Date of Award

Spring 2025

Project Type

Dissertation

Program or Major

Chemical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Jeffrey M Halpern

Second Advisor

Nivedita Gupta

Third Advisor

Kang Wu

Abstract

As the biomedical engineering industry grows, so does the need for on-line, continuous monitoring of specific biomolecules in industrial bioreactors. Elastin-like polymers, a thermoresponsive, protein-based macromolecule that mimics the behavior of the naturally occurring elastin protein, may hold the answer in the form of their stimuli-responsive conformation change. Surface-bound ELPs still require characterization, especially under conditions relevant to on-line sensing in bioreactors. The protocol for fabricating ELP-modified electrodes needs to be fine-tuned for reproducibility, with careful consideration for physisorption. Additionally, bioreactors require carefully controlled environments, without the presence of exogenous reagents. Therefore, the stimuli-responsive behavior of ELPs will need to be able to be observed in non-redox mediated, buffered solutions. Without the presence of redox compounds, new analytical techniques need to be developed. Finally, the stimuli response and stability of surface-bound ELPs require further characterization in-situ. Herein, the successful, reproducible modification of gold electrodes with ELPs is performed. The

reproducibility is characterized by electrochemical stripping of the thiol moiety from the

electrode surface to understand the role of physisorption in modification. Organic treatment

options are considered for further reproducibility. Additionally, a novel analytical method is

developed for electrochemical impedance spectroscopy, called Characteristic Feature Analysis. A

residual error and standard deviation error analysis is performed to compare the Characteristic

Feature Analysis methodology to the current standard of electrochemical impedance

spectroscopy analysis, Equivalent Circuit Model analysis. The findings indicate that the

Characteristic Feature Analysis method provides accuracy in frequencies ranges where the

Equivalent Circuit Model struggles. A macro-based program was developed to perform the Characteristic Feature Analysis and the features of the program are reviewed. Finally, the Characteristic Feature Analysis method is used to characterize the temperature stimuli-response of surface-bound ELPs on gold electrodes by in-situ temperature changes as well as the stability of the electrodes over time.

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