Polymer‐Mediated Synthesis of Ferritin‐Encapsulated Inorganic Nanoparticles

Abstract

The fabrication of novel bioinorganic nanostructures by using biological templates with capsid-like architectures has received significant attention. [1][2][3][4][5][6][7] An important archetype of this approach involves the synthesis of polypeptide-encapsulated inorganic nanoparticles within the spheroidal 8-nm-diameter cage of the iron-storage protein, apoferritin. [1,2] Native ferritin consists of 24 polypeptide subunits arranged in 432 symmetry to produce a spherical hollow shell which is permeated by eight hydrophilic and six hydrophobic channels with pore sizes between 0.3-0.5 nm and which encloses a mineral core of hydrated iron oxide. [8] The channels facilitate the influx and efflux of metal ions and small molecules, such that the native iron oxide core can be removed from the protein cage by reductive dissolution and the resulting apoferritin molecules can be reconstituted synthetically with various types of inorganic nanoparticles. Inorganic nucleation occurs specifically within the polypeptide cavity due to metal-ion binding to anionic amino acids located on the internal surface of the cavity, which, in the presence of an appropriate counterion, increase the local supersaturation. In most cases, this is faciliated by intracavity oxidation of the bound metal ions, which lowers the solubility of the product and increases the rate of hydrolysis to produce nanoparticles such as Fe 3 O 4 , [9] MnOOH, [1,10] CoOOH, [11] or Co 3 O 4 . [12] Similarly, reduction of metal ions, anionic complexes, or both within the apoferritin cage can be used to prepare biomimetic ferritins with entrapped Ag, [13] Pd, [14] or CoPt [15] nanoparticles, respectively. Alternatively, ferritins containing uranyl, [1] indium, [16] nickel, [17] or chromium [17] hydrated oxides and hydroxides have been synthesized by using nonredox hydrolysis reactions and slow coprecipitation routes developed for the preparation of ferritin-encapsulated CdS, [18] CdSe, [19] or ZnSe [20] nanoparticles. Some of these biomimetic ferritins have been shown to have functional properties, for example, in magnetic storage [15,21] and imaging [22] and in size-selective catalytic hydrogenation. [14] In addition, by embedding the inorganic nanoparticles within the polypeptide cage, the hybrid nanostructures can be reversibly assembled into higher order superstructures by attach-[*] Dr.

Synthetic and Bioinspired Cage Nanoparticles for Drug Delivery

“…Cavities formed by ferritin can act as a reaction vessel for the fabrication of inorganic nanoparticles with narrow size distribution [58][59][60]. This strategy has been employed by Douglas and coworkers to encapsulate iron oxide (magnetite) nanoparticles into ferritin cavities for potential applications in MRI [61].…”

Optical Waveguiding Organic Nanorods Coated with Reversibly Switchable Fe(II) Spin Transition Nanoparticles

“…Bottom-up nanofabrication of self-assembled multifunctional nanoobjects and study of their uncharted physical properties at the nanoscale level are an active and sophisticated research area of nanoscience and technology [1][2][3][4][5][6][7][8][9][10][11][12][13]. Particularly programming the in situ growth of selfassembled organic and inorganic nanostructures from different molecular components and also their integration to form hybrid nanoscale objects in the same pot is a less explored area.…”

“…Particularly programming the in situ growth of selfassembled organic and inorganic nanostructures from different molecular components and also their integration to form hybrid nanoscale objects in the same pot is a less explored area. A successful groundwork in this discipline might lead to new advanced functional hybrid nanomaterials capable of performing a sensing, electronic, photonic, and mechanical function [1][2][3][4][5][6][7][8][9][10][11][12][13]. For example integration of magnetically bistable inorganic nanoparticles (NPs) and optical wave guiding organic nanostructures could facilitate remote manipulation of the light sensitive spin states of individual NPs through guided laser light.…”

Selective targeting of melanoma by PEG-masked protein-based multifunctional nanoparticles

“…As a consequence, ferritin proteins guarantee excellent size and shape control in metal nanoparticle synthesis, and several materials, such as Fe 3 O 4 , Co 3 O 4 , Mn 3 O 4 , Pt, CoPt, Pd, CdS, CdSe, ZnSe, CaCO 3 , Ag, and Au have been produced within the internal cavity of ferritin proteins. [10][11][12][13][14][15][16][17][18] The small size of ferritins (,20 nm) increases the chances of larger nanoparticles passing human body barriers and reaching specific targets. Indeed, the dimensions of the nanoparticles, which must be small enough to penetrate capillary fenestrations and large enough to avoid rapid clearance through the kidney (the ideal diameter being lower than 50-60 nm and greater than 6-8 nm, respectively), 19,20 are one of the key prerequisites for efficient targeted delivery, together with a long-circulating capability of the carrier and high specificity of the selector towards the target receptor.…”