Graphene oxide-hairpin probe nanocomposite as a homogeneous assay platform for DNA base excision repair screening.

Uracil-DNA glycosylase (UDG) as one of the most important base excision repair enzymes plays a crucial role in protecting the genome from endogenous DNA damage and sustaining the genome integrity. Quantitative activity analysis of UDG is a central challenge and of fundamental importance in bioanalysis. Here, we proposed a novel biosensor constituted by adsorbing a fluorophore-labeled hairpin probe onto the surface of graphene oxide (GO) as a homogeneous assay platform for sensitive UDG activity assay. Active UDG could excise the uracil base in the hairpin probe, and further hydrolysis of the leaving abasic site gave rise to high fluorescence. Thus, it provided a convenient approach for UDG activity quantification. Because of the unique ability of GO in universal fluorescence quenching, a low background fluorescence signal can be obtained for the efficient fluorescence resonant energy transfer from the fluorophore-labeled on the hairpin probe to GO sheet. A quite wide dynamic range from 0.0017 U/mL to 0.8 U/mL was achieved for UDG assay and the detection limit was estimated to be 0.0008 U/mL. The results indicated that this strategy offers a simple, cost-effective, highly sensitive and selective homogeneous detection platform for UDG activity assay related biochemical studies.