A magnetically recyclable protein separation system has been designed and fabricated by combining ferrimagnetic magnetite cores and NiO nanoparticles decorated onto the mesoporous silica shell with a high surface area (see figure). The exposed NiO nanoparticles provide for the selective adsorption of the His-tagged protein from the mixed-protein solution, as well as cell lysate, and the magnetic core allows the particles to be separated from the solution by applying an external magnetic field.