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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Aspherical magnetically modulated optical nanoprobes (MagMOONs)

Jeffrey N. Anker, Caleb Behrend, and Raoul Kopelman

J. Appl. Phys. 93, 6698 (2003); http://dx.doi.org/10.1063/1.1556926 (3 pages) | Cited 16 times

Online Publication Date: 9 May 2003

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Aspherical magnetic particles orient in a magnetic field due to magnetic shape anisotropy. They also emit different fluxes of light from their different geometric faces due to self-absorption and total internal reflection within the particles. The particles rotate in response to rotating magnetic fields and appear to blink as they rotate. We have made pancake and chain shaped particles and magnetically modulated their fluorescent intensities. Demodulating the signal extracts the probe fluorescence from electronic and optical backgrounds dramatically increasing signal to noise ratios. The probes have applications in sensitive and rapid immunoassays, improved intracellular sensors, and inexpensive single molecule analysis. © 2003 American Institute of Physics.
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85.70.Sq Magnetooptical devices
75.50.Tt Fine-particle systems; nanocrystalline materials
78.55.-m Photoluminescence, properties and materials
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy
87.85.Qr Nanotechnologies-design
87.85.Rs Nanotechnologies-applications
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Polarized light transmission of smooth muscle cells during magnetic field exposures

M. Iwasaka and S. Ueno

J. Appl. Phys. 93, 6701 (2003); http://dx.doi.org/10.1063/1.1556927 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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Strong static magnetic fields in the Tesla range have a diamagnetic force on cell components. Within an exposure period of 3 d, such magnetic fields generate a clear alignment of the smooth muscle cell assembly, which is parallel to the direction of the fields. In the present study, behavioral changes in intracellular components were suggested by changes in optical transmission under the influence of magnetic fields of 8 T. The magnetically oriented cells were exposed both in parallel and perpendicularly to the 8 T magnetic fields, and the time course of the polarized light transmission at 500 nm was measured in real time. The perpendicularly exposed cells had a presteady state, which was slow to increase. However, the total change in the intensity of the polarized light was larger than that of the cells exposed in parallel. We observed that no distinct changes in cell morphology including cell membrane components occurred during the 3 h of exposure to the magnetic fields. Based on the results, we concluded that intracellular component motion had a major influence on polarized light transmission under 8 T magnetic fields. We speculated that unconstrained intracellular macromolecules, such as actin fibers and microtubules, rotated due to diamagnetic torque forces during the 3 h of exposure to 8 T magnetic fields. © 2003 American Institute of Physics.
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87.63.L- Visual imaging
87.19.Ff Muscles
87.50.C- Static and low-frequency electric and magnetic fields effects

Determination of binding constant Kb of biocompatible, ferrite-based magnetic fluids to serum albumin

A. C. Tedesco, D. M. Oliveira, Z. G. M. Lacava, R. B. Azevedo, E. C. D. Lima, C. Gansau, N. Buske, and P. C. Morais

J. Appl. Phys. 93, 6704 (2003); http://dx.doi.org/10.1063/1.1555154 (3 pages) | Cited 18 times

Online Publication Date: 9 May 2003

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In this work, we investigated the interaction between molecular-coated magnetic nanoparticles (MC-MNPs) and serum albumin proteins (BSA) through the fluorescence quenching of the tryptophan residue present in BSA after the binding of MC-MNPs to specific sites. Three different biocompatible magnetic fluid (BMF) samples based on magnetite or cobalt–ferrite MNPs coated with citric acid or dextran were used. The binding constant and the stoichiometry of the investigated MNPs indicate that the BMF based on cobalt–ferrite is more site specific and more strongly bound to the BSA than the BMFs based on magnetite. The results may direct the design of new magnetic drug-carriers based on BMFs. © 2003 American Institute of Physics.
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87.15.K- Molecular interactions; membrane-protein interactions
75.50.Mm Magnetic liquids
75.50.Gg Ferrimagnetics
87.14.E- Proteins
87.85.J- Biomaterials
87.15.M- Spectra of biomolecules
87.50.C- Static and low-frequency electric and magnetic fields effects
75.50.Tt Fine-particle systems; nanocrystalline materials

