Allosteric probe-triggered isothermal amplification to activate CRISPR/Cas12a for sensitive electrochemiluminescence detection of Salmonella

We report an electrochemiluminescence (ECL) sensor for Salmonella detection based on allosteric probe as a bio-recognition element and CRISPR/Cas12a as a signal amplification strategy. In the presence of Salmonella, the structure switching occurs on allosteric probes, resulting in their hybridization with primers to trigger isothermal amplification. Salmonella is then released to initiate the next reaction cycle accompanying by generating a large amount of dsDNA, which are subsequently recognized by CRISPR-gRNA for activating the trans-cleavage activity of Cas12a. Furthermore, the activated Cas12a can indiscriminately cut the ssDNA which is bound to the electrode, enabling the release of the ECL emitter porphyrinic Zr metal - organic framework (MOF, PCN-224) and exhibiting a decreased ECL signal accordingly. The linear range is 50 CFU center dot mL(-1)-5 x 10(6) CFU center dot mL(-1) and the detection limit is calculated to be 37 CFU center dot mL(-1). This method sensitively detects Salmonella in different types of real samples, indicating it is a promising strategy for Salmonella detection

Automated summary

We developed an ECL sensor for Salmonella detection using allosteric probe as a bio-recognition element and CRISPR/Cas12a as a signal amplification strategy. The presence of Salmonella triggers structure switching on allosteric probes, leading to isothermal amplification. The released Salmonella initiates the next reaction cycle, generating dsDNA recognized by CRISPR-gRNA to activate Cas12a for trans-cleavage. The activated Cas12a cuts ssDNA bound to the electrode, resulting in the release of ECL emitter MOF and decreased ECL signal. The method shows high sensitivity in detecting Salmonella in real samples.