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Effects of the Oxygenation Level on Formation of Different Reactive Oxygen Species During Photodynamic Therapy
Author(s) -
Price Michael,
Heilbrun Lance,
Kessel David
Publication year - 2013
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12027
Subject(s) - singlet oxygen , chemistry , radical , oxygenation , oxygen , photobleaching , photochemistry , photodynamic therapy , reactive oxygen species , organic chemistry , biochemistry , fluorescence , physics , quantum mechanics , biology , ecology
We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage, but via different photochemical pathways. Upon irradiation, the chlorin termed NP e6 forms singlet oxygen in high yield while the bacteriopheophorbide WST 11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST 11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilling by NP e6 was unaffected. Studies in a cell‐free system revealed that the rates of photobleaching of these agents, as a function of the oxygenation level, were correlated with results described above. Moreover, the rate of formation of oxygen radicals by either agent was more sensitive to the level of oxygenation than was singlet oxygen formation by NP e6. These data indicate that the photochemical process that leads to oxygen radical formation is more dependent on the oxygenation level than is the pathway leading to formation of singlet oxygen.