Manipulating Viral Vector Release from Hydrogel Systems for Controlled Gene Delivery in Therapeutic Angiogenesi

Therapeutic gene delivery to drive neovascularization holds promise as a strategy to treat ischemic diseases. However, despite promising preclinical results, gene delivery for therapeutic angiogenesis has been met with many challenges that have hampered clinical translation. There is a need for improved delivery strategies for administering multiple genetic vectors to drive neovascularization, perhaps simultaneously, in a manner that promotes efficiency and safety. The hypothesis underlying this thesis is that alginate hydrogels can provide spatiotemporal control of dual viral vector delivery of proangiogenic genes.;The initial studies of this thesis examined the capability of alginate hydrogels to encapsulate and release functional viral vectors including lentivirus, adenovirus, and adeno-associated virus. All vectors studied maintained their activity throughout the process of encapsulation and proved capable of release in a manner that was dependent on hydrogel degradation. Alginate hydrogels were used to locally deliver lentivirus to the murine hindlimb, and this approach led to sustained transgene expression and reduced insertional copy numbers in comparison to bolus injections of the same vector.;Further control in vector release was obtained using alginate microgel suspensions. Three processes for generating alginate microgels using microfluidics were developed and compared for their ability to deliver functional lentivirus. The susceptibility of lentivirus to encapsulation conditions was used to identify two of these encapsulation strategies as being feasible for lentivirus delivery. These two processes utilized either external or internal gelation of alginate droplet templates, and provided evidence for the importance of hydrogel mechanical properties in regulating release.;The tunability of vector release was further expanded by creating composite suspensions of microgels that vary drastically in their mechanical properties and rates of degradation. This strategy was used to create release profiles that spanned a spectrum from burst release to lengthy retention. Lentivirus encoding for vascular endothelial growth factor or stromal derived-cell factor 1 were encapsulated within these composite suspensions and the ability to create sequential and patterned expression in myofibers was demonstrated in concept. Lentivectors encoding for VEGF were encapsulated within degradable alginate microgels and demonstrated significant proangiogenic capacity in the chick chorioallantroic membrane assay.;Overall, this work provides new strategies for the spatial and temporally controlled presentation of viral vectors for proangiogenic gene delivery. Furthermore, the development of composite alginate suspensions may prove widely useful for the controlled delivery of multiple factors simultaneously.