DEVELOPMENT AND DEVICE INTEGRATION OF ELECTROCHEMICAL AND COLORIMETRIC SENSORS TOWARDS IMPROVED LARGE-SCALE POINT-OF-NEED TESTING CAPABILITIES

Abstract

Safe and clean water is the most important resource in the modern world, and is not guaranteed, with around 40% of the world population living without access to a reliable clean water source. Without clean water, foodborne pathogens also become much more prevalent as sanitation practices become ineffective. Globally water access and safety is improving on average, primarily driven by infrastructure investment. However, as infrastructure ages and more people are introduced to on-demand clean water options, widespread monitoring is essential to ensure continued safety and progress. Domestically, water and food quality monitoring is becoming increasingly relevant in 2026 as climate change and policy decisions impact the availability and safety of water and food in the United States. Bacterial and heavy metals contaminants are common in older drinking water systems, and local contamination can be overlooked. Chapter One examines this issue, the complexities that arise from the implementation of widespread monitoring, and recent technological and scientific developments towards point of need monitoring for these issues. Chapter Two presents a bead-based electrochemical immunoassay for bacteria detection in food and water samples, allowing an end-user to test a liquid or solid sample for the presence of specific whole-cell bacteria. The assay was developed at Colorado State University and characterized externally at the US Army Combat Capabilities Development Command (DEVCOM) to evaluate Limit of Detection (LoD), ease-of-use, and applicability towards food pathogen monitoring in the field. The assay is based on a traditional ELISA, allowing swapping of biorecognition elements for alternative targets, as shown in the adaptation of the assay between Escherichia coli and Salmonella enterica. Chapter Three presents the design and optimization of a 3D-printed electroanalytical sensor for point of need detection of 3,4-Methylenedioxymethamphetamine (MDMA) in unknown tablet samples. The low-cost fabrication, ease-of-use, and disposable electrode design of the sensing system allows utilization at the point of need for unknown sample characterization. By 3D-printing the electrode, low-cost and disposable sensors are easily manufactured at scale in-lab, allowing extensive field deployment and testing. The electrode system was used for MDMA standardization, and subsequent detection of MDMA content in real-world seized unknown samples. Chapter Four presents a 3D-printed preconcentration system in combination with a foldable reagent delivery and colorimetric readout card for instrumentation-minimal detection of heavy metals in water samples. By using specific chromogenic reagents for each heavy metal and pre-concentrating on paper, EPA-relevant limits of detection are achieved at a fraction of typical lab analysis cost. A smartphone is utilized for data analysis and readout, allowing usage of the device at the point of need within 30 minutes, as compared to the typical method of sample storage and transport to a central lab. The development and implementation of pathogen, heavy metal, and drug compound sensors into point-of-need devices and testing programs has the potential to radically transform the availability and ease of collection of a wide range of critical data. By utilizing easily swappable and commercially available components, we found that our cost-effective electrochemical assay for bacterial pathogens could be transferred to an external lab and utilized in complex and varied samples for successful bacterial quantification and detection. The use of 3D-printed electrodes for MDMA detection allowed us to analyze real-world samples and easily determine drug dosage, an important step towards point-of-need testing for harm reduction. Finally, the use of a low-cost detection card and preconcentration system, and a smartphone-based quantification method allows an easier path to widespread environmental testing for heavy metal contaminants at relevant limits. Overall, the work in this dissertation demonstrates the power of simple and reliable engineering improvements to analytical systems for point of need testing. It is my hope that this work furthers the fields of analytical, environmental, and biochemistry by providing a small stepping stone towards widespread usage of low-cost analytical devices.