Magnetic liquid-phase immunoassay using magneto-resistive sensor

Tatsuhito Sakakibara, Kohei Noguchi, Takashi Yoshida, Keiji Enpuku

Research output: Contribution to journalArticlepeer-review


We have improved a liquid-phase immunoassay technique using Brownian relaxation of magnetic markers. In this method, we can magnetically distinguish bound markers from unbound (free) markers without using time consuming washing process for marker separation. In order to improve the performance of the present method, we first decreased the noise of the detection system using a magneto-resistive (MR) sensor. Employing the serially connected three MR sensors, peak-to-peak noise of the system was reduced to 26.9 pT, which was 1/√3 less than the conventional one MR sensor system. Next, we developed a new method to perform the binding reaction between antigen and magnetic marker in the presence of magnetic field. In this case, magnetic moments of the bound markers were aligned due to this reaction field, and as a result, signal from the bound markers became large without causing agglomeration of free markers. Finally, we performed the liquid-phase detection of biotins. We could detect 2.5×105 biotins existing in 60 μl sample solution, indicating high sensitivity of the present method.

Original languageEnglish
Pages (from-to)21-27
Number of pages7
JournalResearch Reports on Information Science and Electrical Engineering of Kyushu University
Issue number1
Publication statusPublished - Jan 1 2015

All Science Journal Classification (ASJC) codes

  • Computer Science(all)
  • Electrical and Electronic Engineering


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