Superficially mesoporous Fe 3 O 4 @SiO 2 core shell microspheres: Controlled syntheses and attempts in protein separations

Superficially mesoporous Fe3O4@SiO2 core shell microspheres have been synthesized by complex multi-step reactions. The microspheres show three-layered structure: a magnetic core encapsulated by a layer of dense silica and another layer of mesoporous silica. These Fe3O4@SiO2@mesoporous SiO2 microspheres (FSMM) are around 50-100 nm. The outer porous shell can provide much larger surface area than traditional nonporous Fe3O4@SiO2 core shell particles, which is beneficial for enrichment and purification applications. The presence of the superparamagnetic core allows the particles to be isolated and recycled easily by external magnetic field. The pore size of the mesoporous layer of FSMM is further enlarged (E-FSMM) by hydrothermal treatment. The surface of FSMM and E-FSMM are modified with protein G for enrichment and separation of Immunoglobulin G (IgG). FSMM particles exhibit IgG binding capacity of 41 mg/g, while the binding capacity of E-FSMM is as high as 51 mg/g due to the larger pore size facilitating protein binding. (C) 2014 Elsevier Inc. All rights reserved.