Facile fabrication of DNA biosensors based on oxidized carbon black and graphite oxide

We investigated electrochemical sensors based on graphite oxide (GrO) and oxidized carbon black (CbO). GrO and CbO were synthesized by the modified Hummers method. We determined the degree of functionalization using Fourier transform infrared spectrometry (FT-IR). Single-stranded DNA (ssDNA) probes were synthesized with a 5’ primary amine for attachment. These ssDNA oligonucleotides were immobilized on GrO and CbO using standard 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) coupling. This formed an amide bond between DNA-amine and carboxyl groups on GrO and CbO. GrO and CbO were used instead of graphite in a carbon paste material. This significantly enhanced the sensitivity of the biosensor for the reverse-complementary DNA.
We detected reverse-complimentary DNA using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) in a ferricyanide solution. The solution was spiked with the ssDNA oligonucleotide with the reverse-complementary sequence of the immobilized probe. The change in current or impedance was measured. We present early work on optimizing the fabrication method for DNA-functionalized carbon electrodes. Working electrodes were fabricated by drop-casting the active material onto a glassy carbon electrode surface.