Developing Novel Sensing Tools for Hormones and Neurotransmitters in Complex Biological Systems

Abstract

Disruptions in hormone and neurotransmitter signaling and metabolism cause many common disorders, including diabetes, a disorder caused by disruption of glucagon and insulin secretion in pancreatic islet cells, and hyperparathyroidism, a disorder caused by an over-secretion of parathyroid hormone that disturbs calcium homeostasis throughout the body. Improving treatments for these disorders requires new methods for accurate detection and quantification of the hormones and neurotransmitters released, as many of these compounds are not detected by existing optical or electrochemical techniques. Furthermore, crucial physiological functions rely on dynamic concentration changes of multiple hormones, neurotransmitters, or ions occurring at the same time; as such, understanding a given pathway often necessitates the measurement of multiple analytes simultaneously. This dissertation presents improvements to existing electrochemical and electrophysiological techniques, aiming to optimize them for use in neuroendocrine systems. In Chapter 2, a lipid membrane-based ion-selective electrode facilitates Ca2+ quantification in small volume samples. Polymer scaffolds incorporated into these black lipid membranes significantly improve their stability, enabling them to withstand greater electrical potentials and mechanical challenges for longer periods of time. To better characterize interactions between the polymer scaffold and the lipid membrane, Chapter 4 explores the polymer scaffold in another lipid environment, the lipid nanodisc, for the first time. Particle size measurements, thermal characterization, and temporal analysis provide further information on the molecular basis for the increased stability facilitated by the polymer scaffold. In Chapter 3, dual-barrel pipettes fabricated with carbon-fiber microelectrodes enable precision positioning for real-time detection and quantification of exocytosis in single-cell amperometry experiments. Together, these developments expand the tools available to study neuroendocrine signaling in real time and provide a foundation for the design of robust, multifunctional sensors.