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

We designed an amplified detection strategy for the sensitive determination of lead ions (Pb) based on a target-triggered nuclear acid cleavage of Pb-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, 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 (HO) to produce the electrochemical signal which was recorded by chronoamperometry. Benefiting from the Pb-dependent DNAzyme, the proposed method can selectively detect Pb in the presence of other metal ions. The newly designed biosensor exhibited a good linear relationship ranging from 0.005 to 1000nmolL with a low detection limit of 2pM (S/N = 3) for Pb. This Pb-dependent DNAzyme based ultrasensitive biosensor showed high sensitivity and selectivity, providing potential application for Pb detection in naturally contaminated sewage and spiked drinking water samples.