PET imaging, using the bone tracer Na18F, allows the non-invasive location of atherosclerotic plaques that are at risk of rupture. However, the spatial resolution of PET is only 4-5 mm, limiting the mechanistic information this technique can provide. In this thesis, the use of fluorescence and Raman imaging to elucidate the mechanism of micro-calcification within atherosclerotic plaques has been investigated. A number of fluorescent probes to detect fluoride and calcium have been synthesised. One of the fluoride probes has been shown to be selective for fluoride however, the concentration of fluoride required to activate the probe is order of magnitudes higher than the amount of Na18F used for PET imaging making it problematic to use for future studies. On the other hand, a calcium probe has been shown to: selectively bind to hydroxyapatite (HAP); permit visualisation and quantification of HAP in both vascular and bone cell models; and effectively stain cultured aortic sections and whole mouse aorta for OPT imaging. Building on these preliminary data, fluorescence imaging and immunohistochemistry (IHC) imaging of both healthy and atherosclerotic tissue that were previously subjected to PET imaging, were successfully carried out showing the ability of the probe to detect HAP in human vascular tissue. IHC staining for Osteoprotegerin (OPG) and Osteopontin (OPN), two bone proteins recently detected in vascular tissue, showed the co-localization of OPG with the probe. Conversely, the OPN was shown to localize in areas surrounding high OPG and probe signal. To determine the exact composition of vascular calcification, Raman spectroscopy was also used. It is believed that the biosynthetic pathway to HAP passes through a series of transitional states; each of these has different structural characteristics which can be studied using Raman spectroscopy. In particular, HAP has a strong characteristic Raman peak at 960 cm-1. An increase in HAP concentration has been detected by Raman in both calcified cell models and aortic sections. When human vascular tissue was analysed, an additional peak at 973 cm-1 was present suggesting the presence of whitlockite (WTK) in this tissue as well as HAP.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:763969 |
| Date | January 2018 |
| Creators | Sim, Alisia Mara |
| Contributors | Hulme, Alison ; Dweck, Marc ; Nudelman, Fabio |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/33151 |
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