Electrochemiluminescence Resonance Energy Transfer System: Mechanism and Application in Ratiometric Aptasensor for Lead Ion

In this paper, a novel electrochemiluminescence resonance energy transfer (ECL-RET) system from O-2/S2O82- to a kind of amino-terminated perylene derivative (PTC-NH2) was demonstrated for the first time, which was then applied to construct a ratiometric aptasensor for lead ion (Pb2+) detection. First, gold-nanoparticles-functionalized fullerene nanocomposites (AuNPs@nano-C-60) were coated on a glassy carbon electrode (GCE), and then thiol-modified assistant probes (APs) were attached on AuNPs@nano-C60/GCE. Then the resultant electrode was hybridized with capture probes (the aptamer of the Pb2+, abbreviated as CPs) to generate DNA duplexes, which could induce PTC-NH2 to be intercalated into the dsDNA grooves by the electrostatic adsorption. Herein, ECL dual peaks at -0.7 V (vs Ag/AgCl) and -2.0 V (vs Ag/AgCl) were obtained when the prepared aptasensor was detected in air-saturated S2O82- solution, which could be attributed to the emission of excited dimmers (pi-excimers) (1(NH2PTC)2*) and (1)(O-2)(2)*, respectively. In the presence of Pb2+, the dsDNA was unwound, and Pb2+ G-quadruplex structure was generated because of the highly specific affinity between Pb2+ and CPs, which made the PTC-NH2 release from the electrode surface. As a result, the ECL signal at -0.7 V was decreased, and the ECL signal around -2.0 V was increased. By measuring the ratio of ECL intensities at two excitation potentials, the developed aptasensor exhibited the linear response range from 1.0 x 10(-12) M to 1.0 x 10(7) M with a detection limit of 3.5 x 10(-13) M (S/N = 3) for Pb2+, which could offer an alternative analytical method with excellent properties of high selectivity, accuracy, and sensitivity.