AntiPD-L1 antibody conjugated Au-SPIOs nanoplatform for enhancing radiosensitivity and triggering anti-tumor immune response.

To improve radiotherapy effect by inducing more toxicity for tumors and less for normal tissue and switching immunosuppressive microenvironment caused by expression of PD-L1 and tumor-associated macrophages (TAMs) to immunoreactive microenvironment, we designed a PD-L1-targeted nanoplatform consisting of gold nanoparticles and superparamagnetic iron oxide nanoparticles (antiPD-L1-SPIOs@PLGA@Au). In vivo T2-weighted images, the best contrast effect of tumor was achieved two hours after intravenous injection of antiPD-L1-SPIOs@PLGA@Au. The tumor control caused by irradiation combined with antiPD-L1-SPIOs@PLGA@Au was better than that by radiotherapy alone in clone formation assay and B16F10 subcutaneous tumor model. Radiosensitivity enhancement induced by the addition of antiPD-L1-SPIOs@PLGA@Au was achieved by increasing ROS production and attenuating DNA damage repair. AntiPD-L1-SPIOs@PLGA@Au could promote the polarization of tumor-associated macrophages (TAMs) to M1 and reverse the immunosuppression caused by TAMs. By increasing the expression of CRT in tumor and blocking the PD-L1/PD pathway, antiPD-L1-SPIOs@PLGA@Au with radiation activated the anti-tumor immune response. In conclusion, antiPD-L1-SPIOs@PLGA@Au could be used as a radiosensitizer and a MRI contrast targeting PD-L1, with the functions of blocking the PD-L1/PD-1 immune checkpoint pathway and reversing the immunosuppression caused by TAMs.