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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

An investigation into the electrogenerated chemiluminescence of near-infrared quantum dots for application in biomedical sensing

Stewart, Alasdair J. January 2014 (has links)
The objective of this work is two-fold; investigation of the electrochemical and electrochemiluminescent (ECL) properties of near-infrared (NIR) quantum dots (QDs) in buffer and whole blood; and their subsequent incorporation into ECL biosensing systems with potential application in whole blood analysis. QDs exhibited size-dependent optical and electrochemical properties with the largest QDs demonstrating ECL emission in the NIR region (811 nm). This should improve light penetration through whole blood, a prediction that has not yet been investigated for the ECL process. NIR QDs were shown to be flexible ECL emitters and optimisation of system parameters was implemented to obtain maximum ECL performance. This was achieved using a QD-chitosan film on a glassy carbon electrode with potassium persulfate co-reactant in phosphate buffered saline at pH 7.4. Intense reductive and oxidative ECL signals were generated directly in whole blood, which was at least ten times more intense than t hat achieved using visible region emitting QDs. The response exhibited sensitivity to blood samples spiked with clinically relevant analytes, homocysteine and dopamine, establishing the viability of NIR ECL as a detection method from whole blood. To expand the integration of NIR QDs into biosensing systems, a selective biosensor for cholesterol was developed that exhibited good stability, specificity and a clinically relevant linear range (1-5 mM). Detection in human serum was possible, however, radical quenching in whole blood limited its use as a biosensor in this environment in its current form, demonstrating the complications that can arise with analysis from such a complex matrix. For that reason, an alternative biosensor design that used conditions optimised in earlier work was used to improve system sensitivity. Fabrication of an immunosensor for IgG resulted in an ECL signal that was detected in whole blood. Following significant development, it is envisaged such a system can form the basis of a new generation of NIR ECL biosensors capable of detection directly from whole blood.
182

Alkali metal zincate chemistry : the importance of structure and stoichiometry on reactivity

Herd, Emma January 2014 (has links)
Focusing on the area of cooperative bimetallic reagents, this report aims to advance our understanding on the construction and reactivity of alkali metal zincates. Extending previous studies on the synthesis of dialkyl(amido)zincates, unsolvated lithium zincate [LiZn(HMDS)Me₂] 4a was prepared by a cocomplexation approach, and its interaction with a range of Lewis basic solvents of varying denticity was examined. The effect of these donors on constitution and stability was assessed, resulting in the determination of a novel dialkyl(amido)zincate, [(PMDETA)LiZn(HMDS)Me₂] 5, containing an unusual terminal amido ligand. The influence of the amido group in these mixed-metal systems was also studied. Using the amide [NHDipp]⁻, a new family of lithium zincates has been synthesised, leading to the characterisation of the first dialkyl(amido)zincates based on a primary amide - [(PMDETA)LiZn(NHDipp)Me₂] 10 and [(THF)₃LiZn(NHDipp)(Me)₂] 11. X-ray crystallographic studies evidenced that, depending on the donor solvent employed, novel zincate formulations can be accomplished - as demonstrated by the isolation of the unprecedented zinc-rich zincate [LiZn₂(NHDipp)₂(Me)₃(THF)₃] 12, containing an unusual 2:1 zinc to lithium ratio. By synthesising the homoaryl lithium zincates [LiZnPh₃] 15 and [Li₂ZnPh₄] 16, and investigating their reactivity towards several electron-deficient N-heterocycles, a new transition metal free method enabling the efficient, regioselective arylation of acridine has been developed. Isolation of key reaction intermediates such as [(THF)₃Li(NC₁₃H₉-9-Ph)] 17, has provided important clues as to how these bimetallic systems operate. The reactivity of trimetallic mixtures based on [Zn(OPiv)₂·2LiCl] 27 and ArMgCl towards N-heterocyclic molecules was also investigated. Although unreactive towards arylation, new light has been shed on the constitution, reactivity and stability of these multi-component reagents. Finally, the bulky bis(amido)silyl ligand [Ph₂Si(NDipp)²⁻] has been successfully incorporated into two novel zincates, [{Na(THF)₆}+{(Ph₂Si(NDipp)₂)ZnEt}⁻] 29 and [(Ph₂Si(NDipp)₂)Zn(TMP)Na(THF)] 30, which have been employed in the regioselective zincation of benzothiazole and pyrrole, yielding the novel compounds [Na(THF)₂Zn(Btz)₃]₂ 31 and [Na₂(THF)₄Zn(NC₄H₄)₄]∞ 32.
183

