A steric hindrance-regulated autocatalytic CRISPR/Cas12a system for direct and amplification-free microRNA detection.

We constructed a CRISPR/Cas12a autocatalytic system based on a miRNA-triggered overhang blocker (OB) cleavage-recombination framework, in which Cas12a sequentially removed steric hindrance to initiate cyclic autocatalysis, enabling exponential signal amplification for visual miRNA detection without target pre-amplification, thereby overcoming direct Cas12a recognition limitations for point-of-care diagnostics.