Magnetic split-flow thin fractionation of magnetically susceptible particles.

We recently built a magnetic separation system to extend the applications of split-flow thin (SPLITT) fractionation to magnetically susceptible particles. Here, we characterize the magnetic SPLITT system using magnetically susceptible particles and ion-labeled particles. The flow axis of separation channel was orientated parallel and perpendicular to gravitational forces to exclude and include, respectively, gravitational effects on separation. Both operating modes were used to test the theory experimentally, with emphasis on the parallel mode. The magnetic susceptibilities of carrier and ion-labeled particles were varied, and various ion-labeled and unlabeled particles were studied experimentally, resulting in successful separation of labeled particles, yeasts, and cells from unlabeled ones. The minimal difference in magnetic susceptibility (delta(chi)) required for complete particle separation was about 1.75 x 10(-5) [cgs], corresponding to about 10(9) labeling ions per particle in this study. The throughput was around 7.2 x 10(8) particles/h using the present setup. Magnetic SPLITT fractionation shows good potential for use in obtaining particles magnetic susceptibilities from a simple theoretical treatment.     

New method of blood typing using analytical magnetapheresis

We report a new method of blood typing based on the agglutination of red blood cell (RBC) with serum-treated magnetic particles in analytical magnetapheresis. Blood typing of ABO was demonstrated. The agglutination patterns of RBCs are different for different blood types and can be used to determine the ABO blood typing in analytical magnetapheresis. Six samples can be tested in each run. The running time was less than 10 min. Magnetic particles were prepared in the laboratory. The amount of RBCs needed for the agglutination test was about 1.0 microl of adult blood. The blood typing of ABO was used to illustrate the capable applications of analytical magnetapheresis to nonmagnetic samples like cells without magnetic labels. Analytical magnetapheresis has a great potential for cell related analysis.     

Preparation of magnetically doped multilayered functional silica particles via surface modification with organic polymer

Magnetically modified functional particles are emerging as one of the most promising candidate in numerous multidisciplinary applications. In this research, a simple process has been developed to prepare magnetically modified aminated silica (SiO₂) particles. Herein, submicron‐sized SiO₂ particles were modified with poly(methylmethacrylate‐methacrylic acid) by seeded polymerization without any stabilizer. The carboxyl groups localized near the particles surface were then covalently linked with ethylene diamine to prepare aminated composite particles. Iron ions were then precipitated on the surface of aminated composite particles to obtain magnetically doped functional SiO₂ particles. The preparation of such particles was confirmed by scanning electron microscopy, Fourier transform infrared, ¹H NMR, X‐ray photoelectron spectroscopy and thermogravemetric analyses. Relative measurement of adsorption study of different biomolecules suggested that magnetically doped functional silica particles are comparatively hydrophobic. Copyright © 2012 John Wiley & Sons, Ltd.     

Directed assembly of BaFe12O19 particles and the formation of magnetically oriented films

We have studied the preparation of oriented BaFe(12)O(19) films produced using electrophoretic deposition (EPD). Highly anisotropic, platelike BaFe(12)O(19) particles were synthesized under hydrothermal conditions, and from these particles, stable suspensions were prepared in 1-butanol by the addition of dodecylbenzene sulfonic acid as a surfactant. The interplay of the interaction forces between the suspended particles and the forces acting on the particles during the EPD directed the particles' assembly in the plane of the substrate. The most significant effect on the orientation of the films was the diameter-to-thickness ratio of the particles, which was experimentally confirmed with X-ray analyses, electron microscopy, and magnetic measurements. The abnormal grain growth that accompanied the sintering at 1150 °C further improved the overall orientation of the films, which showed highly anisotropic magnetic behavior with a remanent-to-saturation magnetization ratio exceeding 0.8.     

Determination of magnetic susceptibility of various ion-labeled red blood cells by means of analytical magnetapheresis

