Evaluation of the efficacy of first- and second-generation photosensitizers by optical monitoring of tryptophan degradation

The effectiveness of photosensitizers (PSs) is the most important aspect of photodynamic therapy (PDT) of cancer. To evaluate that, the photobleaching of tryptophan (Trp) and the stability of PSs in laser-irradiated aqueous solutions of PSs and Trp were studied by monitoring their characteristic absorptions. Among the six PSs studied, the first-generation PS Zn-5,10,15,20-tetra(4-N-allylpyridyl)porphine and the second-generation PS sulfonated Al-phthalocyanine belong to the same top-performing statistical tier, with no significant difference in reactive oxygen species (ROS) formation rates ([Formula: see text]) and exhibit high stability under irradiation. Aqueous solutions of Trp and PSs provide a simple and reliable system for selecting the most effective PSs using UV–visible spectrophotometry.