Ferritin-based drug delivery systems: Hybrid nanocarriers for vascular immunotargeting

Genetically Modified Ferritin Nanoparticles with Bone-Targeting Peptides for Bone Imaging

Bone homeostasis plays a major role in supporting and protecting various organs as well as a body structure by maintaining the balance of activities of the osteoblasts and osteoclasts. Unbalanced differentiation and functions of these cells result in various skeletal diseases, such as osteoporosis, osteopetrosis, and Paget’s disease. Although various synthetic nanomaterials have been developed for bone imaging and therapy through the chemical conjugation, they are associated with serious drawbacks, including heterogeneity and random orientation, in turn resulting in low efficiency. Here, we report the synthesis of bone-targeting ferritin nanoparticles for bone imaging. Ferritin, which is a globular protein composed of 24 subunits, was employed as a carrier molecule. Bone-targeting peptides that have been reported to specifically bind to osteoblast and hydroxyapatite were genetically fused to the N-terminus of the heavy subunit of human ferritin in such a way that the peptides faced outwards. Ferritin nanoparticles with fused bone-targeting peptides were also conjugated with fluorescent dyes to assess their binding ability using osteoblast imaging and a hydroxyapatite binding assay; the results showed their specific binding with osteoblasts and hydroxyapatite. Using in vivo analysis, a specific fluorescent signal from the lower limb was observed, demonstrating a highly selective affinity of the modified nanoparticles for the bone tissue. These promising results indicate a specific binding ability of the nanoscale targeting system to the bone tissue, which might potentially be used for bone disease therapy in future clinical applications.

Apoferritin nanocages for targeted delivery of idarubicin against breast cancer cells

In recent years, nanotechnology has attracted attention for its capability to diagnose and remedy diverse tumors successfully.  Protein nanocarriers as a platform of targeted drug delivery can be used to reduce toxicity and improve the effect of anticancer drugs. Idarubicin (IDR) is a chemotherapy drug that is classified as an anthracycline antitumor. In this study, IDR was encapsulated within horse spleen apoferritin (HsAFr) nanocarriers. Encapsulation was obtained through disassembling apoferritin into subunits at pH 2 and subsequently reassembling it at pH 7.4 in the presence of IDR. Transmission electron microscopy, UV-vis, and fluorescence spectroscopy techniques showed that drug molecules are loaded within apoferritin. Intrinsic fluorescence information exhibited that the encapsulation does not have any effects on the tertiary structure of the protein. Drug loading and entrapment efficiency were found to be 7.15% and 84.75%, respectively. Comparison of anticancer activities in HsAFr-IDR and free drug IDR was made via the MTT viability technique in a human breast cancer cell line (MCF-7).

H-Ferritin nanoparticle-mediated delivery of antibodies across a BBB in vitro model for treatment of brain malignancies

Brain cancers are a group of neoplasms that can be either primary, such as glioblastoma multiforme (GBM), or metastatic, such as the HER2+ breast cancer brain metastasis. The brain represents a sanctuary for cancer cells thanks to the presence of the blood brain barrier (BBB) that controls trafficking of molecules, protecting the brain from toxic substances including drugs. Considering that GBM and HER2+ breast cancer brain metastases are characterized by EGFR and HER2 over-expression respectively, CTX- and TZ-based treatment could be effective. Several studies show that these monoclonal antibodies (mAbs) exert both a cytostatic activity interfering with the transduction pathways of EGFR family and a cytotoxic activity mainly through the immune system activation via the antibody dependent cell-mediated cytotoxicity (ADCC). Since the major limitation to therapeutic mAbs application is the presence of the BBB, here we use a recombinant form of human apoferritin (HFn) as a nanovector to promote the delivery of mAbs to the brain for the activation of the ADCC response. Using a transwell model of the BBB we proved the crossing ability of HFn-mAb. Cellular uptake of HFn-mAb by human cerebral microvascular endothelial cells (hCMEC/D3) was demonstrated by confocal microscopy. Moreover, after crossing the endothelial monolayer, HFn-conjugated mAbs retain their biological activity against targets, as assessed by MTS and ADCC assays. Our data support the use of HFn as efficient carrier to enhance the BBB crossing of mAbs, without affecting their antitumoral activity.

