A DNA Nano Firework for Imaging and Inhibitor Screening of Flap Endonuclease 1 in Living Cells

In situ observation of changes in theactivityof marker proteins in living cells is crucial for both biomarker-baseddisease diagnosis and drug screening. Flap endonuclease 1 (FEN1) hasbeen recognized as a broad-spectrum cancer biomarker and therapeutictarget. However, simple and reliable methods for in situ studying the FEN1 activity changes in living cells are limited.Here, we introduce a nano firework as a fluorescent sensor to senseand report FEN1 activity changes in living cells through FEN1 recognizingthe substrates on the surface of the nano firework to release andrestore the fluorescence of the prequenched fluorophores. We verifiedthe high selectivity, anti-interference ability, stability, and quantitativeperformance of the nano firework in tubes and living cells, respectively.A series of controlled experiments have demonstrated that the nanofirework could accurately report changes in FEN1 activity in differentcells, enabling "sensors in, results out" in the mannerof simple addition to the cell culture medium. Using an insilico molecular docking study and experiments, we also exploredthe ability of the nano firework for rapid screening of FEN1 inhibitorsand found two new candidate compounds myricetrin and neoisoliquritin,which could be used as FEN1 inhibitors for further research. Theseperformances of the nano firework suggest that it can be used in high-throughputscreening applications, providing a promising tool for biomarker-basednew drug discovery.