Sinoporphyrin sodium (DVDMS) is a novel photosensitizer with high photodynamic therapy (PDT) effect. Reasons for its high photo-activity were investigated according to the study of photophysical characteristics of DVDMS. Extinction coefficients (ϵ) of DVDMS at 405 nm and 630 nm are 4.36 × 105 and 1.84 × 104 M-1.cm-1; fluorescence quantum yield (ΦF) is 0.026; quantum yield of lowest triplet state formation is 0.94 and singlet oxygen quantum yield (Φδ) is 0.92. Although Φδ of DVDMS is only 10% higher than that of Photofrin® (0.83), the extinction coefficient of DVDMS at 630 nm is 10-fold greater than that of Photofrin®. This leads to its higher singlet oxygen generation efficiency (μ Φδ). The higher μ Φδ of DVDMS can result in an effective reduction of dosage (1/10 of Photofrin®) reaching the same cytotoxic effect as Photofrin®. Even though ΦF is approximately equal to that of Photofrin®, brightness (μ ΦF) of DVDMS is 10-fold greater than that of Photofrin® because of the 10-fold greater extinction coefficient. Thus, fluorescence diagnosis ability of 0.2 mg/kg DVDMS is comparable to that of 2 mg/kg Photofrin® used in PDT. Overall, the 10-fold greater extinction coefficients are responsible for the high brightness and singlet oxygen generation efficiency of DVDMS.
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