Axial-ligand-cleavable silicon phthalocyanines triggered by near-infrared light toward design of photosensitizers for photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a novel phototherapy for the treatment of cancer that uses NIR light and conjugates antibody-IR700, silicon phthalocyanine photosensitizer. A key feature NIR-PIT light-induced axial ligand cleavage IR700, which finally causes cytotoxicity. Here, we focused on protonation IR700 anion radical during photochemical process. The Gibbs energy in reaction derivatives with different ligands was calculated. These calculations suggested order efficiency corresponds to basicity (i.e. alkoxy > siloxy (IR700) phenoxy oxycarbonyl), confirmed by photoirradiation experiments synthesized compounds. Thus, significantly dependent ligand. Our findings suggest PIT reagent an derivative bearing group would show better efficacy than IR700.