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Proceedings Paper

Comparison of high-intensity pulsed and continuous-wave irradiation on benzoporphyrin derivative-induced photosensitization of bladder cancer cells
Author(s): Heyke Cacile Diddens; Robert Gillies; Tayyaba Hasan
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Paper Abstract

Benzoporphyrin derivative, monoacid ring A (BPD-MA) is a second generation porphyrin photosensitizer, with a significant absorption at 692 nm. The ability of two different lasers (a high-intensity pulsed ruby laser, and a continuous wave (cw) argon-ion laser pumped dye laser) in producing photodynamic damage to human bladder carcinoma cells in vitro under similar conditions was compared. Cells incubated in 0.14 (mu) M BPD-MA for 3 hours were irradiated with 1 or 3 J/cm2 with either pulsed or cw irradiation at 694 nm. Cell survival was determined using an MTT assay. With the ruby laser essentially no phototoxicity was observed at the high intensity pulsed irradiances used, whereas 38% and 6% survival rates were observed for 1 and 3 J/cm2, respectively, using cw irradiation. Possible explanations for the lack of BPD-MA phototoxicity using the ruby laser are: rapid photodegradation, saturation and excitation into higher excited states of the sensitizer. No BPD-MA photodegradation was observed in 1.4 (mu) M BPD-MA in 10% fetal calf serum solutions using the ruby laser. However, an oxygen-dependent photodegradation with the formation of a chlorin-type photoproduct was observed in these solutions using cw irradiation. A simple calculation indicated that the high pulse irradiances used in this study (4.4 X 107 W/cm2) were approximately 3 orders of magnitude greater than required for the onset of saturation. If higher excited states (Sn or Tn) are populated, they do not undergo any photochemistry resulting in phototoxicity or in photoproduct formation. These results show that with the low saturation threshold of BPD-MA, the choice of source and irradiance are important considerations in planning a therapeutic regime.

Paper Details

Date Published: 17 August 1994
PDF: 6 pages
Proc. SPIE 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, (17 August 1994); doi: 10.1117/12.182936
Show Author Affiliations
Heyke Cacile Diddens, Medizinisches Laserzentrum Luebeck (Germany)
Robert Gillies, Wellman Labs. of Photomedicine, Massachusetts General Hospital (United States)
Tayyaba Hasan, Wellman Labs. of Photomedicine, Massachusetts General Hospital (United States)

Published in SPIE Proceedings Vol. 2134:
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards
Steven L. Jacques; David H. Sliney; Michael Belkin, Editor(s)

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