Kinetics of Ferritin Self-Assembly by Laser Light Scattering: Impact of Subunit Concentration, pH, and Ionic Strength

Ferritins, the cellular iron repositories, are self-assembled, hollow spherical nanocage proteins composed of 24 subunits. The self-assembly process in ferritin generates the electrostatic gradient to rapidly sequester Fe(II) ions, thereby minimizing its toxicity (Fenton reaction). Although the factors that drive self-assembly and control its kinetics are little investigated, its inherent reversibility has been utilized for cellular imaging and targeted drug delivery. The current work tracks the kinetics of ferritin self-assembly by laser light scattering and investigates the factors that influence the process. The formation of partially structured subunit-monomers/dimers, at pH ≤ 1.5, serves as the starting material for the self-assembly, which upon increasing the pH exhibits biphasic behavior (a rapid assembly process coupled with subunit folding followed by a slower reassembly/reorganization process) and completes within 10 min. The ferritin self-assembly accelerated with subunit concentration and ionic strength (t_1/2 decreases in both the cases) but slowed down with the pH of the medium from 5.5 to 7.5 (t_1/2 increases). These findings would help to regulate the ferritin self-assembly to enhance the loading/unloading of drugs/nanomaterials for exploiting it as a nanocarrier and nanoreactor.

Harnessing molecular recognition for localized drug delivery

A grand challenge in drug delivery is providing the right dose, at the right anatomic location, for the right duration of time to maximize therapeutic efficacy while minimizing off-target toxicity and other deleterious side-effects. Two general modalities are receiving broad attention for localized drug delivery. In the first, referred to as "targeted accumulation", drugs or drug carriers are engineered to have targeting moieties that promote their accumulation at a specific tissue site from circulation. In the second, referred to as "local anchoring", drugs or drug carriers are inserted directly into the tissue site of interest where they persist for a specified duration of time. This review surveys recent advances in harnessing molecular recognition between proteins, peptides, nucleic acids, lipids, and carbohydrates to mediate targeted accumulation and local anchoring of drugs and drug carriers.

tLyP-1 Peptide Functionalized Human H Chain Ferritin for Targeted Delivery of Paclitaxel

PURPOSE

The aims of this study were to test the feasibility, targeting specificity and anticancer therapeutic efficacy of CendR motif tLyP-1 functionalized at the N-terminal of ferritin for paclitaxel (PTX) delivery.

METHODS

A tumor homing and penetrating peptide tLyP-1 was fused to the N-terminal of human H chain ferritin (HFtn) to generate a dual-targeting nanoparticle delivery system. PTX molecules were encapsulated into the HFtn nanocage using the disassembly/assembly method by adjusting pHs. Cellular uptake was examined by confocal laser scanning microscopy (CLSM) and flow cytometry. The MTT assay was used to test the cytotoxicity of various PTX-loaded NPs against MDA-MB-231 and SMMC-7721 tumor cells. The wound healing and cell migration assays were conducted to assess the inhibitory effect on cell motility and metastasis. The inhibition effect on the SMMC-7721 tumor spheroids was studied and penetration ability was evaluated by CLSM. The antitumor efficacy of PTX-loaded NPs was assessed in MDA-MB-231 breast cancer xenografted in female BALB/c nude mice.

