Doctor of Philosophy
Luyt, Leonard G.
The advent of molecular imaging as a discipline has drastically improved our ability to understand the biochemical and cellular events that drive life, death and disease. This thesis will document the discovery of new metal chelators for Re/99mTc, new methods of incorporating these metals into peptide structures, as well as new fluorescent compounds. These novel methods and compounds may be used in the development of molecular imaging probes for single photon emission computed tomography (SPECT) and optical imaging techniques, with applications for differentiating cancerous tissue from benign and healthy.
Chapter 2 discusses the development of a dual modality Re/99mTc imaging probe for fluorescence/SPECT imaging for evaluating CXCR4 expression in cancer cells. The T140 derivative contains a 4-amino-1,8-naphthalimide chelator to bind rhenium or technetium-99m for fluorescence or SPECT imaging. The rhenium coordinated peptide retained high affinity for CXCR4 and was able to detect cells expressing the receptor by fluorescence microscopy. However, little uptake of the technetium-99m labelled peptide was observed in CXCR4 expressing tumors in a murine model.
Chapter 3 aims to address the shortcomings of the naphthalimide chelation system discussed in chapter 2. Three 4-amino-1,8-naphthalimides containing chelators with a positive, neutral or negative charge were synthesized and coordinated with rhenium. All three complexes had photophysical properties that were compatible with confocal fluorescence microscopy and showed uptake in cells that was dependent on charge. All three ligands were radiolabelled with technetium-99m in high radiochemical yield and purity.
Chapter 4 discusses the development of a beta-hairpin forming peptide containing a 2,2’-bipyridine moiety to chelate Re/99mTc. A novel amino acid based on 3,3’-diamino-2,2’-bipyridine was synthesized, and incorporated into a peptide. Circular dichroism spectroscopy indicated a lack of secondary structure, but formation of secondary structures resembling a beta-sheet was possible upon the addition of 2,2,2-trifluoroethanol (TFE). However, metal coordination resulted in unstable complexes that were unable to be isolated.
Chapter 5 discusses the development of 2,2’-bipyridine-based fluorophores for the detection of intracellular Zn(II). Two benzimidazole functionalized bipyridines were found to have a fluorescence response to Zn(II) that was compatible for detection by confocal fluorescence microscopy. Both ligands displayed fluorescence in benign prostate cells due to Zn(II) coordination but not in prostate cancer cells. These ligands are promising candidates for the detection of Zn(II) in ex vivo prostate tissues for differentiating malignant tissue from benign and healthy.
Turnbull, William, "The Development of Metal Complexes as Components of Fluorescent and Nuclear Imaging Probes" (2018). Electronic Thesis and Dissertation Repository. 5517.