Catalytic hairpin assembly assisted target-dependent DNAzyme nanosystem coupled with AgPt@Thi for the detection of lead ion

An ultrasensitive electrochemical biosensor for detection of lead ions (Pb 2+ ) is proposed based on catalytic hairpin assembly and target-induced DNAzyme signal amplification strategy. Polyethyleneimine-reduced graphene oxide (PEI-rGO) combined with [email protected] nanosheets ( [email protected] NSs) are used as electrode substrate modification materials, which not only increase the specific surface area but also exhibit stronger conductivity than pure PEI-rGO or [email protected] NSs. Hairpin chain 1 (HP 1 ) is immobilized on the surface of modified electrode by Au–S. Then trigger (Tr) DNA can induce the opening of the HP 1 hairpin, thus exposing the binding sequence to hybridize with Hairpin chain 2 (HP 2 ) and catalyzing the opening and binding of the hairpin HP 2 . The process is cyclic and will produce abundant HP 1 -HP 2 duplex strands. When Pb 2+ is present, it can catalyze DNAzyme (Pb 2+ -HP 2 ) to specifically cut the substrate chain HP 1 , and only a partial sequence of HP 1 remains on the surface of the electrode. Finally, the signal probe ( [email protected] ) can be hybridized with the part of the HP 1 sequence after being cut to generate a significant electrical signal. Under optimal conditions, the Pb 2+ concentration measured by prepared electrochemical biosensor has a good linear relationship in the range of 0.05 pM–5 nM, and the detection limit is 0.028 pM. This method can be used for the trace detection of Pb 2+ in tap water samples, and it also provides a platform for the detection of other targets.