RESULTS

Compared with HFtn-PTX, in vitro studies demonstrated that the tLyP-1-HFtn-PTX displayed enhanced intracellular delivery and better cytotoxicity and anti-invasion ability against both SMMC-7721 and MDA-MB-231 cells. The better penetrability and growth inhibitory effect on SMMC-7721 tumor spheroids were also testified. In vivo distribution and imaging demonstrated that the tLyP-1-HFtn-PTX NPs were selectively accumulated and penetrated at the tumor regions. Verified by the breast cancer cells model in BABL/c nude mice, tLyP-1-HFtn-PTX displayed higher in vivo therapeutic efficacy with lower systemic toxicity.

CONCLUSION

Ferritin decorated with tumor-homing penetration peptide tLyP-1 at the N terminal could deliver PTX specifically inside the cell via receptor-mediated endocytosis with better efficacy. The peptide tLyP-1 which is supposed to work only at the C terminus showed enhanced tumor tissue penetration and antitumor efficacy, demonstrating that it also worked at the N-terminal of HFtn.

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.

Biomimetic and bioinspired silicifications: Recent advances for biomaterial design and applications

The rational design and controllable synthesis of functional silica-based materials have gained increased interest in a variety of biomedical and biotechnological applications due to their unique properties. The current review shows that marine organisms, such as siliceous sponges and diatoms, could be the inspiration for the fabrication of advanced biohybrid materials. Several biomolecules were involved in the molecular mechanism of biosilicification in vivo. Mimicking their behavior, functional silica-based biomaterials have been generated via biomimetic and bioinspired silicification in vitro. Additionally, several advanced technologies were developed for in vitro and in vivo immobilization of biomolecules with potential applications in biocatalysis, biosensors, bioimaging, and immunoassays. A thin silica layer could coat a single living cell or virus as a protective shell offering new opportunities in biotechnology and nanomedicine fields. Promising nanotechnologies have been developed for drug encapsulation and delivery in a targeted and controlled manner, in particular for poorly soluble hydrophobic drugs. Moreover, biomimetic silica, as a morphogenetically active biocompatible material, has been utilized in the field of bone regeneration and in the development of biomedical implantable devices. STATEMENT OF SIGNIFICANCE: In nature, silica-based biomaterials, such as diatom frustules and sponge spicules, with high mechanical and physical properties were created under biocompatible conditions. The fundamental knowledge underlying the molecular mechanisms of biosilica formation could inspire engineers and chemists to design novel hybrid biomaterials using molecular biomimetic strategies. The production of such biohybrid materials brings the biosilicification field closer to practical applications. This review starts with the biosilicification process of sponges and diatoms with recently updated researches. Then, this article covers recent advances in the design of silica-based biomaterials and their potential applications in the fields of biotechnology and nanomedicine, highlighting several promising technologies for encapsulation of functional proteins and living cells, drug delivery and the preparation of scaffolds for bone regeneration.

Ferritin as a Platform for Creating Antiviral Mosaic Nanocages: Prospects for Treating COVID-19

Infectious diseases are a continues threat to human health and the economy worldwide. The latest example is the global pandemic of COVID-19 caused by SARS-CoV-2. Antibody therapy and vaccines are promising approaches to treat the disease; however, they have bottlenecks: they might have low efficacy or narrow breadth due to the continuous emergence of new strains of the virus or antibodies could cause antibody-dependent enhancement (ADE) of infection. To address these bottlenecks, I propose the use of 24-meric ferritin for the synthesis of mosaic nanocages to deliver a cocktail of antibodies or nanobodies alone or in combination with another therapeutic, like a nucleotide analogue, to mimic the viral entry process and deceive the virus, or to develop mosaic vaccines. I argue that available data showing the effectiveness of ferritin-antibody conjugates in targeting specific cells and ferritin-haemagglutinin nanocages in developing influenza vaccines strongly support my proposals.

