Fluorescence quenching competitive immunoassay in micro droplets

Jun Feng, Guomin Shan, Bruce D. Hammock, Ian M. Kennedy

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


A fluorescence quenching competitive immunoassay in micro droplets was applied to the sensitive detection of the pyrethroid insecticide, esfenvalerate. Laser induced fluorescence from rhodamine dye was used as a marker. The competitive immunoreaction was performed in micro droplets generated by a vibrating orifice aerosol generator system with a 10-μm diameter orifice. Fluorescence that was emitted from the droplets was detected by a 1/8 m imaging spectrograph with a 512×512 thermoelectrically cooled, charged-coupled device camera. The conjugate of esfenvalerate with rhodamine exhibited similar fluorescence to that of pure rhodamine 6G. When anti-esfenvalerate antibodies were added to the droplets, the fluorescence decreased. The reduction in emission was due to a strong quenching effect that arises from the interaction between the protein and rhodamine molecules following the antigen-antibody reaction. When a sample of esfenvalerate was added to the droplets, the release of the conjugated rhodamine from the antigen-antibody complex allowed the fluorescence signal to recover. An assay in a picoliter droplet sample was shown to enable detection down to approximately 0.1 nM. A very small mass of analyte could be detected with this method. A sample of river water was used to gauge the impact of matrix effects and was shown to give rise to negligible interference with the immunoassay.

Original languageEnglish (US)
Pages (from-to)1055-1063
Number of pages9
JournalBiosensors and Bioelectronics
Issue number8
StatePublished - Aug 1 2003


  • Esfenvalerate
  • Fluorescence
  • Immunoassay
  • Micro droplet
  • Quenching

ASJC Scopus subject areas

  • Biotechnology
  • Analytical Chemistry
  • Electrochemistry


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