Strontium Ion Concentration Research Articles

Impact of Strontium, Magnesium, and Zinc Ions on the In Vitro Osteogenesis of Maxillary Sinus Membrane Stem Cells.

Human Maxillary Sinus Membrane Stem Cells (hMSMSCs) contribute significantly to bone formation following maxillary sinus floor augmentation (MSFA). The biological behavior of mesenchymal stem cells is notably influenced by varying concentrations of magnesium (Mg2+), strontium (Sr2+), and zinc (Zn2+) ions; however, their specific effects on hMSMSCs have not been comprehensively studied. We isolated hMSMSCs and identified their mesenchymal stem cell characteristics by flow cytometry and multilineage differentiation experiments. Subsequently, the hMSMSCs were cultured in media containing different concentrations of these metal ions. The proliferation and viability of hMSMSCs were assessed using CCK-8 and Calcein AM/PI staining. After osteogenic induction, cells were evaluated for alkaline phosphatase (ALP) activity, ALP staining, and Alizarin Red staining. Additionally, qRT-PCR was used to detect differences in osteogenic gene expression, and immunofluorescence staining was used to observe variations in OCN protein levels. The results indicated that 1 mM Mg2+, 0.01 mM Sr2+, and 0.001 mM Zn2+ significantly improved the proliferation and activity of hMSMSCs. These concentrations also notably enhanced ALP secretion, increased bone-related gene expression, and augmented osteocalcin expression and formation of extracellular calcium nodules, thereby improving osteogenic differentiation. However, higher concentrations of Mg2+, Sr2+, and Zn2+ decreased cell viability and osteogenic differentiation. Mg2+, Sr2+, and Zn2+ promote osteogenic differentiation and proliferation of hMSMSCs in a concentration-dependent manner, indicating that the type and concentration of ions in the extracellular environment can significantly alter hMSMSCs behavior, which is a crucial consideration for material design in maxillary sinus elevation applications.

Adsorption and safe immobilization of Sr ions in modified zeolite matrices

In the present study, an Iranian natural zeolite (Sabzevar region) was evaluated as a natural adsorbent for the elimination and immobilization of strontium ions from an aqueous solution. For improving the adsorption efficiency of strontium ion, the zeolite surface was modified by the Schiff base ligand of bis (2-hydroxybenzaldehyde)1,2-diaminoethane (H2L). The natural zeolite and zeolite/H2L were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET and scanning electron microscope (SEM). Analysis of the natural zeolite showed that the zeolite is from the type of clinoptilolite and has a crystalline structure with the specific surface area 29.74 m2/g. The results showed that strontium adsorption onto modified zeolite increases compared to unmodified zeolite from 64.5% to 97.2% (at pH = 6). The effective parameters pH, adsorbent dosage, initial concentration of strontium ions, contact time, temperature, and interfering ions, were studied and optimized. The maximum adsorption efficiency was confirmed by modified zeolite and found to be 97.5% after 60 min of equilibrium time at pH 6, 0.05g as adsorbent dosage, and at 25 °C. Adsorption of strontium was confirmed by Langmuir model with maximum adsorption capacity of 10.31 mg/g. Kinetic studies showed that the adsorption of strontium ions on the adsorbent follows pseudo-second-order (PSO) model. Also, the thermodynamics of the adsorption process indicated that the adsorption of strontium on zeolite/H2L is an endothermic and spontaneous process, and the adsorption mechanism is a combination of physical and chemical adsorption. Finally, to manage the secondary waste generated from the adsorption process, strontium ions were immobilized in a zeolite structure. The results showed that the stabilization is well done with the thermal preparation process. After thermal treatment at 25–900 °C, modified zeolite satisfactorily retains strontium during back-exchange tests with NaCl solution. According to the results, the amount of strontium released from the adsorbent phase decreases from 52.6 to 1.6% with increasing heat treatment temperature.