Construction of a tumor microenvironment pH-responsive cleavable PEGylated hyaluronic acid nano-drug delivery system for colorectal cancer treatment

In order to improve active tumor targeting, tumor cell uptake efficiency and circulation time of doxorubicin (DOX) in vivo, we constructed a cleavable PEGylated hyaluronic acid nano-drug delivery system (HA-mPEG2k-DOX) based on a tumor microenvironment pH-responsive imine bond. In this study, HA-mPEG2k-DOX can self-assemble into stable nanoparticles (HA-mPEG2k-DOX NPs) with a particle size of 50 nm. And the NPs can efficiently target CD44 positive CT26 cells and the pH-responsive cleavable PEG shell can be detached under weakly acidic environments and effectively promote the cellular uptake of HA-DOX NPs. Compared with DOX·HCl, the HA-mPEG2k-DOX NPs can significantly increase the DOX circulation time by 12.5 times, efficiently target the tumor tissues of CT26 tumor-bearing mice and remain for 72 hours. Therefore, the antitumor results in vivo indicated that the HA-mPEG2k-DOX NPs have the best anti-tumor effect while reducing the toxicity of the DOX. Overall, the cleavable PEGylated HA-mPEG2k-DOX NPs responding to pH-sensitive imine bonds, while actively targeting CD44-positive tumor cells, improve the dilemma of cellular uptake and delivery by the PEGylated nano delivery system.

Advances in encapsulin nanocompartment biology and engineering

Compartmentalization is an essential feature of all cells. It allows cells to segregate and coordinate physiological functions in a controlled and ordered manner. Different mechanisms of compartmentalization exist, with the most relevant to prokaryotes being encapsulation via self-assembling protein-based compartments. One widespread example of such is that of encapsulins-cage-like protein nanocompartments able to compartmentalize specific reactions, pathways, and processes in bacteria and archaea. While still relatively nascent bioengineering tools, encapsulins exhibit many promising characteristics, including a number of defined compartment sizes ranging from 24 to 42 nm, straightforward expression, the ability to self-assemble via the Hong Kong 97-like fold, marked physical robustness, and internal and external handles primed for rational genetic and molecular manipulation. Moreover, encapsulins allow for facile and specific encapsulation of native or heterologous cargo proteins via naturally or rationally fused targeting peptide sequences. Taken together, the attributes of encapsulins promise substantial customizability and broad usability. This review discusses recent advances in employing engineered encapsulins across various fields, from their use as bionanoreactors to targeted delivery systems and beyond. A special focus will be provided on the rational engineering of encapsulin systems and their potential promise as biomolecular research tools.

Development of a Novel Dual-Order Protein-Based Nanodelivery Carrier That Rapidly Targets Low-Grade Gliomas with Microscopic Metastasis in Vivo

Clinically diagnosing low-grade gliomas and microscopic metastatic tumors in the spinal cord using magnetic resonance imaging (MRI) is challenging, as the blood-brain barrier (BBB) almost completely excludes the MRI contrast agent gadopentetate dimeglumine, GdDTPA (Magnevist), from the brain. The development of a more efficient, safe, and broad-spectrum glioma diagnosis and treatment would therefore have a great clinical value. Based on the high expression levels of both transferrin receptor 1 (TfR1) and low-density lipoprotein receptor-related protein 1 (LRP1) in BBB-related cells and glioma cells, we designed a novel protein nanoparticle, ferritin-HREV107-Angiopep-2 (Fn-Rev-Ang). We found that Fn-Rev-Ang rapidly crossed the BBB in mice and had drug-loading properties. Moreover, the brain MRI signal intensity ratio associated with Fn-Rev-Ang-GdDTPA was higher than that associated with Fn-GdDTPA alone. Importantly, gliomas with diameters below 1 mm and microscopic metastatic tumors in the spinal cord were successfully detected in mice by MRI with Fn-Rev-Ang-GdDTPA, which is not possible using the current clinical MRI technology. In addition, Fn-Rev-Ang-loaded doxorubicin had a strong inhibitory effect on mouse brain gliomas and their metastasis, which significantly prolonged the animal survival time. Thus, our newly constructed Fn-Rev-Ang nanodelivery carrier may help expand the use of MRI to the early diagnosis and treatment of microscopic tumors, thereby offering a possible basis for improving the survival rate of patients with gliomas and microscopic spinal metastatic tumors.

