Visible assay for glycosylase based on intrinsic catalytic ability of graphene/gold nanoparticles hybrids

A sensitive, rapid and label-free assay for colorimetric detection of human 8-hydroxyguanine glycosylase (hOGG1) was proposed based on the tunable catalytic ability of graphene/gold nanoparticles (graphene/Au-NPs) hybrids and the terminal protection of hOGG1. In presence of H2O2, the hybrids were capable of catalyzing the oxidation of color developing reagent, causing a concomitant change in color. Due to the excellent controllability, the capacity could be inhibited by adsorption of ssDNA onto the hybrids sheets and recovered when the adsorbed ssDNA was digested by exonuclease. The terminal protection of hOGG1 could irreversibly interrupt the digestion of the captured ssDNA (containing the oxidative damage site) by the exonuclease, thus preventing the catalytic ability of graphene/Au-NPs from being recovered. The original color change which related to the concentration of the protected ssDNA facilitated quantitative detection of hOGGl activity. Compared with conventional methods for hOGG1 detection, the presented assay without any labeling process greatly simplified the operation steps and reduced the analysis time. This approach performed a linear response for hOGG1 activity from 0.02 to 0.11 U/μL with a detection limit of 0.0016 U/μL, and realized the quantification of hOGG1 activity in real cell lines.