Ferritin-based anticancer metallodrug delivery: Crystallographic, analytical and cytotoxicity studies

Unlocking the Power of Human Ferritin: Enhanced Drug Delivery of Aurothiomalate in A2780 Ovarian Cancer Cells

Aurothiomalate (AuTM) is an FDA-approved antiarthritic gold drug with unique anticancer properties. To enhance its anticancer activity, we prepared a bioconjugate with human apoferritin (HuHf) by attaching some AuTM moieties to surface protein residues. The reaction of apoferritin with excess AuTM yielded a single adduct, that was characterized by ESI MS and ICP-OES analysis, using three mutant ferritins and trypsinization experiments. The adduct contains ~3 gold atoms per ferritin subunit, arranged in a small cluster bound to Cys90 and Cys102. MD simulations provided a plausible structural model for the cluster. The adduct was evaluated for its pharmacological properties and was found to be significantly more cytotoxic than free AuTM against A2780 cancer cells mainly due to higher gold uptake. NMR-metabolomics showed that AuTM bound to HuHf and free AuTM induced qualitatively similar changes in treated cancer cells, indicating that the effects on cell metabolism are approximately the same, in agreement with independent biochemical experiments. In conclusion, we have demonstrated here that a molecularly precise bioconjugate formed between AuTM and HuHf exhibits anticancer properties far superior to the free drug, while retaining its key mechanistic features. Evidence is provided that human ferritin can serve as an excellent carrier for this metallodrug.

Encapsulation of copper phenanthroline within horse spleen apoferritin: characterisation, cytotoxic activity and ability to retain temozolomide

Protein capsules are promising drug delivery vehicles for cancer research therapies. Apoferritin (AFt) is a self-assembling 12 nm diameter hollow nanocage with many desirable features for drug delivery, however, control of drug retention inside the protein cage remains challenging. Here we report the encapsulation of copper(ii)-1,10-phenanthroline (Cu(phen)) within the horse spleen AFt (HSAFt) nanocage, by diffusion of the metal through the pores between the protein subunits. Transmission electron microscopy revealed the formation of organised copper adducts inside HSAFt, without affecting protein integrity. These structures proved stable during storage (>4 months at -20 °C). Exposure to physiologically relevant conditions (37 °C) showed some selectivity in cargo release after 24 h at pH 5.5, relevant to the internalisation of AFt within the endosome (60% release), compared to pH 7.4, relevant to the bloodstream (40% release). Co-encapsulation of temozolomide, a prodrug used to treat glioblastoma multiforme, and Cu(phen) enabled entrapment of an average of 339 TMZ molecules per cage. In vitro results from MTT and clonogenic assays identified cytotoxic activity of the Cu(phen), HSAFt-Cu(phen) and HSAFt-Cu(phen)-TMZ adducts against colorectal cancer cells (HCT-116) and glioblastoma cells (U373V, U373M). However, the presence of the metal also contributed to more potent activity toward healthy MRC5 fibroblasts, a result that requires further investigation to assess the clinical viability of this system.

On the mechanism of action of arsenoplatins: arsenoplatin-1 binding to a B-DNA dodecamer

The reaction of Pt-based anticancer agents with arsenic trioxide affords robust complexes known as arsenoplatins. The prototype of this family of anticancer compounds is arsenoplatin-1 (AP-1) that contains an As(OH)2 fragment linked to a Pt(II) moiety derived from cisplatin. Crystallographic and spectrometric studies of AP-1 binding to a B-DNA double helix dodecamer are presented here, in comparison with cisplatin and transplatin. Results reveal that AP-1, cisplatin and transplatin react differently with the DNA model system. Notably, in the AP-1/DNA systems, the Pt-As bond can break down with time and As-containing fragments can be released. These results have implications for the understanding of the mechanism of action of arsenoplatins.

