A Light Responsive Nanoparticle-Based Delivery System Using Pheophorbide A Graft Polyethylenimine for Dendritic Cell-Based Cancer Immunotherapy

In this study, the photochemical internalization (PCI) technique was adopted in a nanoparticle-based antigen delivery system to enhance antigen-specific CD8+ T cell immune response for cancer immunotherapy. Pheophorbide A, a hydrophobic photosensitizer, grafted with polyethylenimine (PheoA-PEI) with endosome escape activity and near-infrared imaging capability was prepared. A model antigen ovalbumin (OVA) was then complexed with PheoA-PEI to form PheoA-PEI/OVA nanoparticles (PheoA-PEI/OVA NPs) that are responsive to light. Flow cytometry analysis revealed increased endocytosis in a murine dendritic cell line (DC2.4) that was treated with PheoA-PEI/OVA NPs compared to free OVA. Generation of reactive oxygen species (ROS) in DC2.4 cells was also confirmed quantitatively and qualitatively using 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA). Confocal laser scanning microscopy (CLSM) further demonstrated that the PheoA-PEI/OVA NPs enhanced cytosolic antigen release after light stimulation. Moreover, Phe...