Double-Interface Binding of Two Bioactive Compounds with Cage-Like Ferritin

Ferritin is a cage-like carrier protein with multiple interfaces, allowing for the encapsulation and delivery of biologically active molecules. In this study, hesperetin was covalently conjugated to the outer surface of ferritin to fabricate hesperetin covalently modified ferritin (HFRT) at pH 9.0. This conjugation resulted in a binding equivalent of hesperetin to ferritin of 12.33 ± 0.56 nmol/mg. After covalent binding, the free amino content of HFRT decreased and the secondary and tertiary structures of HFRT were changed relative to the structure of control ferritin. In addition, HFRT successfully retained the cage-like structure of ferritin and exhibited reversible self-assembly property regulated by pH shifts. Taking advantage of this property, quercetin was encapsulated into the inner surface of HFRT with an encapsulation ratio of 14.0 ± 1.36% (w/w). The modification with hesperetin improved the digestive stability of ferritin and enhanced the stability of encapsulated quercetin against thermal treatment compared to unmodified ferritin. This study explored the functions of the double interfaces of ferritin by covalent and non-covalent binding of two different bioactive compounds. The results can help guide the functionalization of the ferritin cage as a nanocarrier in food application.

Targeting drug delivery in the vascular system: Focus on endothelium

The bloodstream is the main transporting pathway for drug delivery systems (DDS) from the site of administration to the intended site of action. In many cases, components of the vascular system represent therapeutic targets. Endothelial cells, which line the luminal surface of the vasculature, play a tripartite role of the key target, barrier, or victim of nanomedicines in the bloodstream. Circulating DDS may accumulate in the vascular areas of interest and in off-target areas via mechanisms bypassing specific molecular recognition, but using ligands of specific vascular determinant molecules enables a degree of precision, efficacy, and specificity of delivery unattainable by non-affinity DDS. Three decades of research efforts have focused on specific vascular targeting, which have yielded a multitude of DDS, many of which are currently undergoing a translational phase of development for biomedical applications, including interventions in the cardiovascular, pulmonary, and central nervous systems, regulation of endothelial functions, host defense, and permeation of vascular barriers. We discuss the design of endothelial-targeted nanocarriers, factors underlying their interactions with cells and tissues, and describe examples of their investigational use in models of acute vascular inflammation with an eye on translational challenges.

Development of Tumor-Targeted Indocyanine Green-Loaded Ferritin Nanoparticles for Intraoperative Detection of Cancers

Indocyanine green (ICG) is a fluorescent dye with a strong emission in the near-infrared spectral range that allows deep signal penetration and minimal interference of tissue autofluorescence. It has been employed in clinics for different applications, among which the more interesting is certainly near-infrared fluorescence image-guided surgery. This technique has found wide application in surgical oncology for lymph node mapping or for laparoscopic surgery. Despite ICG being useful for tracking loco-regional lymph nodes, it does not provide any information about cancer involvement of such lymph nodes or lymphatic vessels, lacking any tumor-targeting specificity. However, the clinical need in surgical oncology is not only a specific tracking of metastatic nodes but also the intraoperative detection of micrometastatic deposits. Here, we have exploited a nanotechnological solution to improve ICG usefulness by its encapsulation in H-ferritin (HFn) nanocages. They are natural protein-based nanoparticles that exhibit some very interesting features as delivery systems in oncological applications because they display specific tumor homing. We show that HFn loaded with ICG exhibits specific uptake into different cancer cell lines and is able to deliver ICG to the tumor more efficiently than the free dye in an in vivo model of TNBC. Our results pave the way for the application of ICG-loaded HFn in fluorescence image-guided surgery of cancer.