Biological investigation of a citrate-coated cobalt–ferrite-based magnetic fluid

S. Kückelhaus, V. A. P. Garcia, L. M. Lacava, R. B. Azevedo, Z. G. M. Lacava, E. C. D. Lima, F. Figueiredo, A. C. Tedesco, and P. C. Morais

J. Appl. Phys. 93, 6707 (2003); http://dx.doi.org/10.1063/1.1558665 (2 pages) | Cited 9 times

Online Publication Date: 9 May 2003

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The present study reports on several in vivo biological tests carried out with a cobalt–ferrite, citrate-coated, magnetic fluid sample developed for biomedical purposes. Systematic biological investigation was performed after endovenous injection in mice. Morphological analysis showed magnetic nanoparticle (MNP) infiltration in the parenchyma or vessels of all investigated organs. Nevertheless, at the investigated dose and period of treatment, no cell damage or inflammatory processes were observed. Cytometry alterations and genotoxic effects were not observed. Although precipitation of MNPs in tissues may be taken as undesirable, the absence of morphological alterations is very promising. The data show that the investigated sample is biocompatible and useful for biomedical applications. © 2003 American Institute of Physics.
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87.85.J- Biomaterials
75.50.Gg Ferrimagnetics
75.50.Mm Magnetic liquids
87.17.-d Cell processes
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
87.50.C- Static and low-frequency electric and magnetic fields effects

Investigation of lipid peroxidation and catalase activity in magnetic fluid treated mice

M. L. L. Freitas, L. P. Silva, J. L. Freitas, R. B. Azevedo, Z. G. M. Lacava, P. I. Homem de Bittencourt, R. Curi, N. Buske, and P. C. Morais

J. Appl. Phys. 93, 6709 (2003); http://dx.doi.org/10.1063/1.1558671 (3 pages)

Online Publication Date: 9 May 2003

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The increasing interest in magnetic fluids (MFs) for biomedical applications demands a deeper knowledge of their effects in biological systems. To evaluate the in vivo response of a MF sample based on magnetite nanoparticles stabilized by a precoating double layer of dodecanoic acid plus ethoxylated polyalcohol (MFDE), the inflammation-related oxidative stress and antioxidant tissue response were both addressed in this study. MFDE sample was intraperitoneally administrated to mice at three different doses. The lipid peroxidation and the antioxidant defense induced in the liver and spleen were evaluated, respectively, by thiobarbituric acid-reactive substances (TBARS) and catalase activity, 1, 14, and 28 days after MFDE treatment. The liver and spleen responded with a huge increase in TBARS after MFDE treatment. We observed that oxidative changes as well as the variations in the liver catalase activity were time and MFDE-dose dependent. © 2003 American Institute of Physics.
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87.15.R- Reactions and kinetics
75.50.Mm Magnetic liquids

Magnetic micromachines prepared by ferrite plating technique

K. Nishimura, H. Uchida, M. Inoue, M. Sendoh, K. Ishiyama, and K. I. Arai

J. Appl. Phys. 93, 6712 (2003); http://dx.doi.org/10.1063/1.1556928 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2003

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By the sterolithography technique and the ferrite plating, we fabricated three types of magnetic micromachines which coated Fe3O4, Co0.39Fe2.61O4, and Co0.45Fe2.55O4, respectively. The stereolithography technique enables one to form the spiral-shape resinous templates and the ferrite plating enables one to coat the ferrites uniformly onto these templates from an aqueous solution. The total machine weight is light because a resin of the template body is almost the same density as water. We verified that the machines swim freely and wirelessly in water by applying a rotational magnetic field. As these machines coated with ferrites have the biocompatibility, there is the possibility of medical microrobots which swim in the human body for medical operations. © 2003 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
87.80.-y Biophysical techniques (research methods)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Verification of magnetic field gradient effects on medium convection and cell adhesion

