Herein, a p-n quenching photoelectrochemical (PEC) biosensor is constructed for the ultrasensitive detection of miRNA-21 which the SnO₂/CdCO₃/CdS ternary composite nanomaterial is used as a signal indicator and the Y-type DNA structure stabilized p-type CuS quantum dot (QD) is employed as a signal quencher. Constructing the cascade energy level structure by using three photosensitive materials, in which stannic oxide (SnO₂) is used as the photoactive material and cadmium sulfide (CdS) and cadmium carbonate (CdCO₃) are served as the sensitizers. The prepared SnO₂/CdCO₃/CdS cascade co-sensitization structure with significantly improved photocurrent signal can inhibit the recombination of photogenerated electrons and holes, thereby dramatically enhancing the initial photocurrent response. Amounts of single strands DNA (assistant DNA) are output via the exponential strand displacement amplification (E-SDA) when miRNA-21 is present. The output assistant DNA can stabilize the CuS QD by forming stable Y-type DNA nanostructure on the surface of SnO₂/CdCO₃/CdS modified electrode. Therefore, the PEC signal of SnO₂/CdCO₃/CdS ternary composite nanomaterial is greatly quenched, because of the competitive consumption of exciting light energy and electron donors, as well as the steric effect of Y-type DNA structure. The linear range of the biosensor is from 10 fM to 1 μM with the detection limit down to 3.25 fM.

本文中，构建了用于超敏检测miRNA-21的pn猝灭光电化学（PEC）生物传感器，该传感器以SnO ₂ / CdCO ₃ / CdS三元复合纳米材料为信号指示剂，且Y型DNA结构稳定的p型CuS量子点（QD）被用作信号猝灭剂。通过使用三种光敏材料构建级联能级结构，其中氧化锡（SnO ₂）被用作光敏材料，而硫化镉（CdS）和碳酸镉（CdCO ₃）被用作敏化剂。制备的SnO ₂ / CdCO ₃具有显着改善的光电流信号的/ CdS级联共敏化结构可以抑制光生电子和空穴的复合，从而显着增强初始光电流响应。当存在miRNA-21时，通过指数链置换扩增（E-SDA）输出一定数量的单链DNA（辅助DNA）。通过在SnO ₂ / CdCO ₃ / CdS修饰电极的表面形成稳定的Y型DNA纳米结构，输出辅助DNA可以稳定CuS QD 。因此，SnO ₂ / CdCO ₃的PEC信号/ CdS三元复合纳米材料由于激发光能和电子供体的竞争性消耗以及Y型DNA结构的空间效应而大大淬灭。生物传感器的线性范围为10 fM至1μM，检测极限低至3.25 fM。