A framework nucleic acid -based cascade-amplified self-sustaining electrochemical ratiometric sensor for miRNA detection

Electrochemical sensors are often limited in stability and reliability due to influences such as probe modification density and electrode surface degradation. This study constructed an electrochemical ratiometric biosensor based on framework nucleic acid (FNA), cascade catalytic hairpin assembly (CHA), and hybridization chain reaction (HCR), achieving efficient and accurate detection of miRNA-21. Compared to traditional one-dimensional DNA electrochemical ratiometric sensors, the strong rigidity of FNA prevents probe entanglement and enhances the stability of reference probes. Notably, the introduction of a bulge loop structure provides the framework with better functional versatility. Furthermore, the application of cascade amplification endows the ratiometric sensor with enhanced adaptability for detecting low-abundance targets. By employing this sensing approach, miRNA-21 can be quantified across an extensive linear concentration range (100 aM to 100 pM), with a detection limit of 45 aM. Compared to conventional ratiometric sensors, the proposed self-sustaining FNA-based electrochemical ratiometric sensor demonstrates superior stability, accuracy, and sensitivity, showing great potential for applications in bioanalysis and medical diagnostics.