Aptamer assisted CRISPR-Cas12a strategy for small molecule diagnostics.

Molecular diagnostics are vital for the identification, prevention, and treatment of numerous diseases and are of particular demand in point-of-care (POC) settings. Nevertheless, most reported biosensors based on the CRISPR-Cas system have focused on nucleic-acid targets. Here, we report a versatile diagnostic strategy for small molecules called Molecular Radar (Random Molecular Aptamer-Dependent CRISPR-Assist Reporter), The workflow is simple, convenient, and rapid (conducted at 37 °C in under 25 min), indicating the substantial potential of the proposed assay could be adapted into a biosensor for POC settings and on-site molecular diagnostics. This strategy is based on the CRISPR Cas12a-assisted fluorescence reporter system that consists of Cas12a, CRISPR RNA (crRNA), a single-stranded DNA (ssDNA) probe labeled with a fluorophore at the 5' end and a quencher at the 3' end (F-Q probe), and a single-stranded DNA aptamer for the target molecule. In the presence of a target molecule, the aptamer binds to this small molecule with high specificity and affinity, resulting in a decrease of aptamer hybridized to the crRNA-Cas12a duplex. This decrease in activated Cas12a leads to a significant reduction in fluorescence signal. In this study, adenosine-5'-triphosphate (ATP) was selected as model target molecule and an ATP detect method was developed with high specificity and sensitivity with a linear range from 25 to 500 μM and a detection limit of 104 nM. Moreover, the particular characteristics of CRISPR-Cas12a that we report here for the first time have enriched our understanding of Cas12a and provided guidance for further research on CRISPR-Cas12a-based biosensors.