Protein cages and virus-like particles: from fundamental insight to biomimetic therapeutics

Protein cages (viral and non-viral) found in nature have evolved for a variety of purposes and are found in all kingdoms of life. The main functions of these nanoscale compartments are the protection and delivery of nucleic acids e.g. virus capsids, or the enrichment and sequestration of metabolons e.g. bacterial microcompartments. This review focuses on recent developments of protein cages for use in immunotherapy and therapeutic delivery. In doing so, we highlight the unique ways in which protein cages have informed on fundamental principles governing bio-nano interactions. With the enormous existing design space among naturally occurring protein cages, there is still much to learn from studying them as biomimetic particles.

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.

The nanostructured secretome

The term secretome, which traditionally strictly refers to single proteins, should be expanded to also include the great variety of nanoparticles secreted by cells (secNPs) into the extracellular space, which ranges from high-density lipoproteins of a few nanometers to extracellular vesicles and fat globules of hundreds of nanometers. Widening the definition is urged by the ever-increasing understanding of the role of secNPs as regulators/mediators of key physiological and pathological processes, which also puts them in the running as breakthrough cell-free therapeutics and diagnostics. "Made by cells for cells", secNPs are envisioned as a sweeping paradigm shift in nanomedicine, promising to overcome the limitations of synthetic nanoparticles by unsurpassed circulation and targeting abilities, precision and sustainability. From a longer/wider perspective, advanced manipulation would possibly make secNPs available as building blocks for future "biogenic" nanotechnology. However, the current knowledge is fragmented and sectorial (the majority of the studies being focused on a specific biological and/or medical aspect of a given secNP class or subclass), the understanding of the nanoscale and interfacial properties is limited and the development of bioprocesses and regulatory initiatives is in the early days. We believe that new multidisciplinary competencies and synergistic efforts need to be attracted and augmented to move forward. This review will contribute to the effort by attempting for the first time to rationally gather and elaborate secNPs and their traits into a unique concise framework - from biogenesis to colloidal properties, engineering and clinical translation - disclosing the overall view and easing comparative analysis and future exploitation.

Application of Electrically Conducting Nanocomposite Material Polythiophene@NiO/Frt/GOx as Anode for Enzymatic Biofuel Cells

In this work, nano-inspired nickel oxide nanoparticles (NiO) and polythiophene (Pth) modified bioanode was prepared for biofuel cell applications. The chemically prepared nickel oxide nanoparticles and its composite with polythiophene were characterized for elemental composition and microscopic characterization while using scanning electron microscopy. The electrochemical characterizations of polythiophene@NiO composite, biocompatible mediator ferritin (Frt) and glucose oxidase (GOx) catalyst modified glassy carbon (GC) electrode were carried out using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and charge-discharge studies. The current density of Pth@NiO/Frt/GOx bioanode was found to be 5.4 mA/cm². The bioanode exhibited a good bio-electrocatalytic activity towards the oxidation of the glucose. The experimental studies of the bioanode are justifying its employment in biofuel cells. This will cater a platform for the generation of sustainable energy for low temperature devices.

Modular protein-DNA hybrid nanostructures as a drug delivery platform

With the increasing number of identified intracellular drug targets, cytosolic drug delivery has gained much attention. Despite advances in synthetic drug carriers, however, construction of homogeneous and biocompatible nanostructures in a controllable manner still remains a challenge in a translational medicine. Herein, we present the modular design and assembly of functional DNA nanostructures through sequence-specific interactions between zinc-finger proteins (ZnFs) and DNA as a cytosolic drug delivery platform. Three kinds of DNA-binding ZnF domains were genetically fused to various proteins with different biological roles, including targeting moiety, molecular probe, and therapeutic cargo. The engineered ZnFs were employed as distinct functional modules, and incorporated into a designed ZnF-binding sequence of a Y-shaped DNA origami (Y-DNA). The resulting functional Y-DNA nanostructures (FYDN) showed self-assembled superstructures with homogeneous morphology, strong resistance to exonuclease activity and multi-modality. We demonstrated the general utility of our approach by showing efficient cytosolic delivery of PTEN tumour suppressor protein to rescue unregulated kinase signaling in cancer cells with negligible nonspecific cytotoxicity.

