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 work

Correspondence: Ruiyuan Liu; Yinuo Tu, Email ruiyliu@smu.edu.cn; tuyinuo@gzhmu.edu.cn

Purpose: 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