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@INPROCEEDINGS{Krause:1019314,
      author       = {Krause, Hans-Joachim},
      title        = {{M}agnetic {B}iosensing and {F}requency {M}ixing {M}agnetic
                      {D}etection},
      reportid     = {FZJ-2023-05288},
      year         = {2023},
      abstract     = {For selective detection and quantification of biomolecular
                      targets, we use magnetic label-based immunoassays employing
                      the highly specific interaction between antigens and
                      antibodies bound to magnetic nanoparticle (MNP) markers,
                      which are measured by frequency mixing magnetic detection
                      (FMMD). Superparamagnetic MNP exhibit a nonlinear
                      magnetization. Upon magnetic excitation at two distinct
                      frequencies f1 and f2 incident on the sample, the
                      nonlinearity gives rise to the generation of intermodulation
                      frequencies. Coaxial coils provide magnetic excitation at
                      frequency f1 while the MNP are driven near magnetic
                      saturation with a driving frequency incident on the sample.
                      Response signals generated at linear combination frequencies
                      f1 ± n×f2 are picked up by a detection coil,
                      differentially connected to a reference coil, and are
                      demodulated in the magnetic reader device. The appearance of
                      the mixing components is highly specific to the nonlinearity
                      of the magnetization curve of the particles. The method
                      yields a very large dynamic range of detection, extending to
                      more than 4 orders of magnitude in the number of particles.
                      Analysis of the phase of the response gives information on
                      the magnetic relaxation of the MNP, and thus on their
                      hy-drodynamic size and binding state. Variation of
                      excitation amplitudes or a static magnetic offset field
                      enables determining the size distribution of the magnetic
                      cores of the MNP. With the FMMD technique, magnetic sandwich
                      immunoassays for various biomolecular targets have been
                      successfully realized, exhibiting improved detection limits
                      as compared to conventional techniques like ELISA.},
      month         = {Aug},
      date          = {2023-08-27},
      organization  = {4th European BioSensor Symposium 2023,
                       Aachen (Germany), 27 Aug 2023 - 30 Aug
                       2023},
      subtyp        = {Invited},
      cin          = {IBI-3},
      cid          = {I:(DE-Juel1)IBI-3-20200312},
      pnm          = {5241 - Molecular Information Processing in Cellular Systems
                      (POF4-524) / DFG project 445454801 - Kombinierter
                      Feldeffekt-/Magnet-Immunsensor-Chip für den
                      markierungsfreien Nachweise von Biomarkern (FEMIC)
                      (445454801)},
      pid          = {G:(DE-HGF)POF4-5241 / G:(GEPRIS)445454801},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1019314},
}