A graphene nanosensor for detection of small molecules

This paper presents an aptamer-based graphene nanosensor capable of detecting small molecules. To address difficulties in direct detection of small moelcules associated with their low electric charges, we use a competitive sensing approach as demonstrated with dehydroepiandrosterone sulfate (DHEA-S) as a target analyte, which is a small molecular steroid hormone with important applications in clinical diagnostics. A DHEA-S aptamer is captured by a complementary short DNA probe immobilized on the graphene and released upon exposure to DHEA-S in solution due to the binding between DHEA-S and the aptamer. The aptamer release is detected by measuring the change in the conductivity of graphene. Experimental results show that the time rate of aptamer release from the graphene is inversely proportional to DHEA-S concentration in solution. Thus, the nanosensor can potentially enable label-free, specific and quantitative measurement of DHEA-S and other small molecules.