Constraint of DNA on functionalized graphene improves its biostability and specificity

Graphene, a single-layer carbon crystal, is attracting increasing attention from the physical, chemical, and biomedical fields^[1] as a novel nanomaterial with many exceptional features including excellent electrical conductivity, high surface-tovolume ratio, remarkable mechanical strength, and biocompatibility.^{[1a, c, 2]} Recently, functionalized graphene has been successfully used in many biomedical and bioassay applications and shows promising potentials in these fields. For instance, Liu et al. used PEGylated graphene oxide for delivery of waterinsoluble cancer drugs to cancer cells. ^[1f] The Berry group demonstrated a graphene-based biodevice for bacterium assay and DNA detection.^[3] Lu et al. designed a graphene-based biosensor platform for DNA and protein detection.^[4] Ang et al. developed a pH sensor using solution-gated epitaxial graphene. ^[5] Czarnecki et al. explored the use of graphene as a functional interface for tissue scaffolds and medical implants.^[1h] Undoubtedly, a better understanding of the molecular interactions between graphene and biomolecules will accelerate its use in biological applications. Here, we chose to study the interactions between functionalized graphene and DNA, a fundamental core component in living systems. The interactions between DNA and nanomaterials, as well as the effects on DNA have been explored and utilized to develop sensitive biosensors, robust DNA carriers, and targeted drugdelivery systems.^[6] Single-walled carbon nanotubes (SWNTs) and DNA were used to study the interaction between biomolecules and fabricated biosensors, in which the enhanced biostability^[6b] and specificity^[6c] of DNA were reported. Limited studies on the interactions between nucleosides and graphene demonstrate the adsorption of nucleobases onto graphene via π-stacking effects.^[7] However, there are no studies exploring the interactions betweenDNAand graphene or the effects of graphene on DNA itself, studies that are necessary to understand the behaviour of DNA-graphene complexes and apply graphene in developing novel biomedical and bioassay platforms. Our study revealed that the singlestranded DNA constrained on functionalized graphene can be effectively protected from enzymatic cleavage. Furthermore, the constraint of DNA on the graphene improves the specificity of its response to complementary DNA.