Thermo-alkaline-activated ZrFe-MOF interface for ultrasensitive electrochemical MiRNA biosensing.

We developed a highly sensitive electrochemical sensor based on zirconium-iron metal-organic frameworks (ZrFe-MOF) for the precise detection of ultra-low abundance miRNA-21. The construction of this sensor, through an innovative thermal alkaline activation strategy, exposed abundant binding sites on the surface of ZrFe-MOF, significantly improving aptamer (Apt) loading efficiency, thereby, achieving unprecedented sensitivity with a wide linear range (100 aM-10 nM, R² = 0.997) and a record-low detection limit of 19.33 aM - outperforming existing methods by 1-2 orders of magnitude. Besides, the biosensor successfully discriminates miRNA-21 expression profiles in breast cancer cell lines and breast adenocarcinoma (MDA-MB-231 vs. MCF-7 vs. MCF-10 A), showing high consistency with qPCR results. This work not only demonstrates a novel binding-site engineering strategy for nucleic acid detection but also presents a clinically viable platform for early cancer diagnosis with superior sensitivity, specificity, and reproducibility. This thermal-alkaline activation strategy could be extended to other bimetallic MOFs for multiplex miRNA detection, with future efforts targeting sensor miniaturization for point-of-care use. Current challenges include balancing the material's electron transfer efficiency with long-term storage stability and verifying the sensor's performance in large-scale clinical cohort samples.