CRISPR/Cas12a-enhanced single-molecule counting for sensitive detection of flap endonuclease 1 activity at the single-cell level

We develop a new fluorescent biosensor for flap endonuclease 1 (FEN1) assay based on CRISPR/Cas12-enhanced single-molecule counting. This biosensor is simple, selective, and sensitive with a detection limit of 2.325 × 10-5 U and it is applicable for inhibitor screening, kinetic parameter analysis, and quantifying cellular FEN1 with single-cell sensitivity.