Novel molecular photosensitizer with simultaneously GSH depletion, aggregation inhibition and accelerated elimination for improved and safe photodynamic therapy

The major challenges in photodynamic therapy (PDT) are the neutralization of cytotoxic reactive oxygen species (ROS) by the excessive antioxidant glutathione (GSH) in tumor cells, high self-aggregation of most photosensitizers (PSs), and long time to protect from light after treatment. Thus, to develop the molecular PSs for the improved and safe PDT in clinic, a novel and versatile PS (Mal-Pc) has been designed by di-substituting maleimides to the axial positions of silicon (Ⅳ) phthalocyanine. Owning to the conjugation of maleimides, Mal-Pc can not only entry tumor cells more easily and faster, but also can react with the intracellular overexpressed GSH after entry. In addition, upon electrophilic reaction with GSH, the inhibition of self-aggregation of Mal-Pc has been demonstrated by the restoration of the fluorescence emission in aqueous media. As a result, the intracellular ROS levels and photocytotoxicity of Mal-Pc are dramatically enhanced. Finally, the high hydrophilicity of the product GS-conjugates facilitates Mal-Pc eliminate from the normal cells more rapidly. Overall, this work revealed the high potential of the versatile molecular Mal-Pc for highly efficient and safe PDT in clinical translation.