Flexible access to an array of optically-enriched conformationally-locked bicyclic morpholines and approaching bridged bicyclic piperazines

Dunn, Rachael E. B. January 2014 (has links)
Over recent years, bridged heterocycles have emerged as desirable targets within the pharmaceutical industry. More specifically, pharmaceutical partners have become interested in exploring the bioactivity of bridged morpholines, as well as bridged piperazines. Despite the interest in these types of compounds, there is a lack of routes into these scaffolds which allow for diversification surrounding the core scaffold. Consequently, the focus of this study was to develop preparative access into these synthetically challenging, strained bicyclic 6,5-systems. The aim was for the developed routes to be practically accessible, robust, and indeed flexible, to allow a diverse array of compounds to be obtained. Initially, work focused on the synthesis of the bridged morpholine scaffold, with, in the first instance, a racemic route being targeted. The initial proposed bridged morpholine precursor, an (Sa(B,(Sb(B-unsaturated ester, was synthesised, however, the key final step to deliver the desired bridged morpholine proved to be unsuccessful. Following on from this, an alternative epoxide derivative was also prepared, but unfortunately did not deliver the corresponding bridged morpholine moiety. Following a series of computational studies, whereby the final (cyclisation) step for a variety of substrates was investigated, an alternative aldehyde precursor was explored. A successful synthesis to this compound was developed, and pleasingly this compound reacted to form the first bridged morpholine product within this programme. It was then shown that the route developed was sufficiently flexible to allow a further ten novel bridged morpholine compounds to be synthesised. Having developed a racemic synthesis, it was then decided to explore the possibility of performing the route asymmetrically. In this regard, the original racemic route was utilised with optically pure starting material, however, it was found that many steps in the racemic synthesis caused the original stereogenic center to epimerise. Through an extensive optimisation study, a route was established to deliver a key bridged morpholine scaffold without any appreciable loss in chirality. In addition, a key intermediate towards another further bridged morpholine scaffold was also obtained with an elevated enantiomeric ratio. The final part of this study focused on utilising the developed bridged morpholine synthesis to allow a range of bridged piperazines to be obtained. Although no bridged piperazines were synthesised, several key intermediates towards the desired piperazine series were obtained, which will allow for further research in this area to be continued.
184

2D and 3D optical imaging of SERS nanotags intracellularly

McAughtrie, Sarah January 2014 (has links)
Adoption of a multi-marker nanotag approach will led to better disease characterisation whilst simultaneously enabling targeting of multiple disease markers or organelles. The employed nanotag method controllably aggregated nanoparticles with 1,6-hexamethylene diamine (1,6-HMD), before polymer coating with polyvinylpyrrolidone (PVP) and labelling with small molecule reporters; 4-mercaptopyridine (MPY), 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), 4-nitrobenzenethiol (NBT) and 2-naphthalenethiol (2-NPT). Within a multiple component suspension reporters were identified by their unique peak and when present within single cells or populations they were additionally identified using component direct classical least squares (DCLS). Within a single cell three of the four components (MPY, DTNB and NBT) were positively identified. 2D SERS imaging can monitor nanotag uptake but it provides no conclusive evidence of cellular inclusion. The simultaneous determination of cellular uptake and nanotag identification was however achieved using combined 3D Raman and SERS imaging. Three of the four components were detected within a single cell and by combining 2D sections from the 3D images it was possible to determine their intracellular location. Determination of intracellular localisation was achieved using principal component analysis (PCA) since it resulted in the resolution of a subcellular compartment. However, the ultimate success of the system will only be realised when active targeting is demonstrated. Nanotags were functionalised with peptide sequences specific for the endoplasmic reticulum (ER) and trans-Golgi network (TGN). Both nanotag systems were found to locate within lipid rich regions of the cell but they could not be positively confirmed as the ER or TGN. To identify these structures and confirm localisation, further chemometric methods must be investigated including hierarchical cluster analysis (HCA). In conclusion, the SERS nanotags were suitable imaging agents for 2 and 3D cell interrogation. 3D imaging simultaneously permitted organelle resolution and the intracellular localisation of the SERS nanotags. Targeting systems were developed and in future work their localisation within organelles will be confirmed by the application of advanced chemometric methods.
185

