Determination of the binding reaction between avidin and biotin by relaxation measurements of magnetic nanoparticles

Kötitz, R.; Weitschies, Werner; Trahms, Lutz; Brewer, W. D.; Semmler, Willi

doi:10.1016/s0304-8853(98)00580-0

Cited by 140 publications

(101 citation statements)

References 5 publications

Supporting

Mentioning

100

Contrasting

Order By: Relevance

“…Because of the exponential particle size dependence, the Néel relaxation is orders of magnitude slower than the Brownian relaxation for sufficiently large particles (for reasonable material parameter values B N τ τ ≈ for particles with radii of 10-11 nm). This feature allows the discrimination of particles bound to specific biological entities [12] from particles embedded in body fluids, thus forming the basis for SPION imaging by MRX. The property was used, e.g., to image the accumulation of intravenously injected SPIONs in the spleen and liver of a mouse by MRX [13], or to quantify the aggregation of magnetic nanoparticles in cell cultures [14].…”

Section: Introductionmentioning

confidence: 99%

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

Dolgovskiy

Lebedev

Colombo

et al. 2015

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

The discrimination of immobilised superparamagnetic iron oxide nanoparticles (SPIONs) against SPIONs in fluid environments via their magnetic relaxation behaviour is a powerful tool for bio-medical imaging.Here we demonstrate that a gradiometer of laser-pumped atomic magnetometers can be used to record accurate time series of the relaxing magnetic field produced by pre-polarised SPIONs. We have investigated dry in vitro maghemite nanoparticle samples with different size distributions (average radii ranging from 14 to 21 nm) and analysed their relaxation using the Néel-Brown formalism. Fitting our model function to the magnetorelaxation (MRX) data allows us to extract the anisotropy constant K and the saturation magnetisation M S of each sample. While the latter was found not to depend on the particle size, we observe that K is inversely proportional to the (time-and size-) averaged volume of the magnetised particle fraction. We have identified the range of SPION sizes that are best suited for MRX detection considering our specific experimental conditions and sample preparation technique.

show abstract

Section: Introductionmentioning

confidence: 99%

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

Dolgovskiy

Lebedev

Colombo

et al. 2015

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

show abstract

“…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.…”

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

View full text Add to dashboard Cite

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...

show abstract

“…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

855

636

View full text Add to dashboard Cite

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.

show abstract

Determination of the binding reaction between avidin and biotin by relaxation measurements of magnetic nanoparticles

Cited by 140 publications

References 5 publications

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

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

Electrochemical Biosensors - Sensor Principles and Architectures

Contact Info

Product

Resources

About