A CRISPR-Cas12a-powered, quantum dot-based and magnetic nanoparticle-assisted (QD-CRISPR-MNP) biosensor for the screening of Salmonella

Rapid detection methods are urgently needed to help prevent the spread of Salmonella among food products. Herein, a CRISPR-Cas12a-powered, quantum dot-based and magnetic nanoparticle-assisted (QD-CRISPR-MNP) biosensor was proposed for the screening of Salmonella. The QD-CRISPR-MNP biosensor was designed and fabricated relying on the CRISPR-Cas12a system for better guidance of the coupling between magnetic nanoparticles (MNPs) and quantum dots (QDs). In this biosensor, the activity of the CRISPR-Cas12a system was unlocked by Salmonella and displayed collateral cleavage activity towards linker DNAs, which inhibited the coupling of the MNPs and QDs. Then, Salmonella could be quantitatively detected by simply measuring the fluorescence emitted by the QDs on the MNPs surface. This biosensor showed good detection performance for Salmonella with a detection limit of 86 CFU mL−1, and exhibited a satisfactory specificity as well. Moreover, it overcomes the low fluorescence quantum yields and the possible high fluorescence background noise in conventional dye-based CRISPR detection platforms, acting as a powerful alternative for the detection of foodborne pathogens.