Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface reactivity of different sets of glasses and glass-ceramics belonging to the SiO(2)-P(2)O(5)-CaO-MgO-K(2)O-Na(2)O system have been investigated. The attention was focused on the role of their composition on the bioactivity kinetics, in terms of pH modifications, silica-gel formation and its evolution toward hydroxycarbonatoapatite, after different times of soaking in simulated body fluid. Glasses and glass ceramics have been characterized by thermal analysis, SEM-EDS observations and phase analysis (XRD). XPS measurements have been carried out on the most representative set of sample in order to evaluate the evolution of the surface species during the growth of silica-gel and hydroxycarbonatoapatite. The response of murine fibroblast 3T3 to the material before and after a conditioning pre-treatment (immersion in SBF) has been investigated on the same set of samples in order to point out the role of the bioactivity mechanism on cell viability. The main differences among the various glasses have been related to the modifier oxides ratio and to the MgO content, which seems to have an influence on the glass stability, both in terms of thermal properties and surface reactivity. The surface characterization and in vitro tests revealed few variations in the reactivity of the different glasses and glass-ceramics in their pristine form. On the contrary, the different surface properties before and after the pre-treatment in SBF seem to play a role on the biocompatibility of both glass and glass-ceramics, due to the different ion release and hydrophilicity of the surfaces, affecting both cell viability and protein adsorption.
 ...
PMID:Early stage reactivity and in vitro behavior of silica-based bioactive glasses and glass-ceramics. 1870 58

A 57% SiO(2), 3% Al(2)O(3), 34% CaO and 6% Na(2)O glass (SCNA) has been produced in form of powders and deposited by plasma spray on titanium alloy and stainless steel substrates. The obtained coatings have been subjected to a patented ion-exchange treatment to introduce silver ions in the surface inducing an antibacterial behavior. Silver surface-enriched samples have been characterized by means of X-ray diffraction, SEM observation, EDS analysis, in vitro bioactivity tests, leaching tests by GFAAS (graphite furnace atomic adsorption spectroscopy) analyses, cells adhesion and proliferation, and antibacterial tests using Staphylococcus Aureus strain. In vitro tests results showed that the modified samples acquired an antimicrobial action against tested bacteria maintaining unaffected the biocompatibility of the glass. Furthermore the ion-exchange treatment can be successfully applied to glass-coated samples without affecting the properties of the coatings; the simplicity and reproducibility of the method make it suitable for glass or glass-ceramic coatings of different composition in order to produce coated devices for bone healing and/or prostheses, able to reduce bacterial colonization and infections risks.
 ...
PMID:Surface silver-doping of biocompatible glasses to induce antibacterial properties. Part II: Plasma sprayed glass-coatings. 1898 53

Submicron bioactive glass fibers 70S30C (70 mol% SiO(2), 30 mol% CaO) acting as bone tissue scaffolds were fabricated by electrospinning method. The scaffold is a hierarchical pore network that consists of interconnected fibers with macropores and mesopores. The structure, morphological characterization and mechanical properties of the submicron bioactive glass fibers were studied by XRD, EDS, FIIR, SEM, N(2) gas absorption analyses and nanoindentation. The effect of the voltage on the morphology of electrospun bioactive glass fibers was investigated. It was found that decreasing the applied voltage from 19 to 7 kV can facilitate the formation of finer fibers with fewer bead defects. The hardness and Young's modulus of submicron bioactive glass fibers were measured as 0.21 and 5.5 GPa, respectively. Comparing with other bone tissue scaffolds measured by nanoindentation, the elastic modulus of the present scaffold was relatively high and close to the bone.
 ...
PMID:Electrospun submicron bioactive glass fibers for bone tissue scaffold. 1902 Sep 52

