Uveal melanoma (UM) is the most prevalent primary intraocular malignant tumor in adults with high mortality rate. Recently, immunotherapy has shown great success in other tumors, however, its therapeutic effect in UM is unsatisfactory, possibly due to the insufficient immune cell infiltration and low immunogenicity of UM. Thus, an efficient therapeutic strategy to reverse the immunosuppressive tumor microenvironment is required. Herein, a PD-L1 modified hierarchical structure consisting of a magnetic Fe