Signaling Kinetics of DNA and Aptamer Biosensors Revealing Graphene Oxide Surface Heterogeneity

Abstract

Adsorption of fluorescently labeled DNA and aptamer probes to graphene oxide (GO) has been one of the most popular methods for developing biosensors. In the presence of target analytes, the quenched fluorescence would recover. In this work, we followed the kinetics of the reactions and found that the fluorescence would eventually drop after an initial increase, and this was attributed to the re-adsorption of the desorbed probe DNA molecules. Both a DNA probe and an aptamer for adenosine were used. This re-adsorption was attributed to the surface heterogeneity of GO, and the DNA probes desorbed from relatively weaker binding sites were re-adsorbed on the stronger binding sites. This re-adsorption can be avoided by extensive washing the samples, and also by blocking the GO surface or by heating. This fundamental understanding is important for achieving a stable signal of such biosensors.