小型细胞外囊泡相关的microRNA（sEV-miRNA）是癌症诊断的重要生物标志物。然而，对临床样本中低丰度sEV-miRNA进行快速敏感的检测具有挑战性。在本研究中，我们提出了一种简单的电化学生物传感器，使用DNA纳米线定位催化发夹装配（CHA），也称为多米诺式定位催化发夹装配（DT-LCHA），用于sEV-miRNA1246的检测。DT-LCHA提供了三重放大效果：（i）CHA系统定位在DNA纳米线上，缩短了发夹底物之间的距离，使H1和H2之间的碰撞效率高，并产生了多米诺效应。然后，触发了更多的CHA，捕获探针通过外露出的c位与DT-LCHA结合。（ii）DNA纳米线可以载入大量的电活性物质RuHex作为扩增的电化学信号标记。（iii）DNA纳米线携带多个DT-LCHA，只有一个CHA被触发，DNA纳米线被捕获探针困住，从而大大提高了检测灵敏度，尤其是在目标浓度极低的情况下。由于这种策略中的三重信号放大效应，可以在20分钟内检测到低至24.55 aM浓度的sEV-miRNA，并具有良好的特异性。使用逆转录定量聚合酶链反应确认了测量结果的准确性。此外，该平台在区分早期胃癌患者与健康供体（曲线下面积[AUC]：0.96）以及良性胃肿瘤与早期癌症（AUC：0.77）方面表现良好。因此，该平台在生物传感和临床诊断中具有巨大的潜力。© 2023. BioMed Central Ltd.，Springer Nature的一部分。

Small extracellular-vesicule-associated microRNA (sEV-miRNA) is an important biomarker for cancer diagnosis. However, rapid and sensitive detection of low-abundance sEV-miRNA in clinical samples is challenging. Herein, a simple electrochemical biosensor that uses a DNA nanowire to localize catalytic hairpin assembly (CHA), also called domino-type localized catalytic hairpin assembly (DT-LCHA), has been proposed for sEV-miRNA1246 detection. The DT-LCHA offers triple amplification, (i). CHA system was localized in DNA nanowire, which shorten the distance between hairpin substrate, inducing the high collision efficiency of H1 and H2 and domino effect. Then, larger numbers of CHAs were triggered, capture probe bind DT-LCHA by exposed c sites. (ii) The DNA nanowire can load large number of electroactive substance RuHex as amplified electrochemical signal tags. (iii) multiple DT-LCHA was carried by the DNA nanowire, only one CHA was triggered, the DNA nanowire was trapped by the capture probe, which greatly improve the detection sensitivity, especially when the target concentration is extremely low. Owing to the triple signal amplification in this strategy, sEV-miRNA at a concentration of as low as 24.55 aM can be detected in 20 min with good specificity. The accuracy of the measurements was also confirmed using reverse transcription quantitative polymerase chain reaction. Furthermore, the platform showed good performance in discriminating healthy donors from patients with early gastric cancer (area under the curve [AUC]: 0.96) and was equally able to discriminate between benign gastric tumors and early cancers (AUC: 0.77). Thus, the platform has substantial potential in biosensing and clinical diagnosis.© 2023. BioMed Central Ltd., part of Springer Nature.