Ca Sites Research Articles

Shareability of antibacterial and osteoblastic-proliferation activities of zinc-doped hydroxyapatite nanoparticles in vitro.

Four types of zinc (Zn)-doped hydroxyapatite (Zn-HAp) nanoparticles were prepared using calcium nitrate tetrahydrate as an anti-sintering agent during calcination at 600°C for 1 hr, to prevent calcination-induced aggregation. The Zn content of the nanopowders was determined at 0, 4.3, 9.2, and 14.7% [Zn/(Ca + Zn) × 100] using inductively coupled plasma atomic emission spectroscopic analysis. Based on X-ray diffraction analysis, the products were shown to possess an apatite structure without other crystalline impurities. The cell parameters of Zn-HAp nanoparticles decreased with increasing of Zn content in the HAp structures. This tendency implies that Zn ions substituted for Ca sites in the HAp crystal lattices. To investigate the biological effects of Zn-HAp nanoparticles, cell proliferation activity of MC3T3-E1 osteoblasts and antibacterial activity against Escherichia coli were evaluated in vitro. According to the results obtained, Zn-HAp nanoparticles containing of 14.7% Zn ions was noticeable shown shareability of the conflicting activities at 0.1mg/mL.

The crystal chemistry and electrical properties of Fe doped Ca12Al14O33 (Mayenite)


 
 
 X-ray and neutron powder diffraction have been used to study the crystal chemistry of Fe doped mayenite (Ca12Al14-xFexO33). Solid- state synthesis was used to prepare Ca12Al14-xFexO33 where x = 0, 0.1, 0.2, 0.5 and 0.6 and the citrate gel route was used to prepare Ca12Al14-xFexO33 where x = 0, 0.05, 0.1, 0.2, 0.3 and 0.4. X-ray powder diffraction data indicate that samples with the same composition but synthesized by the citrate gel route were more likely to be phase pure than samples obtained by traditional solid-state synthesis. The refined lattice parameters were observed to increase with increasing Fe concentration, irrespective of the synthesis method. Refined neutron powder data confirm that Fe is going into Al site rather than Ca site. A 2-point probe was used to measure the electrical properties of the Fe doped citrate gel synthesized samples and showed that the resistivity increases for the Fe doped samples compared to the undoped mayenite.
 
 

High throughput synthesis and screening of zinc-doped biphasic calcium phosphate for bone regeneration

Introducing high throughput experimental/screening method into the elements-doped calcium phosphate is expected to greatly increase the efficiency of finding out the most effective doping range. In this work, biphasic calcium phosphate (BCP) was used as the doping matrix and zinc was chosen as the doping element. The zinc-doped BCP with gradient doping content (0–10.0 mol.%) were synthesized by a high throughput chemical precipitation method. The effects of doping content on the phase, structure, morphology and cytological responses of zinc-doped BCP were investigated comparatively. The results showed that BCPs with similar composition while different zinc doping content were successfully prepared, and zinc tended to enter the β-TCP structure by substituting calcium at the Ca(5) and Ca(4) sites. The zinc concentration in powder extracts rose steadily with increasing the doping content of zinc. However, a burst release of zinc in the BCPs into the extracts appeared when the zinc doping content was higher than 6 mol.% and resulted in cell apoptosis. Zinc doping could effectively promote the osteogenic differentiation of bone marrow mesenchymal stem cells and regulated the expression of inflammatory and tissue healing related genes in macrophages for proper doping contents. The in vitro most effective zinc doping content range and doping content was 2.0–2.8 mol.% and 2.4 mol.%, respectively. Furthermore, the most effective zinc doping content was verified by the in vivo osteoinduction experiment conducted in beagle dorsal muscle. This work provides a reference for figuring out the effective doping content range of element in calcium phosphate and paves the way for developing a more bioactive BCP material for bone tissue engineering.

