Ultrasensitive signal amplified immunoassay of medroxyprogesterone acetate (MPA) using the atomic absorption of silver deposited on the surface of gold nanoparticles

An ultrasensitive determination method was developed to detect the trace medroxyprogesterone acetate (MPA) residues in food. The operation procedure was mostly the same as the traditional enzyme-linked immunosorbent assay method. The gold nanoparticle labelled goat anti-rabbit antibody was used here to take the traditional enzyme labelled antibody. Then the gold labelled antibody was used in the immunoassay as usual. The silver was deposited on the surface of the gold nanoparticles on the second antibody. The quantity of the silver on the surface of the gold nanoparticles was dissolved and analysed by the atomic absorption spectrum. Accordingly, the trace analyte MPA could be determined. The range of the determination was from 0.63 to 39.8 ng/ml and the limit of the detection was 0.25 ng/ml.