Group-targeting sulfonamides via an evanescent-wave biosensor based onrational designed coating antigen br

n order to effectively monitor a wide variety of sulfonamides residues in the environment, group-targeting immuno-assay based on the group-specific antibodies has attracted great attentions, which can realize the detection of a groupof contaminants in environment as many as possible even the unrecognized ones. Indirect competitive immunoassay isgenerally adopted for small molecule detection however the rational design of immobilized coating antigen for im-proved recognition capability on the solid surface is far from enough. To cover the research gap, we proposed the de-sign criteria of coating antigen for surface-based indirect competitive immunoassay based on the molecular docking.Taking the group-specific antibodies against sulfonamides (SA) as a proof-of-concept, a hapten with a linking armwith 3 methyl groups was selected to synthesize the coating antigen. Through surface immobilization of coating anti-gen, a portable biosensor for group-targeting immunoassay of sulfonamides was developed and demonstrated excel-lent performance with detection limits lower than 0.6 mu g/L for four SA variants, and the cross-reactivities of148-215 % relative to sulfadiazine. The recovery rates of SAs in liquid milk ranges from 87 to 97 %, which confirmedthe application potential of this method in the determination of SAs. Its capability to measure total SAs in a simple andlow-cost way would pave the way for a variety of applicationfields.