Experimental study on photodynamic diagnosis of cancer mediated by chemiluminescence probe

AbstractA novel method of photodynamic diagnosis of cancer mediated by chemiluminescence probe is presented. The mechanism for photodynamic therapy involves singlet oxygen (1O2) generated by energy transfer from photosensitizers. 1O2 can react with 3,7-dihydro-6-{4-{2-(N′-(5-fluoresceinyl)thioureido)ethoxy}phenyl}-2-methylimidazo{1,2-a}pyrazin-3-one sodium salt (FCLA), which is a Cypridina luciferin analog and a specific chemiluminescence probe for detecting 1O2 and superoxide (O2−). The reaction of FCLA and 1O2 can give emission with peak wavelength at about 532 nm. In the present study, FCLA was chosen as an optical reporter of 1O2 produced from the photosensitization reaction of hematoporphyrin derivative in model solution and in nude mice with transplanted mammary cancer. Photosensitized chemiluminescence from the reaction of FCLA with 1O2 was detected by a highly sensitive Intensified Charge-Coupled Device detector. The chemiluminescence was markedly inhibited by the addition of 10 mmol/l sodium azide (NaN3) to the model solution and minor effects were observed at the addition of 10 μmol/l superoxide dismutase, 20 mmol/l mannitol and 100 μg/ml catalase, respectively, thus indicating that 1O2 generation from photosensitization reaction mainly results in light emission. Experiments in vivo with tumor-bearing mice showed a clear chemiluminescence image of tumor. The study suggests that this novel method may be applicable to the diagnosis of superficial tumors