Fischell Department of Bioengineering
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Item SAMPLE-TO-ANSWER POINT-OF-CARE VIRUS DIAGNOSTIC SYSTEM USING THERMALLY RESPONSIVE ALKANE PARTITIONS(2024) Boegner, David John; White, Ian M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many viral infections can be accurately diagnosed using today’s most sophisticated detection systems. Unfortunately, many of these detection systems fail to benefit society as a whole, but rather favor select areas of the world that are able to install and maintain the infrastructure such diagnostics require. Thus, in an effort to eliminate the barrier of access to diagnosis and treatment in low-and-middle-income areas, portable point-of-care devices are fabricated such that rapid results can be obtained without the need for bulky lab equipment or skilled technicians. An ideal point-of-care diagnostic device can easily collect an untampered sample and limits a patient’s encounter with a clinician to a single visit for both the diagnosis and the treatment. Many so-called point-of-care diagnostics for blood-borne viruses first require blood sample preparation (e.g. centrifugation) prior to testing in the device. Other point-of-care devices sacrifice diagnostic accuracy in favor of speed and portability. Both cases demonstrate our inability to properly distribute the benefits of sophisticated diagnostics worldwide.I present a solution in the form of an affordable handheld diagnostic device with the sensitivity and specificity of benchtop lab equipment and built-in automatic sample preparation. Automatic sample preparation will be achieved using thermally responsive alkane partitions, which are solid at ambient temperatures and liquid at moderately elevated temperatures. When liquid, the alkane partitions allow passage of magnetically activated microbeads coated with material that captures viruses. Despite magnetic beads with virus particles passing through, the alkane partition continues to prevent unwanted sample components (e.g. blood cells, DNases, etc.) from interfering with the virus-detecting mechanism on the other side. To address the lack of sensitivity in many point-of-care diagnostics, the virus-detecting mechanism will feature isothermal amplification which enables detection of attomolar concentrations of virus within 30 minutes without expensive thermo-cycling equipment that standard detection systems require. The novel technology described here is demonstrated in a platform which detects SARS-CoV-2 from blood, a capability currently unachievable in point-of-care settings.Item Functional Polymers for Biosensing Applications(2014) Ayyub, Omar; Kofinas, Peter; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The work presented in this dissertation involves two separate systems. The first system was the investigation of photonic crystals as a chemical and biosensing platform. The second investigation was the fabrication of a point-of-care blood ammonia sensor. The photonic crystal fabricated was composed of the block copolymer polystyrene-b-poly(2-vinylpyridine)(PS-b-P2VP), which when cast into films, self-assembles into a multilayer structure. The P2VP block of the multilayer structure can be quaternized, causing it swell in aqueous media, providing the necessary spacing for it to operate as a 1D photonic crystal for visible wavelengths of light. The reflected wavelength or color of the photonic crystal is dictated by its spacing. Boronic acid functionalities were covalently attached to the P2VP block, which imparts the ability to bind to sugar molecules. When boronic acids bind sugars, such as fructose, the acid ionizes and becomes negatively charged, causing the P2VP block to swell, and changing the reflected color of the photonic crystal. In the following studies the covalent attachment of boronic acid to PS-b-P2VP was characterized. The resulting photonic crystal was then evaluated as a sensitive fructose sensor with a detection limit of 500micromolar. A novel method for the covalent attachment of primary amines to the P2VP block was also investigated. In Chapter 4, the utilization of trimethylsilyl amine protecting groups, allowed for the chemical modification of P2VP with primary amines without compromising the microphase separated nanostructure of the PS-b-P2VP. The primary amine functionality was characterized and shown to be reactive with cross-linking agents such as glutaraldehyde. A point-of-care blood ammonia sensor was engineered utilizing a specific, colorimetric ammonia reaction, termed the indophenol reaction, in conjunction with a cation exchange membrane(CEM). The membrane allowed for the rapid extraction of ammonium ions from whole blood. The extracted ammonia solution was then used with the indophenol reaction, which generates a blue color in the presence of ammonia. The sensor could extract ammonia in 20 minutes and had a detection range of 25-500micromolar in whole human blood with a COD of 0.9573.