H-ferritin-nanocaged doxorubicin nanoparticles specifically target and kill tumors with a single-dose injection

Protein Encapsulation of Experimental Anticancer Agents 5F 203 and Phortress: Towards Precision Drug Delivery

INTRODUCTION

Advancement of novel anticancer drugs into clinical use is frequently halted by their lack of solubility, reduced stability under physiological conditions, and non-specific uptake by normal tissues, causing systemic toxicity. Their progress to use in the clinic could be accelerated by the development of new formulations employing suitable and complementary drug delivery vehicles.

METHODS

A robust method for apoferritin (AFt)-encapsulation of antitumour benzothiazoles has been developed for enhanced activity against and drug delivery to benzothiazole-sensitive cancers.

RESULTS

More than 70 molecules of benzothiazole 5F 203 were encapsulated per AFt cage. Post-encapsulation, the size and integrity of the protein cages were retained as evidenced by dynamic light scattering. ToF-SIMS depth profiling using an argon cluster beam confirmed 5F 203 exclusively within the AFt cavity. Improved encapsulation of benzothiazole lysyl-amide prodrugs was achieved (~130 molecules of Phortress per AFt cage). Transferrin receptor 1, TfR1, was detected in lysates prepared from most cancer cell lines studied, contributing to enhanced anticancer potency of the AFt-encapsulated benzothiazoles (5F 203, Phortress, GW 610, GW 608-Lys). Nanomolar activity was demonstrated by AFt-formulations in breast, ovarian, renal and gastric carcinoma cell lines, whereas GI50 >50 µM was observed in non-tumourigenic MRC-5 fibroblasts. Intracellular 5F 203, a potent aryl hydrocarbon receptor (AhR) ligand, and inducible expression of cytochrome P450 (CYP) 1A1 were detected following exposure of sensitive cells to AFt-5F 203, confirming that the activity of benzothiazoles was not compromised following encapsulation.

CONCLUSION

Our results show enhanced potency and selectivity of AFt-encapsulated 5F 203 against carcinomas derived from breast, ovarian, renal, colorectal as well as gastric cancer models, and offer realistic prospects for potential refinement of tumour-targeting and treatment, and merit further in vivo investigations.

ROS-Mediated Apoptosis and Anticancer Effect Achieved by Artesunate and Auxiliary Fe(II) Released from Ferriferous Oxide-Containing Recombinant Apoferritin

Reactive oxygen species (ROS)-mediated apoptosis is considered a crucial therapeutic mechanisms for artesunate (AS). As an Fe(II)-dependent drug, the anticancer effect of AS is often limited due to insufficient Fe(II) concentration in targeted cells. To overcome this problem, a recombinant apoferritin nanocarrier containing ferriferous oxide (M-HFn) is constructed to produce auxiliary exogenous Fe(II) when delivering AS to cancer cells. Here, the newly fabricated AS-loaded M-HFn nanoparticles (M-HFn@AS NPs) can significantly improve the tumor-specific targeting and intracellular uptake efficiency of AS in human cervical carcinoma cells. After being captured in the acidic cavity of endosomes, M-HFn@AS NPs can simultaneously release Fe(II) and allow AS to activate satisfactory ROS-mediated apoptosis. Furthermore, in vivo studies demonstrate that M-HFn@AS NPs can selectively accumulate in tumors to efficiently inhibit tumor growth. Thus, M-HFn@AS NPs are a promising system to enhance the therapeutic effect of Fe(II)-dependent drugs.

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.

Hypoxia-tropic nanozymes as oxygen generators for tumor-favoring theranostics

Oxygen deficiency is the main obstacle of hypoxia-related theranostics, thus this is a considerable amount of research focusing on the development of methods to supply oxygen by taking advantage of hypoxia-responsive properties of nanoparticles. However, strategies to properly penetrate hypoxic regions by the nanoparticles remains an unmet challenge. In this work, a biomimetic nanozyme capable of possessing catalase-like activity and the efficient direct penetration of hypoxic areas in tumor tissues was developed to supply oxygen based on catalytic tumor microenvironment-responsive reaction, providing substantial tumor hypoxia relief with nearly 3-fold reduction compared to untreated tumor tissues. To demonstrate the advantages of the nanozymes in overcoming hypoxia, a theranostic nanosystem model composed of the core/shell nanozymes and aggregation-induced emission (AIE) molecules was designed. The nanosystem was able to present multi-modal imaging of tumors and modulated the tumor microenvironment for improved photodynamic therapy (PDT) by cascade reactions of therapeutic effector molecules, thereby providing significantly enhanced therapeutic benefits in inhibiting tumor growth and lung metastasis of orthotopic breast cancer. This conceptual study showed the multifaceted features of biomimetic nanozymes as tumor therapeutics and demonstrated the encouraging potential for modulating hypoxia as an application for tumor theranostics.

