A cascade colorimetric sensor based on Meso-UiO-66(Zr)@PtPdNPs nanozyme with triple enzyme activities and...

Staphylococcus aureus (S. aureus) is a common foodborne pathogen that can cause severe illnesses such as food poisoning and toxic shock syndrome, posing a significant threat to public health. Therefore, rapid and highly sensitive detection of S. aureus is crucial for ensuring food safety. In this study, a Meso-UiO-66(Zr)@PtPdNPs nanozyme with triple enzyme activities was synthesized and combined with the RPA-CRISPR/Cas12a system to construct a novel colorimetric platform for S. aureus detection. This platform utilizes the oxidase and peroxidase activities of Meso-UiO-66(Zr)@PtPdNPs to achieve self-driven catalytic cascade signal amplification without the need for external H₂O₂. During the assay, RPA first amplifies the target DNA to activate the trans-cleavage function of CRISPR/Cas12a. The activated CRISPR/Cas12a then degrades the magnetic bead probe (SMBs-S2), preventing it from coupling with the nanozyme probe (Meso-UiO-66(Zr)@PtPdNPs-S1). After magnetic separation, the nanozyme in the precipitate efficiently catalyzes the color development of TMB through the OXD-POD cascade effect. The resulting color intensity reflects the S. aureus levels. This biosensor shows excellent sensitivity and specificity by integrating the specific recognition and cleavage capabilities of the CRISPR system with the robust catalytic performance of the nanozyme. It displays a linear range of 1.5 × 10¹-1.5 × 10⁸ CFU/mL, alongside a 2.6 CFU/mL detection limit. This study provides a novel strategy for the detection of S. aureus in food.