Apatite Crystals Research Articles

Chlorine Isotope Composition of Apatite from the >3.7 Ga Isua Supracrustal Belt, SW Greenland

The study of the oldest surviving rock suites is crucial for understanding the processes that shaped the early Earth and formed an environment suitable for life. The metasedimentary and metavolcanic rocks of the early Archean Isua supracrustal belt contain abundant apatite, the geochemical signatures of which may help decipher ancient environmental conditions. However, previous research has shown that secondary processes, including amphibolite-facies metamorphism, have reset the original hydrogen isotope composition (δD) of apatite from the Isua belt; therefore, δD values are not indicative of primary conditions in the Archean. Here, we report the first in situ chlorine isotope (δ37Cl) analyses by Secondary Ion Mass Spectrometry (SIMS) from Isua apatite, which we combine with information from transmission electron microscopy, cathodoluminescence imaging, and spectroscopy, documenting the micron-scale internal features of apatite crystals. The determined δ37ClSMOC values (chlorine isotope ratios vs. standard mean ocean chloride) fall within a range from −0.8‰ to 1.6‰, with the most extreme values recorded by two banded iron formation samples. Our results show that δ37Cl values cannot uniquely document primary signatures of apatite crystals, but the results are nonetheless helpful for assessing the extent of secondary overprint.

Optical and scintillation properties of Tb-doped apatite single crystals

Optical and scintillation properties of Tb-doped apatite single crystals

Apatite Formation on Zirconia (Y-TZP) Coated with Carbonate Apatite in Simulated Body Fluid

Abstract. Various bioactive calcium phosphates such as hydroxyapatite (HA) and carbonate apatite (CO3Ap) have been widely studied due to their biocompatibility and osteoconductivity when implanted into bone defects. CO3Ap has the ability to adapt bone structure and induce bone regeneration; so that it can be categorized as resorbable bioactive materials. CO3Ap induced much stronger response such as cell adhesion and actin ring formation to osteoclast-like cells rather than HA. The aim of this study is to evaluate the bioactivity on zirconia (Y-TZP) coated with CO3Ap using simulated body fluid (SBF). Twenty Y-TZP ZrO2 disks with a 12-mm diameter and 1-mm thickness were employed as the samples. The disks were divided into two groups which the control group without CO3Ap coating and tested group with CO3Ap coating. Disks samples are dipped into CO3Ap suspension for one minute and stored in 37°C incubator for 24 hours. The disks were soaked in SBF for 1, 4, and 7 day(s) at 36.5°C. The obtained apatite crystals were characterized by scanning electron microscopy (SEM). It was found that the apatite formation on the tested group was greater than the control group. The EDS pattern showed the presence of Ca and P on the control and tested group after SBF soaking, which indicate the apatite deposition on the disks’ surface. However, the Ca and P on the tested group was higher compared to the control group. The formation of apatite layer on the disks’ surface is bioactivity indicator of CO3Ap.

Surface-transformed osteoinductive polyethylene terephthalate scaffold as a dual system for bone tissue regeneration with localized antibiotic delivery.

Multifunctional scaffolds have recently attained superior significance in tissue regeneration due to combinational activity profile that is usually accomplished by separate sequential therapy. Here, we present a dual system comprised of surface-phosphorylated PET fibrous matrix coated with ciprofloxacin-impregnated biodegradable polymer poly (hydroxyethyl methacrylate) aiming at regeneration of bone tissue deprived of bacterial infections, particularly osteomyelitis. The ATR, XPS and FESEM/EDX results provided confirmative evidences for surface phosphorylation of PET and in situ coating of the polymer. Swelling and contact angle measurements demonstrated improved hydrophilicity which is further corroborated by in vitro degradation profile in PBS. Preliminary evaluation by MTT and actin staining proved its biocompatibility while enhanced in vitro mineralization in 1.5X SBF by FESEM/EDX clearly indicate the primary nucleation and secondary growth of beautiful apatite crystals with Ca/P ratio similar to human bone. Alizarin red S and von Kossa staining validated the biomineralization in MG-63 cells. The sequential expression of early and late biomarkers -alkaline phosphatase (ALP) and osteocalcin (OSN)- of osteoblast differentiation in rat bone marrow mesenchymal cells (BMC) has demonstrated osteoinductive nature of the system. The second functionality of the scaffold has been proven by step-wise ciprofloxacin-release profile (in vitro) with ~60% release within 120h. In addition, antibacterial studies of ciprofloxacin- eluted from the scaffold have shown apparent zones of inhibition against Staphylococcus aureus (3.6±0.3cm) and Escherichia coli (3.0±0.8cm). Hence, the surface-transformed PET scaffold function as a dual system as localized antibiotic delivery vehicle against bone infections and undergo self-biomineralization leading to osteoinduction.

