Document Type

Thesis

Date of Degree Completion

Spring 2022

Degree Name

Master of Science (MS)

Department

Chemistry

Committee Chair

Samuel Lohse

Second Committee Member

Carin Thomas-Bradley

Third Committee Member

Yingbin Ge

Abstract

This study investigated the protein adsorption interactions of bovine serum albumin (BSA) with three different functionalized 5 nm gold nanoparticles (AuNPs) in order to determine the binding affinity and total amount of protein adsorbed to each AuNP surface chemistry. AuNPs were synthesized using two different capping agents to display three different surface chemistries: a neutral ω-functionalized thiol ligand (mercapto-ethoxy-ethoxy-ethanol, MEEE), a thiol ligand that is negatively charged at pH 7.4 (mercaptohexanoic acid, MHA), and a mixture of the two ligands (mixed-ligand AuNPs). The interactions of this library of AuNPs with bovine serum albumin (BSA) were investigated using UV-visible absorbance spectroscopy, fluorescence titrations, dynamic light scattering (DLS), and a Bradford protein assay. Fluorescence titrations indicated that the binding affinity of BSA was higher for AuNPs with any negative surface charge density, and that the difference between Kas for the mixed-ligand AuNPs and the MHA-capped AuNPs was not significant. Ka for MHA, MEEE, and mixed-ligand AuNPs were 0.47 ± 0.02 nM-1, 0.40 ± 0.02 nM-1, and 0.48 ± 0.02 nM-1, respectively.Hill plot analysis of the fluorescence titration data indicated that for all three AuNP surface chemistries, BSA exhibited cooperative binding behavior. Measurement of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) suggests that 1 to 2 BSA molecules adsorb to each AuNP, but quantitation of the total protein adsorbed to each AuNP surface chemistry was not possible via Bradford assay due to an inability to adequately separate BSA-AuNP complexes from free BSA.

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