Rapid and separation-free sandwich immunosensing based on accumulation of microbeads by negative-dielectrophoresis

Hyun Jung Lee, Tomoyuki Yasukawa, Hitoshi Shiku, Tomokazu Matsue

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


We report here a rapid and separation-free immunoassay using a dielectrophoresis (DEP) device consisting of an interdigitated microarray (IDA) electrode and a polydimethylsiloxane (PDMS) substrate. On applying an AC voltage to the IDA in a negative-DEP (n-DEP) frequency region, goat anti-mouse immunoglobulin (anti-mouse IgG)-immobilized microbeads moved to the surface of the PDMS substrate placed above the IDA. The microbeads accumulated at designated areas of the PDMS surface that had been precoated with anti-mouse IgG. When the fluorescence microbeads bearing anti-mouse IgG were suspended in an analyte (mouse IgG) solution, the microbeads trapped the analyte to form immunocomplexes on microbeads. The microbeads reacted with mouse IgG accumulated and were captured at the designated areas of the PDMS surface via an antibody-antigen-antibody (sandwich) reaction. The captured microbeads were detected selectively by fluorescence measurements at the focused designated areas, regardless of the presence of uncaptured microbeads suspended in solution. Thus, the separation and washing-out steps usually required for conventional immunoassay are eliminated in the presented procedure. Since the formation of the sandwich structures was accelerated significantly by n-DEP, a period as short as 30 s was sufficient to detect the immunoreaction at the surface. The fluorescence intensity of the captured microbeads at the designated areas increased with analyte concentration in the range 0.01-10 ng/mL. The present procedure therefore yields a rapid, sensitive, and separation-free immunoassay in a simple device.

Original languageEnglish
Pages (from-to)1000-1005
Number of pages6
JournalBiosensors and Bioelectronics
Issue number4
Publication statusPublished - 2008 Dec 1


  • Accumulation
  • Immunosensing
  • Microbeads
  • Negative-dielectrophoresis
  • Re-dispersion
  • Separation-free

ASJC Scopus subject areas

  • Biotechnology
  • Biophysics
  • Biomedical Engineering
  • Electrochemistry


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