A sensitive fluorescence turn-on assay of bleomycin and nuclease using WS2 nanosheet as an effective sensing platform

As an important antitumor drug, bleomycin (BLM) is widely used in the treatment of a variety of cancers. In addition, nucleases play a crucial role in DNA replication, recombination and repair which are associated with cancer development. Thus, the development of BLM and nuclease detection methods is of great significance in cancer therapy and related biological mechanism research. Here, a WS2 nanosheet-based turn-on fluorescent sensing platform for simple, fast and sensitive detection of BLM and nuclease was reported. WS2 nanosheet exhibits different affinity toward ssDNA with different length and excellent fluorescence quenching ability. A fluorescein (FAM)-labeled long ssDNA could be adsorbed on the surface of WS2 nanosheet and the fluorescence was therefore quenched. In the presence of BLM·Fe(II) or S1 nuclease (a ssDNA-specific nuclease which was used as a model enzyme), an irreversible scission of long ssDNA was underwent through the BLM-induced oxidation cleavage or S1 nuclease-induced enzymatic hydrolysis. Short FAM-linked oligonucleotide fragments which could not be adsorbed on the nanosheet surface were then produced, resulting in a weak fluorescence quenching after mixing WS2 nanosheets. Thus, the fluorescence signal was restored. The proposed sensor displays a wide linear range and a high sensitivity with a detection limit of 0.3 nM for BLM and 0.01 U mL(-1) for S1 nuclease. It also exhibits a good performance in complex biological samples. This method not only provides a strategy for BLM or S1 nuclease assay but also offers a potential application in biomedical and clinical study.