Immobilization of DNA probes onto gold surface and its application to fully electric detection of DNA hybridization using field-effect transistor sensor

A field-effect transistor (FET) sensor with a gold sensing electrode (extended-gate FET sensor), on which DNA probes can be immobilized via an Au-S bond, was designed. A method of controlling the surface density of DNA probes immobilized on the bold electrode was developed using a competitive reaction between DNA probes and alkanethiols. The immobilized DNA probe, were characterized using voltammetry and a single-base extension reaction combined with bioluminescence detection. The relationship between DNA probe density and hybridization efficiency was clarified, and it was found that the optimum density for FET sensors was about 2.6 x 10(12) molecules/cm(2). The fully electric detection of hybridized target DNA (about 7 fmol) was achieved by the extended-gate FET sensor with the above DNA probe density. In addition, the surface potential in proportion to the density of both single-stranded DNA and double-stranded DNA immobilized on the gold electrode was successfully obtained using the extended-gate FET sensor.