A CRISPR/Cas12a−MXene Nanozyme Platform for Universal Detection of Trace DNA

The instrument-free detection of specific DNA sequences is critical for point-of-care diagnostics yet remains challenging. To address this, we developed a universal colorimetric biosensing platform integrating the CRISPR/Cas12a system with MXene nanozymes. Target recognition by the Cas12a/crRNA complex triggers trans-cleavage of single-stranded DNA inhibitors, restoring the peroxidase-like activity of MXenes to produce a visible signal. The platform achieved a detection limit of 132 copies/μL for the methicillin-resistant Staphylococcus aureus mecA gene. By incorporating an exponential circular DNA (CirDNA) amplification strategy and rationally designed crRNAs for single-base discrimination, sensitivity was further enhanced, enabling detection of the B-raf proto-oncogene V600E mutation down to 109 aM with 0.5% variant allele frequency. The platform also showed excellent reproducibility and high recovery rates in simulated clinical samples. This work provides a low-cost, label/instrument-free, and highly sensitive universal approach through the synergistic combination of CRISPR/Cas12a programmability, MXene nanozyme activity, and CirDNA amplification.