The fundamental study of therapeutic effect improvement by extracellular photosensitization reaction with free photosensitizer

We studied to improve the photocytotoxicity of extracellular photosensitization reaction by increasing the free photosensitizer concentration and arranging excitation wavelength to free photosensitizer absorption. At the treatment for tachyarrhythmia by photosensitization reaction using talaporfin sodium, photosensitizer binds to serum protein existing in interstitial fluid. The photosensitization reaction by free photosensitizers can damage the myocardial cells efficiently with less serum proteins oxidation. We measured the temperature dependence of free photosensitizer concentration in vitro. The bindings of talaporfin sodium to LDL and HDL was dissociated 12.8% and 6.3%, respectively by temperature change from 18°C to 38°C. The cell lethality with 652 nm corresponding to free talaporfin sodium absorption peak was lower than that with 660 nm corresponding to absorption peak for combined talaporfin sodium to proteins. The photocytotoxicity might not improve by temperature change from a body temperature to 38°C.