The interaction between cationic chlorophyll photosensitizers (PSs) for antimicrobial photodynamic therapy and non-ionic surfactant Tween 80 as a potential carrier system was studied using absorption and fluorescence spectroscopy. The results, analyzed in terms of our approach and the Stern–Volmer approach, indicate that all three PSs form stable molecular complexes with Tween 80, the PS molecules being located at the periphery of surfactant micelles next to hydrophilic head groups. The higher the charge of the macrocyclic cation, the stronger the interaction of PS with the surfactant.
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