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Journal of Environmental Pathology, Toxicology and Oncology

ISSN for PRINT: 0731-8898

Institutional price:	$672.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2006, Volume25

546 pages

Issue price - $344.00

Comparison of Merocyanine 540-Mediated Photodynamic Action on Leukemia Cells Between Pulsed and Continuous Wave Light Sources

Jiyao Chen
Department of Physics, The State Key Lab for Advance Photonic Materials and Devices, Fudan University, Shanghai 200433, China

Naiki K. Mak
Department of Biology, Hong Kong Baptist University, Hong Kong, People's Republic of China

Wongneng Leung
Department of Biology, Hong Kong Baptist University, Hong Kong, China

Naihou Cheung
Department of Physics, Hong Kong Baptist University, Hong Kong, China

Qian Peng, PhD
Pathology Clinic, Rikshospitalet-Radiumhospitalet HF Medical Center, Faculty Division Radiumhospitalet, University of Oslo, Montebello, N-0310 Oslo, Norway

ABSTRACT

Whether a pulsed laser is superior to a continuous wave (CW) light source in photodynamic therapy (PDT) of cancer is still unclear and contradictory in the literature. Although photosaturation of a sensitizer and oxygen depletion in tumor have been considered to be involved during pulsed laser irradiation, there is a lack of experimental data. In the present work several parameters such as the amount of merocyanine 540 (MC540) in cells, the oxygen concentration in cells, and the amount of photos reaching cells during pulsed laser irradiation, were studied to compare the MC540-mediated PDT effects of a pulsed laser and a CW light source on murine myeloid WEH-3B (JCS) cells in vitro. The results showed that the pulsed laser was less effective at cell inactivation than the CW light under the same irradiation dose. However, when the energy of the pulsed laser was reduced from 0.25 to 0.06 mJ/cm² while keeping the total irradiation dose unchanged, the photoinactivation of cells was increased significantly. Based on the measurements and calculations for the present experimental conditions, each cell has about 10⁸ MC540 molecules bound (5 μg/ml MC540 for 1 hr) and receives about 10⁹ photos from 0.25 mJ/cm² of the pulsed laser. The results indicate that the photosaturation of MC540 occurs in the present conditions due to the fact that the photons received by one cell in one laser pulse were much more than the numbers of MC540 molecules bound to one cell. Thus, the photosaturation of the photosensitizer is one of the reasons to explain the different efficiency in cell inactivation between the pulsed laser and CW light.