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Proceedings Paper

Photodynamic therapy and knocking out of single tumor cells by multiphoton excitation processes
Author(s): Iris Riemann; Peter Fischer; Karsten Koenig
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Paper Abstract

Near infrared (NIR) ultrashort laser pulses of 780 nm have been used to induce intracellular photodynamic reactions by nonlinear excitation of porphyrin photosensitizers. Intracellular accumulation and photobleaching of the fluorescent photosensitizers protoporphyrin IX and Photofrin (PF) have been studied by non-resonant two-photon fluorescence excitation of PF and aminolevulinic acid (ALA)-labeled Chinese hamster ovary (CHO) cells. To testify the efficacy of both substrates to induce irreversible destructive effects, the cloning efficiency (CE) of cells exposed to femtosecond pulses of a multiphoton laser scanning microscope (40x/1.3) was determined. In the case of Photofrin accumulation, CEs of 50% and 0% were obtained after 17 laserscans (2 mW?, 16 s/ frame) and 50 scans, respectively. All cells exposed to 50 scans died within 48h after laser exposure. 100 scans were required to induce lethal effects in ALA labeled cells. Sensitizer-free control cells could be scanned 250 times (1.1 h) and more without impact on the reproduction behavior, morphology, and vitality. In addition to the slow phototoxic effect by photooxidation processes, another destructive but immediate effect based on optical breakdown was induced when employing high intense NIR femtosecond laser beams. This was used to optically knock out single tumor cells in living mice (solid Ehrlich-Carcinoma) in a depth of 10 to 100 μm.

Paper Details

Date Published: 10 September 2004
PDF: 7 pages
Proc. SPIE 5462, Biophotonics Micro- and Nano-Imaging, (10 September 2004); doi: 10.1117/12.545583
Show Author Affiliations
Iris Riemann, Fraunhofer-Institut fur Biomedizinische Technik (Germany)
Peter Fischer, JenLab GmbH (Germany)
Karsten Koenig, Fraunhofer-Institut fur Biomedizinische Technik (Germany)
JenLab GmbH (Germany)

Published in SPIE Proceedings Vol. 5462:
Biophotonics Micro- and Nano-Imaging
Dario Anselmetti, Editor(s)

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