Chemical Luminescence Measurement of SingletOxygen Generated by Photodynamic Therapy in Solutions in Real Time

摘要

Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target tissue. Reactive oxygen species (ROS), such as ~1O_2 and superoxide, are believed to be the major cytotoxic agents involved in PDT. Although current PDT dosimetry mostly involves measurements of light and photosensitizer doses delivered to a patient, the quantification of ROS production during a treatment would be the ultimate dosimetry for PDT. Technically, it is very difficult and expensive to directly measure the fluorescence from ~1O_2, due to its extreme short lifetime and weak signal strength. In this paper, Photofrin~® and 635nm laser were used to generate ~1O_2 and superoxide in a PDT in solution. Compound free acid 3,7- dihydro-6-{4-[2-(N'-(5-fluoresceinyl) thioureido) ethoxy] phenyl}-2- methylimidazo{1,2-a} pyrazin-3-one,an Cypridina luciferin analog commonly referred as FCLA, was used as a chemical reporter of ROS. The 532 nm chemiluminescence (CL) from the reaction of the FCLA and ROS was detected with a photon multiplier tube (PMT) system operating at single photon counting mode. With the setup, we have made detections of ROS generated by PDT in real time. By varying the amount of conventional PDT dosage (photosensitizer concentration, light irradiation fluence and its delivery rate) and the amount of FCLA, the intensity of CL and its consumption rate were investigated. The results show that the intensity and temporal profile of CL are highly related to the PDT treatment parameters. This suggests that FCLA-CL may provide a highly potential alternative for ROS detection during PDT.