An DNA Enzyme Electrochemiluminescence Biosensor for Ultra-sensitive Detection of Pb2+ Based on CdS/MoS2 Joint Amplification

Lead (Pb) is one of the most serious heavy metals to human health and ecological environment. Excessive lead can lead brain retardation and liver and kidney damage. In this work, a novel electrochemiluminescence (ECL) biosensor based on CdS quantum dots (CdS QDs)/MoS2 enzyme assist multiple amplification and DNA enzyme was designed to achieve high sensitivity detection of Pb2+. AuNPs-PDDA-MoS2 complex was synthesized as sensing substrate. The thiol-labeled T30695 DNA was assembled on the surface of the electrode via Au-S bonds, following which the amino-labeled ends of the DNA were linked to the CdS QDs by the formation of amide bonds. In the presence of Pb2+, the G bases of DNA sequence formed G- tetraplex (G4) structure, DNA enzymes were then further synthesized. The catalytic oxidation of H2O2 by DNA enzyme and AuNPs-MoS2 composite resulted in a significant decrease of electrochemiluminescence of CdS QDs with H2O2. The detection range of the biosensor was 1.0×10-14 - 5.0×10-11mol/L (R = 0.9992) with a detection limit of 1×10-15 mol/L. This biosensor can detect Pb2+ in real water samples with satisfactory results.