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Proceedings Paper

Multiphoton excitation and photodynamic activity of macromolecular derivatized mTHPC
Author(s): Marc Schneider; Georgi Graschew; Theo A. Roelofs; Evangelos Balanos; Stefan Rakowsky; Hanns-joerg Sinn; Peter M. Schlag
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Paper Abstract

Multiphoton excitation of photosensitizers in photodynamic therapy constitutes a promising approach, because of the increasing tissue penetration for longer wavelength of illumination. In this contribution the photodynamic activity of polyethylene glycol macromolecular derivatized mTHPC upon two-photon excitation is established. To test the photo- activity of the photosensitizer, human colon carcinoma cells, HCT-116, were incubated with 2 (mu) g/ml of mTHPC- CMPEG4 in the nutrition medium. Subsequent pulsed laser irradiation at 784 nm focused down on growing cell monolayers restricts cell vitality clearly within 24 hours after irradiation. To investigate whether an anoxic or euoxic energy transfer mechanism is involved, a uric acid assay was performed to test for the generation of singlet oxygen. Upon single-photon excitation mTHPC-CMPEG4 in TriPEG decomposed uric acid via the generation of singlet oxygen. Using femtosecond pulsed laser irradiation no decomposition of the uric acid was found, implying an anoxic energy transfer mechanism after tow-photon excitation. However, at present, we cannot exclude local hyperthermic effects in the cells containing the photosensitizer to contribute to the photodynamic activity upon two-photon excitation.

Paper Details

Date Published: 29 March 2000
PDF: 6 pages
Proc. SPIE 3909, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy IX, (29 March 2000); doi: 10.1117/12.379882
Show Author Affiliations
Marc Schneider, Academic Hospital Charite of the Humboldt Univ. Berlin and Max Planck Institute of Colloid (Germany)
Georgi Graschew, Academic Hospital Charite of the Humboldt Univ. Berlin (Germany)
Theo A. Roelofs, Academic Hospital Charite of the Humboldt-Univ. Berlin (Germany)
Evangelos Balanos, Academic Hospital Charite of the Humboldt Univ. Berlin (Germany)
Stefan Rakowsky, Academic Hospital Charite of the Humboldt Univ. Berlin (Germany)
Hanns-joerg Sinn, German Cancer Research Ctr. (Germany)
Peter M. Schlag, Academic Hospital Charite of the Humboldt Univ. Berlin (Germany)


Published in SPIE Proceedings Vol. 3909:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy IX
Thomas J. Dougherty, Editor(s)

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