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.

Recent Trends of the Bio-Inspired Nanoparticles in Cancer Theranostics

In recent years, various nanomaterials have emerged as an exciting tool in cancer theranostic applications due to their multifunctional property and intrinsic molecular property aiding effective diagnosis, imaging, and successful therapy. However, chemically synthesized nanoparticles have several issues related to the cost, toxicity and effectiveness. In this context, bio-inspired nanoparticles (NPs) held edges over conventionally synthesized nanoparticles due to their low cost, easy synthesis and low toxicity. In this present review article, a detailed overview of the cancer theranostics applications of various bio-inspired has been provided. This includes the recent examples of liposomes, lipid nanoparticles, protein nanoparticles, inorganic nanoparticles, and viral nanoparticles. Finally, challenges and the future scopes of these NPs in cancer therapy and diagnostics applications are highlighted.

Nanoscale systems for local drug delivery

Many diseases and conditions affect a relatively localized area of the body. They can be treated either by direct deposition of drug in the target area, or by giving the drug systemically. Here we review nanoparticle-based approaches to achieving both. We highlight advantages and disadvantages that nanoscale solutions have for locally administered therapies, with emphasis on the former. We discuss strategies to enable systemically delivered nanoparticles to deliver their payloads at specific locations in the body, including triggering (local and remote) and targeting.

Doxorubicin loaded ferritin nanoparticles for ferroptosis enhanced targeted killing of cancer cells

In recent years, ferroptosis has been investigated widely as a new form of cell death. Development of nanodrugs for ferroptosis induction in cancer cells may be a promising approach for cancer treatment. Here, we developed a type of nanoparticle consisting of the antitumor drug doxorubicin and exogenous ferritin. The drug loading process did not change the size of ferritin obviously. And this nanoparticle could induce the accumulation of ROS and cell ferroptosis for transferrin receptor overexpressed tumor cell, HT29. The ferroptosis process was also confirmed using inhibitors for ferroptosis. The cytotoxicity of this nanoparticle is similar to that of free DOX. This study provides a new strategy for targeting and killing transferrin receptor overexpressed tumor cells.

Ferritin drug carrier (FDC) for tumor targeting therapy

Ferritin is an iron storage protein that plays a key role in iron homeostasis and anti-oxidation of cells. Due to its unique architecture of 24 self-assembling subunits and hollow cavity capable of encapsulating drugs, and an outer surface that can be modified genetically and chemically for additional functionality, ferritin has recently emerged as a promising drug delivery vehicle. Recent research demonstrated that unmodified human heavy chain ferritin binds to its receptor, transferrin receptor 1 (TfR1), in different types of tumor tissues, including lung and breast cancer, thus highlighting the potential use of ferritin for tumor-targeting applications. In this review, we consider the many favorable characteristics of ferritin drug carriers (FDCs) for tumor drug delivery. In particular, compared with antibody-drug conjugates (ADCs), ferritin exhibits superiority in a range of attributes, including drug loading ability, thermostability, and ease of production. Thus, the emergence of FDCs may be the next step in targeted cancer therapy.

Theranostic liposomes as nanodelivered chemotherapeutics enhanced the microwave ablation of hepatocellular carcinoma

Aim: This study aimed to develop indocyanine green- and doxorubicin-loaded liposomes (DILPs) as theranostic nanoplatform for the detection of hepatocellular carcinoma (HCC) and as an efficient chemotherapeutic to enhance microwave ablation. Materials & methods: DILPs were synthesized and thoroughly characterized. Biocompatibility, tumor uptake and accumulation, and synergistic ablation-chemotherapeutic efficiency were systematically explored in them. In addition, human HCC surgical samples were used to test the affinity of DILPs for HCC. Results: The combination of microwave ablation and DILPs enhanced the ablation efficiency of HCC with apparent tumor inhibition. DILPs exhibited excellent diagnostic ability and could detect 2.5-mm HCC lesions via optoacoustic tomography imaging. DILPs had better affinity for human HCC surgical samples compared with normal liver tissue. Conclusion: Theranostic DILPs could serve as promising nanoparticles for treatment and management of HCC in the clinic.

