Janus DNA orthogonal adsorption of graphene oxide and metal oxide nanoparticles enabling stable sensing in serum

While DNA/graphene oxide (GO) conjugates have been widely used for DNA detection, they suffer from non-specific DNA displacement by proteins, making their application in biological samples difficult. To find new materials tightly adsorbing DNA but not proteins, we screened seven metal oxide nanoparticles, all interacting with the phosphate backbone of DNA, while DNA uses its nucleobases to interact with GO. In this regard, DNA is a Janus polymer orthogonally adsorbing GO and metal oxides. The DNA adsorption affinity ranks CoO > NiO > Cr₂O₃ > Fe₂O₃ > Fe₃O₄ > TiO₂ > CeO₂ based on a phosphate displacement assay. Among them, CoO is nearly fully resistant to protein displacement, while NiO has the best limit of detection of 0.24 nM DNA. This study provides fundamental insights into the biointerface chemistry of DNA, and reveals new materials useful for bioanalytical chemistry, DNA separation, and DNA-directed assembly.