Porphyrins are ideal candidates for PDT (Photodynamic therapy). Their ability to localise preferentially in diseased tissue allows specific targeting of cancerous tissue in certain areas. In recent years, linking photosensitisers to sugar moieties has attracted great interest. Glycosylated porphyrins have increased solubility which enhances their uptake into cells, and also selectivity of the porphyrins. Cationic porphyrins have also been studied due their increased solubility and selective accumulation into mitochondria. In this project, we have successfully combined these two properties of water- soluble derivatives of porphyrins to enhance their efficacy as potential PDT agents. Thioglycosylated cationic porphyrins have been synthesised, characterised and their photocytotoxicity assays against human colorectal adenicarcinoma cells (HT-29) assessed. Metalloporphyrins on the other hand were synthesised with the intention of using them as molecular oxygen sensors. Oxygen-dependant changes in phosphorescence lifetime can be used to measure oxygen concentration in biological systems. A versatile method was developed which allowed palladium metal insertion into porphyrin macrocycles. The metalloporphyrins were synthesised, purified and analysed using TLC, MS, 'H NMR and UV spectroscopy. Further functionalisation of the metalloporphyrins was achieved by the selective substitution of the para-fluoro substituent of the pentafluorophenyl group with thiols. In this way, a range of palladium(II) porphyrins were synthesised. Failure of cells to internalise these porphyrins using conventional methods has prompted further considerations of encapsulating them in nanoparticles.