In Vivo mTHPC Photobleaching in Normal Rat Skin Exhibits Unique Irradiance-dependent Features¶
- 1 January 2002
- journal article
- Published by Wiley in Photochemistry and Photobiology
- Vol. 75 (3), 282-8
- https://doi.org/10.1562/0031-8655(2002)075<0282:ivmpin>2.0.co;2
Abstract
We report measurements performed on the normal skin of rats in vivo, which provide information on the photobleaching kinetics and mechanisms of the photosensitizer meso-tetrahydroxyphenyl chlorin (mTHPC). Loss of mTHPC fluorescence was monitored using in vivo fluorescence spectroscopy during photodynamic therapy (PDT) performed using 650 nm laser irradiation. The bleaching was evaluated for irradiances of 5, 20 and 50 mW cm(-2). Two distinct phases of mTHPC photobleaching were observed. In the first phase there was no obvious irradiance dependence in the loss of fluorescence vs fluence. The second phase was initiated by an irradiance-dependent discontinuity in the slope of the bleaching curve, after which the photobleaching rates showed an irradiance dependence consistent with an oxygen-dependent reaction process. To investigate the unusual shape of the in vivo bleaching curves, we measured the PDT-induced changes in O2 concentrations in mTHPC-sensitized spheroids irradiated with 2, 5 and 20 mW cm(-2) of 650 nm light. The oxygen concentration data indicated no unusual features within the range of fluences where the discontinuities in fluorescence were observed during in vivo spectroscopy. The fluorescence from the in vivo bleaching experiments thus reports a phenomenon that is not reported by measurements of the photochemical oxygen consumption in the spheroids.Keywords
This publication has 25 references indexed in Scilit:
- Photodynamic therapy with meta-tetrahydroxyphenylchlorin for basal cell carcinoma: a phase I/II studyBritish Journal of Dermatology, 2001
- Effects of Fluence Rate on Cell Survival and Photobleaching in Meta-Tetra-(hydroxyphenyl)chlorin–photosensitized Colo 26 Multicell Tumor Spheroids¶Photochemistry and Photobiology, 2001
- Photodynamic Properties of Meta-Tetra(hydroxyphenyl)chlorin in Human Tumor CellsRadiation Research, 1999
- Spectroscopic studies of photobleaching and photoproduct formation of meta(tetrahydroxyphenyl)chlorin (m-THPC) used in photodynamic therapy. The production of singlet oxygen by m-THPCJournal of Photochemistry and Photobiology B: Biology, 1998
- Photodynamic Therapy for Early Squamous Cell Carcinomas of the Esophagus, Bronchi, and Mouth With m-Tetra(Hydroxyphenyl) ChlorinJAMA Otolaryngology–Head & Neck Surgery, 1997
- Intraoperative photodynamic therapy with m-tetrahydroxyphenylchlorin for chest malignanciesLasers in Surgery and Medicine, 1996
- In-vivo measurement of fluorescence bleaching of meso-tetra hydroxy phenyl chlorin (mTHPC) in the esophagus and the oral cavityPublished by SPIE-Intl Soc Optical Eng ,1995
- Evaluation of a new photosensitizer, meso‐tetra‐hydroxyphenyl‐chlorin, for use in photodynamic therapy: A comparison of its photobiological properties with those of two other photosensitizersInternational Journal of Cancer, 1994
- Comparison of the photobleaching effect of three photosensitizing agents: Meso-tetra(m-hydroxyphenyl)chlorin, meso-tetra(m-hydroxyphenyl)porphyrin and photofrin during photodynamic therapyLasers in Medical Science, 1994
- Photodynamic therapy with chlorins for diffuse malignant mesothelioma: initial clinical resultsBritish Journal of Cancer, 1991