Ginseng compound K incorporated porous Chitosan/biphasic calcium phosphate composite microsphere for bone regeneration

There is a substantial for the bone graft materials in the clinical field. Porous, stable and biodegradable bone microsphere scaffold using biopolymer chitosan was studied, and biphasic calcium phosphate was added to improve mechanical and osteoconductivity properties later ginseng compound K was added for improving its medicinal properties. They were characterized using FTIR and XRD that showed the apatite crystal in the composite microsphere scaffolds were structurally similar to that of biogenic apatite crystals. Scanning electron microscopy images confirmed the presence of hydroxyapatite on the surface of the composite microspheres. In vitro results infers that the composite microspheres are biocompatible with NIH 3T3 and MG63 cells and capable of supporting growth and spreading of MG-63 cells. Further, Osteogenic markers expression was found to be higher in rat bone marrow stem cells seeded on microsphere scaffolds compared to control. The prepared biocomposite porous microsphere scaffold developed in this study can be used as an alternative for the bone regeneration or bone tissue engineering.

Changes with age (from 0 to 37 D) in tibiae bone mineralization, chemical composition and structural organization in broiler chickens

ABSTRACTBroiler chickens have an extreme physiology (rapid growth rates) that challenges the correct bone mineralization, being an interesting animal model for studying the development of bone pathologies. This work studies in detail how the mineralization, chemistry, and structural organization of tibiae bone in broiler chickens change with age during the first 5 wk (37 D) from hatching until acquiring the final weight for slaughter. During the early growth phase (first 2 wk), the rapid addition of bone tissue does not allow for bone organic matrix to fully mineralize and mature, and seems to be a critical period for bone development at which bone mineralization cannot keep pace with the rapid growth of bones. The low degree of bone mineralization and large porosity of cortical bone at this period might be responsible of leg deformation and/or other skeletal abnormalities commonly observed in these birds. Later, cortical bone porosity gradually decreases and the cortical bone became fully mineralized (65%) at 37 D of age. At the same time, bone mineral acquires the composition of mature bone tissue (decreased amount of carbonate, higher crystallinity, Ca/P = 1.68). However, the mineral part was still poorly organized even at 37 D. The oriented fraction was about 0.45 which means that more than half of apatite crystals within the mineral are randomly oriented. Mineral organization (crystal orientation) had an important contribution to bone-breaking strength. Nevertheless, locally determined (at tibia mid-shaft) bone properties (i.e., cortical thickness, crystal orientation) has only a moderate correlation (R2 = 0.33) with bone breaking strength probably due to large and highly heterogeneous porosity of bone that acts as structural defects. On the other hand, the total amount of mineral (a global property) measured by total ash content was the best predictor for breaking strength (R2 = 0.49). Knowledge acquired in this study could help in designing strategies to improve bone quality and reduce the incidence of skeletal problems in broiler chickens that have important welfare and economic implications.

Novel Bifunctional Nanofiller (Bioactive\Antimicrobial) for Improving Dental Adhesives Efficacy

