A hairpin conformational change-mediated SRH cascade isothermal amplification assisted electrochemical biosensor for Listeria monocytogenes detection.

The rapid and sensitive detection of foodborne pathogens is crucial for safeguarding food safety and public health. In this study, we developed an electrochemical biosensor based on a hairpin conformational change-mediated cascade isothermal amplification strategy for the detection of Listeria monocytogenes in food. The biosensor employs aptamers for specific recognition of the target bacterium. In combination with magnetic separation technology, the concentration of the target bacterium is converted into that of a trigger strand. The trigger strand induces a conformational change in the hairpin structure, thereby initiating a cascade amplification reaction involving strand displacement amplification, rolling circle amplification, and hybridisation chain reaction (SDA-RCA-HCR, SRH), enabling an exponential signal amplification and a significant reduction of the background signals caused by self-cleavage. The proposed biosensor demonstrates a linear detection range of 15 to 1.5 × 108 CFU/mL for Listeria monocytogenes, with a detection limit as low as 5 CFU/mL (S/N = 3). It exhibits great specificity for the target bacterium, effectively distinguishing it from other common foodborne pathogens, and shows satisfactory performance in real food samples, including lettuce, cheese, and chicken. Thus, this work provides an efficient, reliable, and sensitive new method for the rapid detection of foodborne pathogens in complex food matrices.