Nanostructured Polymeric Micelles Carrying Xanthene Dyes for Photodynamic Evaluation

It was evaluated the properties of the xanthene dyes Erythrosin B, Eosin Y and theirs Methyl, Butyl and Decyl ester derivatives as possible photosensitizers (PS) for photodynamic treatments. The more hydrophobic dyes self-aggregate in water/ethanol solutions above 70% water (vol/vol) in the mixture. In buffered water, these PS were encapsulated in Pluronic polymeric surfactants of P-123 and F-127 by two methodologies: direct addition and the thin-film solid dispersion methods. The thin-film solid method provided formulations with higher stabilities besides effective encapsulation of the PS as monomers. Size measurements demonstrated that Pluronic forms self-assembled micelles with uniform size, which present slightly negative surface potential and a spherical form detected by TEM microscopy. The ester length modulates xanthene localization in the micelle, which is deeper with the increase in the alkyl chain. Moreover, some PS are distributed into two populations: one on the corona micelle interface shell (PEO layer) and the other into the core (PPO region). Although all PS formulations show high singlet oxygen quantum yield, promising results were obtained for Erythrosin B esters with the hydrophobic P-123, which ensures their potential as drug for clinical photodynamic applications.