Ferritin Nanocages for Protein Delivery to Tumor Cells

The delivery of therapeutic proteins is one of the greatest challenges in the treatment of human diseases. In this frame, ferritins occupy a very special place. Thanks to their hollow spherical structure, they are used as modular nanocages for the delivery of anticancer drugs. More recently, the possibility of encapsulating even small proteins with enzymatic or cytotoxic activity is emerging. Among all ferritins, particular interest is paid to the Archaeoglobus fulgidus one, due to its peculiar ability to associate/dissociate in physiological conditions. This protein has also been engineered to allow recognition of human receptors and used in vitro for the delivery of cytotoxic proteins with extremely promising results.

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.

Novel Paclitaxel-Loaded Nanoparticles Based on Human H Chain Ferritin for Tumor-Targeted Delivery

Paclitaxel (PTX), an excellent chemotherapeutic antitumor drug, is widely used to treat patients with various cancers. However, its clinical applications are greatly restricted by poor solubility and lack of targeting. Herein, we applied natural human H chain ferritin (HFtn) nanocages that can bind to tumor cells via interacting with the human transferritin receptor 1 (TfR1) leading to its endocytosis as the PTX carrier for the targeted delivery. PTX molecules were encapsulated into HFtn cavity using disassembly/reassembly method through adjusting pH. According to the requirements of drugs suitable for clinical trials, HFtn can be easily purified in high yields with no ligand modification or property modulation. We demonstrated that PTX molecules were successfully encapsulated in the protein nanocages. The HFtn-PTX nanoparticles exhibited similar morphology and structural characteristics to the hollow cage and showed significant cytotoxicity in vitro than the naked PTX. Flow cytometry, confocal laser scanning microscopy, and in vivo imaging of MDA-MB-231 tumor demonstrated the HFtn-PTX nanoparticles targeting ability to tumor cells. Cell apoptosis assay showed that HFtn-PTX had similar apoptotic characteristics on MDA-MB-231 cells as that of the free PTX. HFtn-PTX nanoparticles have higher in vivo therapeutic efficacy and lower systemic toxicity. The BALB/c mice model also confirmed the effectiveness of the nanoparticles. Specifically targeting to tumors and solving the solubility issue of water-insoluble drugs thus alleviating the side effects, HFtn can be an efficient hydrophobic drug delivery nanocarrier for further applications in cancer therapy.

Proanthocyanidin Encapsulated in Ferritin Enhances Its Cellular Absorption and Antioxidant Activity

Proanthocyanidins (PAs) possess superior antioxidant properties and nutritious value, however, low bioavailability and stability limit their applications. Here, we developed a novel method to encapsulate PA dimers successfully into horse spleen apoferritin (apoHSF) using a disassembly/reassembly method based on pH change. The PA-HSF nanoparticles were characterized using fluorescence spectroscopy, transmission electron microscopy, circular dichroism, and high-performance liquid chromatography. One apoferritin cage could approximately encapsulate 25.6 molecules of the PA dimer. The results showed that the encapsulation of the PA dimers protected it from the damage of oxidants and temperature below room temperature would be an appropriate condition for HSF-578 solution storage. Moreover, HepG2 cell monolayer absorption and adhesion analyses indicated that the PA dimers encapsulated within apoHSF cages were more efficient in transport. In addition, it was indicated that the PA-HSF nanoparticles had higher cellular antioxidant activity. The novel strategy provided in this study indicates that the protein cage structures like ferritin have potential to be applied in the field of food nutrition.