Purpose: The objective of this study was to develop novel bio-composite Nanofiller (Quaternary polyethyleneimine\ Hydroxyapatite, QPEI/HAp), which combines the antibacterial activity of polymeric quaternary ammonium salt and the multi-advantages of Hydroxyapatite nanoparticles for improving biological and physico-mechanical properties of Dental Adhesives. Materials and Methods: Hydroxyapatite (HAp) nano rods were produced by hydrothermal process and coated by Polyethyleneimine (PEI) via electrostatic adsorption, followed by two steps polymeric reaction; tertiary amination and quaternization. The resulting powder was characterized using XRD, FTIR and TEM before and after polymer coating, and bioactivity was evaluated after 7 days soaking in simulated body fluid using XRD analysis. An experimental ethanolbased one-bottle adhesive resin was formulated with 0.2, 0.5, 1, 2 and 5% QPEI/HAp nanofiller. The formulated adhesive resins were evaluated for their colloidal stability, antibacterial activity, Ultimate Tensile Strength, and Micro-Shear bond strength to dentin. Results: Powder characterization confirmed successful surface modification of Hydroxyapatite nanoparticles with PEI polymer; the particles presented a high crystallinity with typical chemical groups and mean size around 20 nanometers. XRD analysis revealed nucleation of apatite crystals on the surface of QPEI/HAp nanoparticles after soaking in SBF; confirming their bioactivity. Lower contents of modified nanoparticles showed little or no aggregation tendency and good colloidal stability in the adhesive solution with Zeta potential of 30.6 mV. Antibacterial outcomes of PEI against S. mutans was significantly higher than that of MDPB in Clearfil Protect bond; a commercial adhesive used as control (P<0.05). The addition of 0.2 wt. % modified nano-hydroxyapatite resulted in higher values of Ultimate Tensile and Micro-Shear bond strength than other tested adhesives and commercial Clearfil S3 Bond (all-in-one adhesive); (P<0.05). Conclusion: Incorporation of 0.2 wt. % QPEI-HAp nanoparticles significantly improved the adhesive properties and may be promising multifunctional filler for dental adhesive resin.

Arthroscopic Excision of Calcification in Lateral Collateral Ligament of Knee with Direct Lateral (Bengaluru Chandrashekar) Portal

Calcium apatite deposition disease (CADD) is a common entity characterized by deposition of calcium apatite crystals within and around connective tissues, usually in a periarticular location 1. Many different locations of CADD have been described amongst which, lateral collateral ligament (LCL) of the knee is a rare location 2. The first ever case of calcific deposits in the lateral collateral ligament of the knee was reported by Anderson et al 3 in 2003. A few isolated case reports of LCL calcification are published in the literature 4,5 but arthroscopic excision of calcific deposit in LCL has not been described yet in the literature. Here we are describing 2 cases of arthroscopic excision of calcific deposits in LCL of the knee by a new portal called ‘Direct lateral portal' for the knee.

Mineralogy and genesis of pyrochlore apatitite from The Good Hope Carbonatite, Ontario: A potential niobium deposit

AbstractThe Good Hope carbonatite is located adjacent to the Prairie Lake alkaline rock and carbonatite complex in northwestern Ontario. The occurrence is a heterolithic breccia consisting of diverse calcite, dolomite and ferrodolomite carbonatites containing clasts of magnesio-arfvedsonite + potassium feldspar, phlogopite + potassium feldspar together with pyrochlore-bearing apatitite clasts. The apatitite occurs as angular, boudinaged and schlieren clasts up to 5 cm in maximum dimensions. In these pyrochlore occurs principally as euhedral single crystals (0.1–1.5 cm) and can comprise up to 25 vol.% of the clasts. Individual clasts contain compositionally- and texturally-distinct suites of pyrochlore. The pyrochlores are hosted by small prismatic crystals of apatite (~100–500 μm × 10–25 μm) that are commonly flow-aligned and in some instances occur as folds. Allotriogranular cumulate textures are not evident in the apatitites. The fluorapatite does not exhibit compositional zonation under back-scattered electron spectroscopy, although ultraviolet and cathodoluminescence imagery shows distinct cores with thin (<50 μm) overgrowths. Apatite lacks fluid or solid inclusions of other minerals. The apatite is rich in Sr (7030–13,000 ppm) and rare earth elements and exhibits depletions in La, Ce, Pr and Nd (La/NdCN ratios (0.73–1.14) relative to apatite in cumulate apatitites (La/NdCN > 1.5) in the adjacent Prairie Lake complex. The pyrochlore are primarily Na–Ca pyrochlore of relatively uniform composition and minor Sr contents (<2 wt.% SrO). Irregular resorbed cores of some pyrochlores are A-site deficient (>50%) and enriched in Sr (6–10 wt.% SrO), BaO (0.5–3.5 wt.%), Ta2O5 (1–2 wt.%) and UO2 (0.5–2 wt.%). Many of the pyrochlores exhibit oscillatory zoning. Experimental data on the phase relationships of haplocarbonatite melts predicts the formation of apatite and pyrochlore as the initial liquidus phases in such systems. However, the texture of the clasts indicates that pyrochlore and apatite did not crystallise together and it is concluded that pyrochlores formed in one magma have been mechanically mixed with a different apatite-rich magma. Segregation of the apatite–pyrochlore assemblage followed by lithification resulted in the apatitites, which were disrupted and fragmented by subsequent batches of diverse carbonatites. The genesis of the pyrochlore apatitites is considered to be a process of magma mixing and not simple in situ crystallisation.

