Target triggered cleavage effect of DNAzyme: Relying on Pd-Pt alloys functionalized Fe-MOFs for amplified detection of Pb2+

We designed an amplified detection strategy for the sensitive determination of lead ions (Pb 2+ ) based on a target-triggered nuclear acid cleavage of Pb 2+ -specific DNAzyme as a selectivity interface combined with Pd-Pt alloys modified Fe-MOFs (Fe-MOFs/PdPt NPs) hybrids acting as the signal tag. Streptavidin modified reduced graphene oxide-tetraethylene pentamine-gold nanoparticles (rGO-TEPA-Au) served as a sensor platform for immobilizing more DNAzyme. In the presence of Pb 2+ , the substrate DNA strand can be specifically cleaved at the ribonucleotide site by DNAzyme to produce a new single-DNA on the interface. Then, the hairpin DNA with hybrid strand matched by its complement to the single-DNA was employed to modify the Fe-MOFs/PdPt NPs bioconjugates for signal amplification . Fe-MOFs/PdPt NPs catalyze hydrogen peroxide (H 2 O 2 ) to produce the electrochemical signal which was recorded by chronoamperometry . Benefiting from the Pb 2+ -dependent DNAzyme, the proposed method can selectively detect Pb 2+ in the presence of other metal ions . The newly designed biosensor exhibited a good linear relationship ranging from 0.005 to 1000   nmol   L −1 with a low detection limit of 2   pM (S/N = 3) for Pb 2+ . This Pb 2+ -dependent DNAzyme based ultrasensitive biosensor showed high sensitivity and selectivity, providing potential application for Pb 2+ detection in naturally contaminated sewage and spiked drinking water samples.