Heat sensitive E-helix cut ferritin nanocages for facile and high-efficiency loading of doxorubicin

Ferritin possesses a stable and uniform cage structure, along with tumor-targeting properties and excellent biocompatibility, making it a promising drug delivery vehicle. However, the current ferritin drug loading strategy involves complex steps and harsh reaction conditions, resulting in low yield and recovery of drug loading, which limits the clinical application prospects of ferritin nanomedicine. In this study, we utilized the high-efficiency heat-sensitivity of the multiple channel switch structures of the E-helix-cut ferritin mutant (Ecut-HFn) and Cu2+ assistance to achieve high-efficiency loading of chemotherapeutic drugs in a one-step process at low temperatures. This method features mild reaction conditions (45 °C), high loading efficiency (about 110 doxorubicin (Dox) per Ecut-HFn), and improved protein and Dox recovery rates (with protein recovery rate around 94 % and Dox recovery rate reaching up to 45 %). The prepared ferritin-Dox particles (Ecut-HFn-Cu-Dox) exhibit a uniform size distribution, good stability, and retain the natural tumor targeting ability of ferritin. Overall, this temperature-controlled drug loading strategy utilizing heat-sensitivity ferritin mutants is energy-saving, environmentally friendly, efficient, and easy to operate, offering a new perspective for scaling up the industrial production of ferritin drug carriers.

From the Discovery of Targets to Delivery Systems: How to Decipher and Improve the Metallodrugs' Actions at a Molecular Level

Metals are indispensable for the life of all organisms, and their dysregulation leads to various disorders due to the disruption of their homeostasis. Nowadays, various transition metals are used in pharmaceutical products as diagnostic and therapeutic agents because their electronic structure allows them to adjust the properties of molecules differently from organic molecules. Therefore, interest in the study of metal-drug complexes from different aspects has been aroused, and numerous approaches have been developed to characterize, activate, deliver, and clarify molecular mechanisms. The integration of these different approaches, ranging from chemoproteomics to nanoparticle systems and various activation strategies, enables the understanding of the cellular responses to metal drugs, which may form the basis for the development of new drugs and/or the modification of currently used drugs. The purpose of this review is to briefly summarize the recent advances in this field by describing the technological platforms and their potential applications for identifying protein targets for discovering the mechanisms of action of metallodrugs and improving their efficiency during delivery.

A Leaking-Proof Theranostic Nanoplatform for Tumor-Targeted and Dual-Modality Imaging-Guided Photodynamic Therapy

Objective: A protein-based leaking-proof theranostic nanoplatform for dual-modality imaging-guided tumor photodynamic therapy (PDT) has been designed. Impact Statement: A site-specific conjugation of chlorin e6 (Ce6) to ferrimagnetic ferritin (MFtn-Ce6) has been constructed to address the challenge of unexpected leakage that often occurs during small-molecule drug delivery. Introduction: PDT is one of the most promising approaches for tumor treatment, while a delivery system is typically required for hydrophobic photosensitizers. However, the nonspecific distribution and leakage of photosensitizers could lead to insufficient drug accumulation in tumor sites. Methods: An engineered ferritin was generated for site-specific conjugation of Ce6 to obtain a leaking-proof delivery system, and a ferrimagnetic core was biomineralized in the cavity of ferritin, resulting in a fluorescent ferrimagnetic ferritin nanoplatform (MFtn-Ce6). The distribution and tumor targeting of MFtn-Ce6 can be detected by magnetic resonance imaging (MRI) and fluorescence imaging (FLI). Results: MFtn-Ce6 showed effective dual-modality MRI and FLI. A prolonged in vivo circulation and increased tumor accumulation and retention of photosensitizer was observed. The time-dependent distribution of MFtn-Ce6 can be precisely tracked in real time to find the optimal time window for PDT treatment. The colocalization of ferritin and the iron oxide core confirms the high stability of the nanoplatform in vivo. The results showed that mice treated with MFtn-Ce6 exhibited marked tumor-suppressive activity after laser irradiation. Conclusion: The ferritin-based leaking-proof nanoplatform can be used for the efficient delivery of the photosensitizer to achieve an enhanced therapeutic effect. This method established a general approach for the dual-modality imaging-guided tumor delivery of PDT agents.

