A redox-label immunosensor on basis of a bi-enzyme electrode

Enzymatic analyte recycling results in detection limits at the nanomolar level thus allowing for the coupling to immunoassay detection. For this reason a bifunctional reagent was synthesized, which has the two properties of being a redox active substance, for a bi-enzymatic redox-cycling system on one hand, and as being a competitor, e.g. a label, for the analyte in an immunoassay on the other hand. Such compounds, called redox-labels, enable the construction of a real immunosensor, which works without any addition of substrates. The principle is demonstrated with the determination of 2,4-dichlorophenoxyacetic acid (2,4-D).