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 (Pb2+) based on a target-triggered nuclear acid cleavage of Pb2+-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 Pb2+, 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 (H2O2) to produce the electrochemical signal which was recorded by chronoamperometry. Benefiting from the Pb2+-dependent DNAzyme, the proposed method can selectively detect Pb2+ 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 Pb2+. This Pb2+-dependent DNAzyme based ultrasensitive biosensor showed high sensitivity and selectivity, providing potential application for Pb2+ detection in naturally contaminated sewage and spiked drinking water samples.