Switchable electrochemiluminescence aptasensor coupled with resonance energy transfer for selective attomolar detection of Hg2+ via CdTe@CdS/dendrimer probe and Au nanoparticle quencher

In the present study, an ultrasensitive electrochemiluminescence (ECL) aptasensing assay for selective detection of Hg2+ was designed. In this electrochemiluminescence resonance energy transfer (ECL-RET) approach, Fe3O4@SiO2/dendrimers/QDs exhibited amplified ECL emissions (switch "on" state) and with the hybridization between T-rich ssDNA(S1) immobilized on the Fe3O4@SiO2/dendrimers/QDs and AuNPs modified with complementary aptamer (AuNPs-S2), the ECL of QDs nanocomposites was efficiently quenched (switch "off" state). In the presence of Hg2+ ions, formation of strong and stable T-Hg2+-T complex led to the release of the AuNPs-S2 from double-stranded DNA(dsDNA) and the recovery of the ECL signal of QDs (second signal switch "on" state). Under optimal conditions, Hg2+ can be detected in a wide linear range from 20aM to 2µM with a very low detection limit of 2aM. The proposed ECL aptasensor showed high selectivity for Hg2+ determination compared to other environmentally relevant metal ions at concentration ratio more than 1000 times. The aptasensor was used for detection Hg2+ ions from samples of tap waters, carp and saltwater fishes with satisfactory results. The aptasensor exhibited high sensitivity, wide linear response (11 orders of magnitude), excellent reproducibility and stability. The proposed aptasensor will be a promising candidate for facile and rapid determination of Hg2＋in environmental and fishery samples.