Portland State University. Department of Physics
Date of Publication
Doctor of Philosophy (Ph.D.) in Applied Physics
CA-125, Biomarkers, Interdigitate electrodes, Biosensors, Ovaries -- Cancer -- Diagnosis, Impedance spectroscopy
1 online resource (x, 150 p.) : ill. (some col.)
Electronic biosensors utilizing micron-scale interdigitate electrodes (IDEs) in an SD card format have been developed with the objective of fast, sensitive detection of ovarian cancer biomarkers CA-125, CEA, and He4. The signal generated by the biosensors is a result of electrochemical impedance spectroscopy (EIS), a technique which probes changes that occur in the biosensor's electrical properties when the biosensor has detected one of the target biomarkers. A label-free biosensor has been developed to detect CA-125 in spiked buffer at concentrations between 10 and 80units/mL. A similar label-free biosensor was developed to detect CEA at concentrations between 10ug/mL and 10mg/mL. A biosensor employing a protein-enzyme conjugated label was developed to detect He4 at concentrations ranging from 1.56 to 100ng/mL in spiked buffer. All concentration ranges of CA-125, CEA, and He4 detected by the biosensors include the serum concentration currently used for clinical diagnosis of ovarian cancer. Efforts to improve the signals generated by the biosensors included altering the dimensions and composition of the IDEs used in the initial biosensors through software-created models. Modeled alterations included the size of the electrodes, the shape of the electrodes, and the incorporation of nanomaterials into the IDEs. An ideal geometry for the IDEs was developed through the models and IDEs with those dimensions were fabricated and tested against the IDEs used in the biosensors initially with the model-developed geometry improving the signal generated by the biosensor. Another attempt to improve the biosensor's signal was to generate a single strand of DNA (ssDNA) that would bind to CA-125, called an aptamer, that could be easily incorporated into the sensing layer on the IDEs. Through a multistep selection process nine different aptamers that exhibited binding to CA-125 were identified.
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Whited, Allison Mae, "Investigation of Impedance Spectroscopy for Detection of Ovarian Cancer" (2012). Dissertations and Theses. Paper 68.