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Lowther and Boll in the study of the effect of 2,4,5-TCPAA on etiolated bean leaf discs observed that inhibition of expansion at low concentrations was relieved at high concentrations where growth was equal to that of the light plus Co control. This means that at appropriate concentrations, TCPAA completely replaced Co in the expansion of light-treated leaf discs. [...]

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Intensity-modulated radiation therapy (IMRT) is an advanced mode of high- precision radiation therapy that utilizes computer-controlled x-ray accelerators to deliver precise radiation doses to malignant tumors. The radiation dose is designed to conform to the three-dimensional (3-D) shape of a tumor by modulating the intensity of the radiation beam to focus a higher radiation dose to the tumor while minimizing radiation exposure to surrounding normal tissue. One form of IMRT is known as tomotherapy. Tomotherapy achieves dose conformity to a tumor by modulating the intensity of a fan beam of radiation as the source revolves about a patient. Current available tomotherapy machines use x-ray linear accelerators (linacs) as a source of radiation. However, since linacs are technologically complex, the world- wide use of linac-based tomotherapy is limited. This thesis involves an investigation of Cobalt 60 (Co-60) based tomotherapy. The inherent simplicity of Co-60 has the potential to extend the availability of this technique to clinics throughout the world. The goal of this thesis is to generate two-dimensional (2-D) Co-60 tomotherapy con- formal dose distributions with a computer program and experimentally validate them on ¯lm using a ¯rst generation bench-top tomotherapy apparatus. The bench-top apparatus consists of a rotation-translation stage that can mimic a 2-D tomotherapy delivery by translating the phantom across a thin, "pencil- like" photon beam from various beam orientations. In this thesis, several random and clinical patterns are planned using an in-house inverse treatment planning system and are delivered on ¯lm using the tomotherapy technique. The delivered dose plans are compared with the simulated plans using the gamma dose comparison method. The results show a reasonably good agreement between the plans and the measurements, suggesting that Co-60 tomotherapy is indeed capable of providing state-of-the-art conformal dose delivery. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-04-25 02:20:56.102 / Canadian Institutes of Health Research (CIHR) and the ORDCF’s Ontario Consortium for Image-guided Therapy and Surgery.

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The thesis addresses the potential application of ruthenium(II)-cobalt(III) heterodinuclear complexes as a new selective cancer treatment. The selectivity is to be achieved through the use of visible light to trigger activation of the drug. The majority of work conducted relates to the design and synthesis of the bridging ligand for the final ruthenium(II)-cobalt(III) heterodinuclear complex. In Chapter 2, a potential bridging ligand based on a functionalised terpyridine is described. The intention was to bind the ruthenium(II) metal centre to the terpyridine end of the bridging ligand and have a secondary binding domain available for coordination of the cobalt(III) metal centre. However, a reductive step in the synthetic pathway failed to produce the desired product and this potential bridging ligand had to be abandoned. In Chapter 3, two series of bridging ligands are described. The first of these series is based on Jurgen Sauer’s ‘LEGO’ system. In addition to describing the free synthesis of these ligands, their synthesis on a ruthenium(II) metal centre is described. The second series is based on disubstituted-1,2,4,5-tetrazines. These compounds are only able to be directly synthesised as the non-coordinated ligand. Coordination of these ligands to a single ruthenium(II) metal centre is then described. Ruthenium(II) complexes of both ligand series are then exposed to several transition metals and their ability to coordinate a second metal centre investigated. The formation of ruthenium(II)-cobalt(III) heterodinuclear complexes, using the ligand series detailed in Chapter 3, is described in Chapter 4. These complexes are formed by reacting the ruthenium(II) complex of the bridging ligand with either [Co(en)₂(OTf)₂](OTf) or [Co(tren)(OTf)₂](OTf). These heterodinuclear complexes exhibit photo-activated ligand release, which makes them candidates for development as a potential cancer treatment. The non-bridging ligands coordinated to the cobalt(III) metal centre in Chapter 4 were not cytotoxic. In order to make the system biologically active these ligands need to be changed. Chapter 5 describes how nitrogen mustards (a class of cytotoxic DNA alkylators) could be introduced as the non-bridging ligands. This involves the synthetic strategy of forming the cobalt(III) complex of the alcohol precursor of a nitrogen mustard. This precursor complex is then converted into the nitrogen mustard complex and coordinated to the ruthenium(II) bound bridging ligand. The synthetic strategies outlined in this thesis can be applied to a wide range of potential bridging ligands and could potentially lead to a large number of ruthenium(II)-cobalt(III) heterodinuclear complexes being synthesised. One journal article based on this research has been accepted for publication, in the Australian Journal of Chemistry. Three more articles are in preparation.

This thesis addresses the potential for use of cobalt(III) complexes for functionalisation of lightly oxidised iron surfaces. In Chapter 2 the preparation of cobalt(III) complexes of a series of ligands based on 1,1,1-tris(aminomethyl)ethane is described. The synthesis was approached in two ways. Firstly, preparation of functionalised triol molecules as precursors to functionalised triamine ligands was investigated. This approach utilised the Tollens condensation of aldehydes with formaldehyde. In a second approach, the functionalisation of tetrakis(aminomethyl)methane in which one amine arm has been differentiated was used. The tetraamine was reacted with benzaldehyde and reduced with borohydride ion to give a secondary amine molecule that was then functionalised using alkyl or aryl sulfonyl chloride molecules. Chapter 3 describes the measurement of the binding of some cobalt(III) complexes to the surface of high surface area goethite. It was observed that complexes that have three exchangeable ligands bind more strongly than those with two exchangeable ligands. This is rationalised as being due to there being more bonds to the surface formed by complexes with three exchangeable ligands. It was also observed that complexes with three exchangeable ligands give greater surface coverage than those with two. This is likely due to the larger cross sectional area of the complexes with two exchangeable ligands in comparison to that of those with three, which blocks potential adjacent sites. Preliminary experiments on the use of the contact angle, SEM, EDS and QCM to characterise complex binding are explored in Chapter 4 . The results from the EDS and QCM experiments show that these may be valuable tools for measuring this binding and the subsequent surface properties, but have not yielded detailed results at this point. In Chapter 5 the use of cobalt(III) complexes as inhibitors of corrosion of iron in hydrochloric acid is investigated. All the complexes tested, even those that showed no binding to goethite surfaces, inhibit the corrosion to some degree. The level of inhibition is dependent on the complex, with [Co(tren)Cl2]Cl showing maximum inhibition of 81% and [Co(tame)Cl3] showing maximum inhibition of 53%. For some of the complexes, their concentration in solution over the course of the experiment was monitored by UV-vis. It was found that the complex disappears in a zero order reaction, the rate of which is dependent on the complex. However, the exact nature of this reaction is unknown. Furthermore, it was observed that inhibition of corrosion continues after the complex is no longer observed in solution. There is a difficulty in rationalising the inhibition being dependent on the complex identity, but not its continued presence in solution. Consequently, the mechanism of corrosion inhibition that explains all of these observations is still not known.