The AOPs are based on oxidizing radicals, mainly hydroxyl radicals, while other radicals and active oxygen species such as superoxide radical anions (*O2 ), hydroperoxy radicals (HO2 ), triplet oxygen
(3O2) and organic peroxyl radicals (R-O-O*) are also involved .
Ideally the trapping compound should meet certain conditions such as being water soluble, highly reactive with singlet oxygen, and unreactive with other oxygen species such as triplet oxygen
Nevertheless, both UVA and UVB as well as visible light convert various photosensitizing compounds to excited states which transfer energy to triplet oxygen, thereby generating reactive oxygen species, particularly singlet oxygen.
The triplet carbonyls can transfer energy to triplet oxygen, thereby generating singlet oxygen .
2]) and triplet oxygen may also oxidize 16 to quinone 18, with formation of [sup.
One of the latter aldehydes may be in the triplet state and thus may be a source of energy for conversion of triplet oxygen to singlet oxygen.
ABLADE will aim is demonstrate the efficacy of a novel photo-therapy based on the stimulation of triplet oxygen
at a cellular level which can initiate cell apotosis specifically in tumour cells.
Polyphenols are able to neutralize free radicals, scavenge singlet and triplet oxygen
, and to break down peroxides.
For example singlet oxygen can be produced by a reaction between the dissolved triplet oxygen
and the excited triplet state of erythrosine B.
is a good energy acceptor and it can be excited to its singlet state by energy transfer from a photosensitizer.