An ultra-high-sensitivity electrochemiluminescence aptasensor for Pb2+ detection based on the synergistic signal-amplification strategy of quencher abscission and G-quadruplex generation

Signal amplification provides an effective way to improve detection performance. Herein, an ultrasensitive electrochemiluminescence (ECL) aptasensor for Pb2+ detection was developed based on a dual signal-amplification strategy of the abscission of a quencher and the generation of a G-quadruplex by one-step and simultaneous way. Nitrogen-doped carbon quantum dots linked with complementary DNA (cDNA-NCQDs) at the sensing interface was applied as the quencher of a tris(4,4′-dicarboxylic acid-2,2′-bipyridyl)ruthenium(II) (Ru(dcbpy)32+)/tripropylamine system to minimize the ECL signal due to the intermolecular hydrogen bond-induced energy-transfer process. Upon the addition of Pb2+, its specific binding with the aptamer triggered the abscission of cDNA-NCQDs, accompanied by the formation of G-quadruplex on the surface of the electrode, both of which amplified the intensity of the light emission. The ECL amplification efficiency induced by the above two mechanisms (78.6%) was valuably greater than that of their sum value (69.3%). This synergistic effect resulted in high detection sensitivity of the ECL aptasensor, which allowed to thereby obtain Pb2+ measurements in the range of 1 fM - 10 nM with an ultra-low detection limit of 0.19 fM. The Pb2+-mediated synergistic signal-amplification ECL strategy can provide a new approach for integrating various amplification strategies.