Electrochemical biosensor for sensitive detection of Hg2+ baesd on clustered peonylike copper-based metal-organic frameworks and DNAzyme-driven DNA Walker dual amplification signal strategy

A sensitive electrochemical biosensor was constructed for Hg 2+ detection based on peonylike Cu-MOFs in situ growth of PtPd NPs bimetallic label S 1 and Mg 2+ -dependent DNAzyme-driven DNA Walker dual amplification signal strategy. The hairpin DNA (HP) and signal label [email protected] NPs/S 1 were first used to self-assemble on the gold nanorods/poly (diallyldimethylammonium chloride) functionalized graphene (AuNRs/PDDA-Gr) modified electrode, at this time, Cu ions can undergo a valence change to produce a larger initial signal. Here, we designed S 2 that can perform dual functions and contains two sequences, on was a substrate sequence of the Mg 2+ -dependent DNAzyme and the other was a sequence complementary to HP. In the presence of target Hg 2+ , HP was opened and hybridized with enzymatically sequenced DNA Walker (S 2 ) to preferentially form thymine-Hg 2+ -thymine (T-Hg 2+ -T). Then, DNA Walker exhibited catalytic activity of DNAzyme in the presence of Mg 2+ to continuously cleave [email protected] NPs/S 1 , resulting in a decrease of electrochemical signal. Under optimal conditions, the change of current was linearly related to the negative logarithm of the Hg 2+ concentration in the detection range of 0.001–100 nM with a low detection limit of 0.52 pM. Moreover, the proposed aptasensor was successfully applied in detection of milk powder samples.