The Size Flexibility of Ferritin Nanocage Opens a New Way to Prepare Nanomaterials

5 years ago

The Size Flexibility of Ferritin Nanocage Opens a New Way to Prepare Nanomaterials

Meiliang Li, Guanghua Zhao, Jiachen Zang, Shengli Zhang, Chuanshan Xu, Hai Chen

Ferritins are ubiquitous iron storage proteins where Fe(II) sequestration prevents not only its spontaneous oxidation to Fe(III) but also production of toxic free radicals. Recently, scientists have subverted these nature functions and used ferritin cage structures of nanometer dimensions for encapsulation of guest molecules such as anti-cancer drugs or bioactive nutrients based on pH induced ferritin disassembly and reassembly property. However, prior to this study, ferritin nanocage was required to disassemble only under harsh pH conditions (≤2.0 or ≥11.0), followed by reassembly at near neutral pH. Such harsh conditions can cause protein or guest molecules damage to a great extent during this pH-induced unfolding–refolding process. Here, we provide evidence demonstrating that the apoferritin shell is flexible rather than rigid. Indeed, we found that two large complex molecules, uranyl acetate dihydrate and phosphotungstic acid, can reach the cavity of both plant and animal apoferritin followed by mineralization. Moreover, large organic compound such as curcumin and doxorubicin can also be encapsulated within ferritin cavity by its mixing with protein. This strategy will increase the use of ferritin in nanotechnology, and could be also applicable to other shell-like proteins as templates to prepare nanomaterials. The ferritin shell is demonstrated to be not rigid, and its flexibility increases upon removal of the iron core from holoferritin. Consequently, both organic and inorganic compounds with large size can directly enter into the protein cage, resulting in a new way to fabricate nanomaterials in the emerging field of nanomedicine and tumor imaging.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201701045