Photosensitizers and singlet oxygen

While the correlation of in vitro photosensitization and singlet oxygen yield was good, exceptions were noted for compounds with low pKa values (near 5.0). Thus, at pH 7.4 (cell culture medium), these compounds exist primarily in the unprotonated imine form. It was shown that this form of the dyes is taken up poorly by the cells. However, it should be noted also that the neutral forms of these compounds absorb near 500 nm, with about half the extinction coefficient of the protonated forms absorbing near the mid-600nm range. 

Bartusik D, Aebisher D, Ghogare A, Ghosh G, Abramova I, Hasan T, Gtcct A (2013) A fiberoptic (photodynamic therapy t) pe) device with a photosensitizer and singlet oxygen delivery probe tip for ovarian cancer cell killing. Photochem Photobiol 89 936-941... 

Foote, C., Photosensitized oxidation and singlet oxygen conseqnences in biological systems, in Free Radicals in Biology, Pryor, W.A., Ed., Academic Press, New York, 1976. 

Wang S, Gao R, Zhou F, Selke M (2004) Nanomaterials and singlet oxygen photosensitizers potential applications in photo dynamic therapy. J Mater Chem 14 487-493... 

Ketones Aliphatic ketones formed by autoxidation of lipids also contribute to the flavor of oils and food products. For example, Guth and Grosch (13) identified l-octen-3-one as one of the odor-active compounds in reverted soybean oil. This compound was described as metallic and mushroom-like. The reaction pathway for the formation of l-octen-3-one from the linoleate-10-hydroperoxide via the p-scission route is illustrated in Figure 2. 10-Hydroperoxide of linoleate is not the usual hydroperoxide formed by autoxidation of linoleate however, it is one of the major hydroperoxides formed by the photosensitized oxidation (singlet oxygen reaction) of linoleate (14). 

Fluoroquinolones such as ofloxacin, enoxacin, lomefloxacin and ciprofloxacin have been shown to cause cutaneous phototoxicity and photosensitivity in mice induced by oral administration followed by ultraviolet-A irradiation. These reactions have further been shown to be mediated via reactive oxygen species such as hydroxyl radicals and singlet oxygens and not by generation of toxic photoproducts (44). 

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