Is non-buffered DMEM solution a suitable medium for in vitro bioactivity tests?

Several laboratories had tested bioactivity of the materials in commercially available solution DMEM (Dulbecco's Modified Eagle's Medium) that is normally used for cultivation of cell cultures. The objective of this work was to find out whether it is possible to replace TRIS-buffered SBF currently used for bioactivity tests with the non-buffered DMEM solution. To understand the role of the organic part of the DMEM solution in the process of crystallization, we have prepared non-buffered solution simulating only its inorganic part (identified as I-solution). It was found that under static-dynamic test conditions calcite (CaCO3) and the amorphous phase of calcium phosphate (ACP) formed on the surface of the glass-ceramic (45S5 bioactive glass based) scaffold exposed to both solutions. Additionally, halite (NaCl) formed at the beginning of exposure to DMEM. Hydroxyapatite phase was not detected on the surface in either non-buffered solution. Organic components contained in the DMEM solution failed to prevent formation of crystalline phases. The present results indicate that it is not recommendable to use DMEM for bioactivity tests of glass-ceramic materials due to its low concentration of Ca2+ ions, high concentration of HCO 3- ions and the necessity to maintain sterile environment during the test. © 2014 the Partner Organisations

MINERALOGY OF HALLOYSITES AND THEIR INTERACTION WITH PORPHYRINE

Samples representing two modifications of halloysites, dehydrated (7 Å) and hydrated (10 Å) forms, respectively, were examined with the aim to select suitable candidates for to be used as carriers of porphyrine photoactive molecules. The samples were analysed by powder X-ray diffraction (pXRD), infrared spectroscopy (FT-IR), and high resolution transmission electron microscopy (HRTEM). Chemical composition was also determined. For the determination of cationic exchange capacity (CEC) the silver thiourea method (AgTU) was used. Silver cations concentrations in the solution before and after the interaction were determined by atomic absorption spectrometry (AAS). By the interaction of two pure hydrated halloysites with porphyrine it was found that porphyrine does not intercalate the interlayer space, but it is adsorbed on the outer surface of halloysite. This interaction changed the colour of clay sample from white to green. The changes were also clearly visible on diffuse reflectance spectra (DRS)

Fe 2

Magnetic nanocomposites exhibit promising applications in many areas, for example optics, electronics, biology, medicine, etc. The main goal of this study was to synthesize magnetic ε-$Fe_2O_3$ nanoparticles embedded in amorphous $SiO_2$. These materials were prepared by the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 and 30 wt.%. The structure and properties of the final product were analysed by the Mössbauer spectrometry as well as by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. They strongly depend on the initial conditions of preparation

Fe2O3/SiO2Fe_2O_3/SiO_2 Hybrid Nanocomposites Studied Mainly by Mössbauer Spectroscopy

Magnetic nanocomposites exhibit promising applications in many areas, for example optics, electronics, biology, medicine, etc. The main goal of this study was to synthesize magnetic ε-$Fe_2O_3$ nanoparticles embedded in amorphous $SiO_2$. These materials were prepared by the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 and 30 wt.%. The structure and properties of the final product were analysed by the Mössbauer spectrometry as well as by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. They strongly depend on the initial conditions of preparation

Iron oxide mineralogy in Late Miocene red beds from La

Abstract Free ferric oxides of a red bed series were analyzed by rock-magnetic techniques (IRM component analysis) and by two less traditional methods: visible spectroscopy and voltammetry. All three methods have low limits of detection, making them suited for this type of analysis. The red bed samples studied contained clay minerals, quartz, and calcium carbonate as major constituents. Free Fe oxides occurred at a concentration of 0.3 -2.1%, i.e. in the majority of the samples below the detection limit of X-ray powder diffraction. The combination of the employed analytical techniques enabled to characterize the mineralogy of free ferric oxides and to estimate the ratio of goethite and to hematite. This ratio changes substantially within the section that probably indicates paleoclimatic changes.

Fe(III)-modified montmorillonite and bentonite : Synthesis, chemical and UV-Vis spectral characterization, arsenic sorption, and catalysis of oxidative dehydrogenation of propane

Two major species were identified in Fe-treated montmorillonite: monomeric or dimeric hydroxoaqua cations Fe(OH) - (form I), and polymeric structures with edge-shared Fe(O,OH) (form II). These species have different electron spectra (absorption maximum is 29,600 cm in form I, and 26,000 and 28,000 cm in form II), chemical and thermal stability, and electrochemical behavior. Form I behaves as a partly exchangeable cation in interaction with Cu from Cu-trien solution and Ni from Ni-EDTA, that can be used for selective quantitative analysis. On heating above the dehydration temperature (∼100-150°C) montmorrilonite with Fe in form I is converted to a mica-like structure and Fe ions are fixed more strongly in the montmorillonite structure. Form II behaves similarly to hydrous ferric oxides, but its thermal crystallization to hematite is postponed to ∼500-600°C. The Fe cations in the interlayer space are much less thermally stable than Al pillars in pillared interlayered clays (PILCs). Form I is more active in oxidative dehydrogenation of propane, while form II is the active species in sorption of As and the non-specific combustion of propane. To produce only form II by the treatment of montmorillonite with Fe, its load must be kept below ∼20 wt.%; otherwise the usual hydrous ferric oxides are formed

Durability of carbon-supported manganese oxide nanoparticles for the oxygen reduction reaction (ORR) in alkaline medium

International audienceMnOx/C-based electrocatalysts, prepared by the chemical deposition of manganese oxide nanoparticles on carbon, were tested towards the Oxygen Reduction Reaction (ORR) in their as-synthesized state and after ageing, either in ambient air for a year (mild ageing) or in an O2-saturated molar KOH solution at 80 °C for three weeks (premature ageing). For each electrocatalyst, the morphology and composition were characterised using TEM, XRD and chemical analysis. ORR kinetic parameters were evaluated using the Rotating Disk Electrode (RDE) and Rotating Ring Disk Electrode (RRDE) setups. Whilst the oxygen reduction activity of the electrocatalysts barely changes after mild ageing, it decreases after premature ageing following dramatic modifications to both the chemical and crystalline structures of the carbon-supported MnOx nanoparticles. The peroxide yield also sharply increases after premature ageing. Doping MnOx/C with nickel or magnesium divalent cations is beneficial since it improves both the catalytic activity and selectivity towards the 4-electron ORR pathway, even after ageing