M. Iwasaka, K. Yamamoto, J. Ando, and S. Ueno

J. Appl. Phys. 93, 6715 (2003); http://dx.doi.org/10.1063/1.1558632 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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We investigated the effects of strong static magnetic fields on the convectional flow in a cell culture medium and their consequences on cell adhesion patterns. Gradient magnetic fields of 6 T with 60 T/m affected the convection with floating cell aggregations in a cell culture flask, and reversibly changed the direction of convectional flow. HeLa cells exhibited streamlike-cell distribution patterns in the direction of the applied magnetic field gradient. The study also revealed a promotion of cell orientation by a thermal convectional flow in the medium after magnetic field exposure of MC3T3 cells at 8 T for one day. An application of gradient magnetic fields for the treatment of cell adhesion was proposed using a magnetically modulated convectional flow. © 2003 American Institute of Physics.
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87.50.C- Static and low-frequency electric and magnetic fields effects

Measurement of evoked electroencephalography induced by transcranial magnetic stimulation

Keiji Iramina, Takashi Maeno, Yukio Nonaka, and Shoogo Ueno

J. Appl. Phys. 93, 6718 (2003); http://dx.doi.org/10.1063/1.1558635 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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This study focused on the measurement of evoked potentials induced by transcranial magnetic stimulation (TMS) for observing the neuronal connectivity in the brain. We developed an electroencephalography (EEG) measurement system to eliminate the electromagnetic interaction emitted from TMS. EEG activities 5 ms after TMS stimulation were measured. Using this artifact free amplifier, we investigated the intensity dependence of brain activation induced by TMS. When the stimulus intensity was changed at three levels, TMS-evoked EEG responses were measured. Several components of the evoked potential appeared at 9 ms, 20 ms, and 50 ms after stimulation. A large response appeared at about 9 ms after cerebellar TMS. There was a significant dependence of these responses on the stimulus intensity. During right-hand side motor area stimulation, there was no clear peak of the wave forms within 10 ms latency. Occipital stimulation caused more evoked responses to spread to the center of the brain than at other areas of stimulation. The evoked signal by TMS was possibly conducted posteriorly to anteriorly along the pathways of the neuronal fiber exiting the cerebellum into the cerebral cortex. © 2003 American Institute of Physics.
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87.19.R- Mechanical and electrical properties of tissues and organs
87.50.C- Static and low-frequency electric and magnetic fields effects

Magnetic measurements on human erythrocytes: Normal, beta thalassemia major, and sickle

Lama Sakhnini

J. Appl. Phys. 93, 6721 (2003); http://dx.doi.org/10.1063/1.1540171 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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In this article magnetic measurements were made on human erythrocytes at different hemoglobin states (normal and reduced hemoglobin). Different blood samples: normal, beta thalassemia major, and sickle were studied. Beta thalassemia major and sickle samples were taken from patients receiving lifelong blood transfusion treatment. All samples examined exhibited diamagnetic behavior. Beta thalassemia major and sickle samples showed higher diamagnetic susceptibilities than that for the normal, which was attributed to the increase of membrane to hemoglobin volume ratio of the abnormal cells. Magnetic measurements showed that the erythrocytes in the reduced state showed less diamagnetic response in comparison with erythrocytes in the normal state. Analysis of the paramagnetic component of magnetization curves gave an effective magnetic moment of μeff=7.6 μB per reduced hemoglobin molecule. The same procedure was applied to sickle and beta thalassemia major samples and values for μeff were found to be comparable to that of the normal erythrocytes. © 2003 American Institute of Physics.
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87.14.E- Proteins
87.17.-d Cell processes
87.19.X- Diseases
87.50.C- Static and low-frequency electric and magnetic fields effects

Effects of intense magnetic fields on sedimentation pattern and gene expression profile in budding yeast

Masateru Ikehata, Masakazu Iwasaka, Junji Miyakoshi, Shoogo Ueno, and Takao Koana