Construction Protocol of Drug-Protein Cage Complexes for Drug Delivery System

Ferritin is one of the most promising drug delivery system (DDS) carriers because of its uniform nanosize, biodistribution, efficient cellular uptake, and biocompatibility. Conventionally, a disassembly/reassembly method that requires pH change has been used for the encapsulation of molecules in ferritin protein nanocages. Recently, a one-step method in which a complex of ferritin and a targeted drug was obtained by incubating the mixture at an appropriate pH, was established. Here, we describe two types of protocols, the conventional disassembly/reassembly method, and the novel one-step method for the construction of a ferritin-encapsulated drug using doxorubicin as an example molecule.

Evaluation of Auranofin Loading within Ferritin Nanocages

Auranofin (AF), a gold(I) compound that is currently used for the treatment of rheumatoid arthritis and is in clinical trials for its promising anticancer activity, was encapsulated within the human H-chain and the horse spleen ferritin nanocages using the alkaline disassembly/reassembly protocol. The aim of the work was to highlight possible differences in their drug loading capacity and efficacy. The drug-loaded ferritins were characterized via UV-vis absorption spectroscopy and inductively coupled plasma-atomic emission spectroscopy to assess AF encapsulation and to define the exact amount of gold atoms trapped in the Ft cavity. The crystal structures allowed us to define the nature of AF interaction with both ferritins and to identify the gold binding sites. Moreover, the biological characterization let us to obtain preliminary information on the cytotoxic effect of AF when bound to the human H-chain.

Protein encapsulation within the internal cavity of a bacterioferritin

The thermal and chemical stability of 24mer ferritins has led to attempts to exploit their naturally occurring nanoscale (8 nm) internal cavities for biotechnological applications. An area of increasing interest is the encapsulation of molecules either for medical or biocatalysis applications. Encapsulation requires ferritin dissociation, typically induced using high temperature or acidic conditions (pH ≥ 2), which generally precludes the inclusion of fragile cargo such as proteins or peptide fragments. Here we demonstrate that minimizing salt concentration combined with adjusting the pH to ≤8.5 (i.e. low proton/metal ion concentration) reversibly shifts the naturally occurring equilibrium between dimeric and 24meric assemblies of Escherichia coli bacterioferritin (Bfr) in favour of the disassembled form. Interconversion between the different oligomeric forms of Bfr is sufficiently slow under these conditions to allow the use of size exclusion chromatography to obtain wild type protein in the purely dimeric and 24meric forms. This control over association state was exploited to bind heme at natural sites that are not accessible in the assembled protein. The potential for biotechnological applications was demonstrated by the encapsulation of a small, acidic [3Fe-4S] cluster-containing ferredoxin within the Bfr internal cavity. The capture of ∼4-6 negatively charged ferredoxin molecules per cage indicates that charge complementarity with the inner protein surface is not an essential determinant of successful encapsulation.

Application Perspectives of Nanomedicine in Cancer Treatment

Cancer is a disease that seriously threatens human health. Based on the improvement of traditional treatment methods and the development of new treatment modes, the pattern of cancer treatment is constantly being optimized. Nanomedicine plays an important role in these evolving tumor treatment modalities. In this article, we outline the applications of nanomedicine in three important tumor-related fields: chemotherapy, gene therapy, and immunotherapy. According to the current common problems, such as poor targeting of first-line chemotherapy drugs, easy destruction of nucleic acid drugs, and common immune-related adverse events in immunotherapy, we discuss how nanomedicine can be combined with these treatment modalities, provide typical examples, and summarize the advantages brought by the application of nanomedicine.

Ferritin nanocomposites for the selective delivery of photosensitizing ruthenium-polypyridyl compounds to cancer cells

Human ferritin platforms containing Ru(ii)-polypyridyl-based photosensitizers effectively target cancer cells and provide cytotoxic effects upon light-activation.

