Ph.D. Dissertation Defense: George Banis
Friday, August 16, 2019
5104 A. James Clark Hall
Development of an Integrated Capsule System for Gastrointestinal-Targeted Biosensing
Dr. William Bentley
Dr. Ian M. White
Non-invasive ingestible microsystems are emerging as a means to address diagnostics challenges in gastrointestinal (GI) healthcare due to the potential to retrieve information at the source and in a personalized approach. This dissertation describes the development of a film-based capacitive sensing strategy and subsequent integration into a capsule-based microsystem that is designed to travel through the GI tract upon ingestion until it passes through the stomach to measure model analytes in duodenal secretions. We develop a sensing system using commercial off-the-shelf components that interface capacitive transducers (range: 0.8-220 pF; sensitivity: 7.3x10^-3) with a smart phone via Bluetooth Low Energy (2.4 GHz). The transducers are designed to measure the change in dielectric constant of interfacing media, which transitions when specific environmental (pH) characteristics are met. We employ coatings, consisting of various formulations of methacrylic acid and methacrylate copolymers, for protecting our system until targeting the pH, and therefore GI region, of interest for sampling. Once dissolved, microfluidic inlets allow access for the media to interface with the sensors. We studied coatings that respond to both acidic (pH 6) conditions, as well as pH sequences via hierarchical coatings. Because the target analytes react with naturally occurring substrates, we investigate label-free sensing of model enzymes such as pancreatic trypsin (20-40 μM) and lipase (10 μM-1 mM), as well as bile salts (0.07-7 %w/v) as a model emulsifier, using films (composed of biomaterials, including gelatin and stearin. To integrate these materials with the desired microsystem, we investigate various film deposition and modification strategies. The system, including the power supply, are manufactured on a printed circuit board and packaged within a 3D-printed capsule structure (13 mm x 35 mm) that maintains dimensions of other clinically utilized ingestible capsule devices. The system is cost effective, user-friendly, biocompatible, and can serve as a highly customizable platform for measuring a variety of desired targets. Using this system, we characterize its potential for utility as a non-invasive platform for targeting multiple GI regions and detecting sensor-compatible biomarkers.