Hairpin-Structured DNAzyme-Initiated Spherical Hybridization Chain Reaction Cascade Enables Highly Sensitive Electrochemical Detection of MicroRNA

Sensitive and accurate detection of low-abundance microRNAs (miRNAs) in complex biological matrices is critical for early disease diagnosis. Herein, we report a homogeneous cascade amplification-based electrochemical biosensing platform that integrates hairpin-structured DNAzyme-assisted target recycling amplification with spherical hybridization chain reaction (SHCR)-enhanced electrochemical signal transduction, enabling highly sensitive detection of miRNA-141 (miR-141). In this strategy, a hairpin recognition probe specifically recognizes miR-141, while DNAzyme-mediated catalytic amplification generates a large quantity of trigger strands to initiate SHCR, yielding amplification products densely labeled with electroactive species and thereby substantially enhancing the electrochemical signal output intensity. The fabricated biosensor exhibits a wide linear dynamic range from 0.1 fM to 1 nM with the limit of detection as low as 0.031 fM. Owing to its excellent selectivity and operational stability, the biosensor reliably discriminates miR-141 from structurally similar miRNAs and effectively detects the target in complex serum samples. Furthermore, practical applicability is demonstrated through analysis of miR-141 expression levels in lysates derived from multiple cancer cell lines. Collectively, this biosensing platform offers a robust and highly sensitive electrochemical assay for tumor-associated miRNAs, supporting early molecular diagnosis of related diseases.