Rapid DNA electrochemical biosensing platform for label-free potentiometric detection of DNA hybridization.

This paper described a novel electrochemical DNA biosensor for rapid specific detection of nucleic acids based on the sulfonated polyaniline (SPAN) nanofibre and cysteamine-capped gold nanoparticle (CA-G(NP)) layer-by-layer films. A precursor film of 3-mercaptopropionic acid (MPA) was firstly self-assembled on the Au electrode surface. CA-G(NP) was covalently deposited on the Au/MPA electrode to obtain a stable substrate. SPAN nanofibre and CA-G(NP) were alternately layer-by-layer assembled on the stable substrate by electrostatic force. Cyclic voltammetry was used to monitor the consecutive growth of the multilayer films by utilizing Fe(CN)(6) as the redox indicator. The (CA-G(NP)/SPAN)(n) films showed satisfactory ability of electron transfer and excellent redox activity in neutral media. Negatively charged probe ssDNA was immobilized on the outer layer of the multilayer film (CA-G(NP)) through electrostatic affinity. Chronopotentiometry and electrochemical impedance spectroscopy were employed to obtain the direct electrochemical readout for probe ssDNA immobilization and hybridization using Fe(CN)(6) in solution as the mediator. While electrochemical impedance spectroscopy led to the characterization of the electron-transfer resistance at the electrode, chronopotentiometry provided the total resistance at the interfaces of the modified electrodes. A good correlation between the total electrode resistances and the electron-transfer resistances at the conducting supports was found. Chronopotentiometry was suggested as a rapid transduction means (a few seconds). Based on the (CA-G(NP)/SPAN)(n) films, the target DNA with 20-base could be detected up to 2.13x10(-13)mol/L, and the feasibility for the detection of base-mismatched DNA was also demonstrated.