J. Appl. Phys. 93, 6724 (2003); http://dx.doi.org/10.1063/1.1556929 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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Effects of magnetic fields (MFs) on biological systems are usually investigated using biological indices such as gene expression profiles. However, to precisely evaluate the biological effects of MF, the effects of intense MFs on systematic material transport processes including experimental environment must be seriously taken into consideration. In this study, a culture of the budding yeast, Saccharomyces cerevisiae, was used as a model for an in vitro biological test system. After exposure to 5 T static vertical MF, we found a difference in the sedimentation pattern of cells depending on the location of the dish in the magnet bore. Sedimented cells were localized in the center of the dish when they were placed in the lower part of the magnet bore while the sedimentation of the cells was uniform in dishes placed in the upper part of the bore because of the diamagnetic force. Genome wide gene expression profile of the yeast cells after exposure to 5 T static MF for 2 h suggested that the MF did not affect the expression level of any gene in yeast cells although the sedimentation pattern was altered. In addition, exposure to 10 T for 1 h and 5 T for 24 h also did not affect the gene expression. On the other hand, a slight change in expressions of several genes which are related to respiration was observed by exposure to a 14 T static MF for 24 h. The necessity of estimating the indirect effects of MFs on a study of its biological effect of MF in vitro will be discussed. © 2003 American Institute of Physics.
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87.17.Jj Cell locomotion, chemotaxis
87.17.Ee Growth and division
87.50.C- Static and low-frequency electric and magnetic fields effects

Magnetosensitive enzyme electrode for hydrogen peroxide sensing

M. Yaoita, M. Iwasaka, and S. Ueno

J. Appl. Phys. 93, 6727 (2003); http://dx.doi.org/10.1063/1.1556930 (3 pages)

Online Publication Date: 9 May 2003

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Peroxidase is one of the magnetosensitive enzymes, and has an important role in scavenging reactive oxygen species. In the present study, a surface of platinum black electrode was laminated by peroxidase molecules, and H2O2 decomposing processes by peroxidase and platinum black were monitored with and without magnetic fields of up to 14 T. An increase in the current reflected a decrease in the activity of peroxidase molecules. The current in the electrode with peroxidase increased significantly depending on the applied magnetic flux intensity. The increases of current during the magnetic field exposures were observed consistently both when the currents were transiently decreasing and at a constant level. It is suggested that the layers of peroxidase molecules on the platinum black cause a distortion by diamagnetic forces acting on the layers, and the distortion is concentrated on a catalytic part in the peroxidase resulting in the observed activity decreases. © 2003 American Institute of Physics.
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82.47.Rs Electrochemical sensors
87.50.C- Static and low-frequency electric and magnetic fields effects
82.39.Fk Enzyme kinetics
82.80.Fk Electrochemical methods
87.14.E- Proteins
87.15.M- Spectra of biomolecules

Conductivity tensor imaging of the brain using diffusion-weighted magnetic resonance imaging

Masaki Sekino, Kikuo Yamaguchi, Norio Iriguchi, and Shoogo Ueno

J. Appl. Phys. 93, 6730 (2003); http://dx.doi.org/10.1063/1.1544446 (3 pages) | Cited 13 times

Online Publication Date: 9 May 2003

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Conductivity tensor images of the rat brain were obtained by a method based on diffusion-weighted magnetic resonance imaging (MRI). Diffusion-weighted images were acquired by a 4.7 T MRI system with motion probing gradients (MPGs) applied in three directions. Conductivities in each MPG direction were calculated from the fast component of the apparent diffusion coefficient and the fraction of the fast component, and two-dimensional conductivity tensor was estimated. Regions of interest (ROIs) were selected in the cortex and the corpus callosum. The mean conductivities in each ROI were 0.014 S/m and 0.018 S/m, respectively. The corpus callosum exhibited higher conductivity anisotropy resulting from anisotropic tissue structures such as axons and dendrites. © 2003 American Institute of Physics.
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87.61.-c Magnetic resonance imaging
87.19.L- Neuroscience
87.19.R- Mechanical and electrical properties of tissues and organs

Spontaneous magnetoencephalography alpha rhythm measurement in a cylindrical magnetic shield employing magnetic shaking

K. Tashiro, K. Nagashima, A. Sumida, T. Fukunaga, and I. Sasada

J. Appl. Phys. 93, 6733 (2003); http://dx.doi.org/10.1063/1.1558637 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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This article shows a demonstration of magnetoencephalography measurement in a cylindrical magnetic shield made of cobalt-based amorphous tape with magnetic shaking. The noise levels of the first-order superconducting quantum interference device gradiometers that operated in the shield were reduced to as low as 40 fT/√Hz at 10 Hz by surrounding it with a simple rf shield made of conductive cloth. We observed spontaneous alpha rhythms from a human brain in this shielding system. Alpha rhythms and their suppression caused by opening the eyes were clearly found, which was also confirmed by electroencephalography measurement from the same volunteer under similar conditions. © 2003 American Institute of Physics.
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87.80.-y Biophysical techniques (research methods)
07.55.Nk Magnetic shielding in instruments
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Multicomponent proton spin–spin relaxation of fibrin gels with magnetically oriented and randomly oriented fibrin fiber structures

