作为一种特殊的逆转录酶，端粒酶在早期癌症诊断和预后中发挥着重要作用，因此，开发有效的传感技术具有至关重要的意义。本研究基于电子传输隧道距离调控策略和DNA酶可引发的生物催化沉淀，开发了一种创新的“开关型”光电化学（PEC）传感平台，用于超敏感评估端粒酶活性。具体地，我们开发了铜铟硫化物量子点（QDs）、石墨碳氮化物纳米片（g-C3N4 NSs）和二氧化钛纳米棒阵列（NRAs）之间的级联内部电场，以实现级联电子提取和空穴传输。借助这样的设计，通过抑制光生电子空穴对的复合，实现了有效的“开启状态”，从而获得逐渐增强的PEC输出。在引入发夹探针H2并通过目标端粒酶驱动引物序列的进一步延伸的情况下，发夹探针H1上标记的铜铟硫化物量子点会被编程展开，导致铜铟硫化物量子点靠近离级联界面较远的工作电极，并伴随着G-四链体/含铁血红素复合物的形成。随着隧道距离逐渐减小和DNA酶引发的生物催化沉淀的推进，光诱导电荷的迁移动力学显著缓慢，伴随光电流强度的降低，从而导致“关闭状态”。在优化条件下，所制备的PEC生物传感器实现了对10至105个细胞·mL-1范围内端粒酶活性的超敏感检测，检测限为3个细胞·mL-1。作为一个概念验证，这种精心设计的方法为端粒酶活性评估中的信号放大提供了新的见解，并且在药物筛选、健康诊断和生物分析方面具有良好的发展潜力。

Telomerase, as a specialized reverse transcriptase, plays a vital role in early cancer diagnostics and prognosis; thus, developing efficient sensing technologies is of vital importance. Herein, an innovative "signal-on-off" photoelectrochemical (PEC) sensing platform was developed for ultrasensitive evaluation of telomerase activity based on an electron-transfer tunneling distance regulation strategy and DNAzyme-triggerable biocatalytic precipitation. Concretely, cascade internal electric fields between CuInS2 quantum dots (QDs), graphitic carbon nitride nanosheets (g-C3N4 NSs), and TiO2 nanorod arrays (NRAs) were developed to realize cascade electron extraction and hole transfer. Enabled by such a design, an effective "signal-on" state to gain a progressively enhanced PEC output was designed by suppressing the photogenerated electron-hole pair recombination. With the introduction of hairpin probe H2 and the subsequent extension of the primer sequence driven by the target telomerase, the CuInS2 QDs labeled with hairpin probe H1 were programmatically unfolded, resulting in CuInS2 QDs' close proximity to the working electrode away from the cascade interface, accompanied by the formation of G-quadruplex/hemin complexes. The gradual undermining of tunneling distance and implantation of DNAzyme-initiating biocatalytic precipitation tremendously induced the sluggish migration kinetics of the photoinduced charge, accompanied by the photocurrent intensity decrement, leading to the "signal-off" state. Under optimized conditions, the as-prepared PEC biosensor realizes ultrasensitive detection of telomerase activity from 10 to 105 cell·mL-1 with a detection limitation of 3 cells·mL-1. As a proof of concept, this well-designed method provides new insights into signal amplification for telomerase activity evaluation and also presents promising potential for further development in drug screening, healthcare diagnostics, and biological assays.