Reduction of the magnetic signal from unbound magnetic markers for magnetic immunoassay without bound/free separation

A. Tsukamoto, H. Kuma, K. Saitoh, A. Kandori, K. Yoshinaga, Y. Sugiura, N. Hamasaki, K. Enpuku

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5 Citations (Scopus)


We investigated the effect of adding magnetic shielding and applying of a compensation field to reduce the magnetic signal from unbound free markers. When the initial immunoassay system was used without the additional shielding box, the signal intensity of the liquid markers normalized by the weight of the Fe3O4 was 1/2700 of the dried markers. By installing the additional shielding box, the reduction factor was improved to 1/10,000. We successfully reduced the magnetic signal of the liquid marker further by applying a compensation field. The magnetic signal of the free marker obtained by applying a compensation field of -18 nT was 1.4 mΦ0, which was close to the system noise level. Field compensation at the very local area just around the SQUID is sufficient for reducing of the magnetic signal from the free marker.

Original languageEnglish
Pages (from-to)1024-1028
Number of pages5
JournalPhysica C: Superconductivity and its applications
Issue numberSUPPL.
Publication statusPublished - Oct 1 2007


All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

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