Hepatocellular Carcinoma Growth Retardation and PD-1 Blockade Therapy Potentiation with Synthetic High-density Lipoprotein

The long progression-free survival (PFS) of patients with inoperable hepatocellular carcinoma (HCC) tumors is an unmet clinical need. Imaging-guided in situ ablation and vaccination with nanoplatforms could be a promising way to achieve durable disease control and long PFS. In the present work, we show that a biomimetic nanoplatform, namely, synthetic high-density lipoprotein (sHDL), can transport photothermal agent DiR and other drugs preferentially into the cytosol of HCC cells, enabling imaging-guided combination therapy for HCC in vivo. With a single injection, the sHDLs reduced the tumor burden, triggered immunogenic cell death (ICD), promoted dendritic cell (DC) maturation, and induced CD8⁺ T cell responses, which together sensitized the tumors to PD-1 blockade. Tumor remission and immune protection were achieved using sHDL loaded with DiR and a stimulator of interferon genes agonist vadimezan, in conjunction with a PD-1 blockade. The replacement of vadimezan with the chemotherapeutic mertansine potentiated ICD of HCC cells, but the drug interfered with DC maturation and subsequent CD8⁺ T cell priming, resulting in unsatisfactory disease control. Our work provides a generalizable nanoplatform for the combined photothermal ablation and immunotherapy of HCC and highlights the importance of cancer-cell-specific ICD induction and simultaneous DC activation during in situ vaccination.

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.

Everolimus Nanoformulation in Biological Nanoparticles Increases Drug Responsiveness in Resistant and Low-Responsive Breast Cancer Cell Lines

Everolimus (Eve) is an FDA approved drug that inhibits mammalian target of rapamycin (mTOR). It is employed in breast cancer treatment even if its responsiveness is controversial. In an attempt to increase Eve effectiveness, we have developed a novel Eve nanoformulation exploiting H-ferritin nanocages (HEve) to improve its subcellular delivery. We took advantage of the natural tumor targeting of H-Ferritin, which is mediated by the transferrin receptor-1 (TfR1). Breast cancer cells overexpressing TfR-1 were successfully recognized by H-Ferritin, displaying quick nanocage internalization. HEve has been tested and compared to Eve for in vitro efficacy in sensitive and resistant breast cancer cells. Nanoformulated Eve induced remarkable antiproliferative activity in vitro, making even resistant cell lines sensitive to Eve. Moreover, the antiproliferative activity of HEve is fully in accordance with cytotoxicity observed by cell death assay. Furthermore, the significant increase in anticancer efficacy displayed in HEve-treated samples is due to the improved drug accumulation, as demonstrated by UHPLC-MS/MS quantifications. Our findings suggest that optimizing Eve subcellular delivery, thanks to nanoformulation, determines its improved antitumor activity in a panel of Eve-sensitive or resistant breast cancer cell lines.

Ferritin variants: inspirations for rationally designing protein nanocarriers

Ferritin, a natural iron storage protein, is endowed with a unique structure, the ability to self-assemble and excellent physicochemical properties. Beyond these, genetic manipulation can easily tune the structure and functions of ferritin nanocages, which further expands the biomedical applications of ferritin. Here, we focus on human H-ferritin, a recently discovered ligand of transferrin receptor 1, to review its derived variants and related structures and properties. We hope this review will provide new insights into how to rationally design versatile protein cage nanocarriers for effective disease treatment.

Downregulation of TfR1 promotes progression of colorectal cancer via the JAK/STAT pathway

Background: Colorectal cancer (CRC) is one of the most prevalent gastrointestinal malignancies. The incidence of CRC has been rapidly increasing in China. Transferrin receptor 1 (TfR1) is a key regulator of cellular iron homeostasis. Several studies have demonstrated TfR1 overexpression in a variety of human tumors, but the association between TfR1 and CRC remains unclear.

Methods: TfR1 expression was evaluated in six CRC cell lines and tumor tissues. A total of 201 CRC patients were included for immunohistochemistry and 19 pairs of frozen tissues were used for real-time PCR. Cell proliferation, cell cycle, cell migration and invasion, and in vivo carcinogenesis were tested after downregulation of TfR1 by lentivirus. Protein microarray and Western blot analyses were used to explore the underlying mechanisms of TfR1 in CRC.