High resolution Fourier transform infrared spectroscopy for the qualitative analysis of explosive precursors in the vapour phase

Carlysle, Felicity January 2014 (has links)
Fourier transform infrared spectroscopy (FTIR) has applications in many areas of forensic science. The ability to produce information rich spectra is of particular use for the characterisation and discrimination of materials. High resolution FTIR can produce even more detailed spectra and therefore improved characterisation and discrimination. However, the production of information rich spectra requires suitable statistical tools for analysis, with multivariate analysis often used. The mid infrared region contains the 'fingerprint region' which is used for the detection and identification of many different materials, and is therefore an area of investigation in the field of explosives detection. This research aimed to utilise high resolution mid infrared FTIR for the characterisation of explosive precursors in the vapour phase. Detailed examination of the spectra produced would provide information on spectral regions that could be applied as targets for detection systems, for example those based upon Quantum Cascade Lasers (QCLs). By building up detailed knowledge of the spectra produced by different materials this research aimed to determine the most suitable spectral regions for the identification of explosive precursors. In addition, this research aimed to investigate whether it was possible to use high resolution FTIR to discriminate between laboratory grade materials and their shop bought counterparts containing additives and impurities. Acetone, alcohols and hydrogen peroxide were analysed in this work. The research also aimed to determine whether brand discrimination was still viable following concentration of two hydrogen peroxide containing brands. The ability to identify that a material had been concentrated but tie it back to its brand would be of great significance for intelligence gathering. The findings of this research demonstrate that high resolution FTIR can successfully be applied to the characterisation of explosive precursors and, in combination with chemometric techniques, discriminate between different precursor brands even following concentration of the precursor material.
186

Determination and speciation of mercury in sediment and related samples from Greece and Scotland

Cavoura, Olga January 2014 (has links)
Mercury is a global pollutant. Research is needed to improve methods for Hg detection and improve understanding of its biogeochemical cycle and risks to human health. In this study, a simple, colorimetric method utilising the reaction of Hg with copper(I)iodide was characterised and adapted for screening marine samples, and the speciation and relationships of Hg with other sediment parameters in contaminated environments was examined. Field application of the colorimetric method indicated Hg concentrations in sediments from West Scotland, U.K., and Kifissos River, Greece, were below Canadian sediment quality guideline values of 0.13 and 0.17 mg/kg for marine and freshwater sediment respectively, whereas sediment from the Falkirk area of the Union Canal, U.K., and Elefsina Bay, Greece, had Hg concentrations above probable effect levels (0.49 and 0.7 mg/kg). Total sediment Hg concentrations, determined quantitatively using cold-vapour atomic absorption spectrometry (AAS), ranged from 0.220 to 2.96 mg/kg in Elefsina Bay. Concentration was influenced by proximity to nearshore pollution sources but was not found to vary seasonally or be related to sediment organic matter content. Sequential extraction indicated that Hg speciation - hence mobility - varied between sites. No Hg was detected in the fish Mugil Cephalus indicating no threat to humans from consumption. Total sediment Hg concentrations in the Union Canal ranged from 22 to 1200 mg/kg. Both sequential extraction and speciation analysis using thermodesorption AAS indicated that ca.>70% of the Hg present was mobile. Analysis by gas chromatography inductively coupled plasma mass spectrometry showed that the methylmercury content was <0.03% of the total Hg content. A negative relationship was found between total Hg concentration and % methylmercury (r² = 0.60). Ethylmercury was detected in the samples and weak positive relationships determined between methylmercury and ethylmercury and organic matter content, while low pH appeared to favoured the partitioning of methylmercury into the water column.
187

Flexible access to an array of enantiomerically-enriched oxabisipidines and their use as chiral ligands in asymmetric synthesis

