time of the cement pastes is 4–11 min for the initial one and 10–17 min for the final one when the concentration of diluted phosphate is in a range of 0.5–1.0 mol/l. The compressive strengths of the hardened cements with different molar ratios of Sr/(Sr+Ca) after subjected an immersion in simulated body fluid (SBF) increase uniformly from 1 day to 5 days, where they get maximum values, respectively, but then decrease till to 2 weeks. Especially for the CPC-1, with a Sr/(Sr+Ca) molar ratios of 5% in cement powder composition, the largest compressive strength gained at 5 days is 66.57 MPa and the lowest one gained at 2 weeks is 44.75 MPa, which matches the value of human bones and can be expected to use in clinic application in repairing the nonloading sites on account of the positive result of cytotoxicity test of the extracts of Sr-containing calcium phosphate cement (Sr-CPC).

Solubilization of metal phosphates by Rhizoctonia solani

The effects of different temperatures and pH on the growth and solubilization of insoluble calcium phosphate, cobalt phosphate, manganese phosphate, strontium hydrogen phosphate and zinc phosphate by Rhizoctonia solani on solidified media were assessed. Solubilization of the metal phosphates was monitored by the production of a clear zone around or underneath the fungus. R. solani efficiently solubilized all five metal phosphates except cobalt phosphate when grown on medium at pH 7. Solubilization activity by R. solani decreased with increasing pH on medium containing calcium phosphate but increased on strontium hydrogen phosphate-amended medium. The uptake of metals by the mycelia was unaffected by the pH of the medium or the growth temperature. Small quantities of crystals were produced in the agar when R. solani was grown on calcium phosphate- and strontium hydrogen phosphate-amended media and these were identified as calcium or strontium sulphates respectively: there appeared to be little or no production of insoluble oxalates although a role for oxalate in the overall solubilization process cannot be discounted. These results are discussed in relation to their physiological and environmental significance, and the important roles of fungi in effecting transformations of insoluble metal-containing compounds in the environment.

Investigation of the Alkaline Earth Phosphates: Crystal Structure of a New Strontium Hydrogen Phosphate Form

Investigation of the Alkaline Earth Phosphates: Crystal Structure of a New Strontium Hydrogen Phosphate Form

Investigation of the Alkaline Earth Phosphates: Synthesis and Crystal Structure of a New Strontium Hydrogen Phosphate Form

The hydrothermal synthesis, initial characterization (EDX analysis, IR, X-ray powder pattern), and X-ray single-crystal structure are reported for a new form of strontium hydrogen phosphate (γ-SrHPO4). The cell is orthorhombic, space group Pbca (No. 61) with a=8.131(3) Å, b=9.258(5) Å, c=18.084(7) Å, V=1361.31(2) Å3, and Z=16. The structure was determined from 1272 observed reflections to a final R value of 0.039. The atomic arrangement consists of two kinds of anionic layers (P(1) and P(2)) lying parallel to (001), formed by closed dimers and infinite chains of H-bonded HPO2−4 groups, respectively. These sheets are linked to each other via Sr2+ cations. Comparison to the crystal structure of CaBa(HPO4)2 is also given, the two compounds exhibiting the same arrangement.

Crystal Structure of Sr-Substituted Hydroxyapatite Synthesized by Hydrothermal Method

Single crystals of Sr-substituted hydroxyapatite, (Ca9.42Sr0.18 H0.8(PO4)6(OH)2, up to 0.2 × 0.2 × 5 mm3 maximum size were grown hydrothermally from calcium hydrogenphosphate (CaHPO4) and strontium hydrogenphosphate (SrHPO4) in a long tube-type autoclave using a temperature gradient technique. The single crystals, containing 1.92 mole% Sr to (Ca + Sr) and having a (Ca + Sr)/P atomic ratio of 1.60, had a hexagonal-prismatic shape with density of 3.207 g/cm3. The crystal had a hexagonal system, space group P63/m with a = 9.3920(7) Å, c = 6.890(1) Å, and Z = 1. A hexagonal-prismatic crystal, 165 × 165 × 231 μ3 in size, was used for crystal structure refinement. The atomic parameters in P63/m were refined to R = 5.9% and RwÅ = 6.3% with 2018 independent reflections. The preferential substitution site of Sr for Ca was determined as the Ca(1) site.