Cargo loading within ferritin nanocages in preparation for tumor-targeted delivery

Ferritins are spherical iron storage proteins within cells, composed of 24 subunits of two types, heavy-chain ferritin (HFn) and light-chain ferritin. Ferritins auto-assemble naturally into hollow nanocages with an outer diameter of 12 nm and an interior cavity 8 nm in diameter. Since the intrinsic tumor-targeting property of human HFn was first reported in 2012, HFn has been extensively explored for tumor-targeted delivery of anticancer drugs and diagnostic molecules, including radioisotopes and fluorophores, as well as inorganic nanoparticles (NPs) and chemotherapeutic drugs. This protocol provides four detailed procedures describing how to load four types of cargoes within HFn nanocages that are capable of accurately controlling cargo loading: synthesis of inorganic metal nanoparticles within the cavity of a wild-type human HFn nanocage (Procedure 1, requires ~5 h); loading of doxorubicin into the cavity of a wild-type human HFn nanocage (Procedure 2, requires ~3 d); loading Gd3+ into the cavity of a genetically engineered human HFn nanocage (Procedure 3, requires ~20 h); and loading 64Cu2+ radioisotope into the cavity of a genetically engineered human HFn nanocage (Procedure 4, requires ~3 h). Subsequent use of these HFn-based formulations is advantageous as they have intrinsic tumor-targeting capability and lack immunogenicity. Human HFn generated as described in this protocol can therefore be used to deliver therapeutic drugs and diagnostic signals as multifunctional nanomedicines.

Interaction of Platinum-based Drugs with Proteins: An Overview of Representative Crystallographic Studies

Pt-based drugs are widely used in clinics for the treatment of cancer. The mechanism of action of these molecules relies on their interaction with DNA. However, the recognition of these metal compounds by proteins plays an important role in defining pharmacokinetics, side effects and their overall pharmacological profiles. Single crystal X-ray diffraction studies provided important information on the molecular mechanisms at the basis of this process. Here, the molecular structures of representative adducts obtained upon reaction with proteins of selected Pt-based drugs, including cisplatin, carboplatin and oxaliplatin, are briefly described and comparatively examined. Data indicate that metal ligands play a significant role in driving the reaction of Pt compounds with proteins; non-covalent interactions that occur in the early steps of Pt compound/protein recognition process play a crucial role in defining the structure of the final Pt-protein adduct. In the metallated protein structures, Pt centers coordinate few protein side chains, such as His, Met, Cys, Asp, Glu and Lys residues upon releasing labile ligands.

Spectroscopic Analysis of Apoferritin Associates with the Water-Soluble Porphyrins

The association behavior of apoferritin species with the anionic porphyrins, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H₂ TPPS^4- ) and its zinc(II) complex (ZnTPPS^4- ), which are water-soluble even in acidic solutions, was investigated for the first time through UV-Vis absorption and fluorescence spectroscopy in order to evaluate a potential ability of apoferritin as a stimuli-responsive molecular capsule. The absorption maximum wavelengths of both porphyrins were redshifted and the fluorescence intensity decreased, indicating the effective association between apoferritin species and the porphyrins, although it depended on the pH adjustment procedure. At pH 2, the ZnTPPS^4- associated with apoferritin subunits without demetallating and protonating, while the free base porphyrin formed the J-aggregate of the diprotonated species (H₄ TPPS^2- )_n , with extremely low fluorescence. As the concentration of apoferritin subunits increased, the H₂ TPPS^4- -subunits associates were formed accompanied by recovering the fluorescence. The association stoichiometries of 1 or 2 subunits/porphyrin obtained under neutral and acidic conditions. The significantly large association constant of ZnTPPS^4- as compared with that of H₂ TPPS^4- indicated that the coordination to the zinc(II) center strongly contributes to the association in addition to the electrostatic interaction between apoferritin subunits and the porphyrin under acidic conditions.

Arsenoplatin-Ferritin Nanocage: Structure and Cytotoxicity

Arsenoplatin-1 (AP-1), the prototype of a novel class of metallodrugs containing a PtAs(OH)₂ core, was encapsulated within the apoferritin (AFt) nanocage. UV-Vis absorption spectroscopy and inductively coupled plasma-atomic emission spectroscopy measurements confirmed metallodrug encapsulation and allowed us to determine the average amount of AP-1 trapped inside the cage. The X-ray structure of AP-1-encapsulated AFt was solved at 1.50 Å. Diffraction data revealed that an AP-1 fragment coordinates the side chain of a His residue. The biological activity of AP-1-loaded AFt was comparatively tested on a few representative cancer and non-cancer cell lines. Even though the presence of the cage reduces the overall cytotoxicity of AP-1, it improves its selectivity towards cancer cells.