PH, Ion Release Capability, and Solubility Value of Premixed Mineral Trioxide Aggregates

The current study aimed to compare the pH, solubility value, and ion release capability of premixed mineral trioxide aggregates (MTAs) versus conventional pulp capping materials before and after setting. The following materials were used: resin-modified calcium silicate cement (TheraCal LC<sup>®</sup>, TLC), resin-modified calcium hydroxide cement (Ultra-Blend<sup>TM</sup> plus, UBP), and 2 kinds of premixed MTA (Endocem MTA<sup>®</sup> premixed regular 〔EMPR〕 and Well-Root<sup>TM</sup> PT 〔WRP〕). The specimens of each material were prepared before and after setting and were immersed in distilled water. The materials’ pH and solubility value were assessed. Next, three kinds of ion (calcium, sulfide, and strontium) released by pulp capping materials were evaluated via inductively coupled plasma atomic emission spectrometry. In the after-setting group, the pH of TLC and UBP decreased. However, the pH of the premixed MTAs increased with time. TLC released a higher concentration of strontium ion compared with the other materials. Meanwhile, EMPR released a significantly high concentration of sulfide ion (<i>p</i> < 0.05). In the after-setting group, the 2 kinds of premixed MTAs released a significantly higher concentration of calcium ion compared with the other materials (<i>p</i> < 0.05). In the after-setting group, EMPR had a significantly low solubility value (<i>p</i> < 0.05). The Kruskal-Wallis test, followed by the Mann-Whitney U test with Bonferroni correction, was used in statistical analysis. In conclusion, resin-modified calcium silicate cement, modified calcium hydroxide cement, and the 2 kinds of premixed MTAs had an alkaline pH and low solubility value and they released various concentrations of ions after setting.

Photosynthesis and growth of Amaranthus tricolor under strontium stress

Amaranthaceae are effective plants for cleaning soil contaminated by heavy metals and radionuclides. In this paper, Amaranthus tricolor was used to investigate the response of the plant photosynthesis to various concentration of strontium ions (0.2, 0.6, 3 and 6 mM), in order to determine the possibility of A. tricolor to remediate strontium contamination. The results showed that strontium ions (0.2–6 mM) had effect on light energy conversion and utilization in A. tricolor. Low level of strontium (0.2 mM) promoted the energy utilization in A. tricolor, while higher Sr concentration (3 mM or higher) increased the excess light energy in the plants. Under strontium stress of 6 mM, the acceptor side of PSII in A. tricolor leaves was more vulnerable to strontium stress than the donor side. Furthermore, strontium stress led to accumulation of QA− and block in QB downstream of the electron transfer chain in PSII of A. tricolor leaves. The tolerance ability of A. tricolor to strontium and remediation is also reflected in its biomass and strontium content in plants. Strontium at 3 mM or below promoted the growth of A. tricolor, while higher concentration inhibited the plant growth, but without obvious wilting or curling of leaves. The maximal dry weight increased by 36.29% in shoots, and 60.14% in roots when the spiked-strontium concentration reached 0.2 mM. The maximal strontium content achieved 8.75 mg/g dry wt in shoots, and 1.71 mg/g dry wt in roots respectively, when strontium concentration was 6 mM. Transfer factors (TFs: ratio of Sr content in shoots to that in roots) of strontium in A. tricolor ranged from 2.85 to 5.93, while bio-concentration factors (BCFs: ratio of Sr content in shoots to that in solutions) ranged from 22.57 to 49.66. In summary, A. tricolor showed the excellent potential to remediate strontium contamination.