Michihiro Takeuchi, Masaki Sekino, Kikuo Yamaguchi, Norio Iriguchi, and Shoogo Ueno

J. Appl. Phys. 93, 6736 (2003); http://dx.doi.org/10.1063/1.1558639 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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We investigated the effect of structural differences in fibrin fibers on the T2 relaxation time. Fibrin fibers have the characteristic of orienting parallel to high magnetic fields during polymerization. Two fibrin gels were polymerized from a fibrinogen solution with and without a 7.05 T magnetic field. Water molecules in the fibrin gel that were polymerized in the high magnetic field exhibited only one relaxation time T2=0.35 s, whereas, water molecules in the fibrin gel that were not exposed to a magnetic field during polymerization had at least two exponential components in the T2 relaxation. The long component, T2=0.35 s, was the same order as the T2 of the fibrinogen solution (=0.41 s) and the fibrin gel polymerized in the high magnetic field. The short component was T2=0.07 s. This difference is attributed to a change in the magnetic dipole–dipole interactions between water molecules and fibrin fibers. © 2003 American Institute of Physics.
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82.35.Pq Biopolymers, biopolymerization
87.15.-v Biomolecules: structure and physical properties
87.50.C- Static and low-frequency electric and magnetic fields effects
87.61.-c Magnetic resonance imaging
82.70.Gg Gels and sols

Current distribution image of the rat brain using diffusion weighted magnetic resonance imaging

K. Yamaguchi, M. Sekino, S. Ueno, and N. Iriguchi

J. Appl. Phys. 93, 6739 (2003); http://dx.doi.org/10.1063/1.1558651 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2003

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In this article, we report that the apparent diffusion coefficient (ADC) of rat brain tissue increased by applied external electrical currents. A subtraction magnetic resonance imaging (MRI) map of ADCs with and without applied currents was obtained to quantitatively evaluate the effect of the electrical currents on ADC. The ADC in tissue was directly estimated by the mean diffusivity (MD), or the sum of the diagonal elements of the diffusion tensor Trace(D)/2. Anisotropic diffusion was estimated by fractional anisotropy FA(D). The experimental results show that the MD with applied currents of 4, 6, 8, and 10 mA increased by 6%, 8%, 16%, and 40%, respectively. The mechanism is partially explained by the movement of ions through extracellular space in tissue. © 2003 American Institute of Physics.
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87.19.L- Neuroscience
87.61.Tg Clinical applications
02.10.Ud Linear algebra

Nerve excitation and recovery processes under strong static magnetic fields

Yawara Eguchi, Shoogo Ueno, and Hozumi Tatsuoka

J. Appl. Phys. 93, 6742 (2003); http://dx.doi.org/10.1063/1.1556931 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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The membrane excitation and refractory processes of nerve fibers exposed to strong static magnetic fields of 8 T were studied. Sciatic nerve bundles of frogs were electrically excited by a pair of pulses with varying interpulse intervals, and the compound action potentials were measured under magnetic field exposures. Our experimental results show that the conduction velocity was not affected by 8 T magnetic fields; however, the membrane excitation during the recovery process in the relative refractory period was enhanced by 10% of maximal peak of nerve excitation by magnetic field exposure for 3 h. In this study, the optimal time interval for increased membrane excitation during the recovery process was between 1.0 and 1.1 ms. In other words, membrane excitation during the recovery process in the relative refractory period was affected by the magnetic fields just after Na+ channels were inactivated. © 2003 American Institute of Physics.
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87.17.-d Cell processes
87.50.C- Static and low-frequency electric and magnetic fields effects
87.16.Uv Active transport processes
87.19.R- Mechanical and electrical properties of tissues and organs
87.16.D- Membranes, bilayers, and vesicles
87.19.L- Neuroscience
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