Liquid-phase immunoassay using relaxation measurement of magnetic markers

Tomokazu Hirata, Takashi Yoshida, Keiji Enpuku

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1 Citation (Scopus)


We have developed a liquid phase immunoassay technique using the Brownian relaxation of magnetic markers. In order to achieve this, we used large polymer beads to fix the bound markers. The bound and unbound (free) markers were magnetically distinguished using the difference in their Brownian relaxation. We used MR (magneto-Resistive) sensor for the signal detection. In order to achieve high sensitivity and low noise of the sensor, we used a modulation technique called set/reset operation. Using this method, magnetic field resolution of the MR sensor was improved by about three times. We also set up a magnetic shield to prevent the influence of an environmental magnetic field. We show that the present system could detect 20 ng of magnetic markers. We also demonstrate the detection of 13.8 amol/ml of biotin with the present liquid-phase immunoassay technique.

Original languageEnglish
Pages (from-to)25-30
Number of pages6
JournalResearch Reports on Information Science and Electrical Engineering of Kyushu University
Issue number1
Publication statusPublished - Jan 2013

All Science Journal Classification (ASJC) codes

  • General Computer Science
  • Electrical and Electronic Engineering


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