Triblock polyadenine probe-based electrochemical DNA sensor by integrating 3D DNAzyme walker and strand displacement for ultrasensitive and rapid detection of Pb2+

Electrochemical DNA sensors have exhibited excellent advantage for the ultrasensitive detection of trace targets. However, the multi-step electrode modification process for sensitivity improvement and low controllability of electrode assembly limit their further application. In this work, a novel triblock polyadenine probe-based electrochemical DNA sensor was established for ultrasensitive and rapid determination of Pb2+. In the presence of the target, copious double strands (LD) were obtained through DNAzyme walker and strand displacement reaction. Triblock polyadenine probe (TPP) was then utilized to specifically capture LD on the electrode surface and construct duplex carriers for intercalating methylene blue. Consequently, on account of the introducing of non-electrode-modification signal-recognition-amplification strategies and TPP, the proposed DNA sensor dispensed with complex electrode modifications. Meanwhile, high sensitivity was guaranteed due to multiple amplification strategies without any natural enzymes, special devices or synthesis of inorganic materials. Under the optimized conditions, multiple modules with coordinated combination achieved the detection limits of 0.039 pM, superior to most published methods. Considering the flexible design of DNA sequences, the sensing platform developed in this work could be applied in the detection of various targets.