Biomimetic Materials Synthesis from Ferritin-Related, Cage-Shaped Proteins

Abstract

Protein cages are characterized by a quaternary structure consisting in an assembly of multiple subunits endowed with highly similar three-dimensional structures. These assemblies enclose hollow spaces that can be used as ideal templates for the encapsulation of nano-material cargos. Indeed, the uniformity of the quaternary structure guarantees the attainment of nanoparticles (NPs) that are highly homogeneous in both size and shape, and the interior of the cage provides an isolated environment, shielded from bulk solution, where chemical reactions can take place. The protein surface is decorated by diverse chemical groups (i.e., primary amines, carboxylates, thiols) that can be genetically and/or chemically manipulated in order to confer specific functionalities to the nano-cage. Further advantages of protein cages include their usually remarkable stability, which is generally higher than that of liposome-based molecules, and high solubility in water, as well as the fact that protein-encapsulated NPs can be produced in industrial strains on large-scale, high yield (grams or even kilograms) and low cost. Finally, the determination of the threedimensional structures of protein-cages at the atomic level has provided relevant information to understand the biomineralization processes and design protein variants aimed at the creation of new functional biomaterials.