Ultrasensitive detection of flap endonuclease 1 using a chemiluminescence optical fiber biosensor with hybridization chain reaction

Abstract

Flap endonuclease 1 (FEN1) is an important biomarker involved in tumor progression and can catalyze the cleavage of DNA with a bifurcated structure at the 5′ end, while its expression is so low in cancer cells that accurate and sensitive quantification is quite challenging. In this study, we propose a novel sensing method for sensitively detecting FEN1 in HeLa cells by combining chemiluminescent optical fiber sensors (COFSs) with an enzyme-free hybridization chain reaction (HCR) amplification strategy. The free 5′-flap produced by FEN1-specific cleavage of the bifurcated structure double-stranded DNA is captured by the COFS modified with a hairpin capture probe to trigger HCR amplification. Signal conversion is achieved by introducing the streptavidin-modified horseradish peroxidase on the fiber surface to catalyze chemiluminescent substrates based on the specific binding between biotin and streptavidin. The chemiluminescence emission is transmitted by the same optical fiber and recorded as the sensing response. With this approach, excellent analytical performance for FEN1 detection is achieved, with a wide linear range of 10 fM to 75 pM, a limit-of-detection as low as 3.4 fM and good specificity. The method is successfully applied for the determination of FEN1 in HeLa cell lysate samples with satisfactory accuracy, the results of which are consistent with those from the ELISA assays. Our study indicates that with the essential advantages of high sensitivity, excellent integration and portability, the COFS combined with a suitable efficient amplification strategy can perform ultrasensitive determination of biomarkers and will have valuable potential applications in various fields of point-of-care testing.