Development of colloidal gold-based immunochromatographic assay for the rapid detection of medroxyprogesterone acetate residues

One-step membrane-based competitive colloidal gold-based immunoassays in lateral-flow formats for the rapid detection of medroxyprogesterone acetate (MPA) were developed. Nitro-cellulose membrane strip was separately coated with goat anti-rabbit IgG (control line) and MPA hapten-OVA conjugate (test line). Anti-MPA polyclonal antibody labelled with colloidal gold particles was firstly incubated with MPA. 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 lateral flow of 5 µg/kg for detecting MPA standard solution, and the limit of detection was 10 µg/kg for detecting the MPA spiked in swine urine and liver. The assay time for test was less than 5 min, suitable for rapid testing on-site.