Detection of Nucleic Acid with Extended Gate Field Effect Transistor Label-free and without Amplification

Jyun-Er Ou Yang（歐陽均兒）, Ming-Pei Lu, Yee-Lu Zhao, Keng-Hui Su, Yu-Ching Chen, and Yuh-Shyong Yang*

Department of Biological Science and Technology, National Yang Ming Chiao Tung University 

Current analysis of nucleic acids generally requires amplification and labeling of the target molecules. Time and cost have been obstacles for many unmet needs that involve nucleic acid detection. In this report, we demonstrated that, by using extended gate transistor (EGFET) and a transducer, a direct and real-time sensing of DNA molecules at aM range can be achieved. This result indicates that nucleic acid in biological samples can be detected label-free and without amplification in a short time. In addition, we have developed a recovery system by using a complementary DNA sequence to remove the target sequence that hybridized with the probe immobilized on the biochip. This method can be used to verify the false-positive/negative signal of the detection platforms. Different length of DNA targets were prepared in this study to examine the variations of sensitivity with DNA target size. Due to the significant chage difference with the length of DNA target, we are able to propose the charge effect on the electric response of the EGFET device. This result is also compared with our previous study with nanowire field effect transistor. The principle and structure of EGFET and how it may function as a sensitive biosensing device are illustrated and discussed.