Intramolecular Electrochemiluminescence Resonant Energy Transfer Biosensor Utilizing Ir-Grafted 2D Hf-MOL and Circular DNA Walker for Ultrasensitive Detection of microRNA-21 in Non-Small-Cell Lung Cancer Diagnostics

The rapid advancement in non-small-cell lung cancer (NSCLC) diagnostics demands ultrasensitive biosensors for detecting microRNA-21 (miRNA-21), a pivotal prognostic biomarker. An innovative electrochemiluminescence (ECL) biosensor was developed that leverages ECL resonance energy transfer (ECL-RET) as the primary amplification mechanism for ultrasensitive detection. The biosensor integrated a two-dimensional hafnium-based metal-organic layer (Hf-MOL) functionalized with iridium complexes (Ir-Hf-MOL), which serves as an efficient ECL emitter. Enhanced sensitivity is achieved through precise spectral overlap and Förster radius optimization, enabling stable energy transfer from Hf-MOL to Ir-COOH. The structural rigidity of Ir-Hf-MOL further contributed to suppressing nonradiative decay through restricted molecular motion. Charge transfer feasibility is validated via density functional theory (DFT), while a circular DNA walker-mediated amplification strategy is incorporated to augment specificity and signal amplification. The optimized system achieves an exceptional linear range from 1 aM to 1 nM, with a low detection limit of 0.76 aM. Rigorous evaluations of selectivity, stability, and recovery rates (99.4-103.2%) in human serum and Bland-Altman plots confirm clinical applicability. This work establishes a transformative biosensing platform for miRNA-21 detection, emphasizing ECL-RET-driven innovation, and advances diagnostic strategies for NSCLC.