MicroRNAs (miRNAs) have been identified as important biomarkers with great significance for diagnosis and treatment of various diseases. However, their unique properties, such as small size, high sequence homology, and low abundance, make quantitative analysis of miRNAs extremely challenging. Herein, we reported a cascade catalytic hairpin assembly (CCHA) for sensitive and selective detection of miRNA with three kinds of hairpin probes (HP1, HP2, and HP3). In the presence of target miRNA, a series of toehold-mediated intermolecular DNA strand displacement and hybridization was activated among HP1, HP2, and HP3 to assembly numbers of DNA nanoobjects. During this period, the fluorescence response was greatly intensified to indicate the presence and expression level of interested target miRNA. We have demonstrated that the proposed method exhibits a high assay sensitivity to detect low concentration target and an excellent sequence specificity to distinguish even a single-nucleotide difference in vitro. Moreover, we also demonstrated that our design enables the intracellular imaging of miRNA in live cancer and normal cells. These results showing the promising potential of our CCHA for powerful biosensing, clinic diagnosis, or prognosis.

MicroRNAs（miRNAs）已被确定为重要的生物标志物，对各种疾病的诊断和治疗具有重要意义。然而，它们独特的特性，如小尺寸、高序列同源性和低丰度，使得 miRNA 的定量分析极具挑战性。在这里，我们报道了一种级联催化发夹组装（CCHA），用于使用三种发夹探针（HP1、HP2 和 HP3）灵敏和选择性地检测 miRNA。在存在目标 miRNA 的情况下，HP1、HP2 和 HP3 之间的一系列立足点介导的分子间 DNA 链置换和杂交被激活，以组装数量的 DNA 纳米对象。在此期间，荧光反应大大增强，以表明感兴趣的目标 miRNA 的存在和表达水平。我们已经证明，所提出的方法对检测低浓度靶标具有很高的测定灵敏度，并且在体外甚至可以区分单核苷酸差异。此外，我们还证明了我们的设计能够对活癌细胞和正常细胞中的 miRNA 进行细胞内成像。这些结果显示了我们的 CCHA 在强大的生物传感、临床诊断或预后方面的巨大潜力。