Mitochondria-Targeting Type-I Photodynamic Therapy Based on Phenothiazine for Realizing Enhanced Immunogenic Cancer Cell Death via Mitochondrial Oxidative Stress

Zeyu Duan,1,* Lie Li,1,* Qiyu Zhan,1 Jian Chen,1 Qiyan Li,1 Ruiyuan Liu,1,* Yinuo Tu2,* 1Biomaterials Research Center, School of Biomedical Engineering, Southern Medical University, Guangzhou, 510515, People’s Republic of China; 2Guangzhou Institute of Cancer Research, the Affiliated Cancer Hospital, Guangzhou Medical University, Guangzhou, Guangdong, 510095, People’s Republic of China*These authors contributed equally to this workCorrespondence: Ruiyuan Liu; Yinuo Tu, Email [email protected]; [email protected]: Photo-immunotherapy faces challenges from poor immunogenicity and low response rate due to hypoxic microenvironment. This study presents Rh-PTZ, a small organic molecule with a D-π-A structure, that simultaneously amplifies mitochondria-targeted type-I PDT-dependent immune stimulation for the treatment of hypoxic cancer.Methods: The hydrophobic Rh-PTZ was encapsulated into F127 to prepare Rh-PTZ nanoparticles (Rh-PTZ NPs). The type-I ROS generation ability, mitochondrial targeting capacity, and ICD triggering effect mediated by Rh-PTZ NPs under LED light irradiation were investigated. Based on a 4T1 subcutaneous tumor model, the in vivo biological safety assessment, in vivo NIR fluorescent imaging, and the efficacy of PDT were assessed.Results: Rh-PTZ could efficiently accumulate in the mitochondrial site and induce O2•− and •OH burst in situ under LED light irradiation, thereby causing severe mitochondrial dysfunction. Rh-PTZ can amplify mitochondrial stress-caused immunogenic cell death (ICD) to stimulate the immune response, promote the maturation of sufficient dendritic cells (DCs), enhance the infiltration of immune cells, and alleviate the tumor immunosuppressive microenvironment.Conclusion: The mitochondria-targeting type-I PDT holds promise to enhance photo-immunotherapy for hypoxia tumor treatment and overcoming the limitations of traditional immunotherapy.Keywords: Photo-immunotherapy, immunogenic cell death, Type-I photosensitizers, mitochondrial targeting