A target-triggered ultra-sensitive aptasensor for simultaneous detection of Cd and Hg using MWCNTs-Au NPs modified electrode.

A sensitive electrochemical assay for simultaneously detecting cadmium ion (Cd) and mercury ion (Hg) with the aptamer as recognition unit was established, in which methylene blue (MB) and target-triggered in-situ generated Ag nanoclusters (Ag NCs) were identified as signal reporters. Multi-walled carbon nanotubes and gold nanoparticles composites were prepared with polyethyleneimine to amplify electrical signals of screen-printed electrodes. Due to the particular base sequences, MB labeled Cd aptamer paired with ssDNA through T-Hg-T structure with Hg. Notably, the C-rich structure in ssDNA acted as a template for the generation of Ag NCs, which could induce differential pulse voltammetry signals corresponding to Hg concentrations. This electrochemical aptasensor exhibited detection limits of 94.01 pg/mL and 15.74 pg/mL for Cd and Hg, respectively. The developed aptasensor allowed for practical application to tea and vegetable samples with satisfactory accuracy. This work possesses potential in developing biosensing technologies for simultaneous determination of multiple heavy metals.