Release of a novel peptide from ferritin nanocages: A new tool for therapeutic applications

The development of new drug delivery systems for targeted chemotherapy release in cancer cells represents a very promising tool. In this contest, protein-based nanocages have considerable potential as drug delivery devices. Notably, ferritin has emerged as an excellent candidate due to its unique architecture, surface properties and high biocompatibility. A promising strategy might then involve ferritin cargos for specifical release of AntiMicrobial Peptides endowed with anticancer activity to cancer cells. In this paper, we encapsulated the TRIL analogue of Temporin-L peptide within a ferritin nanocage and evaluated the cargo biological properties. The results demonstrated a reduced haemolytic activity of the peptide and a selective cytotoxicity activity on cancer cells likely mediated by oxidative stress while having no effects on non-tumoral cells. The combination of the properties of ferritin with TRIL, might open up the way to the development of novel peptide delivery systems for future pharmaceutical applications.

Iron Accumulation in Ferritin

Understanding the iron accumulation process in ferritin protein nanocages has remained a centerpiece in the field of iron biochemistry/biomineralization, which ultimately has implications in health and diseases. Although mechanistic differences of iron acquisition and mineralization exist in the superfamily of ferritins, we describe the techniques that can be used to investigate the accumulation of iron in all the ferritin proteins by in vitro iron mineralization process. In this chapter, we report that the non-denaturing polyacrylamide gel electrophoresis coupled with Prussian blue staining (in-gel assay) can be useful to investigate the iron-loading efficiency in ferritin protein nanocage, by estimating the relative amount of iron incorporated inside it. Similarly, the absolute size of the iron mineral core and the amount of total iron accumulated inside its nanocavity can be determined by using transmission electron microscopy and spectrophotometry, respectively.

Hyperthermostability of prawn ferritin nanocage facilitates its application as a robust nanovehicle for nutraceuticals

The favorable physicochemical properties are essential for the application of protein-based nanovehicles in the field of biomaterials. Herein, we found that the thermal stability of Marsupenaeus japonicus ferritin (MjFer) (T_m = 109.1 ± 0.4 °C) is markedly higher than human H-chain ferritin (HuHF) (T_m = 87.7 ± 0.3 °C), although they share a high structural similarity. Multiple results indicated that the promoted thermal stability of MjFer is mainly derived from the salt bridges located at the C₃ interface. Consequently, MjFer exhibits strong protective effects on encapsulated curcumin upon exposure at high temperatures. In contrast, most of the curcumin loaded HuHF composites precipitated rapidly under the same conditions. These findings elucidated the molecular mechanism of the hyperthermostability of MjFer and illustrated that MjFer could act as a robust insulation nanocarrier for bioactive compounds against various thermal treatments.

Immunogenicity study of engineered ferritins with C- and N-terminus insertion of Epstein-Barr nuclear antigen 1 epitope

Human ferritin heavy chain, an example of a protein nanoparticle, has recently been used as a vaccine delivery platform. Human ferritin has advantages of uniform architecture, robust thermal and chemical stabilities, and good biocompatibility and biodegradation. There is however a lack of understanding about the relationship between insertion sites in ferritin (N-terminus and C-terminus) and the corresponding humoral and cell-mediated immune responses. To bridge this gap, we utilized an Epstein-Barr Nuclear Antigen 1 (EBNA1) epitope as a model to produce engineered ferritin-based vaccines E1F1 (N-terminus insertion) and F1E1 (C-terminus insertion) for the prevention of Epstein-Barr virus (EBV) infections. X-ray crystallography confirmed the relative positions of the N-terminus insertion and C-terminus insertion. For N-terminus insertion, the epitopes were located on the exterior surface of ferritin, while for C-terminus insertion, the epitopes were inside the ferritin cage. Based on the results of antigen-specific antibody titers from in-vivo tests, we found that there was no obvious difference on humoral immune responses between N-terminus and C-terminus insertion. We also evaluated splenocyte proliferation and memory lymphocyte T cell differentiation. Both results suggested C-terminus insertion produced a stronger proliferative response and cell-mediated immune response than N-terminus insertion. C-terminus insertion of EBNA1 epitope was also processed more efficiently by dendritic cells (DCs) than N-terminus insertion. This provides new insight into the relationship between the insertion site and immunogenicity of ferritin nanoparticle vaccines.

Construction of thermally robust and porous shrimp ferritin crystalline for molecular encapsulation through intermolecular arginine-arginine attractions

Protein colloid crystals are considered as high porous soft materials, presenting great potentials in nutrients and drug encapsulation, but protein crystal fabrication usually needs precipitant and high protein concentration. Herein, an easy implemented approach was reported for the construction of protein colloid crystals in diluted solution with shimp ferritin as building blocks by taking advantage of the strength of multiple intermolecular arginine-arginine interactions. The X-ray single-crystal structure reveals that a group of exquisite arginine-arginine interactions between two neighboring ferritin enable them self-assembly into long-range ordered protein soft materials. The arginine-arginine interactions mediate crystal generation favored at pH 9.5 with 200 mM NaCl, and the resulting colloid crystals exhibit high thermal stability (90 °C for 30 min). Importantly, the interglobular cavity in colloid crystals is three times larger in volume than that of intrinsic ferritin cavity in each unit cell, which can be used for molecular encapsulation.

Spatially controlled assembly of affinity ligand and enzyme cargo enables targeting ferritin nanocarriers to caveolae

One of the goals of nanomedicine is targeted delivery of therapeutic enzymes to the sub-cellular compartments where their action is needed. Endothelial caveolae-derived endosomes represent an important yet challenging destination for targeting, in part due to smaller size of the entry aperture of caveolae (ca. 30-50 nm). Here, we designed modular, multi-molecular, ferritin-based nanocarriers with uniform size (20 nm diameter) for easy drug-loading and targeted delivery of enzymatic cargo to these specific vesicles. These nanocarriers targeted to caveolar Plasmalemmal Vesicle-Associated Protein (Plvap) deliver superoxide dismutase (SOD) into endosomes in endothelial cells, the specific site of influx of superoxide mediating by such pro-inflammatory signaling as some cytokines and lipopolysaccharide (LPS). Cell studies showed efficient internalization of Plvap-targeted SOD-loaded nanocarriers followed by dissociation from caveolin-containing vesicles and intracellular transport to endosomes. The nanocarriers had a profound protective anti-inflammatory effect in an animal model of LPS-induced inflammation, in agreement with the characteristics of their endothelial uptake and intracellular transport, indicating that these novel, targeted nanocarriers provide an advantageous platform for caveolae-dependent delivery of biotherapeutics.