Results: TfR1 expression was higher in CRC tissues than in normal tissues (57.2% vs 22.9%, P＜0.001). TfR1 expression was obviously higher in CRC tissues with well differentiation (P＝0.008), no lymph node metastasis (P＝0.002), no distant metastasis (P＝0.006), no vascular invasion (P＜0.001) and early TNM stage (P＝0.013). CRC patients with TfR1-positive expression had a better survival than those with TfR1-negative expression (P＝0.044). Downregulation of TfR1 expression inhibited cell proliferation, promoted cells from G1 phase to S phase and facilitated cell migration and invasion. Knockdown of TfR1 also suppressed tumor growth in BALB/C-nu mice. Protein microarray and Western blot analyses showed that the Janus protein tyrosine kinase/signal transducer and activator of transcription pathway was activated along with downregulation of TfR1 expression.

Conclusion: Though TfR1 was overexpressed in colorectal cancer tissues, there was evidence that downregulation of TfR1 could promote cancer progression.

Design and site-directed compartmentalization of gold nanoclusters within the intrasubunit interfaces of ferritin nanocage

BACKGROUND

Protein nanocages have emerged as popular nanocarriers for either drug delivery or biotemplates for the preparation of nanomaterials. However, only three interfaces, namely exterior surface, intersubunit and inner cavity, have been used as reaction sites for the above purposes with all known protein nanocages. On the other hand, how to control the site of Au NCs formed within a targeted protein template while maintaining the functionality of protein itself remains challenging.

RESULTS

In this work, inspired by compartmentalization in living systems, we firstly come up with the conception of "intrasubunit interfaces", located within subunit of protein nanocage. We built a new, specific compartment for fabrication of gold nanoclusters by genetic modification of the inherent ferroxidase center located within four-α-helix bundle of each ferritin subunit. This newly built compartment not only realizes the site-directed synthesis of gold nanoclusters but also has no effect on the functionality of ferritin itself such as encapsulation by its inner cavity. These redesigned composites can be further applied as fluorescent imaging agent and carriers for preparation of hybrid nanomaterials.

CONCLUSIONS

The designing strategy of intrasubunit interfaces opens a new way for future applications of cage-like proteins.

Designed Two- and Three-Dimensional Protein Nanocage Networks Driven by Hydrophobic Interactions Contributed by Amyloidogenic Motifs

Precise manipulation of protein self-assembly by noncovalent interactions into programmed networks to mimic naturally occurring nanoarchitectures in living organisms is a challenge due to its structural heterogeneity, flexibility, and complexity. Herein, by taking advantage of both the hydrophobic forces contributed by the "GLMVG" motif, a kind of amyloidogenic motif (AM), and the high symmetry of protein nanocages, we have built an effective protein self-assembly strategy for the construction of two-dimensional (2D) or three-dimensional (3D) protein nanocage arrays. According to this strategy, "GLMVG" AMs from β-amyloid 42 were grafted onto the outer surface of a 24-mer ferritin nanocage close to its C₄ symmetry channels, initially resulting in the production of subgrade 2D nanocage arrays and ultimately generating 3D highly ordered arrays with a simple cubic packing pattern as the reaction time increases. More importantly, the reversibility and the formation rate of these protein arrays can be modulated by pH. This work provides a de novo design strategy for accurate control over 2D or 3D protein self-assemblies.

Nanomaterial-Based Modulation of Tumor Microenvironments for Enhancing Chemo/Immunotherapy

The tumor microenvironment (TME) has drawn considerable research attention as an alternative target for nanomedicine-based cancer therapy. Various nanomaterials that carry active substances have been designed to alter the features or composition of the TME and thereby improve the delivery and efficacy of anticancer chemotherapeutics. These alterations include disruption of the extracellular matrix and tumor vascular systems to promote perfusion or modulate hypoxia. Nanomaterials have also been used to modulate the immunological microenvironment of tumors. In this context, nanomaterials have been shown to alter populations of cancer-associated fibroblasts, tumor-associated macrophages, regulatory T cells, and myeloid-derived suppressor cells. Despite considerable progress, nanomaterial-based TME modulation must overcome several limitations before this strategy can be translated to clinical trials, including issues related to limited tumor tissue penetration, tumor heterogeneity, and immune toxicity. In this review, we summarize recent progress and challenges of nanomaterials used to modulate the TME to enhance the efficacy of anticancer chemotherapy and immunotherapy.

Magnetoferritin: Process, Prospects, and Their Biomedical Applications

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel magnetic nanomaterial with good biocompatibility and flexibility for biomedical applications. Recently, it has been demonstrated that MFt had tumor targetability and a peroxidase-like catalytic activity. Thus, MFt, with its many unique properties, provides a powerful platform for tumor diagnosis and therapy. In this review, we discuss the biomimetic synthesis and biomedical applications of MFt.