Full-visible-spectrum lighting enabled by site-selective occupation in the high efficient and thermal stable (Rb, K)2CaPO4F: Eu2+ solid-solution phosphors

Tuning the luminescent properties of phosphors by crystal-site engineering is a good and efficient strategy for developing high-quality white light-emitting diodes (WLEDs). However, it is still challenging to modulate the cyan to red spectral emission in a single matrix and activator phosphor to obtain multicolor output and achieve full-visible-spectrum lighting. Herein, the strategy to manipulate site-selective occupation of Eu2+ activators by substituting the cation Rb+ with K+ is reported to obtain a versatile color output. The large-scale redshift regulation of emission spectrum from cyan to red was achieved in fluor-phosphate Rb2-yKyCaPO4F: 0.0085Eu2+ (R2-yKyCPOF: 0.0085Eu2+) (0 ≤ y ≤ 1.8) phosphors, which is designed by using Rb2CaPO4F: 0.0085Eu2+ (RCPOF: 0.0085Eu2+) cyan-emitting phosphor. The redistribution of Eu2+ ions in Rb1, Rb2, and Ca sites is achieved by introducing the cation K+ to substitute Rb+, and R2-yKyCPOF: 0.0085Eu2+ (0 ≤ y ≤ 1.8) is kept in the pure phase. Furthermore, the mixed phosphors of RCPOF: 0.0085Eu2+, RKCPOF: 0.0085Eu2+, and R0.2K1.8CPOF: 0.0085Eu2+ show excellent optical performance and good thermal stability. Full-visible spectrum lighting is successfully achieved with the combination of a 395 nm NUV chip and the blend of phosphor-converted WLEDs. The K+ substitution reported in this paper can support a project for warm WLEDs by manipulating the distribution of Eu2+ activator among different cation sites.

Effects of common ions on the flotation of fluorapatite and dolomite with oleate collector

In this study, the effects of common ions, especially Ca2+, on the reverse flotation of fluorapatite and dolomite in acidic conditions with NaOL collector were investigated using micro-flotation, zeta potential, contact angle, adsorption analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory-based first principal calculations. It is found that the dolomite flotation recovery was enhanced and the fluorapatite flotation was depressed by the addition of CaCl2 at pH 5. For dolomite, in the presence of CaCl2, the solubility of metal ions was increased, especially for Ca2+. The Ca and Mg sites exposed on the dolomite surface, increased the NaOL adsorption, thus, enhancing the dolomite flotation. However, the formation of Ca(H2PO4)2 species on fluorapatite surface inhibit its flotation.

Activation mechanism of calcium hydrolysate on the spodumene surface and its effect on the adsorption of collector

Calcium chloride is an important activator for spodumene flotation; however, its mechanism has been controversial. In this study, density functional theory (DFT) calculation was taken to investigate the adsorption of reagents from the atomic and electronic microscopic perspective, and the activation mechanism of calcium was discovered. Results show that the reaction of the O in the H2O with the Al on the mineral surface reduces the bonding strength between the collector and the Al sites, making spodumene recovery by flotation impossible in the absence of active ions. The Ca2+ can bond with two adjacent O atoms of the spodumene surface. However, the weak adsorption strength makes spodumene difficult to be activated effectively at neutral pH. The hydroxyl group in Ca(OH)+ and Ca(OH)2 strongly bonds with Al sites on the surface, significantly improving the adsorption strength of these components, and the adsorption strength of Ca(OH)2 is the highest. However, the Ca(OH)2 have a greater steric hindrance effect on the adsorption of the collector on the Al sites, resulting in the collector adsorbing on the Ca site of the spodumene surface in the bidentate adsorption form. Hence, Ca(OH)2 cannot effectively improve the flotation recovery effect of spodumene. After the Ca(OH)+ treatment, the O atoms of the collector bond with Ca and Al atoms on the surface, resulting in the great increase of collector adsorption strength. Thus, the species of Ca(OH)+ is the sole effective active component in spodumene flotation.

The substitution modulation on Ca site of CaTiO3 for transparent conductive oxides from first principles study

This work targets abundant and eco-friendly CaTiO3 as the host to perform the electronic modulation by inequivalent substitution, to address the current material limitation of transparent conductive oxides (TCOs). Through the effective assistance from universal structure predictor USPEX, a series of investigations around Ca1-xAxTiO3 (A = Na, Ag and Al) (0 ≤ x ≤ 1) is carried out, including phase transitions, the critical concentration of defect compensation, optimal recipes concluded from electronic structure and the ability of carrier transport. This approach attempts to boom the diversity of alternative perovskite-based TCOs, and opens a brand-new perspective to engineer the innovative material design for the sustainable TCOs demand.

