Optimizing Label-Free DNA Electrical Detection on Graphene Platform

The anodized epitaxial graphene (EG) electrode demonstrates a high level of performance for electrochemical impedance as well as differential pulse voltammetry detection of immobilized DNA and free DNA, respectively, at solid liquid interfaces. On the anodized EG surface, because of the presence of oxygen functionalities as well as pi conjugated domains, the anchoring of the DNA probe can be achieved by either covalent grafting or noncovalent pi-pi stacking readily. The effect of different binding modes on the sensitivity of the impedimetric sensing was investigated. Equivalent circuit modeling shows that the sensitivity of EG to DNA hybridization is controlled by changes in the resistance of the molecular layer as well as the space charge layer. The linear dynamic detection range of EG for DNA oligonucleotides is in the range of 5.0 x 10(-4) to 1 x 10(-6) M. In addition, with the use of differential pulse voltammetry, single stranded DNA, fully complimentary DNA, as well as single nucleotide polymorphisms can be differentiated on anodized EG by monitoring the oxidation signals of individual nucleotide bases.