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 O₂/S₂O₈^2– 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-C₆₀) 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 S₂O₈^2– solution, which could be attributed to the emission of excited dimmers (π-excimers) (¹(NH₂–PTC)₂*) and ¹(O₂)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 × 10^–12 M to 1.0 × 10^–7 M with a detection limit of 3.5 × 10^–13 M (S/N = 3) for Pb²⁺, which could offer an alternative analytical method with excellent properties of high selectivity, accuracy, and sensitivity