2007 Volume 35 Issue 8 Pages 486-492
PDT is based on the generation of singlet oxygen (1O2) in a photochemical reaction among a tumor-accumulated photosensitizer, irradiation light, and oxygen in a tumor, and the detection of 1O2 is very important for understanding the mechanism of PDT. We used a near-infrared detection system to detect a 1270nm emission that was derived from the 1O2. Utilizing this system, we detected the generation of 1O2 from Photofrin dissolved in water or injected in a HeLa tumor-bearing mouse. We showed the irradiation power dependence of the generation of 1O2 in 5-ALA-mediated PDT with 9L cells and 9L tumor-bearing rats. High-power irradiation reduced the generation of 1O2 more than that with low power, and an MTT assay revealed that more 9L cells were killed by low-powered irradiation. In tumors, low-powered irradiation resulted in efficient tumor necrosis. Generations of 1O2 in ICG and TiO2 irradiation are also described.