Protecting redesigned supercharged ferritin containers against protease by integration into acid-cleavable polyelectrolyte microgels

HYPOTHESIS

The application of ferritin containers as a promising drug delivery vehicle is limited by their low bioavailability in blood circulation due to unfavorable environments, such as degradation by protease. The integration of ferritin containers into the polymeric network of microgels through electrostatic interactions is expected to be able to protect ferritin against degradation by protease. Furthermore, a stimuli-responsive microgel system can be designed by employing an acid-degradable crosslinker during the microgel synthesis. This should enable ferritin release in an acidic environment, which will be useful for future drug delivery applications.

EXPERIMENTS

Nanoparticle/fluorophores-loaded ferritin was integrated into microgels during precipitation polymerization. The integration was monitored by transmission electron microscopy (TEM)² and fluorescence microscopy, respectively. After studying ferritin release in acidic solutions, we investigated the stability of ferritin inside microgels against degradation by chymotrypsin.

FINDINGS

About 80% of the applied ferritin containers were integrated into microgels and around 85% and 50% of them could be released in buffer pH 2.5 and 4.0, respectively. Total degradation of the microgels was not achieved due to the self-crosslinking of N-isopropylacrylamide (NIPAM). Finally, we prove that microgels could protect ferritin against degradation by chymotrypsin at 37 °C.

Cancer-Targeted Controlled Delivery of Chemotherapeutic Anthracycline Derivatives Using Apoferritin Nanocage Carriers

The interactions of chemotherapeutic drugs with nanocage protein apoferritin (APO) are the key features in the effective encapsulation and release of highly toxic drugs in APO-based controlled drug delivery systems. The encapsulation enables mitigating the drugs' side effects, collateral damage to healthy cells, and adverse immune reactions. Herein, the interactions of anthracycline drugs with APO were studied to assess the effect of drug lipophilicity on their encapsulation excess n and in vitro activity. Anthracycline drugs, including doxorubicin (DOX), epirubicin (EPI), daunorubicin (DAU), and idarubicin (IDA), with lipophilicity P from 0.8 to 15, were investigated. We have found that in addition to hydrogen-bonded supramolecular ensemble formation with n = 24, there are two other competing contributions that enable increasing n under strong polar interactions (APO(DOX)) or under strong hydrophobic interactions (APO(IDA) of the highest efficacy). The encapsulation/release processes were investigated using UV-Vis, fluorescence, circular dichroism, and FTIR spectroscopies. The in vitro cytotoxicity/growth inhibition tests and flow cytometry corroborate high apoptotic activity of APO(drugs) against targeted MDA-MB-231 adenocarcinoma and HeLa cells, and low activity against healthy MCF10A cells, demonstrating targeting ability of nanodrugs. A model for molecular interactions between anthracyclines and APO nanocarriers was developed, and the relationships derived compared with experimental results.

Nanobody-A versatile tool for cancer diagnosis and therapeutics

In spite of the successful use of monoclonal antibodies (mAbs) in clinic for tumor treatment, their applications are still hampered in therapeutic development due to limitations, such as tumor penetration and high cost of manufacture. Nanobody, a single domain antibody that holds the strong antigen targeting and binding capacity, has demonstrated various advantages relative to antibody. Nanobody is considered as a next-generation of antibody-derived tool in the antigen related recognition and modulation. A number of nanobodies have been developed and evaluated in different stages of clinical trials for cancer treatment. Here we summarized the current progress of nanobody in tumor diagnosis and therapeutics, particularly on the conjugation of nanobody with functional moieties. The nanobody conjugation of diagnostic agents, such as radionuclide and optical tracers, can achieve specific tumor imaging. The nanobody-drug conjugates can enhance the therapeutic efficacy of anti-tumor drugs and reduce the adverse effects. The decoration of nanobody on nanodrug delivery systems can further improve the drug targeting to specific tumors. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Recent advances in protein metalation: structural studies

Recent advances in structural studies unveiling the basis of the metal compounds/protein recognition process are discussed.

