Development of new bis(thiosemicarbazonates) and investigations into their potential as molecular imaging and therapeutic agents

Abstract

Chapter 1 – Introduction, describes medical imaging modalities focussing on molecular imaging agents for SPECT and PET, where examples of dual modal imaging with either technique or theranostics (simultaneous diagnosis and therapy) are highlighted. Significant examples of imaging probes using technetium and rhenium are included with an emphasis on emerging zinc, copper, gallium and indium complexes. Development of metal complexes conjugated to agents enabling targeting of receptors is described as well as hypoxia and its diagnosis and therapy. Chapter 2-5 describe the synthesis and characterisation of bis(thiosemicarbazonato) ligands (Chapter 2) and zinc & copper (Chapter 3), gallium (Chapter 4) and indium (Chapter 5) complexes. An interesting isomerism is explored using Density Functional Theory (DFT). The complexes are investigated for their suitability as molecular imaging probes, firstly by testing their spectroscopic properties using UV-visible and fluorescence spectroscopies. This is followed by assessing their stability, utilising the aforementioned techniques with biologically relevant media in solution and in biological cells in vitro, using fluorescence lifetime imaging microscopy (FLIM). Laser scanning confocal microscopy is used to investigate cell uptake demonstrating localisation within organelles. Furthermore, gallium and indium complexes are evaluated for their potential as hypoxia imaging agents, in vitro in addition to the investigation of indium complex nuclear and chromosomal uptake. Lastly, copper and gallium complexes are studied in nude mice with PC-3 xenografts under normoxic conditions (by the Jason Lewis Group, MSKCC, NYC). Chapter 6. Compounds introduced in chapters 2-5 are studied and compared for their in vitro cytotoxicity using MTT and LDH assays. MTT assay is used to determine a quantitative value of toxicity, to enable a direct comparison of all compounds tested and in cancerous and non-cancerous cell lines. LDH assay on the other hand, provides insight into the mechanism of molecular action upon the cell membrane, which may explain differences obtained using MTT assay in this study and trypan blue experiments, which relies upon membrane integrity. Chapter 7 explores methods of attaching a targeting agent, a bombesin analogue, to the bis(thiosemicarbazonato) complexes. Novel complexes are characterised and subsequently investigated in cells for cytotoxicity and by confocal microscopy and FLIM. Chapter 8 describes a summary of this thesis. Chapter 9 contains the entire experimental data for the work of this thesis.

Date of Award	1 Feb 2013
Original language	English
Awarding Institution	University of Bath
Supervisor	Sofia Pascu (Supervisor)