PhD Oral Exam - Sofia Nieves Casillas Popova, Chemistry

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Electro-spun (e-spun) nanofibers represent a versatile platform for biomedical applications, including wound dressings and implantable scaffolds for localized drug delivery. Among these, poly(vinyl alcohol) (PVA) electro-spun nanofibers have attracted attention due to their thermal and chemical stability, high absorption capacity, electro-spinnability, and excellent biocompatibility. However, their high-water solubility leads to the rapid loss of structural integrity in aqueous environments, requiring stabilization via chemical or physical crosslinking. While typical chemical crosslinks including acetal, ester, and carbamate bonds have been widely used, these linkages present challenges such as poor degradability and potential toxicity for their biomedical applications.

My PhD research investigates boronic ester chemistry as an effective crosslinking strategy to fabricate stimuli-responsive degradable PVA e-spun nanofibers for their application as wound dressings or implantable devices for localized drug delivery to prevent tumor recurrence. Commercially available and newly synthesized diboronic acids were evaluated as degradable crosslinkers and the resulting nanofibrous mats were analyzed for their structural, physical, and functional properties. Nanofibers exhibited tunable degradation in response to pH, diol concentration, and reactive oxygen species such as hydrogen peroxide. This approach enabled the fabrication of nanofibers that retain their dimensional and structural integrity in aqueous environments while allowing controlled degradation and drug release upon exposure to specific stimuli. Depending on the application, the nanofiber mats were assessed for wound healing or implantable drug delivery performance.

Overall, my research establishes a versatile platform for designing multi-stimuli-responsive nanofibrous materials with tunable degradation and highlights their potential for a range of biomedical applications.