Development of colloidal gold-based immunochromatographic assay for the rapid detection of ricin toxin in food samples

A rapid, sensitive immunochromatographic (IC) assay was developed to detect ricin toxin in assay buffer and food samples. The assay was based on the sandwich format using a monoclonal antibody (mAb) and a polyclonal antibody (pAb) of two distinct specificities. The ricin-containing sample was added to the membrane and allowed to react with pAb-coated particles. The mixture was then passed along the porous membrane by capillary action past the mAb in the detection zone, which would bind the particles that had ricin bound to their surfaces, giving a red colour within the detection zone with an intensity proportional to the ricin concentration. In the absence of ricin, no immunogold was bound to the solid-phase antibody. With this method, 30 ng/ml of ricin toxin was detected in less than 10 min, and the assay also showed no cross-reactivity with abrin toxin.