Double-wing switch nanodevice-mediated primer exchange reaction for the activity analysis of cancer biomarker FEN1

DNA damage repair is one of the foremost factors leading to changes in tumor drug resistance. The analysis of Flap endonuclease 1 (FEN1), a kind of pivotal enzyme in various DNA metabolic pathways, has been of great support to tumor research and the development of chemotherapeutics. Nevertheless, few analytical techniques can achieve quantitative and simplified FEN1 measurement. Here, we constructed a double-wing switch nanodevice (DWSN)-mediated primer exchange technique for rapid and label-free quantification of FEN1 activity. Target FEN1 triggered the generation of numerous telomeric repeat fragments in different lengths through recognizing the three-base mismatched sites on the DWSN to release the 5 '-Flaps. Further binding to the fluorescent dye ThT resulted in significantly enhanced fluorescence. This study broke the limitation of traditional single-site identification and demonstrated good sensitivity and specificity with detection limits up to 0.55 mU. Besides, the extraordinary analytical performance allowed the method to be utilized to monitor FEN1 extracted from cells and clinical serum samples and to compare the effect of targeted FEN1 inhibitors.