Analytical magnetapheresis is a newly developed technique for separating magnetically susceptible particles. The magnetically susceptible particles are deposited on a bottom plate after flowing through a thin (< 0.05 cm) separation channel under a magnetic field applied perpendicular to the flow. Particles with various magnetic susceptibilities can be selectively deposited and separated by adjusting the applying magnetic force and flow rates. Magnetic susceptibility is an important parameter for magnetic separation. Magnetic susceptibility determination of various ion-labeled red blood cells (RBCs) using analytical magnetapheresis with a simple theoretical treatment is reported in this study. Susceptibility determination is based on the balance between maximal channel flow rate and magnetically induced flow rate for deposition. We tried a new approach to determine particle magnetic susceptibilities using a balance of magnetic and drag forces to control magnetically induced particle velocities. The Er3+, Fe3+, Cu2+, Mn2+, Co2+, and Ni2+ ions were used to label RBC at various labeling concentrations for susceptibility determination. The susceptibilities determined for various ion-labeled RBC under two magnetic field intensities fell within a 10% range. The average viabilities of various ion-labeled RBCs were 96.1 +/- 0.8%. The susceptibility determination generally took less than 10 min. Determined susceptibilities from analytical magnetapheresis differed by 10% from reference measurements using a superconducting quantum interference device (SQUID) magnetometer. The cost and time for analysis is much less using analytical magnetapheresis. This technique can provide a simple, fast, and economical way for particle susceptibility determinations.     

Nearly monodispersed core-shell structural Fe3O4@DFUR-LDH submicro particles for magnetically controlled drug delivery and release

Nearly monodispersed magnetic Fe(3)O(4)@DFUR-LDH submicro particles containing the anticancer agent DFUR were prepared via a coprecipitation-calcination-reconstruction strategy of LDH materials over the surface of Fe(3)O(4) particles, and present well-defined core-shell structure, strong magnetization and obvious magnetically controlled drug delivery and release properties.     

Mechanical properties of magnetically oriented epoxy

The microstructure of an epoxy system oriented in high magnetic fields (15–25 T) has been observed to consist of highly oriented domains at the molecular level along the direction of the applied field. The changes in the microstructure have been characterized as a function of the magnetic‐field strength and have been investigated microscopically and with wide‐angle X‐ray diffraction. The mechanical properties of the epoxy have been examined in light of nanoindentation experiments at different load levels. The basic results of the experimental investigations for the effect of high magnetic fields on the structure and property of the epoxy are presented. Nanoindentation testing has revealed large differences in the nanomechanical behavior for thermomagnetically processed epoxy specimens. The differences can be ascribed to the microstructural changes (reorientation) of the polymer at the molecular level. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1586–1600, 2004     

Optical properties of magnetically doped cholesterics

We have computed the optical diffraction pattern for linearly polarized light incident normal to the twist axis (phase grating mode) of a magnetically doped cholesteric (ferrocholesteric). The intrinsic Faraday rotation of the magnetic grains results in extra orders of diffraction. Also we find diffraction for any azimuth of the incident vibration. Further, using the Jones N matrices we have worked out the optical properties for light propagation along the twist axis on the very low wavelength side of the reflection band. We find that the medium behaves very differently from a normal cholesteric.     

New magnetically responsive polydicarbazole-magnetite nanoparticles

Magnetically responsive COOH-polydicarbazole-magnetite nanocomposites have been prepared by chemical oxidation of three COOH-dicarbazole monomers and - in the presence of magnetite nanoparticles. These functionalized nanoparticles have been tested for DNA hybridization experiments.     

Nano-Fe3O4-encapsulated silica particles bearing sulfonic acid groups as a magnetically separable catalyst for green synthesis of 1,1-diacetates

Sulfonic acid-functionalized silica-coated nano-Fe₃O₄particles (Fe₃O₄@SiO₂–SO₃H) serve as a novel heterogeneous catalyst for the synthesis of acylals by direct condensation of aldehydes with acetic anhydride under solvent-free conditions at room temperature in short reaction times and excellent yields. The catalyst could be easily separated from the final product using an external magnet and reused several times without consequential loss of reactivity.     

Magnetite nanoparticles/chiral nematic liquid crystal composites with magnetically addressable and magnetically erasable characteristics

A magnetite (Fe₃O₄) nanoparticle/chiral nematic liquid crystal (N*-LC) composite was prepared and filled into a planar treated cell. The Fe₃O₄ nanoparticles had been modified by oleic acid so that they could be better dispersed in the composite. When a magnetic field was scanned on the outer surface of the cell locally, Fe₃O₄ nanoparticles moved towards the inner surface of the cell correspondingly, and the black expected information was displayed. When the magnet was applied to the opposite outer surface, the information was erased. After polymer network walls were prepared in the composite, the resolution of the information displayed increased. Then, through the formation of hydrogen bonds between the nanoparticles and chiral pyridine compound (CPC) doped in the composite, the pitch length of the N*-LC could be adjusted by altering the intensity of the applied magnetic field. The composite doped with CPC could potentially be used as a material for a type of reflective colour paper with magnetically controllable characteristics.     

