An electrochemical aptasensor based on gold-modified MoS2/rGO nanocomposite and gold-palladium-modified Fe-MOFs for sensitive detection of lead ions

Abstract In this work, an electrochemical aptasensor was proposed by using gold-modified molybdenum disulfide/reduced graphene oxide (Au@MoS2/rGO) nanocomposite and gold-palladium (AuPd)-modified MIL-88 (Fe) metal-organic frameworks (AuPd@Fe-MOFs) for sensitive detection of lead ions (Pb2+). The 8-17 DNAzyme consisting of a substrate strand (Apt1) and a catalytic strand (Apt2) was used to construct the aptasensor. Au@MoS2/rGO nanocomposite was applied as the sensing platform to immobilize the mercapto-group-labeled Apt1. Meanwhile, AuPd@Fe-MOFs was employed to label Apt2, which showed excellent catalytic ability toward H2O2. In the presence of Pb2+, the Apt1 of the DNAzyme was catalytically cut off, decreasing the amount of AuPd@Fe-MOFs. The current response was correlated to the Pb2+concentration, thereby achieving Pb2+ detection. Under the optimal experimental conditions, the fabricated aptasensor showed a highly linear response for Pb2+ in the range from 5.0 pmol/L to 2.0 μmol/L, with a detection limit of 0.07 pmol/L. Additionally, the proposed electrochemical aptasensor exhibited excellent selectivity, stability and reproducibility. Moreover, the proposed aptasensor demonstrated good performance in real water sample analysis, making it promising for use in Pb2+ detection in environmental monitoring.