Polypyrrole-BaFe2O4 sensing layer for detection of strontium ion in aqueous solution using surface plasmon resonance curves fitting

The low concentration of strontium, calcium, and barium were measured with a surface plasmon resonance curve fitting technique. Polypyrrole-BaFe2O4 nanocomposite was prepared using electro-polymerization of pyrrole in the presence of magnetic nanoparticles. The thickness of the layer in the range of 6.3 and 62.2 nm the analytical methods such as Fourier transform infrared spectroscopy, energy dispersive spectroscopy, and field emission scanning electron microscopy authenticated the polypyrrole-BaFe2O4 nanocomposite formed on the surface of the gold layer. The prepared layers were used to detect and measure the low concentration of strontium, calcium, and barium ions in aqueous solution using surface plasmon resonance technique and the optical parameter, angle of resonance, resonance angle shift and affinity constant were achieved using curve fitting based on minimizing the sum of squared errors. Consequently, the degree of adsorption for the detection of strontium is about 91.3%, and the sensitivity of the polypyrrole-BaFe2O4 nanocomposite layer for the detection of strontium is about 0.006° that is more than other ions.

Insights into the Composite Scale Formation and Coprecipitation Behavior of CaSO4 and SrSO4 at different salinity level

The dependency of the calcium sulfate (CaSO4) deposit formation on the presence and concentration of co-precipitating ions, is a fundamental question to the advancement of crystallization science. In this paper, the thermodynamics and kinetics of the static precipitation of 47.5 mM calcium sulfate, in isolation and presence of strontium sulfate (SrSO4) as common co-crystallizing salt, are examined at 30°C. The deposition of pure and composite sulfate scales is studied by varying the salinity of the medium from 0.35 to 1.50 M NaCl. To evaluate the effect of the co-precipitating, strontium ion concentration was altered from 0 to 20.0 mM. In order to elucidate the crystallization mechanism in terms of reaction rate and extent, the concentration of the free scaling ions, including that of Ca2+, SO42− and Sr2+, is systematically monitored at different intervals until equilibrium is achieved. Moreover, crystal deposits collected at regular intervals from the isothermal incubation experiments are characterized for changes in their microstructure, morphology, and elemental distribution, to establish correlations with the data obtained on the evolution of the solution composition. The analysis of the crystallographic properties of the deposits substantiates the dependency of the thermodynamics and kinetics of the CaSO4 precipitation process on the salinity and co-existence of supersaturated SrSO4 in the mixture. Particularly, the morphology of calcium sulfate deposits is altered in the presence of SrSO4, which corroborates the assumption of co-crystal interactions. These results indicate that heterogeneous crystal nucleation and growth of the mixed salts can be prompted at temperatures and salinity conditions as low as 30°C and 0.35 M, when the concentration of Sr2+ is increased up to 20.0 mM. Using the Pitzer model derived ion activity coefficients, discrepant thermodynamic solubility product constant (Ksp) values are also determined for the pure salts when these co-precipitate in mixed systems. Reaction kinetics for calcium sulfate crystallization is also highly sensitive to the ionic strength effect as well as to the presence and concentration of strontium ions. Accordingly, these observations confirm the need to account for both contributing and non-contributing ions in assessing the thermodynamics and kinetics of crystal formation.

The structural and bioactive behaviour of strontium-doped titanium dioxide nanorods

In the present work, various concentrations of strontium ions loaded titanium dioxide nanorods and common titanium dioxide nanorods (control) were synthesized by electrochemical anodization technique to get the implant with superior bioactivity. Cell viability and antibacterial efficacy studies were estimated using MTT assay and solid agar medium. The characterisation results confirmed that Sr2+ was successfully incorporated into TiO2 nanorods. Compared with common TiO2 nanorods (control), Sr2+ loaded TiO2 nanorods showed higher surface roughness, adhesion strength, and water wetting angle. MTT assay showed better cell response on Sr-TiO2 nanorod surface as compared to control and the antibacterial test showed that Sr2+ loaded TiO2 nanorods have superior antibacterial activity against pathogenic bacterial strain E. coli and S. aureus. Sr2+ incorporated TiO2 nanorod arrays can be used as a potential candidate for hard tissue implant applications.

