Split G‑Quadruplex-Programmed Fluorescent Platform for Low Background Signal and Sensitive Nonsmall Cell Lung...

Lung cancer remains a leading cause of cancer-related mortality worldwide, with nonsmall cell lung cancer (NSCLC) accounting for approximately 85% of cases. Herein, we develop a split G-quadruplex-programmed fluorescent platform integrating exonuclease III (Exo-III)-assisted dual signal amplification for ultrasensitive detection of the NSCLC-related miRNA let-7a. This platform incorporates two synergistic background-suppression strategies: immobilization of sensing components on a microplate to remove interfering substances and enzymatic cleavage byproducts, and the employment of malachite green as an aggregation-induced emission fluorophore that activates only upon specific G-quadruplex binding. The Exo-III-mediated dual recycling mechanism substantially enhances detection sensitivity. Under optimized conditions, the platform achieves an exceptionally low detection limit of 0.76 fM with a wide linear range from 1 fM to 50 nM. The method exhibits excellent specificity for discriminating let-7a from homologous miRNAs, high recovery rates (97.6-104.3%) in serum samples, and strong correlation with qRT-PCR. This simple, robust platform holds great promise for early NSCLC diagnosis and clinical monitoring.