Immobilization of DNA molecules on a gold plate for an extended gate FET sensing chip

We have proposed an electrochemical detection method for DNA molecules based on an extended gate field effect transistor (EGFET) sensing chip which consists of one gold plate for molecule recognition and FET part for signal transduction. DNA Probes were immobilized on the gold plate by forming mixed monolayers of thiolated single-stranded oligonucleotide (HS-ssDNA) and alkanethiols, like 6-hydroxy-1-hexanethiol (6-HHT). Electrode reaction corresponding to the reductive desorption of the adsorbed monolayers in strong alkali solution was presented for quantification of surface density of DNA by using fast cyclic voltammetry (FCV). The passivation effects of surface modification with different functional groups on the potential behavior of the gold electrode were also examined. It was feasible to use EGFET chip for detection of DNA hybridization reaction, that the hybridization efficient was estimated to be about 40%.