Goldie, Laura January 2015 (has links)
A broad series of optically-enriched oxabispidine scaffolds incorporating a range aryl, heteroaryl, and alkyl side arms has been successfully prepared, utilising an optically-pure common oxazine intermediate and commercially available aldehydes. In efforts towards establishing efficient access to such molecules, a fully optimised route, which is amenable to the preparation of the optically-pure oxazine on a multigram scale, has been developed. In addition to the development of a general trifluoromethanesulfonic acid-activated intramolecular Mannich-type cyclisation protocol, which is accommodating to a wide range of aldehyde substrates, alternative conditions have also been developed for more challenging substrates. More forcing conditions utilising p-toluenesulfonic acid at elevated temperatures have been utilised for highly electron-rich aldehyde substrates, whereas the employment of a benzotriazole additive was required for enolisable alkyl aldehyde substrates. In addition to the broad range of bicyclic oxabispidines prepared under the conditions described, a more synthetically challenging and structurally complex tricyclic derivative has also been successfully prepared. Further to the investigations into the scope of the developed approach to the construction of such scaffolds, efforts to confirm the proposed Mannich-type cyclisation mechanism, both experimentally and computationally, are disclosed. Additionally, a number of NMR studies have been performed to confirm the stereochemistry of the family of oxabispidine derivatives. With a library of enantiomerically-enriched oxabispidines in hand, manipulation of the nitrogen functionalities was undertaken to allow the preparation of further oxabispidine derivatives, which could have potential applications as ligands in asymmetric synthesis, as well as derivatives of interest to pharmaceutical industry partners. Following this work, a programme of research centred on the utilisation of oxabispidine scaffolds within the arena of magnesium-mediated asymmetric deprotonation processes was undertaken. Initial investigations focused on the use of the phenyl-substituted bis-secondary oxabispidine, with studies into the formation of both the corresponding magnesium bisamide and lithium amide species. Such endeavours indicated that the chiral amine species must be introduced as the bis-HCl salt. Investigations into the use of such amide base species in the deprotonation of 4-tert-butylcyclohexanone to generate the corresponding enantioenriched enol phosphate product were undertaken. Whilst under lithium-mediated conditions, promising levels of enantioselectivity could be achieved (73:27 er at -78°C), only poor to moderate yields of the desired product were attained. Similarly poor reactivity was observed with the corresponding magnesium-amide base counterpart, with no improvement in the selectivity of the deprotonation process. Altering the substituent of the oxabispidine scaffold to incorporate a more electron-donating group, and therefore a potentially more reactive magnesium amide, did not lead to the desired increase in yield. Furthermore, with a view to increasing the reactivity of the oxabispidine magnesium amide system, the employment of Nmethylated oxabispidine derivatives, bearing both phenyl and methyl side arms, was studied to allow the generation of chelating alkyl magnesium amides. As with previous oxabispidine-derived magnesium amides, these base systems were screened in the deprotonation of 4-tert-butylcyclohexanone, but again only poor yields of the enol phosphate product were recovered (≤ 25% yield at room temperature) with no significant enantioselectivity being observed, despite significant experimental efforts.
188