Ferritin Nanocage: A Versatile Nanocarrier Utilized in the Field of Food, Nutrition, and Medicine

Compared with other nanocarriers such as liposomes, mesoporous silica, and cyclodextrin, ferritin as a typical protein nanocage has received considerable attention in the field of food, nutrition, and medicine owing to its inherent cavity size, excellent water solubility, and biocompatibility. Additionally, ferritin nanocage also serves as a versatile bio-template for the synthesis of a variety of nanoparticles. Recently, scientists have explored the ferritin nanocage structure for encapsulation and delivery of guest molecules such as nutrients, bioactive molecules, anticancer drugs, and mineral metal ions by taking advantage of its unique reversible disassembly and reassembly property and biomineralization. In this review, we mainly focus on the preparation and structure of ferritin-based nanocarriers, and regulation of their self-assembly. Moreover, the recent advances of their applications in food nutrient delivery and medical diagnostics are highlighted. Finally, the main challenges and future development in ferritin-directed nanoparticles’ synthesis and multifunctional applications are discussed.

Nanobody-Ferritin Conjugate for Targeted Photodynamic Therapy

Ferritin is an iron-storage protein nanocage that is assembled from 24 subunits. The hollow cavity of ferritin enables its encapsulation of various therapeutic agents; therefore, ferritin has been intensively investigated for drug delivery. The use of antibody-ferritin conjugates provides an effective approach for targeted drug delivery. However, the complicated preparation and limited protein stability hamper wide applications of this system. Herein, we designed a novel nanobody-ferritin platform (Nb-Ftn) for targeted drug delivery. The site-specific conjugation between nanobody and ferritin is achieved by transglutaminase-catalyzed protein ligation. This ligation strategy allows the Nb conjugation after drug loading in ferritin, which avoids deactivation of the nanobody under the harsh pH environment required for drug encapsulation. To verify the tumor targeting of this Nb-Ftn platform, a photodynamic reagent, manganese phthalocyanine (MnPc), was loaded into the ferritin cavity, and an anti-EGFR nanobody was conjugated to the surface of the ferritin. The ferritin nanocage can encapsulate about 82 MnPc molecules. This MnPc@Nb-Ftn conjugate can be efficiently internalized by EGFR positive A431 cancer cells, but not by EGFR negative MCF-7 cells. Upon 730 nm laser irradiation, MnPc@Nb-Ftn selectively killed EGFR positive A431 cells by generating reactive oxygen species (ROS), whereas no obvious damage was observed on MCF-7 cells. Given that ferritin can be used for encapsulation of various therapeutic agents, this work provides a strategy for facile construction of nanobody-ferritin for targeted drug delivery.

Efficient synergistic combination effect of Quercetin with Curcumin on breast cancer cell apoptosis through their loading into Apo ferritin cavity

Combination of natural agents has received a great attention in cancer treatment because of synergistically increased apoptotic effect on cancer cell lines by triggering several apoptotic signaling pathways. However, the hydrophobic nature, poor bioavailability and low cellular uptake of most natural agents limit their therapeutic effectiveness. The purpose of this study was to design Apoferritin nanoparticles loaded with Quercetin and Curcumin (Que-Cur-HoS-Apo NPs) and to test their synergistic antitumor properties on a breast cancer cell line (MCF7). The physico-chemical characterization of the Que-Cur-HoS-Apo NPs by Size Exclusion Chromatography (FPLC) and Dynamic Light Scattering (DLS) confirmed the encapsulation of the compounds in the protein cage with narrow size distribution in the range 17.4 ± 1.2 nm. Cell viability study indicated that Que-Cur-HoS-Apo NPs were able to exert a more pronounced effect at lower dose on the MCF7 cell line when compared to the free combination of the drugs. The Que-Cur-HoS-Apo system allowed cellular uptake of natural agents thus triggering enhanced apoptosis. These effects were confirmed by Annexin-V/7-AAD Staining Assay and intracellular Reactive Oxygen Species (ROS) quantitative detection. These results suggest the potential of Que-Cur-HoS-Apo NPs as a promising anti-cancer agent in breast cancer therapy and pave the way to examine Que-Cur-HoS-Apo NPs effect in vivo.

