Date of Award

Spring 1-1-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical & Biochemical Engineering

First Advisor

Joel L. Kaar

Second Advisor

Mark P. Stoykovich

Third Advisor

Christopher N. Bowman

Fourth Advisor

Theodore Randolph

Fifth Advisor

Xuedong Liu

Abstract

The rise of personalized medicine, increasing threat of bioterrorism, and growing concern of environmental pollutants necessitates the development of alternative biosensing techniques. Towards this end, we investigated the utility of using chemically and structurally modified photonic hydrogels for optical biosensing applications. Photonic crystal hydrogels are comprised of a crystalline colloidal array polymerized into a stimuli-responsive hydrogel. The crystalline colloidal array is comprised of highly charge nanoparticles that self-assemble into a photonic crystal that Bragg diffracts. The hydrogel is designed to undergo a volume transition in the presence of a target analyte. Altering the hydrogel volume in turn alters the lattice spacing of the photonic crystal, causing the diffraction peak to shift.

Initially, we explored the use of photonic hydrogels for the detection of enzymatic phosphorylation through the fabrication of kinase-responsive optically diffracting materials. The responsive nature of the hydrogel was confirmed via diffraction measurements and was seen to exhibit a time- and dose-dependent response. A theoretical model for swelling in ionic polymer networks was then utilized to elucidate the key parameters that modulate response sensitivity. The determined parameters were experimentally tuned and a detection limit of 0.1 U/µL was achieved in a 2 h reaction time.

We then developed a photonic hydrogel approach for DNA detection. Via hybridization events with a complementary probe strand, we were able to detect down to picomole amounts of a target p53 sequence. Moreover, we demonstrated that this approach could readily detect a single base pair mutation in the target strand. We further showed that this approach is sensitive to epigenetic changes through the detection of a fully methylated form of the target sequence.

Lastly, we developed a high-throughput glucose- and ethanol-responsive photonic crystal hydrogel for monitoring microbial fermentation. A platform was developed for the fabrication of photonic hydrogels in 96-well plates to allow for rapid detection and the response sensitivity tuned through blending a thermally responsive polymer with hydrophilic and hydrophobic co-monomers. The 96-well platform was then used as a high-throughput method to monitor ethanol production during fermentation growth of Saccharomyces cerevisiae.

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