Tunable Biomolecular Interaction and Fluorescence Quenching Ability of Graphene Oxide: Application to “Turn-on” DNA Sensing in Biological Media

The detection of biomolecules has been a major research focus in science and technology for many decades given its myriad applications in molecular diagnostics,[1,2] environmental monitoring,[3,4] drug discovery,[5] and biological warfare agents detection,[6] among others. A large majority of modern detection assays rely on a labeling strategy where the target molecule is either tagged with a label (e.g., a fluorescent dye[7,8] or a radioisotope[9]) or coupled to an enzyme[10] to generate a detectable signal. Unfortunately, this labeling process often increases the time and expense required to perform the assay and can alter the functionality of the target biomolecules.[5] As such, a detection strategy that can directly target biomolecules without labeling would greatly facilitate the development of reliable, rapid, cost-effective, and easy-to-use biomolecular detection assays. To this end, a wide range of technologies have been evaluated for the direct detection of biomolecules, using surface plasmon resonance (SPR) spectroscopy,[11] microcantilever,[12] and quartz crystal microbalance (QCM);[13] however, the biomolecular detection process in all of these techniques must occur on a stationary solid substrate. This requirement leads to several shortcomings, including cumbersome surface-immobilization of capture molecules, slow binding kinetics due to diffusion limitations, and a distortion of intrinsic biomolecular interactions (the surface-bound nature of the capture molecules can result in undesirable orientation for binding, reduce the degrees of freedom available for capturing the target, and induce non-specific binding of targets),[14,15] all of which can deteriorate detection performance (reliability, reproducibility, sensitivity, and specificity).