Development of an immunochromatographic strip assay for ractopamine detection using an ultrasensitive monoclonal antibody

A sensitive gold nanoparticle immunochromatographic strip assay and indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) were developed for the detection of ractopamine (RCT), a beta-adrenergic agonist. The immunogen and coating antigen were synthesized by the carbodiimide method and conjugated with keyhole limpet hemocyanin and ovalbumin, respectively. The highly sensitive and specific monoclonal antibody was prepared for RCT, with a 50% inhibition concentration of 0.05ng/ml and had no cross-reactivity with other beta-adrenergic agonists. An ultrasensitive and rapid immunochromatographic strip assay was developed with an RCT cutoff value of 2ng/ml. Both developed methods can be used for RCT detection in swine urine.