An aptasensor for cadmium ions detection based on PEI-MoS₂@Au NPs 3D flower-like nanocomposites and Thi-PtPd NPs...

A novel ultrasensitive electrochemical aptasensor was proposed for quantitative detection of Cd²⁺. To this end, flower-like polyethyleneimine-functionalized molybdenum disulfide-supported gold nanoparticles (PEI-MoS₂ NFs@Au NPs) were used as substrates for the modification of bare gold electrodes (AuE). PEI-MoS₂ NFs@Au NPs not only possessed excellent biocompatibility and large specific surface area to enhance the cDNA loading capacity, but also possessed good conductivity to accelerate the electron transfer rate. Furthermore, the preparation of dendritic platinum-palladium nanoparticles (PtPd NPs) can effectively load Cd²⁺-aptamer. Thionine and aptamers were loaded onto PtPd NPs to construct Thi-PtPd NPs-aptamer signal probes. The signal probes were captured by the cDNA immobilized on the electrode via base-pairing rule, and the signal of Thi was detected by differential pulse voltammetry (DPV). In the presence of Cd²⁺, aptamer-cDNA unwinded, and the combination of aptamer and Cd²⁺ caused the signal probes to fall off the electrode and the electrical signal decreases. Under optimal conditions, the proposed aptasensor exhibited a linear relationship between the logarithm of Cd²⁺ concentration and the current response over a wide range of 1 × 10^-3 nM to 1 × 10² nM, with a detection limit of 2.34 × 10^-4 nM. At the same time, the aptasensor was used to detect Cd²⁺ in tap water with satisfactory results. In addition, it has good reproducibility, selectivity and stability, and has broad application prospects in heavy metal analysis.