Mechanisms of DNA sensing on graphene oxide.

Adsorption of a fluorophore-labeled DNA probe by graphene oxide (GO) produces a sensor that gives fluorescence enhancement in the presence of its complementary DNA (cDNA). While many important analytical applications have been demonstrated, it remains unclear how DNA hybridization takes place in the presence of GO, hindering further rational improvement of sensor design. For the first time, we report a set of experimental evidence to reveal a new mechanism involving nonspecific probe displacement followed by hybridization in the solution phase. In addition, we show quantitatively that only a small portion of the added cDNA molecules undergo hybridization while most are adsorbed by GO to play the displacement role. Therefore, it is possible to improve signaling by raising the hybridization efficiency. A key innovation herein is using probes and cDNA with a significant difference in their adsorption energy by GO. This study offers important mechanistic insights into the GO/DNA system. At the same time, it provides simple experimental methods to study the biomolecular reaction dynamics and mechanism on a surface, which may be applied for many other biosensor systems.