The use of fluorescent imaging probes for the real time detection of cellular malfunctions, such as enzyme over expression has shown promise. Fluorescent dyes with absorption and emission values below 600 nm are limited in their in vivo applications due to high background auto-fluorescence and low resolution images. Employing near infrared (NIR) fluorophores such as cyanine dyes can overcome this disadvantage. Cyanine dyes can be synthesised using solution or solid-phase techniques with the use of solution phase chemistry allowing for larger scale and higher yielding reactions. Utilising a selection of functional groups and varying polymethine chain lengths a cyanine dye library with tuneable absorption and emission wavelengths was synthesised. This thesis gives the first detailed examples of how modifications on heptamethine cyanine dyes alter their cellular uptake and cellular toxicity. Furthermore, a NIR fluorescent microsphere is reported as well as NIR functionalised microspheres with the ability to be tracked within cells. Additional lines of work involved the synthesis of a fluorescent sensor for the visualisation of bacteria. Aminopeptidases are present within the peptidoglycan cell wall of Gram negative bacteria and therefore can be targeted for real time detection of bacteria to aid in the detection of infectious diseases. A coumarin based probe is reported which detects aminopeptidase in gram negative bacteria in vitro.

Tumor metabolism is a highly dysregulated process that is identified as a unique target for therapy. Current philosophy proposes that tumor metabolism is a plastic and flexible process which sustains proliferative and survival advantages. Tumors employ an anaerobic glycolytic pathway resulting in the overproduction of lactate. Additional thinking suggests that the conversion of pyruvate to lactate regenerates the NAD+ pool in the cell, maintaining a sustainable oxidative environment. Regardless of the reasons for lactate overproduction, its excretion and build up in the microenvironment results in acidic tumor microenvironments. Tumor acidosis has been measured with several different methods, but consistently averages from pH 6.6 to 7.0. Tumor acidity can thus be measured as a biomarker for tumor metabolism. This work examines the commonly explored energy pathways available to the cancer cell and a non-invasive MRI method to measure the efficacy of the tumor metabolism targeting agent. Appendix A is an introduction to tumor metabolism pathways and the large list of candidate therapies in interfering with energy production. Glucose, fatty acid, and glutamine metabolisms are all discussed along with PI3K/AKT/mTOR and HIF growth signals and ion transport. Magnetic resonance imaging and positron emission tomography are examined as imaging methods for non-invasively interrogating tumor acidosis. Appendix B presents the findings in a study where tumor metabolism was targeted with an mTOR inhibitor, where tumor growth rate was initially decreased and accompanied by an early, acute increase in tumor extracellular pH with acidoCEST MRI. Chapter 2 discusses the combination of a lactate dehydrogenase inhibitor in conjunction with doxorubicin in a breast cancer model. Tumor extracellular pH was shown to increase when measured with acidoCEST MRI, and an increase in cell death was measured. Chapter 4 discusses the studies and experimental designs that can be done in the near future.

The venom of the Eastern coral snake Micrurus fulvius can cause respiratory paralysis in the bitten patient, which is attributable to -neurotoxins (-NTx). The aim of this work was to study the biodistribution and lymphatic tracking by molecular imaging of the main -NTx of M. fulvius venom. -NTx was bioconjugated with the chelator diethylenetriaminepenta-acetic acid (DTPA) and radiolabeled with the radionuclide Gallium-67. Radiolabeling efficiency was 60%-78%; radiochemical purity 92%; and stability at 48 h 85%. The median lethal dose (LD50) and PLA(2) activity of bioconjugated -NTx decreased 3 and 2.5 times, respectively, in comparison with native -NTx. The immune recognition by polyclonal antibodies decreased 10 times. Biodistribution of -NTx-DTPA-Ga-67 in rats showed increased uptake in popliteal, lumbar nodes and kidneys that was not observed with Ga-67-free. Accumulation in organs at 24 h was less than 1%, except for kidneys, where the average was 3.7%. The inoculation site works as a depot, since 10% of the initial dose of -NTx-DTPA-Ga-67 remains there for up to 48 h. This work clearly demonstrates the lymphatic system participation in the biodistribution of -NTx-DTPA-Ga-67. Our approach could be applied to analyze the role of the lymphatic system in snakebite for a better understanding of envenoming.

