Single-core magnetic markers in rotating magnetic field based homogeneous bioassays and the law of mass action

Dieckhoff, Jan; Schrittwieser, Stefan; Schotter, Joerg; Remmer, Hilke; Schilling, Meinhard; Ludwig, Frank

doi:10.1016/j.jmmm.2014.10.088

Cited by 4 publications

(9 citation statements)

References 18 publications

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“…(25) m denotes a unit vector in the direction of m. Eqs. (22,23,25) are the basic equations of the EFM [25,26].…”

Section: B Effective Field Methodsmentioning

confidence: 99%

“…Quite recently biosensors were proposed [21][22][23] which are based on the response of MNPs with Brownian dynamics to rotating magnetic fields, i.e. to differences in the phase lag between the rotating magnetic moment and the driving field in order to determine the changes in hydrodynamic volume caused by analytes bound to the surface of the MNPs.…”

Section: Introductionmentioning

confidence: 99%

“…In the present paper we therefore study the dynamics of mobile MNPs driven by a rotating magnetic field in order to contribute to an understanding of the physics underlying the functionality of the class of biosensors mentioned [21][22][23]. The ensemble of MNPs is described by a set of kinetic equations proposed earlier [5] for the dynamics of mobile particles treating Brownian and Neél dynamics on equal footing.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

Usadel

2017

Phys. Rev. B

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The rotational dynamics of magnetic nano particles in rotating magnetic fields in the presence of thermal noise is studied both theoretically and by performing numerical calculations. Kinetic equations for the dynamics of particles with uniaxial magnetic anisotropy are studied and the phase lag between the rotating magnetic moment and the driving field is obtained. It is shown that for large enough anisotropy energy the magnetic moment is locked to the anisotropy axis so that the particle behaves like a rotating magnetic dipole. The corresponding rigid dipole model is analyzed both numerically by solving the appropriate Fokker-Planck equation and analytically by applying an effective field method. In the special case of a rotating magnetic field applied analytic results are obtained in perfect agreement with numerical results based on the Fokker-Planck equation. The analytic formulas derived are not restricted to small magnetic fields or low frequencies and are therefore important for applications. The illustrative numerical calculations presented are performed for magnetic parameters typical for iron oxide.

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“…(25) m denotes a unit vector in the direction of m. Eqs. (22,23,25) are the basic equations of the EFM [25,26].…”

Section: B Effective Field Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

Usadel

2017

Phys. Rev. B

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“…The authors demonstrated detection of binding processes of IgG antibodies to magnetic NP labels functionalized by protein G and analyzed the dependence of the measurement signal on the analyte molecule concentration [ 178 ]. It has also been reported that the binding kinetics of analyte molecules to the magnetic NP labels can be interpreted according to the law of mass [ 179 ]. Absolute phase lag values of up to 60° and phase lag differences between samples with and without added analyte molecules of up to 20° were observed [ 179 ].…”

Section: Magnetic Detection Methodsmentioning

confidence: 99%

“…It has also been reported that the binding kinetics of analyte molecules to the magnetic NP labels can be interpreted according to the law of mass [ 179 ]. Absolute phase lag values of up to 60° and phase lag differences between samples with and without added analyte molecules of up to 20° were observed [ 179 ].…”

Section: Magnetic Detection Methodsmentioning

confidence: 99%

Homogeneous Biosensing Based on Magnetic Particle Labels

Schrittwieser

Pelaz

Parak

et al. 2016

Sensors

Self Cite

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The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.

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Homogeneous Differential Magnetic Assay

et al. 2019

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Assays are widely used for detection of various targets, including pathogens, drugs, and toxins. Homogeneous assays are promising for the realization of point-of-care diagnostics as they do not require separation, immobilization, or washing steps. For low concentrations of target molecules, the speed and sensitivity of homogeneous assays have hitherto been limited by slow binding kinetics, time-consuming amplification steps, and the presence of a high background signal. Here, we present a homogeneous differential magnetic assay that utilizes a differential magnetic readout that eliminates previous limitations of homogeneous assays. The assay uses a gradiometer sensor configuration combined with precise microfluidic sample handling. This enables simultaneous differential measurement of a positive test sample containing a synthesized Vibrio cholerae target and a negative control sample, which reduces the background signal and increases the readout speed. Very low concentrations of targets down to femtomolar levels are thus detectable without any additional amplification of the number of targets. Our homogeneous differential magnetic assay method opens new possibilities for rapid and highly sensitive diagnostics at the point of care.

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Single-core magnetic markers in rotating magnetic field based homogeneous bioassays and the law of mass action

Cited by 4 publications

References 18 publications

Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

Homogeneous Biosensing Based on Magnetic Particle Labels

Homogeneous Differential Magnetic Assay

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