Advisor(s)

Pengfei Wang

Committee Member(s)

Gayan Wijeratne
Jun Zhang
Ping Zhang
Sadanandan Velu

Document Type

Dissertation

Date of Award

6-1-2026

Degree Name

Doctor of Philosophy (PhD)

School

College of Arts and Sciences

Department

Chemistry

Abstract

Triterpenoid saponins are amphiphilic glycosides that exhibit a wide range of biological and pharmacological properties, including antifungal, antiviral, molluscicidal, hypoglycemic, and hypocholesterolemic effects. These biological and pharmacological properties make saponins attractive for diverse applications. In this work, we demonstrate three biological applications: (i) immunostimulant vaccine adjuvant, (ii) protein delivery enhancement, and (iii) gene transfection enhancement. In light of the strong structure dependence of saponin activity, expanding the structural diversity of available scaffolds is essential for establishing structure-activity relationships (SAR) across these applications. Here, we expanded our saponin collection through semi-synthetic derivatization and the isolation of new saponins from distinct natural sources. For vaccine adjuvant studies, we extended our prior semi-synthetic work by modifying the side chains of the Momordica cochinchinensis saponins (MS-I and MS-II) to prove adjuvant SAR. Side chain length and rigidity were varied for MS-I, and internal polarity and terminal functionality were varied for both MS-I and MS-II. Adjuvant activity was evaluated in mice using antigen-specific IgG1 and IgG2a antibody readouts to assess Th2- and Th1-associated immunities. To further develop vaccine adjuvant SAR, we characterized saponins isolated from Saponaria officinalis. These saponins, together with targeted side chain derivatization (VSA-1/VSA-2 – type side chains), enabled evaluation of how glycosylation/acetylation patterns and side chain identity jointly shape adjuvant activity. Beyond adjuvanticity, structurally characterized saponins function as protein delivery enhancing agents. Using Saponaria officinalis saponins, we assessed potentiation of the ribosome-inactivating protein saporin as a model for enhanced endocytosis and intracellular protein delivery. Intrinsic cytotoxicity screening and combination assays were used to quantify saponin enabled saporin potentiation by measuring shifts in saporin cytotoxicity in the presence of saponins, as saporin alone lacks both cell entry and endosomal escape. We also evaluated saponins as enhancers of non-viral gene transfer. Natural saponins were first evaluated, followed by semi-synthetic derivatives; MS-I showed low transfection activity, whereas one-step derivatization to VSA-1 significantly increased transfection efficiency. Transfection efficiency was measured by enhancement of poly-D-lysine-mediated pEGFP-N1 transfection in HEK293 cells. Together, these findings establish SAR frameworks for developing next generation saponin-based adjuvants and delivery enhancers.

Keywords

endosomal escape;non-viral DNA delivery;saponins;semi-synthetic saponins;structural-activity relationship study;vaccine adjuvant

Download

Share

COinS