Multiple Functions Integrated inside a Single Molecule for Amplification of Photodynamic Therapy Activity

Nitric oxide (NO) can play both prosurvival and prodeath roles in photodynamic therapy (PDT). The generation efficiency of peroxynitrite anions (ONOO-), by NO and superoxide anions (O-2(center dot-)), significantly influenced the outcome. Reports indicated that such efficiency is closely related to the distance between NO and O-2(center dot-). Thus, in this manuscript, L-arginine (Arg) ethyl ester-modified zinc phthalocyanine (Arg-ZnPc) was designed and synthesized as a photosensitizer (PS) and NO donor. Post light irradiation, the guanido of Arg-ZnPc can be effectively oxidized by the generated reactive oxygen species (ROS) in the PDT process to release NO. Such a strategy could ensure O-2(center dot-) and NO generation in the same place at the same time to guarantee effective ONOO- formation. In addition, NO has other multiple synergistic cancer treatment functions, including tumor tissue vasodilatation for drug extravasation promotion, P-glycoprotein (P-gp) downregulation for drug efflux inhibition, and glutathione depletion for cancer cell endogenous antioxidant defense destruction. In vitro and in vivo results indicated that the effective ONOO- formation and multiple functions of Arg-ZnPc could synergistically enhance its PDT activity and ensure satisfactory cancer treatment outcome.