Red and blue ferritin nanomagnets by dye-labeling to the protein shell

We report a flexible route to chemically modify the ferritin nanomagnet. Two dye-labeled ferritins (red- and blue-ferritin) have been prepared by covalently coupling the derivatives of the reactive orange 16 and Remazol brilliant blue R, respectively, to the ferritin surface lysine residues. The study of the particles by transmission electron microscopy showed that the native iron core ferritin remains intact after chemical functionalization of the protein shell. Likewise, magnetic measurements showed that the superparamagnetic properties of the iron core are preserved.