Enzyme responsive nanomaterials for cancer applications

Kalafatovic, Daniela January 2014 (has links)
Expression levels of enzymes dictate the difference between health and disease in many cases, including cancer. This leads scientists to explore strategies to incorporate enzyme sensitivity in materials where the goal is to achieve dynamic and targeted changes in material properties to influence cancer cells. Peptide amphiphiles were designed (PhAc-FFAGLDD (1a) and GFFLGLDD (2a) and their expected products of enzyme cleavage PhAc-FFAG (1b) and GFFLG (2b)) such that, upon cleavage by a disease-associated enzyme, reconfigure from micellar aggregates to fibres. After the designed peptides (1a, 1b, 2a, 2b) were shown to be suitable for controlling the morphology of the supramolecular aggregates based on peptide length, hydrophobicity and charge, the enzyme triggered micelle to fibre transition was explored. Following this it was investigated whether the micelles were capable to perform as mobile vehicles for encapsulation and release of hydrophobic drugs. It was observed that the assembled fibres provide a scaffold for prolonged drug delivery due to the partial entrapment (localised depots) of the drug and the intrinsic biodegradable nature of peptide carriers themselves. The capacity of retention of doxorubicin in the hydrophobic core of the micelles followed by its entrapment in the fibres was exploited in the development of a method for visualisation of fibre formation around cancer cells. In vitro studies were performed on human cancer cell lines using different types of microscopy. MMP-9 activity was quantified in the mentioned cancer cell lines. In addition, preliminary toxicity studies of the designed peptides to cancer cells were performed. Being purely peptidic (compared to conventional aromatic or aliphatic peptide amphiphiles), these systems have the advantage of being non toxic to cells and can be used as carriers for doxorubicin in vivo. They are currently tested on animal models where the cancer growth is slowed down by administration of doxorubicin loaded peptides compared to doxorubicin only. Another, complementary system was investigated based on crosslinked polymer particles- microgels as a possible way to obtain enzyme responsive materials. Amine rich microgels, poly(VAM-co-BEVAME) were synthesised and functionalised post-polymerisation with peptides. Due to aggregation issues these systems were not further explored for biomedical applications.
189

Analysis of RNA stability in forensic specimens

McCallum, Nicola Ann January 2015 (has links)
Ribonucleic acid (RNA) analysis presents a unique, novel opportunity to answer a wide range of questions in forensic science. The dynamicity of the transcriptome has led to it being suggested as a novel source of diagnostic information in forensic pathology. However, RNA is exceptionally labile. This research has characterised the post-mortem degradation behaviour of tissue RNA in an animal model, the laboratory mouse; with the aim of identifying a post-mortem interval during which gene expression analysis provides informative and reliable results. It was extremely encouraging that over the three day post-mortem interval examined, the yield of RNA from skeletal muscle, kidney, liver and heart tissue did not fall to such a level that it became unanalysable. Interestingly, individual RNAs were found to exhibit unique decay behaviour during the post-mortem interval; some significantly more stable than others. In the tissues of mice decomposed at room temperature, RNAs remained stable for at least the first 12 hours post-mortem; after which the observed differential decay skewed their expression profiles. This poses an interpretational obstacle for gene expression data where an extended time lag exists between death and sampling, and highlights the requirement for future work to consider novel data normalisation strategies. Overall, it is suggested that using RNA degradation as an indicator of post-mortem interval is fraught with difficulties: such as its dependence on the environmental conditions (specifically ambient temperature), differential RNA decay behaviour between tissue types and storage media, and inherently strong variability between replicates.
190

The development of copper complexes as medical imaging agents

Dunbar, Lynsey January 2015 (has links)
Studies building on existing research into the development of in vivo oxidant sensors which could be used as magnetic resonance (MR) imaging agents for the early detection of oxidative stress have been carried out. A series of N₂S₂ copper macrocyclic systems have been synthesised building on previous studies. The compounds have been modified at various positions to further enhance the suitability of these species as magnetic resonance imaging agents. The modifications include the introduction of oxo and sulfur based pendant arms at the nitrogen donor atoms, the introduction electron withdrawing and electron donating groups at various positions on the ring and the use of softer donor atoms to produce an S₄ and S₃N system. The stability and suitability of the complexes were challenged using a number of techniques including spectrophotometric titrations, cyclic voltammetry and T₁ relation NMR. The stability of the copper centre of the macrocycles was challenged with a biologically relevant sequestration agent (bovine serum albumin). It was found that 5 coordinate copper macrocycles are the most stable. The electrochemical reversibility of the complexes was tested using cyclic voltammetry to identify which compounds were capable of redox reversibility. A sulfur based pendant arm complex (compound 52) showed promise. Studies using ascorbate and hypochlorite demonstrate that this compound will survive chemical reduction and re-oxidation returning an acceptable percentage reversibility. To assess the potential of all of the complexes for use as imaging agents, the effect of the complexes on the T₁ relaxation time was tested over a range of concentrations. This was compared with a Gd-DTPA control and original parent complex (compound 2). The modifications made very little difference to the T₁ relaxation times. Although the relaxivity is low the studies indicates that the modified complexes may have some viability for use and warrant further investigation.

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