Date of Award

Winter 2022

Project Type

Dissertation

Program or Major

Chemical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Young Jo Kim

Second Advisor

Young Jo Kim

Third Advisor

Kyung Jae Jeong

Abstract

In this dissertation, I investigated the metal-chelating ability and redox activity of phenoliccompounds from different sources for biomedical applications. Eumelanins are the naturally occurring biopigments that can be found in skin, hair, eyes, or brain of many living organisms. Various functional groups in eumelanin permit it to binding metal ions via comproportionation reaction. I investigated the structure-property relationship of eumelanin by X-ray scattering and electrochemical techniques. I reported the mesoscale structure of eumelanins and its impact on the charge transport. X-ray scattering suggests that eumelanin pigments exhibit the semi-crystalline structure with ordered d-spacings. These unique mesoscale structures further influence the charge transport mechanism with the cations of various sizes. CV measurements with the series of monovalent cations along with electro-kinetic assay proved that the monovalent cations could be transported through NatMel in a capacitance-limited manner. Understanding the structures with consequent electrochemical properties suggest that eumelanins can further be tuned to serve as high-performance naturally-occurring charge storage materials. Pyrogallol is the class of phenolic compounds that can be found from various plants. I present the facile synthesis of poly(pyrogallol) biopolymer and its application as antibacterial agents. Polymerization was performed by autoXII oxidation of pyrogallol in a hydrated condition. Microstructure of poly(pyrogallol) exhibited highly homogenous nanofibrous structure with a diameter of 100.3 ± 16.3 nm. Spectroscopic analysis using FT-IR, Raman, and XPS corroborated the formation of ether (C-O-C) bond between the hydroxyl group and adjacent carbons of the pyrogallol during polymerization. FT-IR and XPS spectra also exhibited the redox-active gallol functional groups on poly(pyrogallol) nanofiber that can be used to release free electrons and protons during oxidation followed by the generation of reactive oxygen species (ROS). The generated ROS from poly(pyrogallol) was used to reject the bacteria, Escherichia coli. which showed the inhibition rate of 56.3 ± 9.7 % and 95.5 ± 2.0 % within 0.5 and 2 h. This finding suggests that poly(pyrogallol) can be served as a naturally occurring antibacterial agent for various biomedical and environmental applications.

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