MoS2 nanosheets as an effective fluorescence quencher for DNA methyltransferase activity detection

As one of the inorganic graphene analogues, two dimensional MoS2 nanosheets have been drawing extensive attention in the past few years due to their remarkable structural and electronic properties. Herein, a simple signal-on fluorescence DNA methyltransferase (MTase) activity assay using a MoS2 nanosheet mediated fluorescence quenching strategy is described. Briefly, substrate DNA is designed to possess a double-stranded DNA (ds-DNA) segment containing the recognition sequence of DNA adenosine methyltransferase (Dam) and a single-stranded DNA (ss-DNA) segment for anchoring the substrate DNA to MoS2 nanosheets via van der Waals interactions. Once the substrate DNA is absorbed onto MoS2 nanosheets, the fluorescence of the fluorophores labeled to the end of the ds-DNA region is quenched. When the substrate DNA is methylated by Dam, fluorescence is recovered resulting from the release of the fluorophore labeled segment cleaved by the methylation sensitive restriction endonuclease DpnI. Since the fluorescence recovery directly reflects the methylation level, the Dam MTase activity can be quantified accordingly. Based on this assay, a linear range of 0.2–20 U mL−1 is achieved with high sensitivity and selectivity. Furthermore, the inhibitor screening ability is well demonstrated.