Antisense oligonucleotides-Laden UiO-66@Au nanohybrid for enhanced radiotherapy against hypoxic tumor by dual-inhibition of carbonic anhydrase IX

Hypoxia-acquired radioresitance is considered to be a major factor responsible for the clinical failure of radiotherapy. Carbonic anhydrase IX (CA IX), a hypoxia-induced cell-surface enzyme involved in pH regulation of hypoxic solid tumors, has been acknowledged as a desirable target for cancer therapy. Herein, we developed a dual exogenous/endogenous CA IX inhibition strategy using core/satellite-like metal-organic framework (UiO-66)/gold nanoparticles (Au NPs) nanohybrids as a therapeutic platform for hypoxia-relief enhanced RT of triple negative breast cancer. The UiO-66 matrix supported the Au NPs generation in situ and would decompose inside tumor cells by the high-concentration phosphates to release p-phthalic acid (PTA), a original building skeleton of the UiO-66 matrix, to inhibit CA IX, while the decorated Au NPs served as radiosensitizers to potentiate the sensitivity of tumor cells to X-ray and yet provided active sites for CA IX antisense oligonucleotide (ASO) loading via formation of stable Au-S bond to knockdown CA IX. The dual inhibitory manner, exogenous inhibition from PTA and endogenous inhibition from CA IX ASO, largely alleviated the hypoxia-induced resistance and synergized with Au NPs-mediated radiosensitization to afford super therapeutic outcome in vitro and in vivo, supporting the feasibility of our synergistic RT strategy in hypoxic tumor management.

Hydroxyapatite and lead-substituted hydroxyapatite near-surface structures: Novel modelling of photoemission lines from X-ray photoelectron spectra

X-ray photoelectron spectroscopy (XPS) is one of the main tools for hydroxyapatite (HA) surface characterization in developing materials for biomedical and heterogeneous catalysis. Despite the XPS technique's potential to correlate binding energies with existing photo-emitter sites on near-surfaces, few previous studies analyzed this aspect for HA and metal-substituted HA surfaces. In this work, we theoretically reconstructed the XPS spectra of stoichiometric HA and lead-substituted hydroxyapatite (PbCaHA, Ca10-xPbx(PO4)6(OH)2; x = 2, 10) using a first-principles linear combination of atomic orbitals embedded cluster approach and periodic supercell band structures within the framework of Density Functional Theory (DFT). We take into account photoemission lines contributions from Ca(1), Ca(2), Pb(1) and Pb(2) sites located on surface and near-surface depths (up to ∼15 Å) along the (001) and (100) surfaces. The calculated DFT spectra of HA and PbCaHA were compared with high-resolution XPS spectra previously characterized by synchrotron X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). A combined theoretical and experimental approach enables decoding of the complex structure of HA and PbCaHA in XPS spectra. It was found that XPS binding energies profiles depend significantly on photo-emitters from near-surface sites and surface crystallographic orientation. The main Ca 2p3/2 envelope peak in HA is predominantly from Ca(1) and Ca(2) sites (∼347.4 eV), while the weaker peak is due to the Ca(2) site only (∼345.0 eV). Variations on HA nanoparticle morphology could be a critical factor for changes in XPS binding energies' profile.

Texture and Geochemistry of Scheelites in the Tongshankou Deposit in Daye, Hubei, China: Implication for REE Substitution Mechanism and Multistage W Mineralization Processes

The Tongshankou skarn deposit in the Edong ore district is a typical metasomatic deposit associated with adjacent granodiorite porphyry and carbonate rocks. Using comprehensive microscopic observations, mineralogical and geochemical analysis, scheelite grains in the skarns can be classified into three major types, showing multi-stage mineralization characteristics. In the redox fluid environment, scheelites that occur with garnets usually have affinity to garnets, while in later skarn phases others exist with oxides and sulfides. They can be subdivided by trace elements, such as Nb and Eu, to discuss the detailed ore-forming process. Scheelites have three typical substitution mechanisms including: 2Ca2 + ⇌ REE3 + +Na+ (1); Ca2 + + W6 + ⇌ REE3 + +Nb5+(2); and 3Ca2 + ⇌ 2REE3++ □Ca (□Ca = Ca site vacancy) (3). Plagioclase or various hydrothermal stages can cause Eu anomalies to fluctuate from positive to negative, and these processes can cause particular zonation in W and Mo contents in scheelites. This study highlights the use of texture and geochemistry of scheelites in skarn deposits, depicting the W mineralization processes.

