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@PHDTHESIS{Pourshahidi:1018219,
      author       = {Pourshahidi, Ali Mohammad},
      title        = {{F}requency mixing magnetic detection for characterization
                      and multiplex detection of superparamagnetic nanoparticles},
      volume       = {100},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2023-04615},
      isbn         = {978-3-95806-727-1},
      series       = {Schriften des Forschungszentrums Jülich Reihe Information
                      / Information},
      pages        = {X, 149},
      year         = {2023},
      note         = {Dissertation, RWTH Aachen University, 2023},
      abstract     = {Magnetic immunoassays (MIA) are gaining interest in modern
                      bioanalytical methods. A readout method employed for
                      detection of superparamagnetic biomarkers is based on the
                      principles of magnetic particle spectroscopy. The method of
                      Frequency Mixing magnetic Detection (FMMD) involves the
                      excitation of magnetic nanoparticles (MNPs) using a dual
                      frequency alternating magnetic field. MIA methods using FMMD
                      as detection principle have shown a high potential to be
                      used in point-of-care testing. On the other hand, it is
                      often desired in biosensing to perform multiplex detection,
                      that is the measurement of two or more analytes within a
                      single sample. For methods employing magnetic particle as
                      markers, this means the ability to simultaneously detect
                      different types of magnetic particle in one sample. This
                      thesis initially reports on the required FMMD
                      instrumentation and its latest developments, including a
                      duty-cycle power management strategy and a permanent ring
                      magnet offset module to reduce the adverse effect of
                      temperature variations on measured signals. We discuss the
                      measured phase of the FMMD signal. We elaborate on the
                      influencing factors and their effects using numerical
                      simulation of the signals, and verify the effects through
                      experimental measurements.Moreover, we present a method for
                      discerning the contributions of different MNPs in binary and
                      ternary mixtures by an analysis of their static offset
                      magnetic field-dependent FMMD signals. The mixture samples
                      were analyzed by identifying the best linear combination of
                      the measured reference signals of the pure constituents that
                      best resembled the measured signals of the mixtures. The
                      mixing ratios could be determined with an accuracy of better
                      than $14\%.$ One of the important properties of MNP that has
                      an influence on the FMMD signals is the size of their
                      magnetic core. The FMMD technique can be used to
                      characterize the MNP. However, it has been shown that the
                      largest particles in the sample contribute most of the FMMD
                      signal. This leads to ambiguities in core size determination
                      from mathematical fitting, since the contribution of the
                      small-sized particles is almost undetectable among the
                      strong responses from the large ones. In this thesis, we
                      discuss how to address this ambiguity by modelling thesignal
                      intensity using the Langevin model in thermodynamic
                      equilibrium, which includes a lognormal core size
                      distribution fitted to experimentally measured FMMD data of
                      immobilized MNPs. With the help of an independent
                      determination of the samples’ total iron mass, for
                      instance from inductively coupled plasma optical emission
                      spectrometry, we are able to unambiguously identify the
                      particles’ lognormal core size distribution. The technique
                      has great potential to serve as characterization tool for
                      quality control in MNP synthesis and applications.},
      cin          = {IBI-3},
      cid          = {I:(DE-Juel1)IBI-3-20200312},
      pnm          = {5241 - Molecular Information Processing in Cellular Systems
                      (POF4-524)},
      pid          = {G:(DE-HGF)POF4-5241},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-20240124094141120-4408806-7},
      doi          = {10.34734/FZJ-2023-04615},
      url          = {https://juser.fz-juelich.de/record/1018219},
}