A 45S5 bioactive glass (nominal composition: 46.1 mol.% SiO2, 2.6 mol.% P2O5, 26.9 mol.% CaO, 24.4 mol.% Na2O) was electrothermally poled by applying voltages up to 750 V for 45 min at 200 degrees C, and the thermally stimulated depolarization currents (TSDCs) were recorded. Changes in chemical composition and electrical properties after poling were investigated by TSDC measurements, impedance spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The poling led to the formation of interfacial layers underneath the surface in contact with the electrodes. Under the positive electrode, the layer was characterized by Na+ ion depletion and by a negative charge density, and the layer was more resistive than the bulk. The influence of poling on the bioactivity was studied by immersion of samples in simulated body fluid (SBF) with subsequent cross-sectional SEM/EDX and X-ray diffraction analysis. It was found that poling leads to morphological changes in the silica-rich layer and to changes in the growth rate of amorphous calcium phosphate and bone-like apatite on the glass surface. The bone-like apatite layer under the positive electrode was slightly thicker than that under the negative electrode.
 ...
PMID:Bioactivity of electro-thermally poled bioactive silicate glass. 1909 52

This paper presents a new way of recycling aluminum and iron in boiler slag derived from coal combustion plants, which integrates efficient extraction and reuse of the leached pellets together. The boiler slag was pelletized together with washed coal and lime prior to sintering and then was sintered at 800-1200 degrees C for different periods to produce sintered pellets for the leaching test. An elemental analysis of aqueous solutions leached by sulfuric acid was determined by EDTA-Na(2)-ZnCl(2) titration method. The components and microstructures of the samples, sintered pellets and leached residue were examined by means of XRF, XRD and SEM. XRD analysis indicates that predominate minerals such as kaolinite, quartz, calcium silicide, hematate and metakoalin exist in the boiler slag. An aluminum extraction efficiency of 86.50% was achieved. The maximum extraction efficiency of Fe was 94.60% in the same conditions of that for the maximum extraction efficiency of Al. The extraction efficiencies of Al and Fe increased with an increase in temperature, leaching time and acidity. High Al extraction efficiency was obtained for pellets with high CaO content. The final product of alumina would be used directly for the production of metallic aluminum.
 ...
PMID:Leaching of aluminum and iron from boiler slag generated from a typical Chinese Steel Plant. 1915 93

There is accumulating evidence that strontium (Sr)-containing bioceramics have positive effects on bone tissue repair. The aims of the present study were to evaluate the osteoconductivity of Sr-doped bioactive glass (BG) particles implanted in rat tibia bone marrow, and characterize the neoformed bone tissue by SEM-energy-dispersive X-ray microanalysis. Melt-derived BGs were prepared from a base 45S5 BG. Sr-doped glass (45S5.6Sr) was prepared using 6 wt % SrO as a substitute for the CaO. Histological analysis using undecalcified sections showed that new lamellar bone had formed along the surface of both 45S5 and 45S5.6Sr BG particles within 4 weeks. To evaluate osteoconductivity, affinity indices were calculated. At 30 days after implantation, 45S5 and 45S5.6Sr BGs had almost identical affinity indices (88% +/- 7% and 87% +/- 9%; p > 0.05). Strontium was not detected in the neoformed bone tissue surrounding 45S5.6Sr BG particles. These results indicate that 45S5.6Sr BG particles are osteoconductive when implanted inside the intramedullary canal of rat tibiae, and no alterations in bone mineralization, in terms of Ca/P ratio, were observed in the neoformed bone tissue around 45S5.6Sr BG particles.
 ...
PMID:Osteoconductivity of strontium-doped bioactive glass particles: a histomorphometric study in rats. 1917 15

The work presents the results of application of natural clinoptilolite for immobilization of heavy metal cations (Ag(+), Pb(2+), Cd(2+) and Cr(3+)) from aqueous solutions and uses zeolite to prepare autoclaved building composites. Sorption has been conducted on sodium form of natural clinoptilolite originated from Poland. Clinoptilolite (sodium form containing heavy metal cations) has been applied to obtain new building materials which have good physical properties. Samples produced by autoclaving process showed relatively low bulk density (about 1.35 g/cm(3)). The compressive strength depended on the amount of CaO in the initial mixture. Its maximum value was about 40 MPa. The influence of heavy metal cations on the compressive strength values was insignificant (except for the Cr(3+) ions). However, all the cations modified the microstructure and the ordered state of C-S-H phase. Efficiency of Ag(+), Cd(2+) and Pb(2+) ions immobilization on the mineral matrix was shown. In the work, results of IR spectroscopy, atomic absorption spectroscopy (AAS) studies, X-ray diffraction analysis, SEM observations and technological investigations are presented.
 ...
PMID:Use of clinoptilolite for the immobilization of heavy metal ions and preparation of autoclaved building composites. 1936 99