Rotator Cuff Tenocytes Differentiate into Hypertrophic Chondrocyte-Like Cells to Produce Calcium Deposits in an Alkaline Phosphatase-Dependent Manner

Calcific tendonitis is a frequent cause of chronic shoulder pain. Its cause is currently poorly known. The objectives of this study were to better characterize the cells and mechanisms involved in depositing apatite crystals in human tendons. Histologic sections of cadaveric calcified tendons were analyzed, and human calcific deposits from patients undergoing lavage of their calcification were obtained to perform infrared spectroscopy and mass spectrometry-based proteomic characterizations. In vitro, the mineralization ability of human rotator cuff cells from osteoarthritis donors was assessed by alizarin red or Von Kossa staining. Calcifications were amorphous areas surrounded by a fibrocartilaginous metaplasia containing hypertrophic chondrocyte-like cells that expressed tissue non-specific alkaline phosphatase (TNAP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which are two key enzymes of the mineralization process. Calcific deposits were composed of apatite crystals associated with proteins involved in bone and cartilage development and endochondral bone growth. In vitro, tenocyte-like cells extracted from the rotator cuff were able to mineralize in osteogenic cultures, and expressed TNAP, type X COLLAGEN, and MMP13, which are hypertrophic chondrocytes markers. The use of a TNAP inhibitor significantly prevented mineral deposits. We provide evidence that tenocytes have a propensity to differentiate into hypertrophic chondrocyte-like cells to produce TNAP-dependent calcium deposits. We believe that these results may pave the way to identifying regulating factors that might represent valuable targets in calcific tendonitis.

An experimental calibration of a sulfur-in-apatite oxybarometer for mafic systems

The incorporation of sulfur (S) into the apatite structure and the partitioning of S between apatite and silicate melt (DSap/m) have been proposed to vary systematically as a function of prevailing redox conditions. In this study, we experimentally equilibrated apatite with mafic silicate melt at 1000 °C, 300 MPa and a range of oxygen fugacity (fO2; log fO2 [ΔFMQ] = −1, 0, +0.3, +1.2, and +3 where FMQ is the fayalite-magnetite-quartz mineral redox buffer) to explore the partitioning behavior of S, including different oxidation states of S, between apatite and silicate melt. The data reveal that DSap/m values increase systematically with increasing fO2, from 0.02± 0.01 at log fO2 [ΔFMQ] of −1 to 3.20 ± 0.19 at log fO2 [ΔFMQ] of +3. The bulk S content (∼0.37 and ∼0.28 wt.% S added) imparts a minor influence on DSap/m at reducing conditions.Micro X-ray absorption near edge structure (μ-XANES) spectroscopy at the S K-edge was used to measure, in situ, the oxidation states of S in experimentally crystallized apatite. The S-XANES analyses reveal that with increasing fO2, apatite progressively incorporates S6+ ≫ S2− > S4+ > S1+. The integrated S6+/ΣS peak area ratios and centroid energies (eV) were determined for apatite crystals in apatite from experiments at all fO2 conditions. The orientation effects occurring during S-XANES analyses of apatite were considered by merging spectra from multiple grains with random crystallographic orientation. The S-XANES data reveal that S6+/ΣS peak area ratios and the centroid energies increase systematically with fO2, demonstrating that the S6+/ΣS ratio in apatite can be used as an oxybarometer.The results demonstrate that both the S6+/ΣS and CeV calibration methods are highly sensitive in the redox range of ∼FMQ to ∼FMQ + 1.2 at the conditions and compositions evaluated in this study. As a result, the S-in-apatite oxybarometer is particularly applicable to mafic systems such as mid ocean ridge basalts (MORB), relatively reduced ocean island basalts (OIB), and back-arc basin basalt (BABB). Owing to the ubiquity of apatite in magmatic and magmatic-hydrothermal systems, measuring the concentration and oxidations state(s) of S-in-apatite has the potential to serve as a powerful sulfo- and oxy-barometer for a broad range of natural systems.

