Enhanced CRISPR/Cas12a Fluorimetry via a DNAzyme-Embedded Framework Nucleic Acid Substrate

CRISPR/Cas12a fluorimetry has been extensively developed in the biosensing arena, on account of its high selectivity, simplicity, and rapidness. However, typical CRISPR/Cas12a fluorimetry suffers from low sensitivity due to the limited trans-cleavage efficiency of Cas12a, necessitating the integration of other preamplification techniques. Herein, we develop an enhanced CRISPR/Cas12a fluorimetry via a DNAzyme-embedded framework nucleic acid (FNAzyme) substrate, which was designed by embedding four CLICK-17 DNAzymes into a rigid tetrahedral scaffold. FNAzyme can not only enhance the trans-cleavage efficiency of CRISPR/Cas12a by facilitating the exposure of trans-substrate to Cas12a but also result in an exceptionally high signal-to-noise ratio by mediating enzymatic click reaction. Combined with a functional nucleic acid recognition module, this method can profile methicillin-resistant Staphylococcus aureus as low as 18 CFU/mL, whose sensitivity is approximately 54-fold higher than that of TaqMan probe-mediated CRISPR/Cas12a fluorimetry. Meanwhile, the method exhibited satisfactory recoveries in food matrices ranging from 80% to 101%. The DNA extraction- and preamplification-free detection format as well as the potent detection performance highlight its tremendous potential as a next-generation analysis tool.