Cancer treatment by adoptive immune cell therapy (AIT) is a form of immunotherapy that relies on the in vitro activation and/or expansion of immune cells. In this approach, immune cells, particularly CD8+ T lymphocytes, can potentially be harvested from a tumor-bearing patient, then activated and/or expanded in vitro in the presence of cytokines and other growth factors, and then transferred back into the same patient to induce tumor regression. AIT allows the in vitro generation and activation of T-lymphocytes away from the immunosuppressive tumor microenvironment, thereby providing optimum conditions for potent anti-tumor activity. The overall objective of this study is to: a) develop multi-modality (optical- and radionuclide-based) molecular imaging approaches to study the overall kinetics of labeled adoptively transferred T- lymphocytes in vivo, b) to non-invasively image and assess in-vivo, targeting and retention of adoptively transferred labeled T-lymphocytes at the tumor site. T-lymphocytes obtained from draining lymph nodes of 4T1 (murine breast cancer cell) sensitized BALB/C mice were activated in vitro with Bryostatin/ Ionomycin for 18 hours, and were grown in either Interleukin-2 (IL-2) or combination of Interleukin-7 and Interleukin-15 (IL-7/IL-15) for 13 days, (cells grown in IL-2 called IL2 cells, and cells grown in IL7/15 called IL7/15 cells). In order to validate the methodology and to offer future clinical translation, both direct and indirect cell labeling methods were expanded and employed. The first method was based on direct in vitro cell labeling by lipophilic near-infrared (NIR) fluorescent probe, 1,1- dioctadecyltetramethyl indotricarbocyanine iodide, (DiR), followed by intravenous (i.v.) injection into BALB/C mice for multi-spectral fluorescence imaging (MSFI). The second method was based on indirect labeling of T- lymphocytes through transduction of a reporter gene (cell cytoplasm labeling Herpes Simplex Virus type 1- thymidine kinase (HSV-1 tk). The product of this reporter gene is an enzyme (HSV-1TK) which phosphorylates a radio labeled substrate 2-fluoro-2-deoxy-1 β- D- arabinofuranosyl-5-iodouracil ([124I]-FIAU) for Positron Emission tomography (PET) imaging. ATP based cell viability assay, flow cytometry and interferon-γ (IFN-γ) ELISA were used to investigate if there are any changes in cell viability, proliferation and function respectively, before and after direct and indirect labeling. The results showed that cell viability, proliferation, and function of labeled 4T1 specific T-lymphocytes were not affected by labeling for direct labeling methods at DiR concentration of 320µg/ml. For the indirect labeling method, the viability and proliferation results showed that cell viability decreases as multiplicity of infectious (MOI) increases. In particular, at MOI of 10 almost all cells die 3 days post transduction. At MOI of 5, cells viability was ≤ 30% and at MOI of 2 was ≤ 60%. Cell viability was 80% at MOI of 1. The results of optical imaging were as follows: when the recipient mice with established 4T1 tumors were injected with DiR labeled 4T1 specific T-lymphocytes, the 4T1 specific T-lymphocytes (IL2 cells) infused into tumor-bearing mice showed high tumor retention, which peaked 3 or 6 days post infusion depending on the tumor size and persisted at the tumor site for 3 weeks. In contrast, IL7/15 cells showed lower signal at the tumor site and this peaked on day 8. On the other case when 4T1 tumor cells were implanted 1-week post-infusion of labeled T-lymphocytes. IL2 T-lymphocytes moved out of lymphoid compartments to the site of subsequent 4T1 inoculation within two hours and peaked on day 3 and the signal persisted for 2 more weeks. In contrast with infusion of IL7/15 cells, the signal was barely detected and did not show a similar trafficking pattern as with IL2 cells. The results of the indirect labeling method, PET reporter gene (PRG) system (HSV-1tk / [124I ] FIAU ) showed that both IL2 and IL7/15 cells were successfully transduced as verified ex vivo by real time PCR and western blot. T Cells transduction efficiency was assessed from cell uptake study in comparison to stable transduced Jurkat cells which have transduction efficiency of 100 %. Both IL2 and IL7/15 cells showed lower transduction efficiency (≤ 30%) compared to Jurkat cells. Consequently, PET imaging did not show a detectable signal of transduced T cells in vivo. Biodistribution study was carried out on day 3 post [124I]-FIAU injections. Results were consistent with the optical imaging results, except for IL7/15 cells. Transduced and untransduced IL2 and IL7/15 cells were labeled with DiR and injected ( i.v.) into Balb / C mice and then imaged by both imaging modalities (MSFI and PET) at the same time. MSFI images of transduced IL2 cell showed detectable signal starting from 2 hours, peaked at 72 hours and persisted up to 2 weeks, while IL7/15 cells were detectable at the tumor site starting at 24 hours, peaked at 72 hours and persisted up to 2 weeks. By the end of this study animals were dissected and tissue activities were counted using gamma counting and expressed as % Injected dose/gram of tissue (%ID/gm). Transduced IL2 and IL7/15 cells showed higher %ID/gm than other organs at lungs, liver, spleen, tumor, lymph nodes and bone/bone marrow. IL7/15 cells compared to IL2 cells showed higher %ID/gm at same organs. Neither IL2 nor IL7/15 untransduced DiR labeled cells showed any activity at tumor site, and their activities at other organs was very low compared to transduced cells. To investigate whether labeled T-lymphocytes will localize at tumor metastases or not, and to study the difference in their migration patterns to the tumor site versus tumor metastases, 4T1 tumor cells were successfully transduced with HSV-1tk as confirmed by RT-PCR , western blot and cell uptake study. Transduced 4T1 cells were implanted in the right flank or in the mammary fat pad of the mouse. Serial PET imaging was carried out in the third and fourth week post tumor implantation to know when the tumor will metastasizes. PET imaging showed only signal at the tumor site and no metastasis were detected.

