MXene-integrated CRISPR/Cas12a biosensor with Split activators for direct and rapid fluorescent detection of MicroRNA

Early and accurate cancer diagnosis is essential for reducing cancer-related mortality, and miRNA-21 has emerged as a critical biomarker for the early detection of various malignancies In this study, we developed a novel fluorescence biosensor, termed the MXene-SNA-Cas12a, that enables direct and amplification-free detection of miRNA-21 by integrating the CRISPR/Cas12a system with a chimeric split nucleic acid (SNA) activator and MXene-assisted fluorescence modulation. Specifically, a split activator comprising S12 ssDNA hybridized with miRNA-21 was employed to activate the trans-cleavage activity of Cas12a, effectively overcoming the system's inherent limitation in RNA recognition. Simultaneously, MXene nanosheets served as efficient quenchers by adsorbing FAM-labeled ssDNA reporters through non-covalent interactions and facilitating target-induced strand release, enabling a robust fluorescence "on/off" mechanism. This biosensor demonstrated excellent linearity over a miRNA-21 concentration range of 50 pM-25 nM, with a detection limit as low as 16 pM. It exhibited high specificity and strong resistance to interference, making it well-suited for complex biological environments. Moreover, the programmable nature of the split activator allows for easy adaptation to detect other RNA targets through rational sequence redesign, offering a versatile platform for CRISPR/Cas12a-based RNA diagnostics.