Electrochemiluminescence from a biocatalysis accelerated N-/dissolved O.sub.2 system for microRNA detection

A kind of biocatalyst, laccase, has been employed as a biocompatible coreactant accelerator to efficiently catalyze coreactant (dissolved O.sub.2) for generating high local concentration of superoxide radical (O.sub.2.sup.*-), acquiring high-intense electrochemiluminescence (ECL) emission of ABEI (N-(aminobutyl)-N-(ethylisoluminol))/dissolved O.sub.2 system. Furthermore, a modified strand displacement reaction with excellent amplification efficiency was constructed by replacing traditional single strand DNA to the hairpin DNA as template for triggering the immobilization of more signal probes. As a result, the biosensor for microRNA-21 determination has preeminent selectivity and favorable sensitivity with detection limit down to 80.8 aM. Significantly, the devised strategy has blazed a new path for seeking more coreaction accelerators with splendid biocompatibility thus promoting the application of ternary ECL systems in biological analysis and clinical diagnosis. Graphical abstract