Sorption of cesium and strontium ions by natural zeolite and management of produced secondary waste

The aim of this work is sorptive removal of cesium and strontium ions from aqueous solution using natural zeolite and management of produced secondary waste. Characterization of the natural zeolite was performed by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), and field emission scanning electron microscopy (FE-SEM). The effective parameters on the sorption process such as initial solution pH, adsorbent dosage, and concentration of cesium and strontium ions were optimized by using experimental design method. Based on the results, removal efficiency for cesium ion was about 67.8% at the optimum condition of adsorbent dosage of 0.40 g, pH = 7.23 and Cs+ concentration of 10 mg L−1, and for the strontium ion was about 93.5% at the optimum condition of adsorbent dosage of 0.3 g, pH = 7.9 and Sr2+ concentration of 10 mg L−1. Kinetic studies showed that the removal process follow pseudo-second-order kinetic model for both ions. The sorption results showed that the data for cesium and strontium ions were fitted by Freundlich isotherm better than Langmuir isotherm. Finally, to manage secondary waste produced from the sorption process, the cesium and strontium ions stabilized in zeolite structure and related tests such as compressive strength and leaching were evaluated. The results of waste management section showed that the stabilization process was performed as well by heat preparation process.

Preparation and ion exchange studies of cesium and strontium on sodium iron titanate

Sodium iron titanate (NaFeTiO) inorganic ion exchanger was synthesized and the ion exchange behaviour of cesium, strontium and europium ion on NaFeTiO was studied. The sodium iron titanate was prepared by the hydrolysis of tetraethyl ortho titanate with sodium hydroxide in the presence of ferric chloride at the Ti/Fe mole ratio of 25.7. The ion exchange material was characterized by elemental analysis, sodium exchange capacity, X-Ray diffraction, thermogravimetry, and Raman spectroscopy. The distribution coefficient (Kd, mL/g) of cesium, strontium and europium on NaFeTiO was measured as a function of pH of the aqueous phase, duration of equilibration, concentration of sodium, cesium, strontium and europium ion in aqueous phase. The Kd of cesium gradually increased with increase of pH, and that of strontium also increased up to pH 6 followed by saturation in Kd values. However, the distribution coefficient of europium increased up to pH 4 followed by the precipitation of europium at higher pH values. The rate of ion exchange of cesium and strontium on NaFeTiO was rapid in the initial stages of equilibration followed by the establishment of equilibrium occurring after 200 min. The kinetics of extraction was fitted in to pseudo-first order and -pseudo-second order rate equations. The NaFeTiO was found to follow the ion exchange mechanism, in which the sodium ion from NaFeTiO was exchanged with cesium or strontium ion from aqueous phase. The strontium exchange capacity on NaFeTiO was determined to be 233 mg g−1. The loaded metal ions was recovered using 0.5 M nitric acid.

Strontium ion reinforced bioceramic scaffold for load bearing bone regeneration.

Bone defects in load bearing areas require bone reconstruction with strong biomaterial having mechanical characteristics like cortical bone. Bioceramics are biomaterials that support bone formation as well as provide adequate mechanical properties. A strontium substitution of the bioceramic is expected to further increase its bioactivity by enhancing osteogenesis and protect the bone from osteoclastic resorption. The study involves development, characterization and in vivo testing of a newly developed strontium substituted hydroxyapatite based bioceramic scaffold (SrHAB) with sufficient biomechanical properties. Optimal concentration of strontium ion required for enhanced osteogenic differentiation was identified by comparing three compositions of SrHAB scaffold; namely Sr10HAB, Sr30HAB and Sr50 HAB for their Alkaline phosphatase activity in vitro. The selected Sr10HAB scaffold demonstrated in vivo bone formation with osteogenic differentiation of stromal derived mesenchymal stem cells (MSC) from human and ovine sources in ectopic and ovine models. Thus, Sr10HAB scaffold has a potential for application in load bearing bone requirements of orthopaedics and dentistry.

The Combined Effects of Sr(II) and Poly(Acrylic Acid) on the Morphology of Calcite.

