A cascaded signal amplification strategy combining Au@Cu2O core-shell nanozymes and CRISPR-Cas12a self-cycling for ultrasensitive colorimetric detection of miRNA-21.

As a critical biomarker for early-stage tumor diagnosis, miRNA-21 poses significant challenges for colorimetric detection due to its ultra-low physiological abundance and high sequence homology. In this study, a multi-stage cascade amplification sensing platform was engineered by integrating an entropy-driven molecular circuit with a heterogeneous nanozyme catalytic network. The platform utilizes Catalytic Hairpin Assembly (CHA) for initial signal transduction, coupled with a CRISPR-Cas12a positive feedback self-cycling system to achieve exponential signal amplification. At the signal output interface, Au@Cu2O core-shell nanocomposites, synthesized via epitaxial growth, exhibit significantly enhanced peroxidase-like activity through interfacial electronic coupling. Experimental results demonstrate a limit of detection (LOD) as low as 1.39 fM, with the capacity to precisely discriminate between serum samples from lung cancer patients and healthy individuals.