Electrical Characteristics of Extended Gate FET Sensing Chip Constructed for Detection of DNA

摘要

An extended gate field effect transistor (EGFET) sensing chip has been constructed by using one gold plate electrode for molecule recognition and FET part for signal transduction. By using a 70.7mV DC voltage onto a Ag/AgCl reference electrode, the electrical characteristics of immobilization of the oligonucleotide probe of PI and hybridization with the target single strand DNA of P2 on the EGFET sensing chip were examined in detail. The electrical signals on the change of a threshold voltage (V_T) shift at a constant I_D (3000μA) in V_G-I_D characteristic were obtained, and the V_T shift value due to hybridization was calculated to be 12mV, which may be attributed to the decreased negative charges after hybridization occurred at the gate surface. The surface density of hybridized dsDNA on gold surface of the FET was evaluated to be about 1×10~12molecules/cm~2, indicating that the EGFET was a promising sensing element for biochip.