An Ultrasensitive and Robust CircRNA Nanobiosensor via Magnetic Control Depuration and Catalytic Hairpin Assembly Cascade Amplification for Clinically Accessible Liquid Biopsy

Circular RNA (circRNA), a covalently closed RNA molecule, has demonstrated significant potential as a new emerging biomarker in the field of liquid biopsy due to its unique stability, tissue-specific expression patterns, and dysregulated expression in various diseases. However, the accurate quantification of circRNAs is still a tough problem because of homologous linear RNA influence, low-expression abundance, and concomitant interference in blood. Therefore, in this study, a nanobiosensor integrated with catalytic hairpin assembly (CHA) cascade amplification and magnetic control depuration, which can analyze circRNA expressed in human tissue and blood, was reported. The CHA cascade amplification is achieved by coupling the CHA reaction with subsequent formation of G-quadruplex-hemin DNAzymes, resulting in a remarkable enhancement in specificity and sensitivity. The robustness of the nanobiosensor in tissue and blood samples is supported by magnetic-driven transfer of oligonucleotide probes from the complex biological matrix after target recognition. As a proof of concept, the nanobiosensor was designed and fabricated to detect cSMARCA5, a kind of circRNA highly associated with the occurrence of hepatocellular carcinoma. The nanobiosensor exhibits a broad linear range from 10 fM to 100 nM, with a detection limit as low as 1.93 fM. Furthermore, in clinical validation experiments, the nanobiosensor successfully reveals the expression levels of cSMARCA5 in liver tissue and whole blood samples, from which hepatocellular carcinoma patients are accurately screened out among normal people, thereby providing a highly promising circulating RNA-based liquid biopsy tool with significant potential for clinical application.