The evaluation of the relationship between fetuin-A and traditional and non-traditional cardiovascular risk factors in kidney transplantation recipients

Objectives: Kidney transplantation recipients (KTRs) have higher cardiovascular complications risk compared to the general population. Cardiovascular risk factors (CVRF, Traditional and non-traditional) are widely studied to understand the causes of increased cardiovascular disease (CVD) risk in KTRs. Fetuin-A prevents from vascular calcification (VC) by inhibiting production and collapsing of apatite crystals to the vascular wall. The relationship between fetuin-A levels and CVRF in KTRs was investigated in this study. Methods: Sixty-two KTRs with no prior CVD history participated. Anthropometrical, laboratory (fetuin-A, inflammation markers, antioxidants, lipid peroxidation products) and cardiological (echocardiographic, pulse wave velocity) measurements were performed. Participants were divided into two groups according to normal (≥ 0.5 g/L, n = 32, NFA) and low (< 0.5 g/L, n = 30, LFA) fetuin-A levels according to manufacturer’s reference range, and the results were compared. Results: No significant difference was observed in demographic features, body mass index, systolic and diastolic blood pressures, left ventricle mass index, waist and hip circumferences, left ventricle hypertrophy and waist-hip ratios between the two groups (p > 0.05). The ratios of drug usage such as immunosuppressives, anti-hypertensives and statin were comparable between two groups. Parathormone levels were significantly higher in the NFA group (p = 0.015) and glomerular filtration rate was calculated significantly higher in LFA group (p = 007). The comparison of other CVRF reveals no significant difference (p > 0.05). Conclusions: Although many CVRF improved in KTRs, subclinical inflammation markers were still higher than the healthy population. Identification and early recognition of CVRF in high-risk individuals may contribute to the reduction of cardiovascular mortality. In our study, we observed no significant relationship between fetuin-A levels and CVRFs. We evaluated the relationship between serum fetuin-A levels on cardiovascular risk factors by its role in pathophysiology.

Comparison of human and bovine dental enamel by TEM and t-EBSD investigations

The microstructures of human dental enamel and bovine enamel are compared to each other. To obtain samples for transmission electron microscopy (TEM), focused ion-beam (FIB) milling is used. The preparation of such TEM-slices is found to be very effective when operating the FIB with adapted parameters. After the milling process, the TEM-slices are then thinned by means of the ion beam to achieve samples being transparent for the electron beam. With a home-built sample holder, the electron backscatter diffraction (EBSD) can be operated in the scanning electron microscope (SEM) in transmission mode called t-EBSD. This technique enables the crystallographic orientation measurement on nanometer-sized, non-conducting enamel grains with a reasonable quality. Both TEM and t-EBSD images reveal a similar arrangement of the apatite crystals within the enamel, but it is obvious that the nanostructure of human enamel follows a more complex construction principle. The grain sizes of bovine enamel are much larger, and it is difficult to recognize the chain arrangement as found previously in the human enamel. As a result of the comparison, one can state that the nanostructure of human enamel is clearly more complicated than the bovine counterpart.

Correlative vibrational spectroscopy and 2D X-ray diffraction to probe the mineralization of bone in phosphate-deficient mice.

Bone crystallite chemistry and structure change during bone maturation. However, these properties of bone can also be affected by limited uptake of the chemical constituents of the mineral by the animal. This makes probing the effect of bone-mineralization-related diseases a complicated task. Here it is shown that the combination of vibrational spectroscopy with two-dimensional X-ray diffraction can provide unparalleled information on the changes in bone chemistry and structure associated with different bone pathologies (phosphate deficiency) and/or health conditions (pregnancy, lactation). Using a synergistic analytical approach, it was possible to trace the effect that changes in the remodelling regime have on the bone mineral chemistry and structure in normal and mineral-deficient (hypophosphatemic) mice. The results indicate that hypophosphatemic mice have increased bone remodelling, increased carbonate content and decreased crystallinity of the bone mineral, as well as increased misalignment of crystallites within the bone tissue. Pregnant and lactating mice that are normal and hypophosphatemic showed changes in the chemistry and misalignment of the apatite crystals that can be related to changes in remodelling rates associated with different calcium demand during pregnancy and lactation.

