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Proceedings Paper

Uptake, retention, and phototoxicity of cationic phenoxazines photosensitizers in tumor cells in culture
Author(s): Chi-Wei Lin; Janine R. Shulok; Yau Kai Wong; Louis Cincotta; James W. Foley
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Paper Abstract

Phenoxazine dyes, including several Nile blue analogs, are known to localize selectively in animal tumors. In general, oxazine dyes have low photo-reactivity due to inefficient singlet4riplet crossover of excited states. Structural modifications have yielded a series of halogenated, thia- or phenyl-substituted analogs with different pKa's, hydrophobicities and singlet oxygen yields. In this study, possible correlations of these properties to the uptake, retention and photosensitization activity of these oxazines were examined in a human bladder tumor cell line (MGH..Ul) in culture. The effectiveness of these derivatives in causing photo-killing of tumor cells in vitro, as determined by colony forming assay, correlated well with their singlet oxygen yields indicating that this is likely to be the main mechanism for the photocytotoxicity. Using the derivative with the highest singlet oxygen quantum yield (0.821), over 90% cell kill was achieved at a dye concentration of 5x108 M, which is about 3 orders of magnitude more effective than HPD, indicating that some of these dyes can be potentially effective photosensitizers for tumor therapy. The rates of uptake and efflux do not correlate directly with the pKa's or partition coefficients. Yet the rapid influx and slow efflux of these dyes suggests that dye retention is not dictated by simple rule of diffusion but perhaps related to affinity of the dye with certain cellular components. Experiments with agents which alter cellular membrane potentials indicate that these dyes may have a different uptake mechanism than other cationic dyes in which membrane potentials play a significant role.

Paper Details

Date Published: 1 July 1990
PDF: 6 pages
Proc. SPIE 1203, Photodynamic Therapy: Mechanisms II, (1 July 1990); doi: 10.1117/12.17676
Show Author Affiliations
Chi-Wei Lin, Massachusetts General Hospital and Harvard Medical School (United States)
Janine R. Shulok, Massachusetts General Hospital and Harvard Medical School (United States)
Yau Kai Wong, Massachusetts General Hospital and Harvard Medical School (United States)
Louis Cincotta, Rowland Institute of Science Inc. (United States)
James W. Foley, Rowland Institute of Science Inc. (United States)

Published in SPIE Proceedings Vol. 1203:
Photodynamic Therapy: Mechanisms II
Thomas J. Dougherty, Editor(s)

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