Phthalocyanines as phototherapeutic agents for tumors

Zn(II)-phthalocyanine (ZnPc) is a tetraazaisoindole pigment which can be prepared by chemical synthesis with a high degree of purity, and it efficiently absorbs 680 nm of light. These properties, associated with its ability to generate activated oxygen species (e.g., singlet oxygen) upon photoexcitation, make ZnPc a potential phototherapeutic agent. Actually, upon delivery of ZnPc to tumor-bearing animals after incorporation into liposomal vesicles, the dye was uptaken and retained by the tumor tissue in significant amounts and with a good degree of selectivity. Irradiation of the ZnPc-loaded tumor area with ca. 680 nm of light caused tumor necrosis to an extent which was related to the dye concentration in the tumor.