Exponential amplification reaction-based fluorescent sensor for the sensitive detection of tumor biomarker flap endonuclease 1

Flap endonuclease 1 (FEN1) is a nuclease overexpressed in cells with a high replicate rate, which has been recognized as a potential biomarker in the molecular diagnosis of cancers. In this work, we developed a fluorescent biosensor based on exponential amplification reaction (EXPAR) to realize the rapid and sensitive detection of FEN1. A DNA probe specific for FEN1 is used for the generation of reporter DNA (rDNA), and then the rDNA hybridizes with a template, triggering EXPAR to produce substantial rDNA exponentially. However, when no FEN1 is in the system, the EXPAR will not be initiated because of the lack of rDNA. Derived from the high amplification efficiency of EXPAR, the rapid quantification of FEN1 with a limit of detection (LOD) of 0.5 fM was realized. It is also revealed that this biosensor exhibits good selectivity towards FEN1 under the challenge from real samples including extracts of cells and solid tumors. Furthermore, this sensor was reengineered for the analysis of FEN1 inhibitors, which shows promise in the screening and evaluation of potential drugs targeting FEN1. This work integrates EXPAR into the biosensing of FEN1 for the first time, which provides a promising tool for FEN1-related biomedical investigations.