Determination on the activity of formed CaSO4 for arsenic adsorption during arsenic capture by CaO with the presence of SO2: Experimental and density functional theory study

Impact of SO2 on arsenic capture by CaO during oxy-coal combustion was investigated. The key question was to reveal the role of formed CaSO4 for arsenic capture. Drop tube furnace experiments verified that SO2 largely inhibited arsenic capture by CaO, and the adverse effect was assigned to the plugging and sulfation of CaO. Density functional theory study was further conducted to determine the impact of CaO transition to CaSO4 on arsenic adsorption. While, the feeble gap of adsorption energy between hexahedral As2O3 on CaO (001) surface and hexahedral As2O3 on CaSO4 (001) surface was incongruous with the apparently weakened arsenic capture capability of CaO by SO2. Then deformation of hexahedral As2O3 to chain As2O3 was firstly proposed to improve theoretical calculations, since the high combustion temperature and low deformation energy. Finally, huge adsorption energy gap between chain As2O3 on CaO (001) surface and chain As2O3 on CaSO4 (001) surface was observed. It not only demonstrated the much weaker activity of CaSO4 as opposed to CaO for As2O3 adsorption, but also confirmed the validity of As2O3 deformation. The widely applied hexahedral As2O3 structure was not the factual structure in flue gas during coal combustion, and the deformation should be concerned. Additionally, it was identified that Ca and O sites in CaO (001) surface were active for As2O3 adsorption. While, sulfur atoms in CaSO4 (001) surface were idle for As2O3 adsorption, and restricted the activity of surface O sites for As2O3 adsorption. Meanwhile, the activity of surface Ca sites was not affected by sulfur atoms.

Unraveling U6+, Am3+&Eu3+ ion’s distribution in Ca10(PO4)6F2for radioactive waste immobilization and the associated U6+→ Eu3+energy transfer dynamics for tunable emission characteristics

A combined photoluminescence (PL) and theoretical study has been performed on Ca10(PO4)6F2:U6+ and Ca10(PO4)6F2:U6+,Eu3+ compounds in order to explore Ca10(PO4)6F2 as potential host for radioactive waste immobilization by understanding the distribution U6+, Eu3+ and Am3+ ions among the lattice sites and the related radiation stability. DFT based calculations on various structures with different distribution of U6+, Eu3+ and Am3+ ions showed that Eu3+ and Am3+ ions prefer to occupy the Ca2 sites while the highly charged U6+ ions prefer Ca1 site. This is also supported by the PL lifetime study, which provided two lifetime components with different contribution for both U6+ and Eu3+ ions present at two different lattice sites. The PL study of U6+ doped compounds confirmed the existence of U in the UO22+ form, which makes it as a pure green emitter. Upon co-doping Eu3+ ion, the compounds were transformed to red emitter. Further, there is an energy transfer process from U6+to Eu3+, which shifted the CIE color coordinates towards pure red region while increasing doping level of U6+. This proves U6+ as a good sensitizer for Eu3+ ion. PL study on gamma irradiated U6+ doped Ca10(PO4)6F2 compound also showed excellent radiation stability at Ca2 site.

EEG features of spontaneous recurrent seizures in a mouse model of extended hippocampal kindling

