Carboxyl functionalized magnetic silica beads have the same structure as silica coated magnetic beads. It is also with typical core shell structure. The core is superparamagnetic Fe3O4 nanoparticles which is coated with silica layer as shell. Carboxyl groups are from surface modification of carboxyl treated magnetic silica microspheres. Besides carboxyl groups, there are still some –SiOH groups left on the surface.
Therefore, carboxyl functionalized magnetic silica microspheres are not suitable for separation and purification of protein as well as other biomacromolecule.