Thermal investigations of magnetically hard Fe-Cr-Co alloy

Differential thermal analysis and differential scanning calorimetry were applied to examine magnetically hard Fe-Cr-Co alloy. The spinodal decomposition temperature of this materials was established.

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Zusammenfassung Mittels DTA und DSC wurden hartmagnetische Fe-Cr-Co Legierungen untersucht. Es wurde auf die spinodale Entmischungstemperatur dieser Materialien aufmerksam gemacht.

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The author wishes to thank Mrs K. Chróst and Mr Kloda from the Institute of Material Engineering for the sample preparation and the microscopy investigations.     

Fabrication and modulation of magnetically supramolecular hydrogels

For the fabrication of magnetically supramolecular hydrogels, the aqueous colloidal dispersion of magnetic iron oxide nanoparticles was first stabilized by an amphiphilic poly(epsilon-caprolactone)-poly(ethylene glycol) (PEG-PCL) block copolymer and then mixed with an aqueous solution of a cyclic oligosaccharide. Due to the host-guest interaction between the used block copolymer and the cyclic oligosaccharide in the aqueous mixed system, such a fabrication process could result in the formation of a novel hydrogel nanocomposite with superparamagnetic property, as confirmed by the analyses from rheology and X-ray diffraction as well as magnetization curve measurements. For the resultant magnetically supramolecular hydrogel, its formation kinetics and mechanical strength could be modulated by the amount of the used PEG-PCL block copolymer, the cyclic oligosaccharide, or the incorporated iron oxide nanoparticles.     

Hydrogen-bond strengths by magnetically induced currents

We present here a "non-invasive" computational method to estimate the strength of individual hydrogen bonds using magnetically induced currents. The method is calibrated using H-bonding dimers, and applied on Watson-Crick DNA base pairs and proton wires in carbonic anhydrase.     

Analysis of the bioactivity of magnetically immunoisolated peroxisomes

Peroxisomes produce reactive oxygen species which may participate in biotransformations of innate biomolecules and xenobiotics. Isolating functional peroxisomes with low levels of contaminants would be a useful tool to investigate biotransformations occurring in these organelles that are usually confounded with biotransformations occurring in other co-isolated organelles. Here, we immunoisolate peroxisomes and demonstrate that the impurity level after isolation is low and that peroxisomes retain their biological activity. In this method, an antibody targeting a 70-kDa peroxisomal membrane protein was immobilized to silanized magnetic iron oxide beads (1–4 μm in diameter) coated with Protein A. Peroxisomes from L6 rat myoblast homogenates were magnetically captured, washed, and then analyzed for subcellular composition using enzymatic assays. Based on the ratio of peroxisomal to lysosomal activity, the retained fraction is 70-fold enriched relative to the unretained fraction. Similarly, the ratio of peroxisomal activity to mitochondrial content suggests that the retained fraction is >30-fold enriched relative to the unretained fraction. H₂O₂ production from the β-oxidation of palmitoyl-CoA demonstrated that the isolated peroxisomal fraction was biologically active. Capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) analysis confirmed that the immunopurified fractions were capable of transforming the anticancer drug doxorubicin and the fatty acid analog, BODIPY 500/510 C1C12. Besides its use to investigate peroxisome biotransformations in health and disease, the combination of magnetic immunoisolation with CE-LIF could be widely applicable to investigate subcellular-specific biotransformations of xenobiotics occurring at immunoisolated subcellular compartments.     

Formulation of magnetically perturbed time-dependent density functional theory

A formulation of time-dependent density functional theory (TDDFT) in the presence of a static imaginary perturbation is derived. A perturbational approach is applied leading to corrections to various orders in the quantities of interest, namely, the excitation energies and transition densities. The perturbed TDDFT equations are relatively straightforward to derive but the resulting expressions are rather cumbersome. Simplifications of these equations are suggested. Both the simplified and full expressions are used to obtain equations for first- and second-order corrections to the excitation energy, the first-order correction to the transition density, and the corrections for both quantities to first-order in two different perturbations. This formulation, called magnetically perturbed TDDFT, details how conventional TDDFT calculations can be corrected to allow for the inclusion of a static magnetic field and/or spin-orbit coupling.     

Observation of magnetically induced polarization in a ferrofluid

Light transmitted through a magnetite colloid subjected to a pulsed magnetic field is analyzed to determine particle size. Absorption measurements of light give a measure of the magnetic dipole moment. A comparison with theoretical estimates for particle coagulation is made and implications for medical research are noted.