Magnetorelaxometry—a new binding specific detection method based on magnetic nanoparticles

Lange, James N.; Kötitz, R.; Haller, A.; Trahms, Lutz; Semmler, Willi; Weitschies, Werner

doi:10.1016/s0304-8853(02)00657-1

Cited by 80 publications

(58 citation statements)

References 2 publications

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“…They are stable and nontoxic and can be manipulated with a magnetic field, making it possible to separate target antigens magnetically (3). Methods have been developed to detect small numbers of such particles by using Hall probes (4), giant magnetoresistance arrays (5), atomic force microscopy (6), force-amplified biological sensors (7), and SQUIDs (8-10).Weitschies, Kötitz, and colleagues pioneered the use of SQUIDs for magnetic immunoassays (8,(11)(12)(13)(14)(15)(16). They developed a magnetic relaxation immunoassay in which magnetic particles bound to targets are distinguished from unbound particles by their different relaxation times.…”

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confidence: 99%

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Detection of bacteria in suspension by using a superconducting quantum interference device

Grossman

Myers

Vreeland

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

187

121

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We demonstrate a technique for detecting magnetically labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This sensitive assay quantifies specific bacteria in a sample without the need to immobilize them or wash away unbound magnetic particles. In the measurement, we add 50-nm-diameter superparamagnetic magnetite particles, coated with antibodies, to an aqueous sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a hightransition temperature superconducting quantum interference device, an extremely sensitive detector of magnetic flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Né el relaxation process is detected by the superconducting quantum interference device. The measurements indicate a detection limit of (5.6 ؎ 1.1) ؋ 10 6 L. monocytogenes in our sample volume of 20 l. If the sample volume were reduced to 1 nl, we estimate that the detection limit could be improved to 230 ؎ 40 L. monocytogenes cells. Timeresolved measurements yield the binding rate between the particles and bacteria.A ntibodies are widely used as biological probes to identify specific microorganisms or molecules (1, 2). The antibodies are linked to a label and introduced into the sample, where they bind to the targets of interest and provide a means of detection. Common labels include enzymes, fluorescent dyes, radioisotopes, or magnetic particles. This general technique has various applications. In an immunoassay, the goal is to detect and quantify specific targets. Tagged antibodies can also be used to separate target antigens selectively or to measure the affinity between antibody and antigen. In this article, we present a sensitive method for detecting magnetically labeled bacteria by using a superconducting quantum interference device (SQUID), a highly sensitive detector of magnetic flux. This assay can be used to monitor bacteria in a liquid sample and to determine the rate of binding between antibody-linked particles and bacteria.Magnetic particles have several advantages as labels. They are stable and nontoxic and can be manipulated with a magnetic field, making it possible to separate target antigens magnetically (3). Methods have been developed to detect small numbers of such particles by using Hall probes (4), giant magnetoresistance arrays (5), atomic force microscopy (6), force-amplified biological sensors (7), and SQUIDs (8-10).Weitschies, Kötitz, and colleagues pioneered the use of SQUIDs for magnetic immunoassays (8,(11)(12)(13)(14)(15)(16). They developed a magnetic relaxation immunoassay in which magnetic particles bound to targets are distinguished from unbound particles by their different relaxation times. By using a low-criticalte...

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mentioning

confidence: 99%

“…Weitschies, Kötitz, and colleagues pioneered the use of SQUIDs for magnetic immunoassays (8,(11)(12)(13)(14)(15)(16). They developed a magnetic relaxation immunoassay in which magnetic particles bound to targets are distinguished from unbound particles by their different relaxation times.…”

mentioning

confidence: 99%

Detection of bacteria in suspension by using a superconducting quantum interference device

Grossman

Myers

Vreeland

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

187

121

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“…Therefore, some interesting transduction methods in magnetic biosensing use magnetic remanence and/or relaxation [173,174,175,176], mixed excitation frequency response [177,178], cantilever movements (e.g. force amplified biological sensor, FABS) [179], inductance [180,181], induced current [182] or magnetoresistance, such as giant magnetoresistance (GMR) [183,184,185,186].…”

Section: Magnetic Biosensorsmentioning

confidence: 99%

Electrochemical Biosensors - Sensor Principles and Architectures

Grieshaber

MacKenzie

Vörös

et al. 2008

Sensors

854

636

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Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response.

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“…Magnetic immunoassay techniques that utilize Brownian relaxation of magnetic markers have been developed for liquid-phase detection of biological targets [1]- [16]. In techniques of this type, the bound and free markers are magnetically distinguished using the Brownian relaxation of the markers.…”

Section: Introductionmentioning

confidence: 99%

“…In techniques of this type, the bound and free markers are magnetically distinguished using the Brownian relaxation of the markers. To date, several detection methods, including AC susceptibility [1]- [6], magnetic relaxation [7]- [13], and remanence measurement [14]- [16], have been developed. These methods eliminate the need for a time-consuming washing process for marker separation.…”

Section: Introductionmentioning

confidence: 99%

Improved Liquid-Phase Detection of Biological Targets Based on Magnetic Markers and High-Critical-Temperature Superconducting Quantum Interference Device

Ura

Noguchi

Ueoka

et al. 2016

IEICE Trans. Electron.

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SUMMARYIn this paper, we propose improved methods of liquidphase detection of biological targets utilizing magnetic markers and a high-critical-temperature superconducting quantum interference device (SQUID). For liquid-phase detection, the bound and unbound (free) markers are magnetically distinguished by using Brownian relaxation of free markers. Although a signal from the free markers is zero in an ideal case, it exists in a real sample on account of the aggregation and precipitation of free markers. This signal is called a blank signal, and it degrades the sensitivity of target detection. To solve this problem, we propose improved detection methods. First, we introduce a reaction field, B re , during the binding reaction between the markers and targets. We additionally introduce a dispersion process after magnetization of the bound markers. Using these methods, we can obtain a strong signal from the bound markers without increasing the aggregation of the free markers. Next, we introduce a field-reversal method in the measurement procedure to differentiate the signal from the markers in suspension from that of the precipitated markers. Using this procedure, we can eliminate the signal from the precipitated markers. Then, we detect biotin molecules by using these methods. In an experiment, the biotins were immobilized on the surfaces of large polymer beads with diameters of 3.3 μm. They were detected with streptavidinconjugated magnetic markers. The minimum detectable molecular number concentration was 1.8 × 10 −19 mol/ml, which indicates the high sensitivity of the proposed method. key words: high-critical-temperature superconducting quantum interference device (SQUID), magnetic marker, immunoassays, liquid-phase detection

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Magnetorelaxometry—a new binding specific detection method based on magnetic nanoparticles

Cited by 80 publications

References 2 publications

Detection of bacteria in suspension by using a superconducting quantum interference device

Detection of bacteria in suspension by using a superconducting quantum interference device

Electrochemical Biosensors - Sensor Principles and Architectures

Improved Liquid-Phase Detection of Biological Targets Based on Magnetic Markers and High-Critical-Temperature Superconducting Quantum Interference Device

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