Multiphoton versus single-photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells

Theo A. Roelofs; Georgi Graschew; Marc Schneider; Stefan Rakowsky; Hanns-joerg Sinn; Peter M. Schlag

doi:10.1117/12.424562

24 April 2001 Multiphoton versus single-photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells

Theo A. Roelofs, Georgi Graschew, Marc Schneider, Stefan Rakowsky, Hanns-joerg Sinn, Peter M. Schlag

Author Affiliations +

Proceedings Volume 4262, Multiphoton Microscopy in the Biomedical Sciences; (2001) https://doi.org/10.1117/12.424562
Event: BiOS 2001 The International Symposium on Biomedical Optics, 2001, San Jose, CA, United States

Abstract

In laser-induced fluorescence diagnosis and photodynamic therapy of cancer the applied photosensitizers (PS) are often covalently derivatized with macromolecules to improve their selective accumulation in the cancerous tissue, while maintaining its single-photon excited photophysical properties. In this contribution methoxy-polyethylene glycol (MPEG, MW ~5 kDa) and human serum albumin (HSA, MW ~60 kDa) are used as PS carriers. Multiphoton (MP) excitation of the PS is favorable as compared to single-photon excitation because the penetration depth of the laser light is improved (>5 mm) due to the longer wavelength of the ~200 fs laser pulses used in this case (700-1050 nm). In this study cotton fibers and silica gel beads (<20 mm) were stained with various PS and multiphoton-induced fluorescence was detected with a MP laser scanning microscope. The slopes of the log-log plots of the detected fluorescence intensity versus the laser excitation intensity vary between 1.8-2.6 for the various PS investigated. The excitation wavelength dependence of the MP-induced fluoresence indicates that the excitation cross section maxima can be shifted substantially relative to twice the wavelength of the one-photon absorption maxima. Some PS (photofrin II, purpurin, mTHPC-[MPEG]2 and diaminoanthra-quinone) do not exhibit multiphoton-induced fluorescence. Some derivatized PS (sulforhodamine B, erythrosin B, purpurin) exhibit MP-induced fluorescence, although no single-photon absorption band exists in the spectral region around half the excitation wavelength

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Theo A. Roelofs, Georgi Graschew, Marc Schneider, Stefan Rakowsky, Hanns-joerg Sinn, and Peter M. Schlag "Multiphoton versus single-photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells", Proc. SPIE 4262, Multiphoton Microscopy in the Biomedical Sciences, (24 April 2001); https://doi.org/10.1117/12.424562

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