Near-infrared photochemical internalization: design of a distorted zinc phthalocyanine for efficient intracellular delivery of immunotoxins

In the treatment of cancer, the physical and mental stress on patients and the potential for strong side effects are serious problems; therefore, reliable delivery of drugs into cancer tissue cells is required. We have developed a near-infrared (NIR) photosensitizing dye, Zn6PTPc, for NIR-photochemical internalization (PCI) to achieve gentle and efficient endosomal escape and delivery of antibody drugs, which are known to have high targeting ability but low intracellular activity, into target cancer cells. Zn6PTPc allowed longer wavelengths to be used to achieve higher singlet oxygen generation efficiency by the molecular design based on a distorted π-electron system. The system effectively introduced immunotoxins into cells to significantly inhibit tumor tissue growth. The developed potent NIR photosensitizers facilitated NIR-PCI with high tumor-targeting ability.