A ratiometric electrochemiluminescent biosensor for Con A detecting based on competition of dissolved oxygen

A novel ratiometric electrochemiluminescent (ECL) biosensor was designed for the detection of concanavalin A (Con A) based on two ECL emitters competing for the dissolved oxygen (O₂). In this strategy, CdTe quantum dots (QDs) were used as the cathodic emitter and N-(aminobutyl)-N-(ethylisoluminol) (ABEI) was used as the anodic emitter. With the presence of dissolved O₂ utilized as co-reactant, CdTe QDs showed an ECL emission at - 1.7 V, and ABEI showed an emission at + 0.6 V. Phenoxy-derivatized dextran (Dexp), as a recognition element, was immobilized by graphene oxide functionalized CdTe QDs (G-CdTe QDs) to recognize Con A, and further combine with Dexp, gold and platinum nanoparticles decorated ABEI (Dexp-Au-Pt-ABEI) to form a sandwich structure. With the increasing concentration of analyte Con A, the ECL signal of cathodic CdTe QDs decreased and the anodic response of ABEI increased, thus achieving a ratiometry detection of Con A with a wide linear range from 1.0 × 10^-4 ng/mL to 10 ng/mL. The detection limit was low to 3.0 × 10^-5 ng/mL. This proposed ratiometric ECL biosensor not only conquered the false errors caused by external interferences, but excluded the disability caused by exogenous co-reactant via the application of common dissolved O₂. It also exhibited an excellent stability, selectivity and reproducibility.