Date of Award
Doctor of Philosophy (PhD)
In the United States, ischemia resulting from cardiovascular disease and acute trauma affects nearly 50% of all adults. Therapeutic angiogenesis aims to stimulate the formation of new microvasculature that alleviates hypoxia, reduces tissue morbidity, and improves wound healing. The current primary therapeutic approach is vascular endothelial growth factor (VEGF) injection therapy but is hindered by several challenges. Consequently, bioactive small molecules are being used to target hypoxia-inducible factor-1α (HIF-1α), the master regulator of oxygen-sensing pathways that is responsible for activating angiogenesis in response to tissue hypoxia. However, successful clinical translation of small molecules for therapeutic angiogenesis still faces several challenges including drug solubility, administration route, and biodistribution. The objective of this project was to develop a scaffold to activate and support therapeutic angiogenesis through local delivery a pro-angiogenic small molecule from a bioactive hydrogel matrix. N-oxalylglycine (NOG) is a known HIF-1α stabilizer that works by outcompeting the HIF-1α destabilizing co-factor 2-oxoglutarate for its binding site and prevents the eventual degradation of HIF-1α. We first synthesized a new macromolecular prodrug conjugate of hyaluronic acid with NOG (HA-NOG). Free NOG was released from HA-NOG in a sustained manner in the presence of enzymes (hyaluronidases and esterases) and released NOG stimulated HIF-1α nuclear accumulation, target gene expression, as well as in vitro endothelial cell tubulogenesis. We then evaluated NOG release kinetics and bioactivity from PEG-based monolayer and bilayer hybrid hydrogels incorporating the HA-NOG conjugate in vitro, and found that sustained, local release of NOG from a hydrogel delivery system could increase HIF-1α target gene expression. Previous work from the lab utilized a PEG diacrylate (PEGdA)/HA hybrid semi-interpenetrating network (semi-IPN) hydrogel as a carrier for an HA-based macromolecular prodrug. This hydrogel was effective in sustained release but limited in innate bioactivity to support cellular invasion and remodeling. Therefore, we investigated increasing the concentration of modified naturally derived polymers, gelatin methacrylate (GelMA) and glycidyl methacrylate HA (GMHA), in PEGdA-based hybrid hydrogels. We first created a new, shortened method for purifying GelMA by acetone precipitation. The subsequent hybrid copolymer hydrogel formulation consisted of covalently crosslinked PEGdA, GelMA, and GMHA. Several formulations of the new bioactive PEGdA/GelMA/GMHA hybrid hydrogel demonstrated strong mechanical properties, while also supporting increased cell spreading and migration relative to the previous PEGdA/HA semi-IPN formulation. Overall, the results of this work present a potential new treatment option for ischemic injuries by safely and effectively delivering pro-angiogenic NOG from hybrid hydrogel matrices, as well as show the improved bioactivity of a newly synthesized PEGdA/GelMA/GMHA hybrid hydrogel. In the future, this drug delivery system will be evaluated in rodent central nervous system injury models to assess functional recovery.
DeMaria, Andrew, "Development of a Hybrid Hydrogel Drug Delivery System for Treatment of Ischemic Injury" (2021). All Dissertations. 2851.