Electrochemical DNA hybridization detection sensors are widely studied these years because of the potential in applications such as identification of pathogens, diagnosis of genetic diseases, evolution study and forensic or pharmaceutical use, etc. However, traditional DNA detection methods utilizing fluorescence labels are expensive and time-consuming compared to electrochemical methods. In this study, Cordyceps Sinensis (CorS) DNA detection and quantification were done by electrochemical impedance spectroscopy (EIS) firstly. The microelectrodes were fabricated by semiconductor nanofabrication technologies with DNA modification on the sensor surface. The EIS results were fitted to get the solution resistance (R_sol), charge transfer resistance (R_ct) and double-layer capacitance...[ Read more ]

Electrochemical DNA hybridization detection sensors are widely studied these years because of the potential in applications such as identification of pathogens, diagnosis of genetic diseases, evolution study and forensic or pharmaceutical use, etc. However, traditional DNA detection methods utilizing fluorescence labels are expensive and time-consuming compared to electrochemical methods. In this study, Cordyceps Sinensis (CorS) DNA detection and quantification were done by electrochemical impedance spectroscopy (EIS) firstly. The microelectrodes were fabricated by semiconductor nanofabrication technologies with DNA modification on the sensor surface. The EIS results were fitted to get the solution resistance (R_sol), charge transfer resistance (R_ct) and double-layer capacitance (C_dl) of the equivalent circuit model (ECM). The relationship was found between the EIS parameters and the logarithmic concentration of target DNA. The limit of detection (LOD) was calculated to be 1.1nM DNA.

Besides, an extended-gate field-effect-transistor (EGFET) device was also used for CorS DNA detection. The previously mentioned microelectrodes were used as the extended gate for the EGFET. The output of the EGFET was normalized to be three working regimes according to the inversion coefficient (IC): weak inversion (WI), moderate inversion (MI) and strong inversion (SI). The overall sensitivity of the EGFET consisted of the normalized electronic sensitivity (S_e=g_m/I_D), and electrochemical sensitivity characterized by the electrochemical reaction. The EGFET was further set up with a differential pair for real-time detection of CorS DNA with Arduino MCU for data collection. The LOD was determined to be 1.2nM and the specificity was studied between a fully complementary and a mismatched target. Moreover, noise analysis for an EGFET was also conducted in terms of the relationship between the noise spectrum density and SNR with different IC. Additionally, high-electron-mobility-transistor (HEMT) based EGFET was also studied, achieving 2 times higher sensitivity and around 30dB higher SNR compared to CMOS based EGFET.