Abstract
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 language | English (US) |
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Pages (from-to) | 1055-1063 |
Number of pages | 9 |
Journal | Biosensors and Bioelectronics |
Volume | 18 |
Issue number | 8 |
DOIs | |
State | Published - Aug 1 2003 |
Keywords
- Esfenvalerate
- Fluorescence
- Immunoassay
- Micro droplet
- Quenching
ASJC Scopus subject areas
- Biotechnology
- Analytical Chemistry
- Electrochemistry