Ultrasensitive fluorescent biosensor for miRNA-34a detection: Magnetic separation coupled with cascade amplification of duplex-specific nuclease-assisted and hybridization chain reaction.

Lung cancer is the most common and lethal malignancy worldwide, with non-small cell lung cancer (NSCLC) accounting for approximately 85% of cases and exhibiting high mortality rates. MicroRNA-34a (miRNA-34a) is a promising biomarker, therapeutic target, and prognostic indicator for NSCLC, necessitating sensitive and specific detection methods for early diagnosis and improved clinical management. Here, we developed a highly sensitive fluorescent biosensor for miRNA-34a detection by integrating magnetic separation with cascade amplification of duplex-specific nuclease (DSN) and hybridization chain reaction (HCR). Under optimal conditions, the biosensor exhibits a wide linear range (1.0 fM-10.0 nM) and an ultralow detection limit (0.3 fM), with excellent specificity for discriminating against interfering miRNAs. Moreover, the sensor was successfully validated in clinical blood samples, showing excellent agreement with RT-qPCR results. Collectively, this method provides a sensitive and specific tool for trace miRNA-34a detection, demonstrating significant potential for early NSCLC diagnosis and improved patient management.