Biomineralization of calcium carbonate has interesting characteristics of intricate morphology formation with controlled crystal polymorphs. In particular, modification of calcite morphology with diverse additives has been the focus of many biomimetic and bioinspired studies. The possible role of strontium ions in enhancing the morphology-modifying ability of macromolecules was investigated. In the present study, concentrations of strontium ions were comparable to that in seawater, and anionic poly(acrylic acid) and cationic poly(ethylene imine) were used as model macromolecules. When strontium ions were combined with anionic poly(acrylic acid), new types of calcite surfaces, most likely {hk0}, appeared to drastically change the morphology of the crystals, which was not observed with cationic poly(ethylene imine). This behavior of strontium ions was quite similar to that of magnesium ions, which is intriguing because both ions are available from seawater to be utilized during biomineralization.

Synthesis of DtBuCH18C6-coated magnetic metal–organic framework Fe3O4@UiO-66-NH2 for strontium adsorption

The selective adsorption of radioactive strontium is of great importance for environmental protection and human health. In this work, a novel adsorbent for removing strontium ions from aqueous solution was prepared by coating the crown ether 4ʹ,4ʹʹ(5ʹʹ)-di-tert-butyldicyclohexano-18-crown-6 (DtBuCH18C6) onto the porous magnetic metal–organic framework Fe3O4@UiO-66-NH2, which permitted convenient removal of the adsorbent using an external magnetic field. The structure of the synthesized DtBuCH18C6@Fe3O4@UiO-66-NH2 was characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, vibrating-sample magnetometry, and nitrogen adsorption/desorption analysis. The adsorption behavior was evaluated as a function of the HNO3 concentration and contact time and using two adsorption isotherm models. The maximum distribution coefficient values for strontium ions obtained in 7.0 mol L−1 HNO3 solution were 143 mL g−1 and 284 mL g−1 for strontium ion concentrations of 0.005 mg L−1 and 0.05 mg L−1, respectively. The adsorption of strontium ions by the adsorbent obeyed the Freundlich model. Our results indicate that functionalized magnetic metal–organic frameworks may have potential applications in strontium removal.

Development of multilayered biomimetic bone plates: In vitro release assessment

Abstract

Strontium ions promote invitro human bone marrow stromal cell proliferation and differentiation in calcium-lacking media.

In order to investigate the influence of calcium and strontium ion concentration on human bone marrow stromal cells and their differentiation to osteoblasts, different cell culture media have been used. Even though this study does not contain a bone substitute material, the reason for this study was the decrease of cation concentration by many biomaterials, due to induced apatite precipitation. As a consequence, the reduced calcium ion concentration is known to affect osteoblastic development. Therefore, the main focus was put on the question, whether an increased strontium concentration (in the range of mM) might be suitable to compensate the lack of calcium ions. The effect of solely strontium ions-with only calcium in the media resulting from fetal calf serum-was investigated. Commercially available calcium-free medium (modified α-MEM) was tested in comparison with media with varied calcium ion concentrations (0.9, 1.8, and 3.6mM), or strontium ion concentration (0.4, 0.9, 1.8, and 3.6mM). In case of calcium, higher concentrations cause increased proliferation, while differentiation was shifted to earlier points of time. Differentiation was increased by solely strontium ions only at 0.4-0.9mM, while proliferation was highest for 0.9-1.8mM. From these results, it can be concluded that strontium is able to compensate a lack of calcium to a certain degree. Thus, in contrast to calcium ion release, a strontium ion release from bone substitute materials might be applicable for stimulation of bone regeneration without influencing the media saturation.

Microbial Community and in situ Bioremediation of Groundwater by Nitrate Removal in the Zone of a Radioactive Waste Surface Repository.

