Date of Graduation

5-2026

Document Type

Thesis

Degree Name

Bachelor of Science in Chemical Engineering

Degree Level

Undergraduate

Department

Chemical Engineering

Advisor/Mentor

Keisha Walters

Committee Member

William Richardson

Second Committee Member

Jacob Monroe

Third Committee Member

Hyunjin Moon

Abstract

This study investigates the stimuli-responsive behavior of porcine gastric mucin (PGM) as a model for the conjunctival mucous membrane of the human eye to optimize mucoadhesive ophthalmic drug delivery. As a versatile biopolymer, PGM has a dynamic matrix structure that functions as a selectively permeable barrier, regulating transport across mucosal membranes. To improve drug bioavailability and retention in ocular treatments, silica nanoparticles (SiNPs) were modified with varying surface functional groups and incorporated into the mucin at different physiological pH levels to examine the resulting microstructural changes. Leveraging the amphiphilic and negatively charged characteristics of mucin, positively charged and hydrophobic SiNPs may enhance mucoadhesion, retention, and permeability via electrostatic and hydrophobic interactions. The SiNPs were synthesized using the Stöber process and functionalized with (3-aminopropyl)triethoxysilane (APTES) to develop a positive surface charge. Further modification via Michael addition and aminolysis reactions incorporated amine and amide functional groups, respectively, as intermediaries to prepare the surface for grafting of hydrophobic alkyl chains. These modifications provided tunable control over surface hydrophobicity and charge, thereby enhancing mucoadhesion via electrostatic and hydrophobic interactions. The modified SiNPs were integrated into PGM at varying pH levels (5.5, 6.5, and 7.5) relevant to topical ophthalmic medication treatments to examine interfacial stability changes in the mucin structure. Characterization of the neat and functionalized SiNPs, and the resulting mucin-nanoparticle solutions, was conducted using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and scanning electron microscopy (SEM) to verify chemical composition and morphology. Additionally, water contact angle (WCA) and pendant drop surface tension analyses were performed to evaluate hydrophobic-hydrophilic changes in the mucin after the addition of surface-modified nanoparticles. This study aims to optimize the surface chemistry of SiNPs to enhance mucoadhesion and improve the therapeutic efficacy of ophthalmic drug delivery formulations across varying physiological and pharmacological conditions.

Keywords

mucin; opthalmic drug; mucoadhesion; silica nanoparticle; surface modification; therapeutic efficacy

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