Introduction . Epilepsy is a disease characterized by an enduring predisposition to generate epileptic seizures and by the neurobiological, cognitive, psychological, and social consequences of this condition. Temporal lobe epilepsy (TLE) is the most common and often drug-resistant type of epilepsies in the adult and aging populations and has greatly diverse in etiologies and electro-clinical manifestations. Kindling through repeated brief stimulation of limbic structures has long been used as a model of TLE. While classic kindling in a few weeks does not induce spontaneous recurrent seizures (SRS), extended kindling is able to induce SRS in several animal species. The SRS induction by extended kindling is generally not associated with gross brain injury, but rather a loss of subgroups of GABAergic interneurons in the hippocampal hilar region. The lack of observed gross brain injury in extended kindled animals is different from post status epilepticus models in which SRS emergence is accompanied with pronounced brain damage. As such the extended kindling model may help explore epileptogenesis in the absence of major brain pathology as is seen in many patients with TLE. To data, there is limited insight about EEG characteristics of SRS in rodent models of extended kindling. We therefore attempted to provide more information in this area using a mouse model of extended hippocampal kindling (Song et al., 2018; Liu et al., 2019; Frontier Pharmacology). Methods . Male C57 black mice ages 11–13 months were operated to implant intracranial electrodes. Each mouse was implanted with two pairs of bipolar electrodes, one in the hippocampal CA3 for kindling stimulation and local recordings and another in contralateral/ipsilateral hippocampal CA3, dorsomedial thalamus, parietal cortex or entorhinal cortex. Hippocampal kindling (60 Hz for 2 sec) was applied twice daily, and SRS were detected by 24-hour EEG-video monitoring. Age-match mice that received similar electrode implantation and twice daily handling manipulation but not kindling were used as controls. Brain histological examinations were performed in a subset of mice to verify the location of implanted electrodes and to examine potential gross brain lesion. Results . (1) SRS were observed from 47 mice following 80–140 kindling stimulation; no spontaneous seizure was detected in 12 control mice. (2) SRS remained detectable in individual mice up to 4 months after termination of the kindling stimulation. SRS incidences varied in a range of 2–14 events per day but inter-SRS intervals were ≤2 hours for about 65% of SRS events. (3) Most of SRS were featured with EEG ictal discharges and concurrent motor seizures at the Racine scale 3–5. SRS that presented EEG ictal discharges without or with concurrent motor behaviors at the Racine scale 1–2 were also noticeable, particularly in mice with implanted electrode in the dorsomedial thalamus. (4) In ≥1500 SRS events examined, nearly all EEG ictal discharges presented low-voltage signals at onset and such ictal onset appeared to concur in the kindled CA3 and unkindled site despite the latter targeted to different brain structures. (5) CA3 and cortical EEG ictal discharges were not substantially affected by intra-peritoneal injection of lorazepam (a benzodiazepine positive GABAa receptor modulator) but concurrent severe motor seizures were greatly suppressed. Summary . We suggest that epileptogenic network activity encompassing multiple forebrain areas may be responsible for SRS initiation in the mouse model of extended hippocampal kindling. Subcortical structures involving the dorsomedial thalamic circuitry may play an important role in manifestation and/or control of severe motor seizures in this model. Support . EpLink – The Epilepsy Research Program of the Ontario Brain Institute and Natural Sciences and Engineering Research Council of Canada.

Selective flotation of scheelite from calcite using a novel self-assembled collector

Both being Ca-bearing minerals, scheelite and calcite cannot be well separated by froth flotation due to their similar surface properties. To date, there is no report that scheelite and calcite can be well separated using collectors alone (including traditional NaOL and selective Pb-BHA complexes). Therefore, in this study, Pb(NO3)2, benzohydroxamic acid, and sodium oleate with specific combination (Pb-BHA-NaOL) were firstly used to form a novel collector to selectively separate scheelite and calcite. The flotation results of single and binary mixed minerals showed that the mixture of Pb, BHA and NaOL (molar ratio 6:6:1) exhibited excellent separation selectivity for scheelite and calcite at pH 9.0. Zeta potential measurements indicated that the dominant species of Pb-BHA-NaOL were positively charged and had stronger adsorption on negatively charged scheelite surfaces. Infrared spectroscopy and X-ray photoelectron spectroscopy further showed that Pb-BHA-NaOL had strong chemical interaction with Ca sites in the form of Pb(OH)-BHA-OL−, especially with O sites in the form of Pb-BHA+ on scheelite, but had no interaction with O sites on calcite. Therefore, the novel collector proposed in this work can provide a meaningful guide for the design of other novel collectors and have potential application prospects in scheelite flotation.

Heat But Not Mechanical Hypersensitivity Depends on Voltage-Gated CaV2.2 Calcium Channel Activity in Peripheral Axon Terminals Innervating Skin.

