Modifications of protoporphyrin IX fluorescence during ALA-based photodynamic therapy of endometriosis

Modifications of the porphyrin fluorescence during photodynamic treatment of ovarian cells, endometrial adenocarcinoma cells and rat uterus after administration of the porphyrin precursor δ-aminolevulinic acid and exposure with 630 nm laser radiation have been studied. The intracellular and intratissue fluorescence was excited with 407 nm radiation of a krypton ion laser and detected by spectral microscopic imaging using a modified microscope equipped with a slow-scan cooled camera and a liquid crystal filter. In particular, singlet oxygen induced effects due to photobleaching as well as formation of chlorin-type fluorescent photoproducts were detected at around 500, 630 and 670 nm. The photodynamically induced fluorescence modifications were found to vary between cell types. The major fluorescence peak of PP IX was photobleached 63% by a phototoxic fluence of about 20-40 J/cm 2 in cells and within rat endometrium. Higher fluences were required to bleach the fluorescence at around 670 nm due to the formation of fluorescent photoproducts. No significant photoinduced modifications of autofluorescence occurred around 500 nm. © 2006 Elsevier GmbH. All rights reserved.