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Title: Application of analytical techniques for the study of metal-based anticancer complexes
Author: McQuitty, Ruth J.
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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Transition metal coordination complexes show great promise as novel therapeutic agents with new mechanisms of action, but their characterisation, and identification of their target sites present significant challenges. In this thesis a variety of new analytical methods is explored for the study of platinum, ruthenium, osmium and iridium anticancer complexes. High performance liquid chromatography (HPLC) was used to determine the relative hydrophobicity of a series of photoactivatable Pt(IV) diazido complexes of the general type trans,trans,trans-[Pt(N3)2(OH)2(R)(F11]. Interestingly the hydrophobicities did not follow trends based on literature Log P values of individual ligands and did not correlate with the cellular uptake or antiproliferative activity of the drugs. Other factors such as the quantum yield of the complex, and the type of DNA adducts appear to be more important for their efficacy. Chromatography and high-resolution mass spectrometry were used to study the formation of platinum adducts on DNA when the most active complex trans,trans,trans-[Pt(N3)2(OH)2(PYridine)2], 8 was irradiated in the presence of short single strand oligonucleotides 14 bases in length. Complex 8 was found to bind to the oligonucleotides as a {Pt(pyridine)2}2+ adduct. Modifying the wavelength of activation from UVA to 420 nm had no effect on the type of adduct formed, but the higher energy irradiation achieved maximum levels of DNA platination more quickly. Changing the sequence of the oligonucleotide suggested that the photoactivated form of 8 does not favour the formation of the 1,2-(GpG) bisadduct formed by cisplatin and other clinically approved platinum based drugs, but may form 1,3-(GpNpG) or 1,3-(ApNpG) adducts, as is the case with other trans-platinum complexes. Chiral chromatography using cellulose- and amylose-based stationary phases successfully separated the enantiomers of a series of organometallic 'piano stool' anticancer complexes. This appears to be the first successful separation of facially chiral Ru(II) arene complexes, the enantiomers of which were stable in solution for over 3 h. In contrast, separated cyclopentadienyl WI) complexes with chiral metal centres epimerized within 2 h in solution at ambient temperature. Under similar conditions the enantiomers of the Os(II) arene complex [Os(n6-p-cym)(4-(2-pyridylazo)-N,N-dimethylaniline)Ir remained stable, as did those of the ruthenium-based complex [Ru(9,10- diydrophenanthrene)(en)C1r. It was shown that it is possible to separate the diasteriomers of [Ru(t)6-para-cymene)(iminopyridine)I], that can also be resolved by crystallisationtechniques, and hence, decrease the time required to separate the enantiomers. This work will therefore allow exploration of the biological properties of some of these enantiomers A novel technique for the rapid irradiation and detection of light¬senstive species was developed. Photonic crystal fibers (PCFs) were coupled to a mass spectrometer using HPLC tubing and fittings. This continuous flow method of analysis was validated using the photaquation of cyanocobalamin. The PCF system was compared to the conventional cuvette-based approach. No significant difference in the species detected by MS could be found, but the PCF system had the advantage of requiring 20 times less sample (25 pL), and only 15 min of irradiation compared to 10 h by conventional methods. The new PCF-MS system was then used to study the interaction of the photoactivateable ruthenium-based drug [{(e-indan)RuC1}201-2,3-dPa2+ with a range of small molecules that acted as models for intracellular components, e.g. 5'GMP for DNA. The nucleobase binding properties were consistent with those previously reported with plasmid DNA by Magennis et al: a small amount of binding took place in the dark in view of the aquation of the mondentate leaving groups but this dramatically increased upon photoactivation and loss of the arene ligands. The complex was also found to bind to glutathione (GSH), which is known to detoxify metal-based drugs, an observation possibly explaining its poor anticancer activity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RS Pharmacy and materia medica