Voltage-gated CaV2.2 calcium channels are expressed in nociceptors at presynaptic terminals, soma, and axons. CaV2.2 channel inhibitors applied to the spinal cord relieve pain in humans and rodents, especially during pathologic pain, but a biological function of nociceptor CaV2.2 channels in processing of nociception, outside presynaptic terminals in the spinal cord, is underappreciated. Here, we demonstrate that functional CaV2.2 channels in peripheral axons innervating skin are required for capsaicin-induced heat hypersensitivity in male and female mice. We show that CaV2.2 channels in TRPV1-nociceptor endings are activated by capsaicin-induced depolarization and contribute to increased intracellular calcium. Capsaicin induces hypersensitivity of both thermal nociceptors and mechanoreceptors, but only heat hypersensitivity depends on peripheral CaV2.2 channel activity, and especially a cell-type-specific CaV2.2 splice isoform. CaV2.2 channels at peripheral nerve endings might be important therapeutic targets to mitigate certain forms of chronic pain.SIGNIFICANCE STATEMENT It is generally assumed that nociceptor termini in the spinal cord dorsal horn are the functionally significant sites of CaV2.2 channel in control of transmitter release and the transmission of sensory information from the periphery to central sites. We show that peripheral CaV2.2 channels are essential for the classic heat hypersensitivity response to develop in skin following capsaicin exposure. This function of CaV2.2 is highly selective for heat, but not mechanical hypersensitivity induced by capsaicin exposure, and is not a property of closely related CaV2.1 channels. Our findings suggest that interrupting CaV2.2-dependent calcium entry in skin might reduce heat hypersensitivity that develops after noxious heat exposure and may limit the degree of heat hypersensitivity associated with certain other forms of pain.

Adsorption mode of sodium citrate for achieving effective flotation separation of ilmenite from titanaugite

Sodium citrate was introduced as a depressant for ilmenite flotation, and its effect on the activation of ilmenite and depressing titanaugite was investigated. The flotation results showed that ilmenite was effectively separated from titanaugite as a concentrate with a TiO2 grade of 43.62% and recovery of 87.42%. The contact angle analysis revealed that sodium citrate further increased the hydrophobicity of ilmenite and decreased it in the case of titanaugite. The zeta potential results indicated that the adsorbed sodium citrate accelerated the adsorption of sodium oleate on the ilmenite surface, but weakened the adsorption on titanaugite. Inductively coupled plasma mass spectrometry (ICP) and solution chemistry analyses illustrated that sodium citrate improved the flotation of ilmenite and depressed the flotation of titanaugite. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis demonstrated that sodium citrate adsorbed onto ilmenite through Fe3+ and onto titanaugite through the active sites of Ca and Mg.

Adsorption mechanism of efficient flotation separation of scheelite from calcite by a novel mixed collector

The separation of scheelite and calcite is a challenging problem in flotation production. In this study, the effects and mechanisms of oxidized paraffin soap (OPS) and octylphenol polyoxyxyethylene ether with 10 oxyethylene glycol ethers (OP-10) as a mixed collector to collect scheelite from calcite were surveyed by micro-flotation, Fourier transform infrared spectroscopy (FT-IR), surface tension tests, ultraviolet (UV) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The flotation results showed that the recovery of scheelite increased from 57.59% of 50 mg/L OPS to 94.75% of 30 mg/L OPS/OP-10 at pH 8, which proved that OP-10 could reduce the dosage of the OPS, and OPS/OP-10 was suitable for natural pH pulp. The surface tension tests demonstrated that OP-10 reduced the CMC of OPS aqueous solution and enhanced its solubilization. FT-IR analysis confirmed that OPS and OPS/OP-10 had strong chemisorption on the surface of scheelite and calcite. UV analysis further indicated preferential adsorption of OPS compared with OP-10, and the adsorption mechanism of the mixed collector can be confirmed as a co-adsorption. XPS analysis showed that OPS was chemically adsorbed on Ca sites on the scheelite surface, while the characteristic peak of the mixed collector did not shift significantly compared with that of OPS, indicating that OP-10 played a synergistic role mainly by co-adsorbing with OPS on the surface of scheelite. In a word, the mixed collector OPS/OP-10 was utilized for scheelite separation with satisfactory outcomes and exhibited an extensive prospect in scheelite production.

The Physico-Chemical Properties and Exploratory Real-Time Cell Analysis of Hydroxyapatite Nanopowders Substituted with Ce, Mg, Sr, and Zn (0.5-5 at.%).

