Dual-potential ratiometric electrochemiluminescence based on single emitter and single coreactant for the sensitive...

Dual-potential ratiometric electrochemiluminescence (ECL) is in favor of resistance to environmental interference. However, two kinds of emitters or coreactants, and a wide scan potential range (>2 V) are mandatory. This work developed a new dual-potential ratiometric ECL sensor for detection of carcinoembryonic antigen (CEA) using single emitter (luminol) and single coreactant (H₂O₂) with a mild potential range from -0.1 to 0.6 V. Luminol could produce a strong cathodic ECL (E_c) induced by hydroxyl radicals (HO‧) from the reduction of H₂O₂, and a relatively weak anodic ECL (E_a). After the ferrocene modified CEA aptamer (Apt-Fc) was attached, Fc could promote E_a by catalyzing the oxidation of H₂O₂, and reduce E_c by consuming HO‧. With the cycling amplification of the exonuclease I, CEA could substantially reduce the amount of Apt-Fc, resulting in the decrease of E_a and the rise of E_c. So, the ratio of E_c to E_a (E_c/E_a) was used as the detection signal, realizing the sensitive determination of CEA from 0.1 pg mL^-1 to 10 ng mL^-1 with a LOD of 41.85 fg mL^-1 (S/N = 3). The developed sensor demonstrated excellent specificity, stability and reproducibility, with satisfactory results in practical detection.