Oxygen photosensitisation

Newest approaches to singlet oxygen photosensitisation in biological media... 

The process used in the treatment of patients by PDT involves the application of the photosensitiser, either topically or by systemic injection, which then selectively accumulates in the tumour (or lesion). In the next step low energy light is led into the tumour via a fibre optic, where it interacts with the sensitiser and oxygen, causing cell destruction. This is shown schematically in Figure 4.21. 

Type I involves the excited triplet state of the photosensitiser reacting with a substrate, by electron transfer or hydrogen abstraction, giving a radical. This radical reacts with triplet oxygen producing hydroperoxides, which initiate free radical autoxidation. 

Although there are many dyes which can photosensitise the production of singlet oxygen (see section 4.4.1), in PDT the first products of real interest came from haematoporphyrin. Subsequent, studies led to the haematoporphyrin derivatives HpD Stage 1 and Stage 11, which were found to be more active as PTD sensitisers as they localised preferentially in tumours. The first commercially available sensitiser, Photofrin, is based on processed material from HpD Stage 11, and is a complex mixture of monomeric, dimeric and oligomeric e.g. hexamer) porphyrins, in an... 

Harriman, A. et al. (1989) Metallotexaphyrins a new family of photosensitisers for efficient generation of singlet oxygen, Chem. Commun. 314-316. 

Kovalev D, Fujii M. Silicon nanocrystals photosensitised for oxygen molecules. Adv Mater 2005 17 2531 14. 

The photosensitised oxygenation of 5a- and 5 S-cholest-3 enes (8 and 10), and subsequent reduction of hydroperoxy-. 

Porphyrins and related tetrapyrrole macrocyclic ligands are one of the most prominent ligand types in coordination chemistry. Their occurrence in metallo-enzymes, their application as inorganic dyes and photosensitisers, their use as homogeneous catalysts, mainly for oxidation or oxygenation reactions, and their outstanding role in coordination chemistry is in general well documented. ... 

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