Colloidal gold-based immunochromatographic assay for detection of diethylstilbestrol residues

One-step membrane-based competitive colloidal gold-based immunoassays in immunochromatographic formats for the rapid detection of diethylstilbestrol (DES) were developed. Nitro-cellulose membrane strip was separately coated with goat anti-rabbit IgG (control line) and DES hapten-ovalubumin conjugate (test line). Anti-DES polyclonal antibody labeled with colloidal gold particles was first incubated with DES. A positive reaction as a result of the remaining antibody-gold conjugate combining with antigen coated on the membrane was obvious by visual detection, with detection limits for immunochromatographic of 0.5 microg/kg for detecting DES standard solution, and the limit of detection was 5 microg/kg for detecting the DES spiked in swine pork and liver. The assay time for test was less than 5 min, suitable for rapid testing on-site.