Fig. 1.

Illustration of drug loading strategies and modular ferritin platforms. a) Different routes for ferritin drug loading such as 1) chemical conjugation of drugs to ferritin surface, 2) pH- or salt-based assembly and disassembly of drugs inside ferritin, and 3) diffusion of small molecules through the surface pores of ferritin. b) Examples of modular ferritin platforms such as 1) ferritin incorporating Fc-binding peptide for binding targeting antibodies[39], 2) incorporation of unnatural azide-bearing amino acid in ferritin for click coupling to targeting ligands or antibodies (unpublished internal study), 3) ferritin surface conjugated with β-cyclodextrins for rapid drug loading[40], 4) ferritin incorporating protein G and 6X-His tag for antibody or cargo binding[41], and 5) engineered ferritin displaying functional peptides for siRNA delivery[42].