Ferritin nanovehicle for targeted delivery of cytochrome C to cancer cells

In this work, we have exploited the unique properties of a chimeric archaeal-human ferritin to encapsulate, deliver and release cytochrome c and induce apoptosis in a myeloid leukemia cell line. The chimeric protein combines the versatility in 24-meric assembly and cargo incorporation capability of Archaeglobus fulgidus ferritin with specific binding of human H ferritin to CD71, the "heavy duty" carrier responsible for transferrin-iron uptake. Delivery of ferritin-encapsulated cytochrome C to the Acute Promyelocytic Leukemia (APL) NB4 cell line, highly resistant to transfection by conventional methods, was successfully achieved in vitro. The effective liberation of cytochrome C within the cytosolic environment, demonstrated by double fluorescent labelling, induced apoptosis in the cancer cells.

Application of crossflow ultrafiltration for scaling up the purification of a recombinant ferritin

Ferritin proteins are taking center stage as smart nanocarriers for drug delivery due to their hollow cage-like structures and their unique 24-meric assembly. Among all ferritins, the chimeric Archaeoglobus ferritin (HumFt) is able assemble/disassemble varying the ionic strength of the medium while recognizing human TfR1 receptor overexpressed in cancer cells. In this paper we present a highly efficient, large scale purification protocol mainly based on crossflow ultrafiltration, starting from fermented bacterial paste. This procedure allows one to obtain about 2 g of purified protein starting from 100 g of fermented bacterial paste. The current procedure can easily remove contaminant proteins as well as DNA molecules in the absence of expensive and time consuming chromatographic steps.

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

The encapsulation of anticancer metal-based drugs within a protein nanocage represents a valuable strategy to improve the efficacy and selectivity of these compounds towards cancer cells. The preparation, characterization of the in vitro cytotoxicity and X-ray structures of several ferritin-metallodrug nanocomposites (mainly containing platinum-, ruthenium- and gold-based anticancer agents) are here reviewed. The molecular mechanisms of action of these Ft-metallodrug adducts are discussed and future directions in the field are outlined.

Ferritin: A Platform for MRI Contrast Agents Delivery

The search for high relaxivities and increased specificity continues to be central to the development of paramagnetic contrast agents for magnetic resonance imaging (MRI). Ferritin, due to its unique surface properties, architecture, and biocompatibility, has emerged as a natural nanocage that can potentially help to reach both these goals. This review aims to highlight recent advances in the use of ferritin as a nanoplatform for the delivery of metal-based MRI contrast agents (containing Gd3+, Mn2+, or Fe2O3) alone or in combination with active molecules used for therapeutic purposes. The collected results unequivocally show that the use of ferritin for contrast agent delivery leads to more accurate imaging of cancer cells and a significantly improved targeted therapy.

Hypoxia-tropic Protein Nanocages for Modulation of Tumor- and Chemotherapy-Associated Hypoxia

Despite its central role in tumor progression and treatment resistance, poor vascularization that necessitates penetration of therapeutics through tumor extracellular matrix (ECM) constitutes a significant challenge to managing tumor hypoxia via conventional systemic treatment regimens. In addition, methods to target hypoxic tumor cells are lacking. Here, we discovered that human ferritin nanocages (FTn) possess an intrinsic ability to preferentially engage with hypoxic tumor tissues, in addition to normoxic tumor areas. We also developed a simple method of endowing FTn with spatially controlled "mosaic" surface poly(ethylene glycol) (PEG) coatings that facilitate deep penetration of FTn through ECM to reach hypoxic tumor tissues while retaining its inherent hypoxia-tropic property. Hypoxia-inhibiting agents systemically delivered via this surface-PEGylated FTn were readily accumulated in hypoxic tumor tissues, thereby providing significantly enhanced therapeutic benefits compared to the identical agents delivered in solution as a stand-alone therapy or an adjuvant to restore efficacy of conventional systemic chemotherapy.

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.