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Date of Award

2016

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biochemistry & Molecular Biol.

First Advisor

Dr, Michael C. Leopold

Abstract

Uric acid is a diagnostic marker for pregnancy-induced hypertension (PIH) in pregnant women, a condition that can lead to a serious disorder called preeclampsia. An effective first generation amperometric biosensor for uric acid (UA) detection, a clinically relevant analyte, is constructed via layer-by-layer (L-B-L) combination of functional films of polyurethane, electropolymers and xerogel materials on an electrode. In this study, each of four, functional layers used to modify the electrode (the outer polyurethane (PU) selective membrane, the inner selective electropolymer, and the xerogel bi-layer) are systematically probed and tailored for UA permeability and signaling as well as interferent discrimination. PU hydrophobicity and its effect on uric acid permeability is established as are specific aspects of each xerogel layer including the uricase (UOx) species and loading dependence of the inner enzyme-doped xerogel and the outer diffusion-limiting xerogel layer’s homogeneity. Xerogels formed from a variety of silane precursors are examined within the sensing scheme as well. Systematic evaluation of each layer reveals electrodes modified with a specific combination of xerogels formed from hydroxyl-methyl triethoxy silane (HMTES), a polyluminol-aniline electropolymer and 100% hydrophilic polyurethane exhibit impressive uric acid sensing performance: effective sensitivity (0.8 nA/μM), linear response across physiologically relevant UA concentrations (100-700 μM), fast response times (~ 10 sec), low limits of detection (< 10 μM), and selectivity against most common interferents. The optimized sensor exhibited 10 day stability as well as effective shelf-life exceeding 30 days. The presented system rivals or exceeds UA biosensor performance found in the literature, presents an adaptable strategy that may be applied to detecting/monitoring of other medically significant molecules, and offers the possibility of miniaturization for in situ or in vivo remote diagnostic sensing.

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