DNA covalently linked to graphene oxide for biotin-streptavidin interaction assay

Based on terminal protection of small molecule-linked DNA and the covalently linking DNA to graphene oxide (GO) strategy, a high resisting nonspecific probe displacement platform for small molecule-protein interaction assay is proposed in this work. Specifically, the small molecule-linked DNA (probe 1) can be protected from exonuclease-catalyzed digestion upon binding to the protein target of the small molecule, so the DNA strand may hybridize with another DNA strand (FAM and amino dual modified DNA, probe 2) that is previously covalently linked onto GO surface. Such hybridization will result in the fluorescence restoration of FAM. Taking biotin-streptavidin (SA) interaction assay as an example in this work, the linearity, stability and specificity of the covalent sensor were systematically studied and compared to the noncovalent sensor. The covalent sensor can determine the protein in a linear range from 0.15 to 12nM with a detection limit of 0.08nM, which is comparable with that of noncovalent sensor. Though both sensors have similar sensitivity, the covalent one is more resistant to nonspecific probe displacement by proteins. Furthermore, because the covalent sensor can be used for the assay of biotin-SA interaction in serum samples, this novel method is expected to have great potential applications in the future.