NOVEL BIOSENSOR: THE STUDY OF A DUAL IONOPHORE CONCEPT BASED ON AN ION-SELECTIVE ELECTRODE

Xuesong Li

NOVEL BIOSENSOR: THE STUDY OF A DUAL IONOPHORE CONCEPT BASED ON AN ION-SELECTIVE ELECTRODE Abstract by Xuesong Li, Ph.D. Washington State University December 2015 Chair: Bernard J. Van Wie This thesis describes novel biosensors for detecting proteins and cells with bioreceptors connected to a dual ionophore Ion-Selective Electrode (di-ISE). One application is in prostate cancer, the second leading cancer death in America men. For prostate cancer cell detection, an enzyme inhibitor bioreceptor for PSMA, referred to as TG97 developed by a collaborator, was used. Inspired by living neuronal physiology the di-ISE was invented by adding two ionophores, one in each of two separate membrane compartments electrically connected by having the same solutions on the top and bottom sides. One compartment contains K+ ionophore and the other Na+ ionophore. Calibration curve results for differing amounts of K+ ionophore agree with a modified Nicolsky-Eisenman equation based on a Goldman-Hodgkin-Katz model of a neuronal membrane. Simulation of binding was performed by coating with silicone glue as well as by physical coverage of one membrane compartment to show blocking of one ionophore type alters the net membrane potential. Insertion of cholesterol-PEG-biotin (CPB) at the membrane-water interface of one compartment serves to connect a bioreceptor for streptavidin with the di-ISE transducer; even the presence of CPB affects the di-ISE response in a way consistent with the mathematical model. In addition, testing with gelatin coverage simulates protein binding, and further studies with streptavidin capture by CPB confirm not only can the membrane capture proteins, but also biosensor signals are correspondingly altered. After proving di-ISEs have a fast response, are inexpensive, easy to make, and function as a biosensor for proteins, the research was extended to cancer cell biosensing. A cholesterol-PEG-TG97 (CPT) molecule was synthesized and inserted into the electrode membrane, and tested for detection of PSMA-expressing LNCaP cells. Results show di-ISEs are able to capture and sense these cancer cells. Finally, hands-on experiences and student worksheets were demonstrated to enhance classroom learning and extended to the di-ISE biosensor. Future work is needed to make di-ISEs part of clinical point of care prostate cancer diagnosis, extend to other biodetection schemes, and implement the di-ISE into the classroom for instruction about the related concepts.

NOVEL BIOSENSOR: THE STUDY OF A DUAL IONOPHORE CONCEPT BASED ON AN ION-SELECTIVE ELECTRODE

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