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Proceedings Paper

Role of oligomers/aggregates of amphiphilic sensitizers for fluorescent visualization of tumor tissue: investigation of the interaction of haematoporphyrin derivative and Photosan with membranes
Author(s): Ronald Wendenburg; Peter Brakhage; W. Dietel
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Paper Abstract

The most frequently used drug for the fluorescent visualization and photosensitization of tumors is haematoporphyrin derivative (HpD). However, the mode of action of this sensitizer in vivo is not yet entirely understood. From the Photodynamic Therapy it is well known that their efficiency and selectivity increases with increasing amounts of oligomers/aggregates. The 'highly aggregated' HpD (Photofrin II) is also used in the fluorescence diagnostics. However, from the investigation of porphyrins it is known that the oligomers/aggregates fluorescent weakly compared with monomers. The monomers as well as linear chains of monomers (linear dimers and special forms of trimers) have longer fluorescence lifetimes and hence higher quantum yields required for effective fluorescence diagnostics. This discrepancy stimulates the studies of the interaction of HpD containing high concentrations of tumor localizing fraction with membranes and membrane like-structures. The interaction has been investigated by means of fluorescence (OMA-system) and absorption spectroscopy. The results obtained lead to the conclusion that the monomers form the aqueous phase and/or self-associated aggregates which are in equilibrium with the monomers are taken up by the membranes only to a small degree compared with chemically bound oligomers. On the other hand, oligomers are incubated and defolded, and this leads to an increasing amount of linear polymers/monomers in the membranes versus incubation time. This seems to be the dominating process in the fluorescent visualization of cells and tissue, including tumor tissue, when HpD, Photosan or other amphiphilic porphyrins are applied.

Paper Details

Date Published: 4 January 1995
PDF: 8 pages
Proc. SPIE 2324, Optical Biopsy and Fluorescence Spectroscopy and Imaging, (4 January 1995); doi: 10.1117/12.198732
Show Author Affiliations
Ronald Wendenburg, Jena Univ. (Germany)
Peter Brakhage, Jena Univ. (Germany)
W. Dietel, Jena Univ. (Germany)

Published in SPIE Proceedings Vol. 2324:
Optical Biopsy and Fluorescence Spectroscopy and Imaging
Rinaldo Cubeddu; Renato Marchesini; Serge R. Mordon; Katarina Svanberg M.D.; Herbert H. Rinneberg; Georges A. Wagnieres, Editor(s)

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