Starch-Coated Magnetic Iron Oxide Nanoparticles for Affinity Purification of Recombinant Proteins.

Starch-coated magnetic iron oxide nanoparticles have been synthesized by a simple, fast, and cost-effective co-precipitation method with cornstarch as a stabilizing agent. The structural and magnetic characteristics of the synthesized material have been studied by transmission electron microscopy, Mössbauer spectroscopy, and vibrating sample magnetometry. The nature of bonds between ferrihydrite nanoparticles and a starch shell has been examined by Fourier transform infrared spectroscopy. The data on the magnetic response of the prepared composite particles have been obtained by magnetic measurements. The determined magnetic characteristics make the synthesized material a good candidate for use in magnetic separation. Starch-coated magnetic iron oxide nanoparticles have been tested as an affinity sorbent for one-step purification of several recombinant proteins (cardiac troponin I, survivin, and melanoma inhibitory activity protein) bearing the maltose-binding protein as an auxiliary fragment. It has been shown that, due to the highly specific binding of this fragment to the starch shell, the target fusion protein is selectively immobilized on magnetic nanoparticles and eluted with the maltose solution. The excellent efficiency of column-free purification, high binding capacity of the sorbent (100-500 µg of a recombinant protein per milligram of starch-coated magnetic iron oxide nanoparticles), and reusability of the obtained material have been demonstrated.

Magnetic Fractions of PM2.5, PM2.5-10, and PM10 from Coal Fly Ash as Environmental Pollutants.

Characterization of magnetic particulate matter (PM) in coal fly ashes is critical to assessing the health risks associated with industrial coal combustion and for future applications of fine fractions that will minimize solid waste pollution. In this study, magnetic narrow fractions of fine ferrospheres related to environmentally hazardous PM2.5, PM2.5-10, and PM10 were for the first time separated from fly ash produced during combustion of Ekibastuz coal. It was determined that the average diameter of globules in narrow fractions is 1, 2, 3, and 7 µm. The major components of chemical composition are Fe2O3 (57-60) wt %, SiO2 (25-28 wt %), and Al2O3 (10-12 wt %). The phase composition is represented by crystalline phases, including ferrospinel, α-Fe2O3, ε-Fe2O3, mullite, and quartz, as well as the amorphous glass phase. Mössbauer spectroscopy and magnetic measurements confirmed the formation of nanoscale particles of ε-Fe2O3. Stabilization of the ε-Fe2O3 metastable phase, with quite ideal distribution of iron cations, occurs in the glass matrix due to the rapid cooling of fine globules during their formation from mineral components of coal.

Electronic and magnetic states of Fe ions in Co2FeBO5.

The ludwigite Co2FeBO5 has been studied experimentally using 57Fe Mössbauer spectroscopy and theoretically using DFT + GGA calculations. The room-temperature Mössbauer spectra are composed of four quadrupole doublets corresponding to the high-spin Fe3+ ions in octahedral oxygen coordination. All components undergo splitting below 117 K due to the magnetic hyperfine fields. The DFT + GGA calculations performed for three models of Fe ion distributions have revealed that the ground state corresponds to the "Fe4(HS)" model with the high-spin Fe3+ ions located at the M4 site and the high-spin Co2+ ions located at the M1, M2, and M3 sites. A ferrimagnetic ground state, with the Co and Fe magnetic moments being nearly parallel to the b-axis and a total magnetic moment of circa 1.1µB f.u.-1, was found. The other Fe distributions cause an increase in the local octahedral distortions and transformation of the spin state. The calculated quadrupole splitting values are in good agreement with the experimental values obtained by Mössbauer spectroscopy.

Biogenic Ferrihydrite Nanoparticles: Synthesis, Properties In Vitro and In Vivo Testing and the Concentration Effect.

Biogenic ferrihydrite nanoparticles were synthesized as a result of the cultivation of Klebsiella oxytoca microorganisms. The distribution of nanoparticles in the body of laboratory animals and the physical properties of the nanoparticles were studied. The synthesized ferrihydrite nanoparticles are superparamagnetic at room temperature, and the characteristic blocking temperature is 23-25 K. The uncompensated moment of ferrihydrite particles was determined to be approximately 200 Bohr magnetons. In vitro testing of different concentrations of ferrihydrite nanoparticles for the functional activity of neutrophilic granulocytes by the chemiluminescence method showed an increase in the release of primary oxygen radicals by blood phagocytes when exposed to a minimum concentration and a decrease in secondary radicals when exposed to a maximum concentration. In vivo testing of ferrihydrite nanoparticles on Wister rats showed that a suspension of ferrihydrite nanoparticles has chronic toxicity, since it causes morphological changes in organs, mainly in the spleen, which are characterized by the accumulation of hemosiderin nanoparticles (stained blue according to Perls). Ferrihydrite can also directly or indirectly stimulate the proliferation and intracellular regeneration of hepatocytes. The partial detection of Perls-positive cells in the liver and kidneys can be explained by the rapid elimination from organs and the high dispersion of the nanomaterial. Thus, it is necessary to carry out studies of these processes at the systemic level, since the introduction of nanoparticles into the body is characterized by adaptive-proliferative processes, accompanied by the development of cell dystrophy and tension of the phagocytic system.

Valleriite, a Natural Two-Dimensional Composite: X-ray Absorption, Photoelectron, and Mössbauer Spectroscopy, and Magnetic Characterization.

Valleriite is of interest as a mineral source of basic and precious metals and as an unusual material composed of two-dimensional (2D) Fe-Cu sulfide and magnesium hydroxide layers, whose characteristics are still very poorly understood. Here, the mineral samples of two types with about 50% of valleriites from Noril'sk ore provenance, Russia, were examined using Cu K- and Fe K-edge X-ray absorption fine structure (XAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), 57Fe Mössbauer spectroscopy, and magnetic measurements. The Cu K X-ray absorption near-edge structures (XANES) spectra resemble those of chalcopyrite, however, with a higher electron density at Cu+ centers and essentially differ from those of bornite Cu5FeS4; the Fe K-edge was less informative because of accompanying oxidized Fe-containing phases. The post-edge XANES and extended XAFS (EXAFS) analysis reveal differences in the bond lengths, e.g., additional metal-metal distances in valleriites as compared with chalcopyrite. The XPS spectra confirmed the Cu+ and Fe3+ state in the sulfide sheets and suggest that they are in electron equilibrium with (Mg, Al) hydroxide layers. Mössbauer spectra measured at room temperature comprise central doublets of paramagnetic Fe3+, which decreased at 78 K and almost disappeared at 4.2 K, producing a series of hyperfine Zeeman sextets due to internal magnetic fields arising in valleriites. Magnetic measurements do not reveal antiferromagnetic transitions known for bornite. The specific structure and properties of valleriite are discussed in particular as a platform for composites of the 2D transition metal sulfide and hydroxide (mono)layers stacked by the electrical charges, promising for a variety of applications.