Engineered indocyanine green and PD-L1 inhibitors co-loaded perfluorochemical double-layered nanodroplets offer effective photoimmunotherapy against colorectal cancer

Colorectal cancer (CRC) ranks the 3rd most common cancer and is the 2nd leading cause of cancer death worldwide, indicating that an effective therapeutic strategy is still urgently desired nowadays. In this study, an emerging indocyanine green (ICG) and anti-programmed cell death ligand 1 monoclonal antibodies (αPD-L1) co-loaded perfluorocarbon double-layer nanodroplets named IPLPNDs were developed for photoimmunotherapy of CRC. The IPLPNDs are able to stabilize the αPD-L1 in the nanocarriers and generate hyperthermia as well as significantly enhanced production of singlet oxygen compared to equal dose of free ICG upon NIR irradiation. Furthermore, the IPLPNDs + NIR can dose-dependently eradicate CT26 cells and subsequently inhibit PD-L1 bioactivity of the survived cells in vitro. Meanwhile, expression levels of HMGB1 and CRT, the two immunogenic cell death (ICD) markers, from the survived cells were elevated 24 h after NIR exposure. Through the animal study, we further demonstrated that the IPLPNDs containing 20-μM ICG and 3-μg/mL αPD-L1 in combination with 1-min NIR irradiation can effectively arrest the growth of CT26 tumor in the mice without generating organ damage, by which the tumor size was merely increased by 56 % while that without drug treatment can be tremendously expanded by 15 folds after 10 days. Moreover, the remained tumors treated by IPLPNDs + NIR indeed showed the least PD-L1 and highest CD8 expressions compared to all the other settings, illustrating the significance of immunogenicity of tumor microenvironment on anticancer efficacy. We reason that such tumor inhibition was carried out by phototherapy followed by ICD-enhanced immunotherapy, a two-stages anticancer process in vivo. Taken together, we anticipate that the developed IPLPND is highly applicable for use in the clinical CRC treatment.