Series nickel catalysts Ni/MgO(x)/CaO(1-)(x) (x=0.3, 0.5, 0.7, Ni: 5 wt%) were prepared and tested in fixed-bed reactor for biomass tar steam reforming, toluene as tar destruction model compound. Different ratios of MgO and CaO were mixed to simulate dolomite as Ni support. Two preparation methods: solid mixing with (SMW) and without water (SM) were used, the preparation methods and concentration of MgO had an important influence on toluene conversion and products. Catalysts prepared by SM method exhibited higher performance on toluene conversion, resulted in higher H(2) yield, and also, higher CO(2) and lower CO selectivity with higher temperature. For the same preparation method, higher concentration of MgO resulted in higher toluene conversion, and also influence on CO, CO(2) selectivity, but no obvious influence on the H(2) yield. Catalysts were characterized by BET, X-ray diffraction (XRD), SEM.
 ...
PMID:Steam reforming of biomass tar producing H2-rich gases over Ni/MgOx/CaO1-x catalyst. 1936 62

In the present study, bioceramic composites with improved mechanical and biological properties were synthesized by sintering mixtures of beta-tricalcium phosphate and SiO(2)-CaO-MgO-P(2)O(5) sol-gel derived bioactive glass at 1000-1200 degrees C. The physical, mechanical, structural and biological properties of the composites were evaluated by appropriate experiments such as microhardness, bending strength, XRD, SEM and MTT. The results showed that 1000 and 1100 degrees C were not appropriate temperatures for sintering the composites and in contrast, the microhardness, bending strength and bulk density significantly increased by increasing in quantity of bioglass phase when the samples were sintered at 1200 degrees C. No significant difference was found between the fracture toughness of the composites and pure beta-tricalcium phosphate. beta-tricalcium phosphate was structurally stable up to 1200 degrees C and did not transform to its alpha form even in the presence of the bioglass phase but migration of magnesium cations from the glass composition into its lattice structure was found by right-shift in XRD patterns, especially when the composite contained higher amount of bioglass component. Calcium silicate was also crystallized in the composition of the composites, which was more detectable in higher sintering temperatures. The results of the MTT test showed that proliferation of human osteosarcoma cells on the composites was considerably better than that of pure beta-TCP.
 ...
PMID:Composite bone substitute materials based on beta-tricalcium phosphate and magnesium-containing sol-gel derived bioactive glass. 1946 30

In this study, composites of beta-tricalcium phosphate (beta-TCP) and sol gel derived bioactive glass (10, 25, and 40 wt %) based on the SiO(2)-CaO-MgO-P(2)O(5) system were prepared and sintered at 1000-1200 degrees C. The mechanical properties were investigated by measuring bending strength, Vickers hardness and fracture toughness. Structural properties were evaluated by XRD and SEM analysis, and the biological properties were studied by soaking the samples in simulated body fluid (SBF) and in contact with osteoblastic cell for viability assay. When the samples were sintered at 1200 degrees C, the mechanical strength increased, up to 34%, by increasing the amount of bioactive glass phase. In contrast, it decreased when the samples were sintered at 1000 and 1100 degrees C. The results showed that the strength could be improved up to 56% when more firing period was used. Incorporation of the bioactive glass phase into beta-TCP increased the microhardness but did not significantly change the fracture toughness. Phase analysis revealed that beta-TCP or magnesium-substituted beta-TCP was the main crystalline phase of the composites beside some calcium silicate crystallized in the bioactive glass phase. Plenty precipitation of calcium phosphate layer onto the surfaces of the beta-TCP/bioactive glass composites soaked in SBF indicated superior bioactivity of these materials compared to pure beta-TCP without any precipitation. The ability of beta-TCP/bioactive glass composites to support the growth of human osteoblastic cells was considerably better than that of pure beta-TCP. These results may be used to indicate which compositions and processing conditions can provide appropriate materials for hard tissue regeneration.
 ...
PMID:Development of beta-tricalcium phosphate/sol-gel derived bioactive glass composites: physical, mechanical, and in vitro biological evaluations. 1950 41


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>