Ultraviolet A (UVA) radiation has been known to generate reactive oxygen species, such as singlet oxygen, in skin, leading to the oxidation of lipids and proteins. This oxidation influences cellular metabolism and can trigger cellular signaling cascades, since cellular membranes and the stratum corneum contain a substantial amount of fatty acids and lipids. Using highly sensitive IR-photomultiplier technology, we investigated the generation of singlet oxygen by fatty acids and lipids. In combination with their oxidized products, the fatty acids or lipids produced singlet oxygen under UVA radiation at 355 nm that is directly shown by luminescence detection. Linolenic or arachidonic acid showed the strongest luminescence signals, followed by linoleic acid and docohexaenoic acid. The amount of singlet oxygen induced by lipids such as phosphatidylcholine was significantly higher compared to the corresponding fatty acids within phospholipids. This result indicates a synergistic process of oxygen radicals and singlet oxygen during irradiation. UVA radiation initiates singlet oxygen generation, which subsequently oxidizes other fatty acids that in turn produce additional singlet oxygen. This leads to an enhancement of UVA-induced damage of fatty acids and lipids, which must enhance the oxidative damages in cells.
Singlet oxygen plays a major role in photodynamic inactivation of tumor cells or bacteria. Its efficacy depends critically on the oxygen concentration [O2], which can decrease in case oxygen is consumed caused by oxidative reactions. When detecting singlet oxygen directly by its luminescence at 1270 nm, the course of the luminescence signal is critically affected by [O2]. Thus, it should be feasible to monitor oxygen consumption during photo-oxidative processes. Singlet oxygen was generated by exciting a photosensitizer (TMPyP) in aqueous solution (H2O or D2O) of albumin. Chromatography shows that most of the TMPyP molecules are unbound, and therefore singlet oxygen molecules can diffuse in the solution. A sensor device for oxygen concentration revealed a rapid decrease of [O2] (oxygen depletion) in the solution during irradiation. The extent of oxygen depletion in aqueous albumin solution depends on the radiant exposure and the solvent. When detecting the luminescence signal of singlet oxygen, the shape of the luminescence signal significantly changed with irradiation time. Thus, local oxygen consumption could be monitored during photodynamic action by evaluating the course of singlet oxygen luminescence.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.