Graphene Oxide Based Biosensing Platform

The conjugation of nanomaterials with biomolecules has allowed for engineering at the nanoscale to build devices which help improve human health and environment. Graphene oxide, a two-dimensional carbon based nanomaterial, has been on the forefront of such endeavors through its use in biosensing and controlled drug release. Herein, graphene oxide is used as a substrate to anchor an aptamer based molecular beacon. Upon presence of mercury, the mercury sensitive aptamer undergoes a conformational change shortening the distance between an excited quantum dot and a quenching gold nanoparticle. As the distance between the two decreases, the efficiency of the fluorescence resonance energy transfer increases – decreasing the intensity of the system. The graphene oxide substrate behaves as a quencher as well, thus varying linker lengths separating the molecular beacon and graphene oxide were used to study the extent of its quenching. It was found at 51 base pairs, and 35 base pairs, the sensitivity of the system was like that of the molecular beacon without any graphene oxide present. At 14 base pairs the graphene oxide quenched the quantum dot’s energy, leading to a decrease in sensor sensitivity. The system exhibited a linear relationship in the nanomolar range throughout all four sensors and the effect of ionic concentration on the performance was also investigated. The detection limit was found to be 16.5 nM, 38.4 nM, 9.45 nM, and 11.38 nM from the no graphene oxide to the 51 base pairs linker respectively.