19 July 1994 Direct phosphorescent detection of primary event of photodynamic action
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Highly phosphorescent photosensitizer Pd-tetra (o-methoxy-p-sulfo) phenyl porphyrin (Pd-MSPP) was used to follow the primary events of photodynamic action - quenching of triplet states by free oxygen in different systems: water solutions of proteins, cells and tissues in vivo and in vitro. The photosensitizer forms complexes with proteins in solutions and biosystems showing remarkable hypsochromic shifts of band and an increase of the quantum yield and lifetime of phosphorescence at the binding to proteins. In absence of oxygen the lifetime of phosphorescence is almost single exponential, and depends on the energy of lowest triplet state of the sensitizer. The photochemical quenching of the triplets by cell components is negligible. In presence of free oxygen the quenching of the sensitizer triplets takes place. The emission spectrum of singlet oxygen with maximum 1271 nm was recorded in water protein solutions and quantum yield of sensitized luminescence was measured. In the systems studied, oxygen consumption was detected and oxygen concentration was estimated in the course of photodynamics by an increase in photosensitizer phosphorescence lifetime, using laser flash photolysis technique. At least two exponential kinetics of the phosphorescence decay shows that the distribution of the free oxygen is not uniform in tissues.
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Anatoly P. Losev, Anatoly P. Losev, Valentin N. Knukshto, Valentin N. Knukshto, Ivan N. Zhuravkin, Ivan N. Zhuravkin, "Direct phosphorescent detection of primary event of photodynamic action", Proc. SPIE 2133, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy III, (19 July 1994); doi: 10.1117/12.179992; https://doi.org/10.1117/12.179992

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