Normal biological function is supported by strict homeostatic regulation and aberrant cellular conditions, where this homeostasis is disrupted, are associated with disease states such as cancer. Small molecule sensors represent powerful tools for the investigation of normal cellular processes and disease progression that have enabled detection of a broad spectrum of biological analytes. Alkyne tagged Raman imaging (ATRI) represents a promising alternative to fluorescence microscopy for the visualisation of intracellular analytes. Raman probes are inherently ratiometric and show discrete spectral profiles before and after reaction with analytes, which has facilitated the quantitative detection of several intracellular species. The determination of intracellular carboxylesterase (CE) activity has typically been achieved using fluorescence microscopy but this approach is hindered by the on/off nature and poor synthetic tractability of the probes required. In Chapter 2, the development of the first Raman CE sensor is described. Bisarylbutadiyne (BADY) probe esters showed different alkyne stretching frequencies (νalkyne) before and after reaction with CEs, which enabled the ratiometric detection of CE activity in live and fixed HepG2 cell populations. The sensor, in combination with spectral phasor analysis (SPA), was then used to assess the viability of healthy and UV-irradiated cells within the same field of view. Intracellular redox states have been quantified using fluorescent methods and surface enhanced Raman spectroscopy (SERS) through detection of glutathione (GSH), the cells prominent redox buffer, or through quantitative assessment of the local reduction potential. In Chapters 3–5, the development of small molecule Raman sensors for the determination of cellular redox states is described. We investigated the effect of structural and electronic changes to BADY scaffolds on the utility of compounds as intracellular sensors. The solubility, sensitivity, reversible reactivity and Δνalkyne value of the probes was examined to inform the development of subsequent sensors. Alkyne-based probes possessing Michael acceptors showed different νalkyne values before and after reaction with thiol species, which indicated the potential of the scaffold for GSH sensing. Redox active BADY sensors were also developed, for which the reduced and oxidised forms showed different alkyne profiles. These compounds hold promise for the quantification of reduction potentials across the cellular landscape.
| Date of Award | 28 Mar 2025 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | EPSRC (Engineering and Physical Sciences Research Council) |
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| Supervisor | Nick Tomkinson (Supervisor) & Robert Edkins (Supervisor) |
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