Proteins are essential components in most processes in living organisms. The detection and quantification of specific proteins can be used e.g. as measures of certain physiological conditions, and are therefore of great importance. This thesis focuses on development of affinity-based bioassays for specific protein detection. The use of Affibody molecules for specific molecular recognition has been central in all studies in this thesis. Affibody molecules are affinity proteins developed by combinatorial protein engineering of the 58-residue protein A-derived Z domain scaffold. In the first paper, solid phase peptide synthesis is investigated as a method to generate functional Affibody molecules. Based on the results from this paper, chemical synthesis has been used throughout the following papers to produce Affibody molecules tailored with functional groups for protein detection applications in vitro and in vivo.   In paper I, an orthogonal protection scheme was developed to enable site-specific chemical introduction of three different functional probes into synthetic Affibody molecules. Two of the probes were fluorophores that were used in a FRET-based binding assay to detect unlabeled target proteins. The third probe was biotin, which was used as an affinity handle for immobilization onto a solid support. In paper II, a panel of Affibody molecules carrying different affinity handles were synthesized and evaluated as capture ligands on microarrays. Paper III describes the synthesis of an Affibody molecule that binds to the human epidermal growth factor receptor type 2, (HER2), and the site-specific incorporation of a mercaptoacetyl-glycylglycylglycine (MAG3) chelating site in the peptide sequence to allow for radiolabeling with 99mTc. The derivatized Affibody molecule was found to retain its binding capacity, and the 99mTc-labeling was efficient and resulted in a stable chelate formation. 99mTc-labeled Affibody molecules were evaluated as in vivo HER2-targeting imaging agents in mice. In the following studies, reported in papers IV-VI, the 99mTc-chelating sequence was engineered in order to optimize the pharmacokinetic properties of the radiolabeled Affibody molecules and allow for high-contrast imaging of HER2-expressing tumors and metastatic lesions. The main conclusion from these investigations is that the biodistribution of Affibody molecules can be dramatically modified by amino acid substitutions directed to residues in the MAG3-chelator. Finally, paper VII is a report on the chemical synthesis and chemoselective ligation to generate a cross-linked HER2-binding Affibody molecule with improved thermal stability and tumor targeting capacity.   Taken together, the studies presented in this thesis illustrate how peptide synthesis can be used for production and modification of small affinity proteins, such as Affibody molecules for protein detection applications. / QC 20100719

Targeting angiogenic vasculature has been validated as a viable approach for cancer imaging and therapy. The tumour vasculature-specific ligand asparagine-glycine-arginine (NGR) peptide targets the isoform of aminopeptidase N (CD13) expressed on endothelial cells lining angiogenic vessels. CD13 has become widely recognized as a rational target for therapeutic development and several NGR-conjugated agents are now in pre-clinical and clinical development. In the current study, a CT image-based approach is used to evaluate the in vivo performance of several NGR-conjugated liposome formulations that vary in terms of NGR density and PEG spacer arm length. Indeed, for the first time it is demonstrated that CT imaging can be used for quantitative and longitudinal assessment of the pharmacokinetics and biodistribution of an actively targeted liposome formulation. In comparison to conventional methods, CT imaging enables visualization of the intratumoural distribution of liposomes and quantification of the fraction of tumour occupied by the vesicles over time.

Targeting angiogenic vasculature has been validated as a viable approach for cancer imaging and therapy. The tumour vasculature-specific ligand asparagine-glycine-arginine (NGR) peptide targets the isoform of aminopeptidase N (CD13) expressed on endothelial cells lining angiogenic vessels. CD13 has become widely recognized as a rational target for therapeutic development and several NGR-conjugated agents are now in pre-clinical and clinical development. In the current study, a CT image-based approach is used to evaluate the in vivo performance of several NGR-conjugated liposome formulations that vary in terms of NGR density and PEG spacer arm length. Indeed, for the first time it is demonstrated that CT imaging can be used for quantitative and longitudinal assessment of the pharmacokinetics and biodistribution of an actively targeted liposome formulation. In comparison to conventional methods, CT imaging enables visualization of the intratumoural distribution of liposomes and quantification of the fraction of tumour occupied by the vesicles over time.

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