Amplification-free sensitive detection of Staphylococcus aureus by spherical nucleic acid triggered CRISPR/Cas12a and Poly T-Cu reporter.

A spherical nucleic acid (SNA, AuNPs-aptamer) into CRISPR/Cas12a system combined with poly T-template copper nanoparticles as fluorescence reporter was fabricated to establish an amplification-free sensitive method for Staphylococcus aureus (S. aureus) detection. This method, named PTCas12a, utilizes the concept that the bifunction of SNA recognizes the S. aureus and triggers the Cas12a cleavage activity. Then, the Cas12a enzyme cleaves the Poly T40 to generate a signal change in Poly T-Cu fluorescence, indicating the presence or absence of the target bacteria. The PTCas12a platform demonstrated a detection limit as low as 3.0 CFU/mL (3 N/S) in a wide response range of 1.0 × 10-1.0 × 10 CFU/mL for S. aureus detection, which holds significant potential in ensuring food safety and preventing the spread of diseases.