Thermal Treatment Greatly Improves Storage Stability and Monodispersity of Pea Seed Ferritin

Plant ferritin in holo form is considered as a novel, ideal iron supplement for human nutrition in the 21st century, but its self-degradation and self-association features limit its application on account of the presence of extension peptide (EP), a specific domain only found in plant ferritin. Although reported chemicals such as Phenylmethanesulfonyl fluoride (PMSF) can inhibit its self-degradation, they are not edible and toxic. In the present work, we found that thermal treatment of pea seed ferritin (PSF) in the range of 60 to 80 °C can prolong the storage time of PSF from 3 days to at least 10 days. In the meanwhile, the aggregated form can be inhibited upon such treatment, therefore promoting its monodispersity. More important, such treatment had little effect on the natural shell-like structure of holo PSF and its iron content. In contrast, thermal treatment at higher temperature (90 °C or above) resulted in a change in ferritin structure. These new findings pave the way to the application of plant ferritin as an iron supplement. PRACTICAL APPLICATION: Thermal treatment at 60 to 80 °C can prolong the storage stability of PSF from 3 days to at least 10 days and prevent it from self-aggregation without affecting the shell-like structure. It has been known that the stability of PSF is closely associated with the bioavailability of iron within PSF. From the standpoint of nutrition, the above-mentioned thermal treatment could be used as a cooking method in our daily life or in food industry to improve the bioavailability of ferritin iron, thereby being beneficial for exploration of plant ferritin as a novel, ideal iron supplement to fight against IDA.

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.

Inlaying Radiosensitizer onto the Polypeptide Shell of Drug-Loaded Ferritin for Imaging and Combinational Chemo-Radiotherapy

Rationale: Ferritin with unique hollow cavity is an emerging protein-based nanoplatform for anticancer-drug delivery, but the in vivo chemotherapeutic effectiveness is still unsatisfactory with such a monotherapy modality, which is urgently in need of improvement. Methods: Here a novel ferritin nanotheranostic with anticancer-drug doxorubicin encapsulated into its hollow interior and nanoradiosensitizer bismuth sulfide nanocrystals inlayed onto its polypeptide shell was synthesized for combinational therapeutic benefits. The formation mechanism of bismuth sulfide nanocrystals based on ferritin has been analyzed. The in vitro and in vivo treatment effects were carried out on HeLa cancer cells and tumor-bearing mice, respectively. The biocompatibility and excretion of the ferritin nanotheranostic have also been evaluated to guarantee their biosafety. Results: The polypeptide shell of ferritin provides nucleation sites for the bismuth sulfide nanocrystals through coordination interaction, and simultaneously inhibits the further growth of bismuth sulfide nanocrystals, rendering the bismuth sulfide nanocrystals like rivets inlaying onto the polypeptide firmly, which can not only strengthen the architectural stability of ferritin to prevent drug burst leakage during systemic circulation, but also act as excellent computed tomography contrast agents and nanoradiosensitizers for in vivo imaging-guided cancer combinational treatments. Conclusions: The design concept of inlaying bismuth sulfide nanocrystals onto the polypeptide shell of doxorubicin-encapsulated ferritin significantly inhibits the tumor growth and simultaneously further broadens the application of ferritin in nanomedicine.

GRP78-targeted ferritin nanocaged ultra-high dose of doxorubicin for hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) remains one of the leading causes of cancer deaths, primarily due to its high incidence of recurrence and metastasis. Considerable efforts have therefore been undertaken to develop effective therapies; however, effective anti-HCC therapies rely on identification of suitable biomarkers, few of which are currently available for drug targeting.

Methods: GRP78 was identified as the membrane receptor of HCC-targeted peptide SP94 by immunoprecipitation and mass spectrum analysis. To develop an effective anti-HCC drug nanocarrier, we first displayed GRP78-targeted peptide SP94 onto the exterior surface of Pyrococcus furiosus ferritin Fn (HccFn) by genetic engineering approach, and then loaded doxorubicin (Dox) into the cavities of HccFn via urea-based disassembly/reassembly method, thereby constructing a drug nanocarrier called HccFn-Dox.

Results: We demonstrated that HccFn nanocage encapsulated ultra-high dose of Dox (up to 400 molecules Dox/protein nanocage). In vivo animal experiments showed that Dox encapsulated in HccFn-Dox was selectively delivered into HCC tumor cells, and effectively killed subcutaneous and lung metastatic HCC tumors. In addition, HccFn-Dox significantly reduced drug exposure to healthy organs and improved the maximum tolerated dose by six-fold compared with free Dox.

