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- Title
Irradiation-Induced Enhancement of Pc 4 Fluorescence and Changes in Light Scattering are Potential Dosimeters for Pc 4-PDT.
- Authors
Ken Kang-Hsin Wang; Wilson, Jeremy D.; Kenney, Malcolm E.; Mitra, Soumya; Foster, Thomas H.
- Abstract
Phthalocyanine 4 (Pc 4) is a promising photosensitizer currently in clinical trials. Photobiological responses to Pc 4 photodynamic therapy (Pc 4-PDT) have been characterized extensively, but relatively little has been done to evaluate dose metrics for this sensitizer. We describe an irradiation-induced increase in fluorescence in tumor cell monolayers. This increase is due solely to enhanced fluorescence from Pc 4, as confirmed by confocal spectroscopy. In EMT6 cells incubated with 250 n M Pc 4 for 24 h, the maximum increase in fluorescence is approximately 3.7-fold above baseline levels. This increase occurs over a range of fluences, 0.05 – 0.6 J cm−2, where clonogenic survival decreases by 3 orders of magnitude. Light scattering measurements performed on similarly treated EMT6 cells in suspension suggested a Pc 4-PDT-mediated mitochondrial swelling of approximately 13% at 0.6 J cm−2, where fluorescence enhancement saturates under these treatment conditions. Fluorescence imaging and light scattering experiments performed at a five-fold lower Pc 4 incubation concentration revealed a reduced fluorescence enhancement at a five-fold higher fluence, which produced comparable mitochondrial swelling. Taken together, these data suggest that Pc 4 is initially aggregated at high local concentration in mitochondria and that irradiation relaxes the quenching of Pc 4 fluorescence through a mechanism that may involve mitochondrial swelling.
- Publication
Photochemistry & Photobiology, 2007, Vol 83, Issue 5, p1056
- ISSN
0031-8655
- Publication type
Academic Journal
- DOI
10.1111/j.1751-1097.2007.00128.x