The goal of the present work was to investigate the physicochemical and radiochemical conditions and the composition of the microbial community in the groundwater of a suspended surface repository for radioactive waste (Russia) and to determine the possibility of in situ groundwater bioremediation by removal of nitrate ions. Groundwater in the repository area (10-m depth) had elevated concentrations of strontium, tritium, nitrate, sulfate, and bicarbonate ions. High-throughput sequencing of the V3–V4/V4 region of the 16S rRNA gene revealed the presence of members of the phyla Proteobacteria (genera Acidovorax, Simplicispira, Thermomonas, Thiobacillus, Pseudomonas, Brevundimonas, and uncultured Oxalobacteraceae), Firmicutes (genera Bacillus and Paenibacillus), and Actinobacteria (Candidatus Planktophila, Gaiella). Canonical correspondence analysis suggested that major contaminant – nitrate, uranium, and sulfate shaped the composition of groundwater microbial community. Groundwater samples contained culturable aerobic organotrophic, as well as anaerobic fermenting, iron-reducing, and denitrifying bacteria. Pure cultures of 33 bacterial strains belonging to 15 genera were isolated. Members of the genera Pseudomonas, Rhizobium, Cupriavidus, Shewanella, Ensifer, and Thermomonas reduced nitrate to nitrite and/or dinitrogen. Application of specific primers revealed the nirS and nirK genes encoding nitrite reductases in bacteria of the genera Pseudomonas, Rhizobium, and Ensifer. Nitrate reduction by pure bacterial cultures resulted in decreased ambient Eh. Among the organic substrates tested, sodium acetate and milk whey were the best for stimulation of denitrification by the microcosms with groundwater microorganisms. Injection of these substrates into the subterranean horizon (single-well push-pull test) resulted in temporary removal of nitrate ions in the area of the suspended radioactive waste repository and confirmed the possibility for in situ application of this method for bioremediation.

Strontium ion can significantly decrease enamel demineralization and prevent the enamel surface hardness loss in acidic environment

Strontium ion may play a role similar to calcium ion in enamel remineralization. The aim of this study was to investigate the effect of strontium ion concentration gradient on the demineralization of enamel. Citric acid and sodium citrate were used to prepare 16 different experimental acidic solutions with four different pH values (2.5, 3.5, 4.5, and 5.5) and four different strontium ion concentrations (0M, 10-4M, 10-3M, and 10-2M). Forty-eight human enamel samples were divided into 16 groups (n=3) and immersed into the 16 different acidic solutions for 3min. The phosphorus ion concentrations in 16 different acidic solutions were measured and compared. The enamel surface hardness was measured with a Vickers hardness tester. The energy dispersive spectrometer was used to detect the strontium ion content in the enamel surface. Addition the strontium ions to the acidic solution could reduce the dissolution of the enamel. At pH 3.5 and pH 5.5, significantly lower phosphorus ion concentrations were detected in the acidic solutions with the addition of 10-2M strontium ions. There was a less reduction of enamel surface hardness, while the strontium ion concentration increased in the acidic solution. At pH 2.5, the addition of 10-4M, 10-3M, or 10-2M strontium ions to the acidic solution resulted in a significant increase in the strontium ion content in the enamel surface. Strontium ion can decrease the dissolution of the enamel and prevent the enamel surface hardness loss in acidic environment.

Biosorption of strontium ions from aqueous solution using modified eggshell materials

Abstract Green composites emphasize renewable starting materials for better economy using biomass materials. Therefore, low-cost composite biosorbent was prepared by modification of eggshell material using heteropoly acid for removal of strontium ions from aqueous solution. The resulted composite was characterized and evaluated for the sorption process using the batch technique. Low concentration of strontium ions was used to evaluate the sorption sensitivity of the prepared composite. The obtained experimental results illustrated that the modification process of eggshell material enhanced the percent uptake from 49.9 to 95.7%. From kinetic studies, the sorption of strontium ions follows the pseudo-second-order kinetic model. The isotherm studies indicated that Langmuir is more applicable than Freundlich isotherm. Moreover, Dubinin–Radushkevich isotherm was studied. Thermodynamic studies revealed that the sorption process is spontaneous and has endothermic nature. Strontium ions can be desorbed from the modified eggshell using HNO3, desorption percent was found to be 96.4%; the results revealed the reusability of the modified eggshell for further sorption.

