An electrochemical sensing platform based on local repression of electrolyte diffusion for single-step, reagentless, sensitive detection of a sequence-specific DNA-binding proteinElectronic supplementary information (ESI) available. See DOI: 10.1039/c4an00096j

In this paper, we report for the first time an electrochemical biosensor for single-step, reagentless, and picomolar detection of a sequence-specific DNA-binding protein using a double-stranded, electrode-bound DNA probe terminally modified with a redox active label close to the electrode surface. This new methodology is based upon local repression of electrolyte diffusion associated with protein-DNA binding that leads to reduction of the electrochemical response of the label. In the proof-of-concept study, the resulting electrochemical biosensor was quantitatively sensitive to the concentrations of the TATA binding protein (TBP, a model analyte) ranging from 40 pM to 25.4 nM with an estimated detection limit of ∼10.6 pM (∼80 to 400-fold improvement on the detection limit over previous electrochemical analytical systems). This paper describes for the first time an electrochemical biosensor, which employs a DNA probe modified with a redox tag close to electrode surface, for picomolar detection of a sequence-specific DNA-binding protein.