An immunomagnetic nanocapsule includes a core, a shell and an outer layer. The shell is formed by a complex, and the complex is fabricated by a combination of fucoidan, oxidized dextran, and a plurality of superparamagnetic iron oxide nanoparticles via a hydrophobic interaction. The core is encapsulated in the shell. The outer layer includes at least one antibody immobilized to outside of the shell to form the outer layer, wherein the antibody is an immune checkpoint inhibitor and/or a T cell expansion antibody.
