Label-free electrochemical aptasensor for ultrasensitive lead ion detection based on flower-like AuNPs@MoS2 and core–shell Pt@Pd bimetallic nanoparticles

A signal-amplified platform was designed to construct a label-free electrochemical aptasensor for lead ions (Pb 2+ ) assay. First, flower-like molybdenum disulfide-supported AuNPs (AuNPs@MoS 2 ) nanocomposites were synthesized and used as substrates for modifying the electrode. The AuNPs@MoS 2 material possessed large surface area and superior biocompatibility, which was beneficial to improve the loading amount of the complementary DNA (cDNA) and amplified the response signal. Importantly, the prepared core–shell Pt@Pd bimetallic nanoparticles (Pt@PdNPs) were used to conjugate with redox marker thionine (Thi) and aptamer (Apt) for further signal amplification; the obtained signal probes (Thi-Pt@PdNPs-Apt) were connected by the cDNA assembled on the electrode through DNA hybridization. Differential pulse voltammetry was performed to monitor the signal of Thi. After incubating of aptasensor with Pb 2+ , the specific recognition of Pb 2 + and Apt resulted in the dissociation of aptamer-cDNA complex, thereby the Thi-Pt@PdNPs-Apt separated from the electrode surface and decreased current response was obtained. The prepared electrochemical sensor exhibited linear response to Pb 2+ in the range 5.0 × 10 −4 –100 nM and a detection limit of 1.0 × 10 −4  nM was achieved. The sensor was applied to the determination of Pb 2+ in actual sample with high sensitivity and accuracy, demonstrating potential applications in heavy metal monitoring. Graphical Abstract