Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection

• We report a novel graphene-rGO double-layer electrochemical biosensor for label-free detection of a DNA sequence, which take the high conductivity from graphene and high electrochemical activity from reduced graphene oxide.
• No deleterious chemicals, complicated immobilization and signal enhancement, target labelling are employed during the DNA immobilization and detection.
• We have also reported the unique performance of dsDNA-rGO interaction on rGO/graphene electrode.
• We combined the technique of label-free DNA detection together with commercial screen printed graphene electrode, which could easily meet the requirement of industrial production.

A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π–π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π–π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10−7 M to 10−12 M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58×10−13 M as determined by three times standard deviation of zero DNA concentration.