ELECTROCHEMICAL SENSING USING FUNCTIONALIZED 3D PRINTABLE MATERIALS FOR POINT-OF-CARE APPLICATIONS

Dalton Lee Glasco

doi:10.7273/000006574

With the impact of Parkinson’s disease (PD) effecting more than 10 million people globally, a push for accessible on-site monitoring has been established. Point-of-care (POC) monitoring focuses on the use of miniature, low-cost, reproducible, and selective sensors. Within this dissertation a focus on 3D printing and electrochemical techniques has generated several novel sensors for detecting PD related analytes. The use of 3D printing provides a low-cost, rapid, customizable, and compatible approach to fabricating functionalized active electrodes and selective membranes. With the combination of both active and passive electrochemical techniques, these functionalized 3D printed materials can be incorporated or used as sensors for the detection and monitoring of pharmaceuticals, blood electrolytes, and neurotransmitters associated with PD. In chapter 2 the introduction and optimization of alkaline assisted electrochemical activation (AAEA) is discussed for 3D printed carbon electrodes (3DpCEs). The AAEA 3DpCEs were compared to a nonactivated and alkaline immersed 3DpCEs. Through this comparison a clear increase in current response and reversibility was determined for AAEA 3DpCEs through cyclic voltammetry characterization. Electrochemical impedance spectroscopy was also completed where AAEA 3DpCEs produced a lower charge transfer resistance compared to both nonactivation and alkaline immersed 3DpCEs. A demonstration of AAEA 3DpCE sensor was also completed for dopamine, a common neurotransmitter associated with PD. For 3DpCEs a specialized modification process is possible with AAEA for improved detection of important PD biomarkers. In chapter 3 further investigation of the AAEA protocol resulted in a selective and sensitive sensor for simultaneous detection of PD related analytes. Through this research the detection of uric acid (UA), an emerging biomarker associated with PD pathology, and levodopa (L-Dopa), a common pharmaceutical used for PD treatment, was completed using differential pulse voltammetry (DPV). Furthermore, L-Dopa was also detected in human sweat using a portable potentiostat and miniaturized electrochemical cell. With the combination of AAEA and 3DpCEs a low-cost approach for integration into noninvasive wearable devices is discussed. In chapter 4 an introduction of the first 3D printed ion-selective electrode (ISE) is described. The exploration of translating conventional fabrication methods for ISEs that use polyvinyl chloride (PVC) support material to 3D printed polymers was completed. Herein, the study of a model ion, tetrabutylammonium (TBA), was completed for both solid and liquid contact configurations of 3D printed ISEs and compared to PVC-based ISEs. A comprehensive study was performed to analyze the compatibility of 3D printed polymer resin and the main ISE components, ion exchanging salt and plasticizer. In comparison to PVC-based, 3D printed ISEs achieved a better reproducibility, linear range, conditioning time, and cost efficiency. This new approach for ISE fabrication provides a rapid, low-cost, and customizable way to create new sensors for POC detection of other important PD related analytes. In chapter 5 the first apomorphine (APO, a pharmaceutical used to treat PD) ISE was introduced using this novel 3D printed ISE fabrication method. Herein, the optimization of an ionophore doped 3D printed ion-selective membrane (ISM) was completed for the selective detection of APO in blood plasma. The introduction of a new ionophore, calix[6]arene, for APO was studied. This 3D printed APO ISE used a novel solid contact configuration with a 3D printed housing and carbon mesh-paste transducer. With 3D printed ISEs able to detect analytes selectively in biological fluids the possibility to incorporate these sensors into POC devices may be achieved. In chapter 6 a 3D printed ISE for the detection of calcium (an important biomarker associated with the progression of PD) in whole blood was evaluated. The optimized calcium ISE was selective in the presence of potential interferents and produced high stability. After characterization of the 3D printed ISE, the sensor was then translated to a paper-based configuration for the detection of calcium in bovine whole blood. After confirming the validity of the 3D printed sensor in a paper-based configuration, the sensor was then translated into a POC paper-based device for on-site analysis. Along with the device other future focuses include the study of using 3DpCEs as ion-to-electron transducers for customizable solid contact ISE configurations, the fabrication and optimization of an enzymatic ISE for the indirect detection of urea, and the fabrication of a 3D printed reference electrode for POC applications.

ELECTROCHEMICAL SENSING USING FUNCTIONALIZED 3D PRINTABLE MATERIALS FOR POINT-OF-CARE APPLICATIONS

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