Simulations and Experiments about the Influence of HMME Concentration in Blood Vessel during a Short Time on Photodynamic Therapy Microvascular Effect

Objective: Study the influence of Hematoporphyrin Monomethyl Ether (HMME) concentration in blood vessel in a rather short time on photodynamic therapy (PDT) microvascular effect by mathematical modeling and animal experiment. Methods: The yields of singlet oxygen in blood vessel in a short time in different animal were simulated by mathematical model, and the yields of singlet oxygen in Leghorn Cocks vessel were simulated when the irradiation time was 20 min with 5 min and 60 min drug-light interval separately. 0.2 ml blood was gotten at 0, 5,15,10,15, 20, 30, 50, 80 min after HMME (10 mg/Kg) was injected intravenously in Leghorn Cocks and was measured by fluorescence spectrophotometer for calculation of HMME concentration. Simultaneity, a square of cock comb (2times2 cm) was randomly irradiated (532 nm, 100 mW/cm²) at 5~25 min and another one was irradiated at 60~80 min, and the change was observed by macroscopy and pathology. Results: Simulations showed that the yield of singlet oxygen in vessels of different animals varied markedly in a short time and correlated with the concentration of photosensitizer in vessels. The produce of singlet oxygen in cock´s blood vessel during 5~25 min PDT is 5.3 times more than that during 60~80 min PDT. Experiments showed that the red color of the square irradiation at 5~25 min was faded, but the color of the square irradiation at 60~80 min had no change. Conclusions: The change of HMME concentration in blood vessel during a short time after intravenous injection have a big influence on the PDT microvascular effect.