MicroRNA (miRNA) has emerged as a promising genetic marker for cancer diagnosis and therapy because its expression level is closely related to the progression of malignant diseases. Herein, a label-free and selective fluorescence platform was proposed for miRNA based on light-up “G-quadruplex nanostring” via duplex-specific nuclease (DSN) mediated tandem rolling circle amplification (RCA). First, a long DNA generated from upstream RCA was designed with the antisense sequences for miR-21 and downstream RCA primer. Upon recognizing miR-21, the resulting DNA–RNA permitted DSN digestion and triggered downstream two-way RCA, and generation of abundant “G-quadruplex nanostring” binding with ZnPPIX for label-free fluorescent responses. In our strategy, the strong preference of DSN for perfectly matched DNA/RNA ensures its excellent selectivity. The developed method generated wide linear response with LOD of 1.019 fM. Additionally, the miR-21 levels in cell extracts have been evaluated, revealing the utility of this tool for biomedical research and clinical diagnosis.

MicroRNA（miRNA）由于其表达水平与恶性疾病的进展密切相关，已成为一种有前景的癌症诊断和治疗遗传标志物。在此，基于通过双链特异性核酸酶（DSN）介导的串联滚环扩增（RCA）点亮“G-四链体纳米线”的miRNA，提出了一种无标记和选择性荧光平台。首先，从上游 RCA 产生的长 DNA 被设计为具有 miR-21 和下游 RCA 引物的反义序列。在识别 miR-21 后，产生的 DNA-RNA 允许 DSN 消化并触发下游双向 RCA，并产生大量与 ZnPPIX 结合的“G-四链体纳米线”以进行无标记荧光反应。在我们的策略中，DSN 对完美匹配的 DNA/RNA 的强烈偏好确保了其出色的选择性。开发的方法产生了 LOD 为 1.019 fM 的宽线性响应。此外，还评估了细胞提取物中的 miR-21 水平，揭示了该工具在生物医学研究和临床诊断中的实用性。