Date of Award

Winter 12-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Master of Arts (AM/MA)

Degree Type

Thesis

Abstract

Siderophores are small molecules synthesized by bacteria to harvest Fe3+ from their environment. In infection scenarios, their production can increase infection virulence by increasing the ability of bacteria to obtain Fe3+ and therefore grow more rapidly. The selective uptake of siderophores in vivo in multi-bacteria environments indicates that this class of molecules has a potential use as selective imaging agents. In this work, DFO-NCS and a library of trihydroxamate siderophores were evaluated as vehicles to deliver 89Zr selectively to bacteria for Positron Emission Tomography (PET) imaging of bacterial infections.

Productive work with radiometals involves thorough knowledge of the element’s chemistry as well as the sources and detrimental effects of any contaminating metal ions present with the radiometal in the reaction mixture. As a case study to determine the factors likely to interfere with the complexation of any given radiometal, the quality control assay used to determine effective specific activity (ESA) of 64Cu was intensely examined. The purpose of this study was to identify sources of cold metal contaminants in the 64Cu production process and to identify which of those metals interfere with the binding of 64Cu to the TETA chelator. The TETA titration method for determining 64Cu ESA has relative standard deviations of 27.6% and 40.3% for repeatability and reproducibility respectively and the chelator TETA is selective for picomolar amounts of Cu2+ in the presence of low millimolar concentrations of Zn2+ and Ni2+.

When the 89Zr-DFO-NCS complex was tested against a panel of cell types, the uptake by human cells (SKBR3), Staphylococcus aureus cells, and Pseudomonas aeruginosa cells was significantly different (pS. aureus. The Zr chemistry and bacterial uptake behavior of a library of trihydroxamate siderophores was then evaluated and compared to that of DFO-NCS. The uptake of 89Zr-DFO-NCS and a siderophore library member (89Zr-V-129) were tested in a murine lung infection model (P. aeruginosa, PA M57-15) and the lung uptake of 89Zr-V-129 was found to be significantly higher in infected mice (p=0.012035) than in control mice. The uptake of 89Zr-DFO-NCS did not differ significantly between control and infected mice (p=0.831). 89Zr-siderophores have been shown to possess potential to be selective, specific PET tracers for imaging bacterial infections in vivo and their utility for infection imaging should be more thoroughly explored.

Language

English (en)

Chair and Committee

Suzanne E. Lapi

Committee Members

Timothy A. Wencewicz, Lee G. Sobotka

Comments

Permanent URL: https://doi.org/10.7936/K7PG1PV4

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