Utilization of Electrochemical Impedance Spectroscopy for the Detection of QSOX1 and CEA

Improved pancreatic cancer diagnostic technology has the potential to improve patient prognosis by increasing cancer screening rates and encouraging early detection of the cancer. To increase the sensitivity and specificity while decreasing the cost and time investment, the emerging detection method of electrochemical impedance spectroscopy (EIS) was tested to detect two pancreatic cancer specific biomarkers. The antibodies of carcinoembryonic antigen and quiescin sulfhydryl oxidase 1 were immobilized individually to gold disk electrodes and tested for binding to their respective antigens. An AC signal of varying potential and a wide frequency sweep was applied to the electrode system and the resulting imaginary impedance values were analyzed. Based off of the highest slope and R-squared values of the collected impedance values, the optimal binding frequencies of QSOX1 and CEA with their antibodies was determined to be 97.66 Hz and 17.44 Hz, respectively. EIS was also used to test for potential multimarker detection by coimmobilizing anti-CEA and anti-QSOX1 to the surface of gold disk electrodes. Each system's impedance response was correlated to the physiological concentration range of CEA and QSOX1 individually. The resulting impedance and concentration calibration curves had R-squared values of 0.78 and 0.79 for the calculated QSOX1 and CEA, respectively. Both markers showed similar trends between the calculated and actual calibration curves for each marker. The imaginary impedance output lacks two independent peaks for the distinct optimal binding frequencies of both biomarkers after signal subtraction and show a large shift in optimal frequencies. From analyzing the co-immobilization data for the calculated and experimentally determined calibration curves of CEA and QSOX1, both curves had different correlation values between imaginary impedance values and concentration. Add and subtracting the experimental and calculated co-immobilization, QSOX1, and CEA signals suggest an oversaturation of QSOX1 used during the experiments.