CONICET | Buscador de Institutos y Recursos Humanos

A major difficulty in photodynamic therapy is the poor solubility of the photosensitizer (PS) under physiological conditions which correlates with low bioavailability. PS aggregation leads to a decrease in the photodynamic efficiency and a more limited activity in vitro and in vivo. To improve the aqueous solubility and reduce the aggregation of 2,9(10),16(17),23(24)-tetrakis[(6-methylpyridin-2-yl)oxy]phthalocyaninatozinc(II) (PcZn), the encapsulation into the biocompatible T1107 poloxamine polymeric micelles was investigated. T1107 (10% wt/vol) were prepared by dissolving the required amount of copolymer in milli-Q water (pH 7?8) at 4°C followed by the equilibration of the system at 25° C. For the incorporation of PcZn into micelles, a 0.5 mM solution of PcZn in acetone was added dropwise to the different micellar systems (5 mL) with magnetic stirring and the samples were shaken for 48 h at 25°C. Morphological evaluation showed the formation of PcZn-loaded spherical micelles in the nanosize range. The UV?visible absorption spectra of PcZn was recorded in DMSO, water-DMSO 2% and polymeric micelle T1107 in the 500-800 nm range. The Q-band of PcZn-loaded micelles displayed a slight broadening as well as a bathochromic shift from 674 to 683 nm in comparison with that obtained in THF. Besides, the two small vibrational bands of PcZn in THF at 609 and 644 nm merged into one broad peak with a maximum at 644 nm. These results suggest that PcZn is present in an aggregated form in the micelle core. However, PcZn is less aggregated upon encapsulation in comparison with PcZn in water?DMSO 2%. Thephotostability of PcZn-loaded micelles was analyzed in water by measuring the decrease in the intensity of the Q-band under irradiation with a red light. PcZn-loaded micelles was photostable and it was more stable than that in water?DMSO 2%. The aqueous solubility of PcZn-loaded micelle was increased up to 35 times.