Colloidal gold probe based rapid immunochromatographic strip assay for cortisol

A rapid and semi-quantitative immunochromatographic strip (ICS) test for cortisol analysis in serum was developed. The test strip was based on a competitive assay format. Colloidal gold nanoparticles were synthesized and coupled with cortisol-3-carboxymethyloxime–adipic acid dihydrazide–bovine serum albumin (F-3-CMO–ADH–BSA) antigen to directly compete with cortisol in human serum samples. F-3-CMO–ADH–BSA–gold label and uncoupled colloidal gold nanoparticles were appropriately characterized using UV–vis spectroscopy, transmission electron microscopy and atomic force microscopy. Anticortisol antibody raised against F-3-CMO–BSA immunogen in New Zealand white rabbits was coated on the NC membrane as test line. Anti-BSA antibody was used as control line. The lower detection limit of the ICS test was 30 ng mL−1 with visual detection and was completed in 10 min. About 30 human serum samples were also analyzed by the developed strip test and their range of cortisol concentration was established. The developed ICS test is rapid, economic and user friendly.