Electrochemical aptasensor for ultrasensitive cadmium detection through hybridization chain-amplified reaction

Detection of cadmium ion (Cd2+) is of great necessity in safeguarding public health by providing accurate information about its presence in food matrices. A signal amplification electrochemical biosensor system with DNA cascade reaction was designed for ultrasensitive determination of Cd2+, in which in-situ synthesized Ag nanoclusters (Ag NCs) were identified as signal reporters. The highly conductive electrode with large active area, produced by gold deposition on the screen-printed electrodes (SPE), was regarded as an electrochemical platform. Cd2+ aptamer (Apt) was immobilized on the Au NPs modified SPE (Au-SPE) through the Au-S bound to capture Cd2+ by conformational change. Meanwhile, the unoccupied Apt was able to be paired with H1 and H2 by base complementation to accelerate the hybridization chain reaction (HCR) cascade, and the in-situ synthesis of Ag NCs on cytosine-rich sequence of H1 to achieve the quantification of Cd2+ according to the linear sweep voltammetry (LSV). The constructed electrochemical aptasensor exhibited a linear range from 0.1 ng/mL to 100 ng/mL, and the detection limit was 0.088 ng/mL for Cd2+ under optimal conditions. This HCR-based electrochemical aptasensor allowed practical application to tea and vegetable samples with satisfactory accuracy, confirming its promising application for rapid detection of targets in complex systems. Therefore, this platform holds promise for the rapid detection of heavy metals.