Liquid Phase Immunoassay Using AC Susceptibility Measurement of Magnetic Markers

Keiji Enpuku, Yuya Tamai, Tetsu Mitake, Masaaki Matsuo, Akira Tsukamoto, Takako Mizoguchi, Akihiko Kandori

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


AC susceptibility measurement of magnetic markers in solution was applied to biological immunoassays. In this method, the markers that bound to biological target can be detected in the presence of unbound markers. The bound markers were distinguished from the unbound ones by using their different frequency dependence of susceptibility. We detected biotin-conjugated polymer beads with avidin-coated Fe3O4 markers. Changes of the susceptibility caused by the binding reaction between them were shown. Good relationship was obtained between the decrease of susceptibility and the number of polymer beads. Sensitivity of the system was estimated as 3 × 10-16 mol/ml in terms of molecular-number concentration.

Original languageEnglish
Article number037001
JournalApplied Physics Express
Issue number3
Publication statusPublished - Mar 2009

All Science Journal Classification (ASJC) codes

  • General Engineering
  • General Physics and Astronomy


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