Doxorubicin and siRNA-PD-L1 co-delivery with T7 modified ROS-sensitive nanoparticles for tumor chemoimmunotherapy.

Tumor cells avoid immunosurveillance during the tumorigenesis, metastasis and recurrence periods thanks to the overexpressed immunosuppressive molecules on their surface. For instance, the programmed cell death 1 ligand (PD-L1) binds with the T-cells' programmed cell death receptor 1 (PD-1) impairing the anti-tumor activity of the host T cells. In this study, a new reactive oxygen species (ROS) responsive nanoparticle (NP), modified with the HAIYPRH (T7) peptide, was developed for the co-delivery of siRNA-PD-L1 and doxorubicin (Dox). These NPs can block the inhibitory signal responding to T cells and enhance cytotoxicity of Dox against tumor cells. The T7 modification binds to the overexpressed transferrin receptor on tumor cells facilitating its cellular uptake. Dox rapid release is then triggered by the high tumor cells cytoplasmic concentration of ROS, leading to cell apoptosis. Our results demonstrated these NPs exhibited a T7-mediated cellular uptake and an intracellular ROS-triggered payloads release in vitro. They also suggested an improved in vivo 4T1 tumor targeting efficiency and chemoimmunotherapy. Most notably, the co-delivery system exhibited a significantly enhanced antitumor effect over Dox-only loaded NPs following prompting the proliferation of T cells by siRNA-PD-L1. In conclusion, these ROS-responsive NPs provided a promising strategy to combine siRNA-PD-L1 immunotherapy and Dox chemotherapy.