Master of Science
Gillies, Elizabeth R.
Stimuli-responsive hydrogels are 3D polymeric structures that offer attractive qualities within the biomedical field due to their excellent biocompatibility and tunability to be employed in drug release, wound healing, and implants. Aliphatic polyesters are biodegradable polymers that naturally degrade by the process of simple ester hydrolysis. Oligo[poly(ethylene glycol) fumarate] (OPF) is a linear polyester containing repeating units of poly(ethylene glycol) and unsaturated fumarate. OPF naturally degrades through hydrolytic cleavage into poly(ethylene glycol) (PEG) and fumaric acid which is a naturally occurring compound found in the Kreb’s cycle. However, in some cases, it would be beneficial to activate or accelerate this degradation in a more controlled manner. This thesis explores the degradative behaviour of OPF functionalized with photoactivatable pendent groups that undergo intramolecular cyclization to cleave the backbone, thereby degrading the polymer. Next, the functionalized OPF is converted into a hydrogel by covalently cross-linking and the gel is characterized by the gel content and equilibrium water content. Hydrogel degradation is examined by 1H NMR spectroscopy and mechanical testing with and without UV light irradiation. It is shown that activation of the pendent groups can accelerate gel degradation.
Summary for Lay Audience
Polymers are large molecules that are composed of repeating units. Currently, there is interest in degrading polymers in response to stimuli such as light, heat, or acid. These degradable polymers are referred to as stimuli-responsive polymers. This thesis aims to explores a new method to trigger the degradation of polymers by introducing units that are responsive to ultraviolet light along the polymer backbone. When these units are activated by light, their reactivity changes and they can slice the backbone at a nearby unit. Overall, this process leads to accelerated degradation of the polymer in the presence of light. The new functional polymer is incorporated into a water-absorbing network, called a hydrogel, and it is shown that degradation of this hydrogel can be accelerated by irradiation with ultraviolet light. Overall, this work provides a proof of concept for a new way to control hydrogel degradation, which could be extended to relevant stimuli in the body for potential applications in new therapies.
Chung, Andrew, "Oligo [poly(ethylene glycol) fumarate] gels with photo-sensitive pendent groups" (2023). Electronic Thesis and Dissertation Repository. 9181.