Graduation Semester and Year

Summer 2025

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Kevin A. Schug

Second Advisor

Daniel W. Armstrong

Third Advisor

Krishnan Rajeshwar

Fourth Advisor

Jongyun Heo

Abstract

Drug delivery systems (DDS) are an increasingly relevant technology, owing to their ability to provide controlled release and to enable the use of otherwise toxic or labile therapeutics. However, these modalities are complex, containing a multitude of species with diverse chemical and physical properties. Their characterization, which involves the assessment of critical quality attributes (CQAs), requires numerous analytical techniques. The high-throughput demands of the biopharmaceutical industry have driven the need to consolidate these characterizations into a single analytical method. Consequently, novel analytical technologies are needed to support multi-attribute characterization. A multimodal liquid chromatography–mass spectrometry (LC–MS) system was developed to facilitate the simultaneous determination of multiple quality attributes of a polymeric hydrogel DDS, including controlled drug release and in vitro hydrogel degradation. At the core of the system was a restricted access media (RAM) column, serving as an intermediary between two chromatographic separation modes: size exclusion chromatography and reversed-phase chromatography. System utility and limitations were evaluated using DDS-representative chemical species with varying hydrodynamic radii and hydrophobicities. The multimodal system was repurposed for a lipid-based DDS to determine encapsulation efficiency (EE). However, over-adsorption on the RAM column necessitated the development of a new intermediary trap-and-elute column. Spongy monoliths modified with polyethyleneimine (PEI) were developed, which demonstrated reduced adsorption, although not completely, as confirmed using stable, isotopically labeled lipid nanoparticles (LNPs). Unexpectedly, the monolith also resolved sub-populations of LNPs via ion exclusion chromatography, prompting further investigation. These sub-populations were analyzed for compositional differences using a two-dimensional LC–MS system. The earlier-eluting species exhibited a higher relative abundance of the ionizable lipid SM-102. Finally, the method was applied as a stability-indicating assay to assess the effects of freeze–thaw cycles.

Keywords

Hydrogel, Lipid nanoparticle, Hyaluronic acid, Polyethyleneimine, Monolith, Degradation kinetics, Stability, Charge heterogeneity

Disciplines

Analytical Chemistry

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