Cation-substituted hydroxyapatite (HA), standalone or as a composite (blended with polymers or metals), is currently regarded as a noteworthy candidate material for bone repair/regeneration either in the form of powders, porous scaffolds or coatings for endo-osseous dental and orthopaedic implants. As a response to the numerous contradictions reported in literature, this work presents, in one study, the physico-chemical properties and the cytocompatibility response of single cation-doped (Ce, Mg, Sr or Zn) HA nanopowders in a wide concentration range (0.5–5 at.%). The modification of composition, morphology, and structure was multiparametrically monitored via energy dispersive X-ray, X-ray photoelectron, Fourier-transform infrared and micro-Raman spectroscopy methods, as well as by transmission electron microscopy and X-ray diffraction. From a compositional point of view, Ce and Sr were well-incorporated in HA, while slight and pronounced deviations were observed for Mg and Zn, respectively. The change of the lattice parameters, crystallite size, and substituting cation occupation factors either in the Ca(I) or Ca(II) sites were further determined. Sr produced the most important HA structural changes. The in vitro biological performance was evaluated by the (i) determination of leached therapeutic cations (by inductively coupled plasma mass spectrometry) and (ii) assessment of cell behaviour by both conventional assays (e.g., proliferation—3-(4,5-dimethyl thiazol-2-yl) 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay; cytotoxicity—lactate dehydrogenase release assay) and, for the first time, real-time cell analysis (RTCA). Three cell lines were employed: fibroblast, osteoblast, and endothelial. When monophasic, the substituted HA supported the cells’ viability and proliferation without signs of toxicity. The RTCA results indicate the excellent adherence of cells. The study strived to offer a perspective on the behaviour of Ce-, Mg-, Sr-, or Zn-substituted HAs and to deliver a well-encompassing viewpoint on their effects. This can be highly important for the future development of such bioceramics, paving the road toward the identification of candidates with highly promising therapeutic effects.

Crystal chemistry and nomenclature of fillowite-type phosphates

ABSTRACT The crystal chemistries of five samples of minerals belonging to the fillowite group were structurally investigated: (A) fillowite from the Buranga pegmatite, Rwanda; (B) fillowite from the Kabira pegmatite, Uganda; (C) johnsomervilleite from Loch Quoich, Scotland; (D) johnsomervilleite from the Malpensata pegmatite, Italy; and (E) chladniite from the Sapucaia pegmatite, Minas Gerais, Brazil. Their crystal structures were refined in space group R (No. 148), using single-crystal X-ray diffraction data, to R1 values of (A) 3.79%, (B) 3.52%, (C) 4.14%, (D) 4.04%, and (E) 5.59%. Unit-cell parameters are: (A) a = 15.122(1), c = 43.258(4) Å; (B) a = 15.125(1), c = 43.198(3) Å; (C) a = 15.036(2), c = 42.972(9) Å; (D) a = 15.090(2), c = 43.050(9) Å; and (E) a = 15.1416(6), c = 43.123(2) Å. The asymmetric unit contains 15 cation sites with coordinations ranging from V to IX, as well as six P sites. The complex structure can be split into three types of chains running parallel to the c axis. These chains are composed of edge- and face-sharing polyhedra. Detailed cation distributions were determined for all five samples, and their comparison allowed us to establish the general formula A3BC11(PO4)9 for fillowite-type phosphates, where A represents the group of sites mainly occupied by Na, B the Ca sites, and C the sites containing the divalent cations Fe2+, Mn, and Mg. This formula was accepted by the CNMNC, and the four valid mineral species occurring in the fillowite group are fillowite (C = Mn), johnsomervilleite (C = Fe2+), chladniite (C = Mg), and galileiite (B and C = Fe2+). Stornesite-(Y) is discredited, since this mineral corresponds to Y-bearing chladniite.

Flotation separation of scheelite and apatite by polysaccharide depressant xanthan gum

Tungsten is a crucial rare metal with extensive application in modern industries and scheelite is the major resource for tungsten production. In this work, xanthan gum (XG), a non-toxic, environmentally friendly polysaccharide, was explored as a depressant of apatite during the scheelite flotation. The results of single mineral flotation and artificial mixed minerals flotation showed that XG exhibited efficient selective depressive effect on apatite rather than on scheelite. The Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis indicated that the chelation action between the –COO– groups and the Ca on apatite surface was responsible for XG chelating adsorption. The firm XG chemisorption on apatite surface hindered subsequent sodium oleate (NaOl) chemisorption. Due to fewer available surface Ca sites and intenser anions group electronegativity on scheelite, the XG adsorption on scheelite surface was weak and it exhibited little effect on following NaOl chemisorption. As a result, the flotation separation of scheelite from apatite was achieved using XG as depressant and NaOl as collector.