Comparison of high-intensity pulsed and continuous-wave irradiation on benzoporphyrin derivative-induced photosensitization of bladder cancer cells

Heyke Cacile Diddens; Robert Gillies; Tayyaba Hasan

doi:10.1117/12.182936

17 August 1994 Comparison of high-intensity pulsed and continuous-wave irradiation on benzoporphyrin derivative-induced photosensitization of bladder cancer cells

Heyke Cacile Diddens, Robert Gillies, Tayyaba Hasan

Author Affiliations +

Proceedings Volume 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards; (1994) https://doi.org/10.1117/12.182936
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

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 (S_n or T_n) 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.

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Heyke Cacile Diddens, Robert Gillies, and Tayyaba Hasan "Comparison of high-intensity pulsed and continuous-wave irradiation on benzoporphyrin derivative-induced photosensitization of bladder cancer cells", Proc. SPIE 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, (17 August 1994); https://doi.org/10.1117/12.182936

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KEYWORDS

Continuous wave operation

Ruby lasers

Bladder cancer

Dye lasers

Pulsed laser operation

Absorption

Bladder

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