Human ferritin nanocarriers for drug-delivery: A molecular view of the disassembly process

Ferritins are natural proteins which spontaneously self-assemble forming hollow nanocages physiologically deputed to iron storage and homeostasis. Thanks to their high stability and easy production in vitro, ferritins represent an intriguing system for nanobiotechnology. Here we investigated the mechanism of disassembly and reassembly of a human recombinant ferritin constituted by the heavy chain (hHFt) exploiting a new procedure which involves the use of minimal amounts of sodium dodecyl sulfate (SDS) and assessed its effectiveness in comparison with two commonly used protocols based on pH shift at highly acidic and alkaline values. The interest in this ferritin as drug nanocarrier is related to the strong affinity of the human H-chain for the transferrin receptor TfR-1, overexpressed in several tumoral cell lines. Using different techniques, like NMR, TEM and DLS, we demonstrated that the small concentrations of SDS can eliminate the nanocage architecture without detaching the monomers from each other, which instead remain strongly associated. Following this procedure, we encapsulated into the nanocage a small ruthenium complex with a remarkable improvement with respect to previous protocols in terms of yield, structural integrity of the recovered protein and encapsulation efficiency. In our opinion, the extensive network of interchain interactions preserved during the SDS-based disassembly procedure represents the key for a complete and correct hHFt reassembly.