Date of Graduation

8-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor

David W. Paul

Committee Member

Ingrid Fritsch

Second Committee Member

Julie Stenken

Third Committee Member

Wesley Stites

Abstract

In vivo oxygen sensing is a critical area of research for medical applications, such as ischemic stroke, but this important topic is not fully understood or resolved. In addition, the best method for calibration of in vivo sensors is as yet undetermined. For all implantable devices, biofouling, the adsorption of biological material to the device surface, is another significant problem with no clear or well-defined solution. One method employed is to apply a protective polymer membrane to the sensor surface in order to minimize the adsorption of biological material. The work described here investigates two polymers applied to a gold electrode for oxygen sensing: polyeugenol (PE) and poly-o-phenylenediamine (PoPD). Polyeugenol, while permeable to oxygen, and unhampering to the overall oxygen sensitivity for the sensor, shows polymer instability, and is therefore not applicable to long-term in vivo sensors. PoPD is shown in these works to be both permeable to oxygen and mechanically stable. PoPD was investigated first on 2 mm gold macroelectrodes to increase the fundamental understanding of PoPD for use with oxygen sensors, as well as better understand the biofouling phenomenon when PoPD-coated electrodes were incubated in protein solutions. In addition, PoPD-coated 2 mm gold electrodes were used in an in vivo simulation study in order to illustrate the problem with present calibration methods for in vivo sensors. PoPD was further investigated using gold microelectrodes in biofouling solutions, as microelectrodes are more suitable towards in vivo work; in addition, a method of in situ recalibration of the biofouled PoPD-coated microelectrode was investigated. Fundamental studies described in this dissertation aim to increase the understanding of the biofouling phenomenon through in vitro simulation studies, as well as propose a method to account for and correct the consequences of this phenomenon.

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