Original-structure-based hapten design strategy and development of a derivatization-free gold-based paper lateral-flow immunoassays for detecting furaltadone metabolite in shrimp

Veterinary drug residues in food-producing animals pose a threat to human health and public safety, and accurate measurement of these drug residues is necessary. However, detecting nitrofuran metabolite residues is challenging because of their low molecular weight and the long derivatisation time required for their indirect detection. Current antibodies produced against these metabolites have limited accuracy and sensitivity owing to the traditional and ineffective hapten design based on the reaction of 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ) with nitrobenzaldehyde. In this study, a new antigen strategy was adopted using an originalstructure-based hapten design combined with a new carrier protein with immunosynergistic effects to produce a monoclonal antibody that could recognise the metabolite of furaltadone (AMOZ) directly without derivatisation with excellent analytical performance. Finally, a gold-based paper lateral flow immunoassay for AMOZ without derivatisation was established with a visual limit of detection of 5 ng/mL, IC50 of 0.97 ng/mL and linear range (IC20 similar to IC80) of 0.45-2.07 ng/mL. The method was sensitive and accurate, and detection was completed within 10 min. This new antigen design strategy provides a theoretical basis and reference for antibody production of other ultrasmall molecules.