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Journal of Biomedical Optics

Intracellular kinetics of ATX-S10·Na(II) and its correlation with photochemical reaction dynamics during a pulsed photosensitization process: effect of pulse repetition rate
Author(s): Satoko Kawauchi; Shunichi Sato; Yuji Morimoto; Makoto Kikuchi
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Paper Abstract

Although photodynamic therapy with pulsed light excitation has interesting characteristics, its photosensitization mechanism has not been fully elucidated. In this study, we showed that the intracellular kinetics of ATX-S10·Na(II), a lysosomal sensitizer, was closely related to photochemical reaction dynamics during photodynamic treatment of A549 cells with nanosecond pulsed light. Fluorescence microscopy revealed that at high frequencies of 10 and 30 Hz the sensitizer initially localized mainly in lysosomes but that it started to be redistributed to the cytosol in certain ranges of radiant exposures. These ranges were found to coincide with a regime of fluorescence degradation with limited oxygen consumption. On the other hand, at 5 Hz, there was no such a discontinuous behavior in the sensitizer redistribution characteristics throughout the period of irradiation; this was consistent with the fact that no reaction switching was observed. Two possible reasons for the appearance of the regime with limited oxygen consumption are discussed: participation of an oxygen-independent reaction and change in the microenvironment for the sensitizer caused by lysosomal photodamage. The pulse frequency-dependent intracellular kinetics of the sensitizer also explains our previous results showing higher cytotoxicity at 5 Hz than at 10 and 30 Hz.

Paper Details

Date Published: 1 January 2006
PDF: 9 pages
J. Biomed. Opt. 11(1) 014005 doi: 10.1117/1.2160387
Published in: Journal of Biomedical Optics Volume 11, Issue 1
Show Author Affiliations
Satoko Kawauchi, National Defense Medical College (Japan)
Shunichi Sato, National Defense Medical College (Japan)
Yuji Morimoto, National Defense Medical College (Japan)
Makoto Kikuchi, National Defense Medical College (Japan)

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