Dual Mode Analysis of Methicillin-Resistant Staphylococcus aureus by the CRISPR/Cas12a-Assisted Exonuclease-Mediated Signal Cycle.

Methicillin-resistant Staphylococcus aureus (MRSA) is the main Gram-positive bacteria isolated from patients with ocular infections and remians a huge threat to public health. Therefore, sensitive and dual-mode analysis of MRSA is of great significance for evaluating MRSA infection. We depicted a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a-based biosensor by integrating the exonuclease III (Exo III)-enhanced fluorescence and colorimetric signals for sensitive and dual-mode analysis of methicillin resistance in MRSA without needing nucleic acid amplification. In this method, Exo III-assisted signal recycling is triggered only when the target mecA gene activates the CRISPR/Cas12a complex, and the HP probes on the surface of magnetic nanoparticles are cleaved by the trans-cleavage activity of Cas12a. Taking the merits of the trans-cleavage activity of the CRISPR/Cas12a system and the Exo III-assisted signal recycling, this approach exhibits an exceptionally elevated detection threshold for the mecA gene. Besides MRSA detection, this accurate and sensitive sensor can be employed to assess additional biomarkers in disease diagnosis by simply changing the crRNA.