Fluorescence quenching competitive fluoroimmunoassay in micro droplets

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The use of micro droplets as a mediumfor sensitive detection in fluorescence-based immunoassays has been explored in two contexts. The competitive immuno-reaction of a pesticide hapten, esfenvalerate, with its antibody was performed in micro droplets generated by a vibrating orifice aerosol generator system with a 10-μm diameter orifice. Fluorescence from Rhodamine 6G was excited by the second harmonic of a Nd:YAG laser and detected by a 1/8 m imaging spectrograph with a 512 × 512 thermoelectrically cooled, charged-coupled device (CCD) 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 due to quenching. When a sample of esfenvalerate was added to the droplets, esfenvalerate and esfenvalerate-rhodamine conjugate competed for binding with the anti-esfenvalerate antibody. The release of the conjugated rhodamine from the antigen-antibody complex allowed the fluorescence signal to recover. The assay in a picoliter droplet sample was shown to enable detection down to approximately 0.1 nM. Micro droplets also exhibit strong cavity-dependent optical behavior that gives rise to lasing action. Lasing from Rhodamine fluorescence was quenched by the addition of a second dye, oxonol, that absorbs in the spectral region where the Rh 6G fluorescence peaked. A very strong impact on the droplet resonances was observed, leading to the possible use of quenching as an assay for oxonol-labeled haptens.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsC.W. Wilkerson, Jr.
Number of pages10
StatePublished - 2002
EventMethods for Ultrasensitive Detection II - San Jose, CA, United States
Duration: Jan 21 2002Jan 22 2002


OtherMethods for Ultrasensitive Detection II
Country/TerritoryUnited States
CitySan Jose, CA


  • Esfenvalerate
  • Immunoassay
  • Laser induced fluorescence
  • Microdroplet
  • Quenching

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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