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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2016

Month Degree Awarded

September

First Advisor

Professor Todd Emrick

Second Advisor

Professor Ryan Hayward

Subject Categories

Polymer Chemistry

Abstract

This thesis examines functional hydrophilic polymers designed in linear and comb architectures and that carry functional moieties in the context of solution assembly and non-viral gene therapy. Specifically, polymers containing cations, zwitterions, and reactive groups are investigated as non-viral gene therapy reagents and at oil-water interfaces on droplets. Cations facilitate complexation of nucleic acids and interaction with cellular and nuclear membranes, while zwitterions impart stimuli-responsive solution properties and biocompatibility. Reactive groups, including alkenes, alkynes, and benzylic methylenes, permit post-polymerization modification leading to tunable polymer properties in solution and at interfaces. This work expands the knowledge base related to solution, interfacial, and DNA complexation properties imparted by the inclusion and arrangement of functional groups within hydrophilic polymers.

Chapters 2-4 discuss polymers having a comb architecture designed for non-viral gene therapy. These polymers contain a polycyclooctene backbone and oligopeptide and zwitterionic pendent groups. Chapter 2 describes comb polymers with Simian Virus 40 nuclear localization sequence (SV40 NLS) pendent groups that interact with receptors on the nuclear membrane to provide enhanced nuclear uptake of complexed DNA. Cell culture experiments revealed a marked effect of oligopeptide orientation on the resulting gene expression levels provided by the NLS-containing comb polymers. Moreover, these polymers outperformed commercial transfection reagents, both in gene expression levels and cell viability. Chapter 3 describes the introduction of zwitterions into these comb polymers and investigates the impact of zwitterions on polymer-DNA complex (or ‘polyplex’) properties. Dispersing small amounts of zwitterion into comb polymers with SV40 NLS and oligolysine pendent groups improved gene expression levels. Chapter 4 describes the synthesis of comb polymers having oligoarginine sequences as pendent groups and properties of the corresponding polyplexes. Compared to oligolysine sequences, oligoarginine facilitated stronger polymer-DNA binding and allowed inclusion of higher loadings of biocompatible zwitterions without compromising the ability of the polymer to complex DNA.

Chapters 5 and 6 investigate zwitterionic polymers at the oil-water interface of emulsion droplets. Experiments in Chapter 5 demonstrate the ability of zwitterionic sulfobetaine methacrylate polymers to stabilize oil-in-water droplets in pure water at room temperature, followed by coalescence upon increasing salt concentration or temperature. Integrating alkene and alkyne groups directly into the zwitterionic moiety allowed inclusion of high loadings of functional groups without interrupting the salt-triggered droplet coalescence exhibited by sulfobetaine homopolymers. Functional group placement was found to greatly impact interfacial properties. Chapter 6 describes the preparation of adhesive droplets from novel sulfur-based zwitterionic polymers. Droplet adhesion was modulated by the presence of salt and nucleophiles, and the resultant stability and adhesiveness of the droplets. The interdroplet interactions were found to dictate the mechanical properties of the emulsion and its stability upon application of centrifugal force.

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