Phthalocyanines are
macrocyclic compounds that can be employed as
photosensitizers in the treatment of various
infections and diseases, as well as in
photodynamic therapy. Nevertheless, a disadvantage for the clinical application of these compounds is their strong tendency to form oligomers (especially dimers), a phenomenon that reduces their efficiency as
photosensitizers. In the present contribution, we have studied the photophysical and photochemical properties of ZnPc and ZnF(16)Pc in an organic
solvent (THF) and liposomal formulations (
DMPC, DPPC and DSPC). Our results show that
dye incorporation into
liposomes decreases its aggregation degree, as revealed by absorption spectra, triplet quantum yield, and
singlet oxygen quantum yield measurements. Additionally, we studied the photodynamic activity of both phthalocyanines in liposomal formulation on human cervical
carcinoma (HeLa) cells. For ZnF(16)Pc the photophysical behavior and
phototoxicity in vitro correlate with the aggregation degree. The dimers are not photoactive and the photochemistry of ZnF(16)Pc depends of the fraction present as monomer. On the other hand, ZnPc aggregation is minimal and its photophysical and photochemical properties are similar in the three
liposomes studied. Nevertheless, its
phototoxicity in vitro is
liposome dependent.