Characteristics of Photocytotoxicity with high peak power pulsed irradiation: Comparison of Photodynamic Therapy with two photosensitizers, Photofrin ® and mono-L-aspartyl chlorin e6 on prostate cancer cell in vitro

We proposed novel depth-controlled photodynamic therapy (PDT) by varying pulsed laser irradiation condition. We focus on photocytotoxicity suppression under high peak power pulsed irradiation to apply this phenomenon to surface intact therapy to preserve healthy wall of a hollow organ. The relation between laser irradiation condition and cell lethality of rat prostate cancer cell with PDT using practical photosensitizers, mono-L-aspartyl chlorine e6 (ME2906) and Photofrinreg was investigated. We found cell lethality suppression from 63% to 20% when the irradiated pulsed 2 peak power density ranged from 0.2 to 1.4 mW/cm² with ME2906 mediated PDT. There was no significant photocytotoxicity suppression in case of Photofrinreg mediated PDT. Singlet oxygen luminescence from the two different kinds of photosensitizer solution was measured. The pulse peak power dependence of singlet oxygen luminescence intensity correlated with the photocytotoxicity. We think the photocytotoxicity suppression with high peak power pulsed irradiation with ME2906 might be useful for the therapeutic depth controlled PDT without damage on the surface of a hollow organ