Indirect printing of hierarchical patient-specific scaffolds for meniscus tissue engineering

The complex meniscus tissue plays a critical role in the knee. The high susceptibility to injury has led to an intense pursuit for better tissue engineering regenerative strategies, where scaffolds play a major role. In this study, indirect printed hierarchical multilayered scaffolds composed by a silk fibroin (SF) upper layer and an 80/20 (w/w) ratio of SF/ionic-doped β-tricalcium phosphate (TCP) bottom layer were developed. Furthermore, a comparative analysis between two types of scaffolds produced using different SF concentrations, i.e., 8% (w/v) (Hi8) and 16% (w/v) (Hi16) was performed. In terms of architecture and morphology, the produced scaffolds presented homogeneous porosity in both layers and no differences were observed when comparing both scaffolds. A decrease in terms of mechanical performance of the scaffolds was observed when SF concentration decreased from 16 to 8% (w/v). Hi16 revealed a static compressive modulus of 0.66 ± 0.05 MPa and dynamical mechanical properties ranging from 2.17 ± 0.25 to 3.19 ± 0.38 MPa. By its turn, Hi8 presented a compressive modulus of 0.27 ± 0.08 MPa and dynamical mechanical properties ranging from 1.03 ± 0.08 MPa to 1.56 ± 0.13 MPa. In vitro bioactivity studies showed formation of apatite crystals onto the surface of Hi8 and Hi16 bottom layers. Human meniscus cells (hMCs) and human primary osteoblasts were cultured separately onto the top layer (SF8 and SF16) and bottom layer (SF8/TCP and SF16/TCP) of the hierarchical scaffolds Hi8 and Hi16, respectively. Both cell types showed good adhesion and proliferation as denoted by the live/dead staining, Alamar Blue assay and DNA quantification analysis. Subcutaneous implantation in mice revealed weak inflammation and scaffold’s integrity. The hierarchical indirect printed SF scaffolds can be promising candidate for meniscus TE scaffolding applications due their suitable mechanical properties, good biological performance and possibility of being applied in a patient-specific approach.

Thorium-poor monazite and columbite-(Fe) mineralization in the Gleibat Lafhouda carbonatite and its associated iron-oxide-apatite deposit of the Ouled Dlim Massif, South Morocco

Recent exploration work in South Morocco revealed the occurrence of several carbonatite bodies, including the Paleoproterozoic Gleibat Lafhouda magnesiocarbonatite and its associated iron oxide mineralization, recognized here as iron-oxide-apatite (IOA) deposit type. The Gleibat Lafhouda intrusion is hosted by Archean gneiss and schist and not visibly associated with alkaline rocks. Metasomatized micaceous rocks occur locally at the margins of the carbonatite outcrop and were identified as glimmerite fenite type. Rare earth element (REE) and Nb mineralization is mainly linked to the associated IOA mineralization and is represented by monazite-(Ce) and columbite-(Fe) as major ore minerals. The IOA mineralization mainly consists of magnetite and hematite that usually contain large apatite crystals, quartz and some dolomite. Monazite-(Ce) is closely associated with fluorapatite and occurs as inclusions within the altered parts of apatite and along cracks or as separate phases near apatite. Monazite shows no zonation patterns and very low Th contents (<0.4 wt%), which would be beneficial for commercial extraction of the REE and which indicates monazite formation from apatite as a result of hydrothermal volatile-rich fluids. Similar monazite-apatite mineralization and chemistry also occurs at depth within the carbonatite, although the outcropping carbonatite is barren, suggesting an irregular REE ore distribution within the carbonatite body. The barren carbonatite contains some tiny unidentified secondary Nb-Ta-U phases, synchysite and monazite. Niobium mineralization is commonly represented by anhedral minerals of columbite-(Fe) which occur closely associated with magnetite-hematite and host up to 78 wt% Nb2O5, 7 wt% Ta2O5 and 1.6 wt% Sc2O3. This association may suggest that columbite-(Fe) precipitated by an interaction of Nb-rich fluids with pre-existing Fe-rich minerals or as pseudomorphs after pre-existing Nb minerals like pyrochlore. Our results most strongly suggest that the studied mineralization is economically important and warrants both, further research and exploration with the ultimate goal of mineral extraction.

