Ultrasensitive Electrochemical Sensor Based On Dnazyme And MoS₂-AuPt Nanocomposites For Detecting Heavy Metal Lead Pollutants In Water

Lead ion(Pb²⁺),as a common environmental pollutant,seriously threatens human health,and can damage the brain and central nervous system even at low concentrations.In this work,a novel Pb²⁺electrochemical DNAzyme sensor was developed for ultrasensitive detection of Pb²⁺in water environment by coupling with the MoS₂-AuPt nanomaterials and hemin/G-quadruplex DNAzyme,which acting as the electrocatalytic signal tag.Streptavidin（SA）modified tin dioxide-functionalized reduced graphene oxide（rGO-SnO₂）/gold nanoparticles（AuNPs）served as a sensor platform for enhancing conductivity and immobilizing more Pb²⁺-specific DNAzyme.In the presence of Pb²⁺,the Pb²⁺-dependent DNAzyme specifically reacted with Pb²⁺,cleaving the substrate strand（SS）into two free fragment and releasing the biotin-modified enzyme strand（Bio-ES）on the electrode.Connecting MoS₂-AuPt nanocomposites labeled with G-rich DNA（G-DNA）strand and exposure of Bio-ES through the Helper DNA,as well as adding hemin to form a hemin/G-quadruplex,the biosensor achieved signal amplification.Chronoamperometry was used to record the electrochemical signal,which was primarily derived from the cocatalysis reduction of H₂O₂ by MoS₂-AuPt nanocomposites and the hemin/G-quadruplex.Under optimal conditions,the designed biosensor exhibited sensitive detection of Pb²⁺from 0.1 pg?mL^-11 to 1000 ng?mL^-1,with a lower detection limit of 38 fg?mL^-1（based on 3σ）.This proposed biosensor is ultrasensitive and specific,representing a potential application for the detection of Pb²⁺in a water environment.