Dysart Jonathan S, Singh Gurmit, Patterson Michael S
Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada.
Photochem Photobiol. 2005 Jan-Feb;81(1):196-205. doi: 10.1562/2004-07-23-RA-244.
Predicting the therapeutic outcome of photodynamic therapy (PDT) requires knowledge of the amount of cytoxic species generated. An implicit approach to assessing PDT efficacy has been proposed where changes in photosensitizer (PS) fluorescence during treatment are used to predict treatment outcome. To investigate this, in vitro experiments were performed in which Mat-LyLu cells were incubated in meta-tetra(hydroxyphenyl)chlorin (mTHPC) and then irradiated with 652 nm light. PS concentration, fluence rate and oxygenation were independently controlled and monitored during the treatment. Fluorescence of mTHPC was monitored during treatment and, at selected fluence levels, cell viability was determined using a colony-formation assay. Singlet oxygen dose was calculated using four different models and was compared with cell survival. For the dose metric based on singlet oxygen-mediated PS photobleaching, a universal relationship between cell survival and singlet oxygen dose was found for all treatment parameters. Analysis of the concentration dependence of bleaching suggests that the lifetime of singlet oxygen within the cell is 0.05-0.25 micros. Generation of about 9 x 10(8) molecules of singlet oxygen per cell reduces the surviving fraction by 1/e.
预测光动力疗法（PDT）的治疗效果需要了解所产生的细胞毒性物质的量。已提出一种评估PDT疗效的间接方法，即利用治疗过程中光敏剂（PS）荧光的变化来预测治疗结果。为对此进行研究，开展了体外实验，将Mat-LyLu细胞置于间四（羟苯基）氯卟啉（mTHPC）中孵育，然后用652 nm光照射。在治疗过程中，对PS浓度、光通量率和氧合作用进行独立控制和监测。在治疗过程中监测mTHPC的荧光，并在选定的光通量水平下，使用集落形成试验测定细胞活力。使用四种不同模型计算单线态氧剂量，并将其与细胞存活率进行比较。对于基于单线态氧介导的PS光漂白的剂量指标，在所有治疗参数下均发现细胞存活率与单线态氧剂量之间存在普遍关系。对漂白浓度依赖性的分析表明，细胞内单线态氧的寿命为0.05 - 0.25微秒。每个细胞产生约9×10⁸个单线态氧分子会使存活分数降低1/e。