Sandwich-Like Nanofibrous Scaffolds for Bone Tissue Regeneration.

Advanced bone healing approaches included a wide range of biomaterials that mainly mimic the composition, structure, and properties of bone extracellular matrix with osteogenic activity. The present study aimed to develop a sandwich-like structure of electrospun nanofibers (NFs) based on polycaprolactone (PCL) and chitosan/polyethylene oxide (CS/PEO) composite to stimulate bone fracture healing. The morphology of the fabricated scaffolds was examined using scanning electron microscopy (SEM). Apatite deposition was evaluated using simulated body fluid (SBF). The physicochemical and mechanical properties of samples were analyzed by Fourier transform infrared, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and universal testing machine. SEM images exhibited a porous three-dimensional structure with NF diameters of 514-4745 nm and 68-786 nm for PCL NFs layer and the sandwich-like NFs scaffolds, respectively. Deposition of apatite crystal on scaffolds started at week 2 followed by heavy deposition at week 8. This was confirmed by measuring the consumption of calcium and phosphorous ions from SBF. Thermal stability of scaffolds was confirmed using DSC and TGA. Moreover, the PCL NF layer in the middle of the developed sandwich structure reinforced the scaffolds with bear load up to 12.224 ± 1.12 MPa and Young's modulus of 17.53 ± 3.24 MPa. The scaffolds' porous structure enhanced both cell propagation and proliferation. Besides, the presence of CS in the outer NF layers of the scaffolds increased the hydrophilicity, as evidenced by the reduction of contact angle from 116.6 to 57.6°, which is essential for cell attachment. Cell viability study on mesenchymal stem cells proved the cytocompatibility of the fabricated scaffolds. Finally, in vivo mandibular bone defect rabbit model was used to confirm the regeneration of a new healthy bone within 28 days. In conclusion, the developed scaffolds could be a promising solution to stimulate bone regeneration.

BIOCOMPATIBILITY OF HAp/CNTs COATING ON Ti6Al4V ALLOY INTO THE SIMULATED BODY FLUID SOLUTION

Hydroxyapatite doped carbon nanotubes (HAp/CNTs) was synthesized successfully as a coating on the surface of titanium alloy (Ti6Al4V) by a scanning potential method. The biocompatibility of the materials soaked into a simulated body fluid solution (SBF) were investigated. SEM images are observed that the formation of new apatite crystals on the surface of Ti6Al4V with HAp or HAp/CNTs coating is better than that of Ti6Al4V. The formed apatite crystals are confirmed by XRD result of Ti6Al4V after 21 soaked days in SBF solution. These results indicated that the coatings of HAp or HAp/CNTs have a good biocompatibility.

High-Temperature thermochemical interactions of molten silicates with Yb2Si2O7 and Y2Si2O7 environmental barrier coating materials

The thermochemical behavior of EBC candidate materials yttrium disilicate (Y2Si2O7) and ytterbium disilicate (Yb2Si2O7) was evaluated with three calcium-magnesium-aluminosilicate (CMAS) glasses possessing CaO:SiO2 ratios relevant to gas turbine systems. Pellet mixtures of 50 mol% EBC powder to 50 mol% CMAS glass powder were heat treated at 1200°C, 1300°C, and 1400°C. The products of these interactions were evaluated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Above glass melting temperatures, exposure of the disilicates primarily resulted in dissolution into the molten glass followed by precipitation of a Ca2RE8(SiO4)6O2 (RE = Yb3+, Y3+) apatite-type silicate and/or rare earth disilicate. In glasses with high CaO concentrations, apatite readily forms while the disilicate material is consumed by the reaction. As CaO content decreases, the disilicate phase becomes the main reaction product. Overall, reactions with yttrium disilicate favored more apatite crystallization than ytterbium disilicate. The viability of using these disilicates in various operating environments is discussed.

Preferred Growth Orientation of Apatite Crystals on Biological Hydroxyapatite Enriched with Bioactive Glass: A Biomimetic Behavior

The morphological, structural, and chemical transformations during the biomineralization process associated with the apatite formation from bovine-derived hydroxyapatite (BHAp) and BHAp/Nagelschmid...