Calcium-deficient Hydroxyapatite as a Potential Sorbent for Strontium

A calcium (Ca)-deficient hydroxyapatite was investigated for its potential to remove Sr2+ from environmentally relevant water. We conducted sorption tests on solutions containing magnesium ion (Mg2+) and calcium ion (Ca2+) as competing cations at a strontium ion (Sr2+) concentration of 0.05 mmol/L. The Ca-deficient hydroxyapatite maintained a high Sr2+ sorption ratio of above 80% in the presence of Mg2+ and Ca2+ at the concentrations between 0.1 and 1.0 mmol/L, whereas the stoichiometric hydroxyapatite showed a lower ratio even in the presence of small amounts of Mg2+ and Ca2+ (72% for Mg2+ and 51% for Ca2+ at 0.1 mmol/L). For solutions with various Sr2+ concentrations between 0.01 and 10 mmol/L, Ca-deficient hydroxyapatite exhibited a higher Sr2+ sorption ratio than stoichiometric hydroxyapatite. The bonding states of Sr2+ on the Ca-deficient hydroxyapatite were evaluated by extended X-ray absorption fine structure measurements. The results indicated that there are specific sorption sites in Ca-deficient hydroxyapatite where Sr2+ is stably and preferentially immobilized.

Influence of Porous Spherical-Shaped Hydroxyapatite on Mechanical Strength and Bioactive Function of Conventional Glass Ionomer Cement

Glass-ionomer-cement (GIC) is helpful in Minimal Intervention Dentistry because it releases fluoride ions and is highly biocompatible. The aim of this study is to investigate the mechanisms by which hydroxyapatite (HAp) improves the mechanical strength and bioactive functioning of GIC when these materials are combined to make apatite ionomer cement (AIC). A conventional GIC powder was mixed with porous, spherical-HAp particles (HApS), crystalline HAp (HAp200) or one of two types of cellulose. The micro-compressive strengths of the additive particles were measured, and various specimens were evaluated with regard to their compressive strengths (CS), fluoride release concentrations (fluoride electrode) and multi-element release concentrations. The AIC was found to release higher concentrations of fluoride (1.2 times) and strontium ions (1.5 times) compared to the control GIC. It was detected the more release of calcium originated from HApS than HAp200 in AIC. The CS of the AIC incorporating an optimum level of HAp was also significantly higher than that of the GIC. These results suggest that adding HAp can increase the release concentration of ions required for remineralization while maintaining the CS of the GIC. This effect does not result from a physical phenomenon, but rather from chemical reactions between the HAp and polyacrylic acid of GIC.

Optical, electrical and magnetic properties of lanthanum strontium manganite La1-xSrxMnO3 synthesized through the citrate combustion method.

Generally, strontium-doped lanthanum manganites (LSM) are materials connected ordinarily as cathodes in the solid oxide fuel cell (SOFC). In this study, the structural, optical, electrical and magnetic properties of La1-xSrxMnO3 (x = 0.2, 0.5, 0.8) synthesized using an organic acid precursor strategy were investigated, based on using citric acid as a fuel. Evidently, the results disclosed that a pure single monoclinic LSM phase was obtained from the thermally treated precursors annealed at 1000 °C with an annealing time of 2 h. The microstructure of the formed sample relied on the Sr2+ ion content. Moreover, a good optical transparency of 45-60% in a wide range of wavelengths between 800 and 1800 nm for all samples substituted by Sr2+ ions was performed. The optical band gap energy was increased from 2.09 to 2.76 eV by increasing the Sr2+ ion molar ratios. The trend in the calculated refractive index, the high frequency dielectric constant (εα) and the static dielectric constant (ε0) of all the produced samples can be linked to an increase in the Sr2+ ion concentration. Moreover, the magnetic properties were enhanced with increasing Sr2+ ion content.