Ultra-sensitive electrochemical DNA biosensor based on a label-free assembling strategy using a triblock polyA DNA probe

Multiblock DNA probe attracted a large amount of scientific attention, for the development of multi-target biosensor and improved specificity/sensitivity. However, the development of multiblock DNA probes highly relied on the chemical synthesis of organic linkers or nanomaterials, which limited their practicability and biological compatibility. In this work, we developed a label-free assembling strategy using a triblock DNA capture probe, which connects 2 DNA probes with its intrinsic polyA fragment (Probe-PolyA-Probe, PAP). The middle polyA segment has a high affinity to the gold electrode surface, leading to excellent reproducibility, stability, and regeneration of our biosensor. Two flanking capture probes were tandemly co-assembled on the electrode surface with consist spatial relationship and exactly the same amount. When combined with the target DNA, the hybridization stability was improved due to the strong base stacking effect of two capture probes. The sensitivity of our biosensor was proved to b...