A Spectroscopic Study on Nanosensors and Porphyrins for Bioimaging

Abstract

Luminescence imaging has grown in development and research over recent years and the desire to expand within the area has increased with it.

The development of PEBBLEs (Probes Encapsulated By Biologically Localised Embedding), luminescent optical nanosensors, presents a new possibility for cellular imaging due to their nanoscale nature. Derivatives of this system have shown great potential in the field of biological imaging as non-invasive probes. Investigations into the photophysical properties of various dyes incorporated into PEBBLEs have been reported in the recent literature, in an attempt to characterise and better understand the system.

This thesis contains the photophysical properties of a series of PEBBLE based optical nanosensors. The work has been presented in sections according to their application or prioritised characteristic.

The first results chapter, Chapter 3, details the photophysical characteristics of a ratiometric pH sensing nanoparticle and the various development steps achieved, looking at how the fluorophores change on entrapement within the polyacrylamide matrix.

Chapter 4 describes the calcium sensing nanoparticles developed, specifically with and without photosensitising porphyrins conjugated to the exterior of the PEBBLE, making probes capable of reporting changes in calcium flux with reactive oxygen species.

Chapter 5 discusses the ability to incorporate hydrophobic fluorophores within the polyacrylamide nanoparticles, and thus introducing their solubility within aqueous solutions.

The more general topic of the luminescence emission properties of porphyrins is covered within Chapter 6 looking at the trication derivative of two well-known porphyrins, TMPyP and ZnTMPyP, and any changes they exhibit in different environments. These form the basis for the porphyrins that were initially introduced to nanoparticles as they are commonly used as examples of the complex structure of porphyrins today.

Finally the results in Chapter 7 detail the photophysical properties of four platinum and palladium porphyrins and their respective nanoconjugates that were synthesised with the application of oxygen sensing in mind.

Chapters 1, 2, 8 and 9 detail a general overview or introduction to the topics discussed, any experimental methods used within, the overall conclusions drawn with an emphasis on future work and an experimental section, respectively.