Locking-Fluorescence Signals Regulated CRISPR/Cas12a\nBiosensor Based on Metal–Organic Framework for Sensitive Detection\nof <i>Salmonella typhimurium</i>

The\nefficient, sensitive, and rapid detection of <i>Salmonella\ntyphimurium</i> (<i>S. typhimurium</i>) in food and\nfood products is important to ensure food safety and health. This\nstudy developed a fluorescence biosensing assay that integrated recombinase-aided\namplification (RAA) and CRISPR/Cas12a with a zeolitic imidazolate\nframework-8@fluorescein sodium (ZIF-8@FLS) nanocomposite for the sensitive\ndetection of <i>S. typhimurium</i>. In this approach, using\nRAA as a preamplification module, CRISPR/Cas12a-AChE as a target recognition\nand dual-enzyme cascade amplification module, and the prepared ZIF-8@FLS\nwith high porosity and rapid pH responsiveness as a fluorescence signal\nexplosive amplification module, the RAA-CRISPR/Cas12a-ZIF-8@FLS biosensor\nwas constructed. Under optimal conditions, it exhibited an excellent\nlinear relationship for <i>S. Typhimurium</i>, with a sensitive\ndetection limit as low as 1.3 × 10<sup>2</sup> CFU/mL and could\ncomplete sample detection within 2 h relying on the RAA and ZIF-8@FLS\nexplosive fluorescence rapid response, demonstrating its significant\nadvantages in specificity, sensitivity, and reliability in food-borne\npathogens detection.