Ogbonna Sochi Judith, Hazama Hisanao, Awazu Kunio
Graduate School of Engineering, Osaka University, Osaka, Japan.
Global Center for Medical Engineering and Informatics, Osaka University, Osaka, Japan.
Photochem Photobiol. 2021 Sep;97(5):1089-1096. doi: 10.1111/php.13411. Epub 2021 Apr 23.
Photobleaching and photoproduct formations are considered essential phenomena in improving the efficacy of photodynamic diagnosis and therapy (PDD and PDT). We investigated the photobleaching of protoporphyrin IX (PpIX) by measuring its concentration with mass spectrometry (MS). The reduction in the concentration of PpIX dissolved in dimethyl sulfoxide was measured during PDD and PDT conditions using lasers with wavelengths of 405 and 635 nm, respectively, at a power density of 10, 50 or 100 mW/cm . The obtained results were compared with the results of conventional fluorescence spectroscopy and previously reported results. Our results demonstrate the variation in the MS-based photobleaching coefficient of PpIX with the power density, while the fluorescence-based photobleaching coefficient was independent of the power density. The results of MS also show faster photobleaching of PpIX in comparison with that obtained from fluorescence. The difference may be attributed to the change in the fluorescence quantum yield of PpIX with its concentration and the effect of fluorescence emission from the PpIX photoproducts. Thus, an MS-based investigation of the photobleaching poses to be a more stable investigation form. Our finding highlights the importance of recognizing the potential significance of these discoveries in the PDD and PDT dosimetry and efficacy.
光漂白和光产物形成被认为是提高光动力诊断和治疗（PDD和PDT）疗效的重要现象。我们通过质谱（MS）测量原卟啉IX（PpIX）的浓度来研究其光漂白。在PDD和PDT条件下，分别使用波长为405和635 nm的激光，功率密度为10、50或100 mW/cm²，测量溶解在二甲基亚砜中的PpIX浓度的降低。将获得的结果与传统荧光光谱的结果以及先前报道的结果进行比较。我们的结果表明，基于MS的PpIX光漂白系数随功率密度而变化，而基于荧光的光漂白系数与功率密度无关。MS的结果还表明，与荧光法相比，PpIX的光漂白更快。这种差异可能归因于PpIX的荧光量子产率随其浓度的变化以及PpIX光产物的荧光发射效应。因此，基于MS的光漂白研究似乎是一种更稳定的研究形式。我们的发现突出了认识到这些发现在PDD和PDT剂量测定及疗效方面潜在重要性的重要性。
