Duplex DNA-functionalized graphene oxide: A versatile platform for miRNA sensing

MicroRNAs (miRNAs) are short, non-coding RNAs, which have emerged as promising next-generation biomarkers for clinical diagnostics. Here, we developed a graphene oxide (GO)-based fluorescent nano-sensor for miRNA sensing with high specificity and sensitivity. GO is a water-soluble derivative of graphene, which has emerged as one of the most popular nanomaterials in the bio-medical field over the last few decades. Common strategies in the design of GO-based sensors rely on the fluorescence quenching capability of GO and the strong adsorption of ssDNA probes on GO surface through pi-pi interactions or hydrogen bonding. Unfortunately, the interaction between DNA and GO is easily interrupted by other molecules present in biological samples, such as proteins, lipids, and nucleic acids, which results in the nonspecific desorption of probes. Therefore, we designed a fluorescence-labeled dsDNA probe, with an embedded locked nucleic acid (LNA). The probe was then attached onto GO by covalent coupling, instead of nonspecific adsorption. The probes on GO recognized the target miRNA sequence specifically and released the fluorescent strand via toehold-mediated strand displacement (TMSD), which furnished the recovery of quenched fluorescence. This platform displayed improved signal to noise ratio with detection limits at the pico-molar levels. We believe that this new GO-based sensor can be a suitable tool for miRNA-based practical diagnostics of diseases, and provides a valuable resource for basic and applied research.