Ferritin Nanocage Conjugated Hybrid Hydrogel for Tissue Engineering and Drug Delivery Applications

Hydrogels have recently been attractive in various drug delivery and tissue engineering applications because of their structural similarities to the natural extracellular matrix. Despite enormous advances in the application of hydrogels, poor mechanical properties and lack of control for the release of drugs and biomolecules act as major barriers for widespread clinical applications. To overcome these challenges, we developed both physically and covalently conjugated nanocage-laden hydrogels between the surface of the nanocage and a gelatin methacryloyl (GelMA) hydrogel matrix. Ferritin and its empty-core equivalent apoferritin were used as nanocages that could be easily incorporated into a GelMA hydrogel via physical bonding. To fabricate covalently conjugated nanocage-laden GelMA hydrogels, ferritin and apoferritin were chemically modified to present the methacryloyl groups, ferritin methacryloyl (FerMA) and apoferritin methacryloyl (ApoMA), respectively. The covalently conjugated FerMA- and ApoMA-GelMA hydrogels offered a better ability to tune mechanical properties compared with those prepared by direct dispersion of ferritin and apoferritin into GelMA hydrogels with physical bonding, without affecting their porosity or cell growth. Furthermore, the ability of the nanocage to release small chemical compounds was confirmed by performing a cumulative release test on fluorescein isothiocyanate (FITC) encapsulated apoferritin and ApoMA incorporated GelMA hydrogels by pH stimulus. Thus, the nanocage incorporated hydrogels have emerged as excellent materials for drug delivery and tissue engineering applications.

Label-free quantitative proteomics of the MCF-7 cellular response to a ferritin–metallodrug complex

Schematic summary of the experimental workflow based on label-free quantitative proteomics.

L-ferritin: A theranostic agent of natural origin for MRI visualization and treatment of breast cancer

The altered regulation of iron uptake and metabolism in cancerous cells, along with the potential of this metal to cause oxidative stress and cell death, makes iron overload an attractive therapeutic strategy for cancer treatment. In this study, the selective uptake of native HoS-ferritin (Horse-Spleen Ferritin) was assessed in TS/A breast cancer cells and compared with benign cystadenoma NMuMG. The higher expression of L-ferritin receptor SCARA5 led to an enhanced uptake in TS/A that is detected by the generation of a negative contrast in the corresponding MR images. The toxicity of HoS-ferritin toward TS/A cells has been investigated in detail in vitro, showing that cellular vitality is inversely related to the amount of internalized iron content. Finally, biodistribution and therapeutic efficacy of HoS-ferritin have been shown for the first time in vivo on a orthotopic breast cancer mice model, suggesting that iron overdose delivered by the HoS-ferritin can trigger selective mechanisms of regulated cell death.

A photosynthesis-inspired supramolecular system: caging photosensitizer and photocatalyst in apoferritin

Inspired by the bioinorganic structure of natural [FeFe]-hydrogenase ([FeFe]-H₂ase) that possesses iron sulfur clusters to catalyze proton reduction to hydrogen (H₂), we design a supramolecular photosystem by sequentially integrating hydrophobic ruthenium complex (as a photosensitizer) and diiron dithiolate complex (as a photocatalyst) into the inner surface or cavity of apoferritin via noncovalent interactions. This platform allows photosensitizer and catalyst to localize in a close proximity and short-distance electron transfer process to occur within a confined space. The resulted uniform core-shell nanocomposites were stable and well dispersed in water, and showed enhanced H₂ generation activity in acidic solution as compared to the homogenous system without apoferritin participation.

AB loop engineered ferritin nanocages for drug loading under benign experimental conditions

Human ferritin has been explored as a potential drug nanocarrier, but extreme conditions (pH ≤ 2.0) are required for the encapsulation of drugs. Here, by engineering the AB loop of ferritin, we obtained a new ferritin variant with no new pores, which can disassemble at pH 3.0 or 4.0 and reassemble at pH 7.0. Consequently, under mild conditions, drugs can be encapsulated within this new ferritin nanocage.