The construction of CRISPR/Cas9-mediated FRET 16S rDNA sensor for detection of Mycobacterium tuberculosis

The simple and efficient detection of nucleic acids is important in the diagnosis of tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tuberculosis). However, base mismatch will lead to false positive and false negative nucleic acid test, which seriously interferes with the accuracy of the final results. Herein, we demonstrated a CRISPR/Cas-9-mediated fluorescent strategy utilizing fluorescence resonance energy transfer (FRET) for the detection of bacteria. High-variable region of M. tuberculosis 16S rDNA fragment was used as the target, and CRISPR/Cas9 was used as the recognition element. The binding of the P1 probe of upconversion nanoparticles (UCNPs) @SiO₂-P1 and the P2 probe of Fe₃O₄@Au-P2 caused the fluorescence quenching of UCNPs. In the presence of the target, the P2 probe hybridized with the target to form double-stranded DNA (dsDNA), which was recognized and cleaved by CRISPR/Cas9, resulting in the breaking of the P1-P2 duplex linkage. UCNPs moved away from Fe₃O₄@Au under a magnetic field, and the fluorescence signal was restored; bacteria were detected under the excitation of a 980 nm laser source. Using the CRISPR/Cas-9-mediated system, the sensor could distinguish single-base mismatches in 10 bases from the protospacer adjacent motif (PAM) region. The limit of detection (LOD) was 20 CFU mL^-1 and the detection time was 2 h. It developed a new way of accurate nucleic acid detection for disease diagnosis.