Conclusion: In conclusion, our findings clearly demonstrate that GRP78 is an effective biomarker for HCC therapy, and GRP78-targeted HccFn nanocage is effective in delivering anti-HCC drug without damage to healthy tissue.

Blood Circulation-Prolonging Peptides for Engineered Nanoparticles Identified via Phage Display

Sustaining blood retention for theranostic nanoparticles is a big challenge. Various approaches have been attempted and have demonstrated some success but limitations remain. We hypothesized that peptides capable of increasing blood residence time for M13 bacteriophage, a rod-shaped nanoparticle self-assembled from proteins and nucleic acids, should also prolong blood circulation for engineered nanoparticles. Here we demonstrate the feasibility of this approach by identifying a series of blood circulation-prolonging (BCP) peptides through in vivo screening of an M13 peptide phage display library. Intriguingly, the majority of the identified BCP peptides contained an arginine-glycine-aspartic acid (RGD) motif, which was necessary but insufficient for the circulation-prolonging activity. We further demonstrated that the RGD-mediated specific binding to platelets was primarily responsible for the enhanced blood retention of BCP1. The utility of the BCP1 peptide was demonstrated by fusion of the peptide to human heavy-chain ferritin (HFn), leading to significantly improved pharmacokinetic profile, enhanced tumor cell uptake and optimum anticancer efficacy for doxorubicin encapsulated in the HFn nanocage. Our results provided a proof-of-concept for an innovative yet simple strategy, which utilizes phage display to discover novel peptides with the capability of substantially prolonging blood circulation for engineered theranostic nanoparticles.

Biomineralization Synthesis of the Cobalt Nanozyme in SP94-Ferritin Nanocages for Prognostic Diagnosis of Hepatocellular Carcinoma

Nanomaterials with intrinsic enzyme-like activities (nanozymes) have emerged as promising agents for cancer theranostics strategies. However, size-controllable synthesis of nanozymes and their targeting modifications are still challenging. Here, we report a monodispersed ferritin-based cobalt nanozyme (HccFn(Co₃O₄)) that specifically targets and visualizes clinical hepatocellular carcinoma (HCC) tissues. The cobalt nanozyme is biomimetically synthesized within the protein shell of the HCC-targeted ferritin (HccFn) nanocage, which is enabled by the display of HCC cell-specific peptide SP94 on the surface of ferritin through a genetic engineering approach. The intrinsic peroxidase-like activity of HccFn(Co₃O₄) nanozymes catalyzes the substrates to make color reaction to visualize HCC tumor tissues. We examined 424 clinical HCC specimens and verified that HccFn(Co₃O₄) nanozymes distinguish HCC tissues from normal liver tissues with a sensitivity of 63.5% and specificity of 79.1%, which is comparable with that of the clinically used HCC-specific marker α fetoprotein. Moreover, the pathological analysis indicates that the HccFn(Co₃O₄) nanozyme staining result is a potential predictor of prognosis in HCC patients. Staining intensity is positively correlated to tumor differentiation degree ( P = 0.0246) and tumor invasion ( P < 0.0001) and negatively correlated with overall survival ( P = 0.0084) of HCC patients. Together, our study demonstrates that ferritin is an excellent platform for size-controllable synthesis and targeting modifications of nanozymes, and the HccFn(Co₃O₄) nanozyme is a promising reagent for prognostic diagnosis of HCC.

Transferrin and transferrin receptors update

In vertebrates, transferrin (Tf) safely delivers iron through circulation to cells. Tf-bound iron is incorporated through Tf receptor (TfR) 1-mediated endocytosis. TfR1 can mediate cellular uptake of both Tf and H-ferritin, an iron storage protein. New World arenaviruses, which cause hemorrhagic fever, and Plasmodium vivax use TfR1 for entry into host cells. Human TfR2, another receptor for Tf, is predominantly expressed in hepatocytes and erythroid precursors, and holo-Tf dramatically upregulates its expression. TfR2 forms a complex with hemochromatosis protein, HFE, and serves as a component of the iron sensing machinery in hepatocytes. Defects in TfR2 cause systemic iron overload, hemochromatosis, through down-regulation of hepcidin. In erythroid cells, TfR2 forms a complex with the erythropoietin receptor and regulates erythropoiesis. TfR2 facilitates iron transport from lysosomes to mitochondria in erythroblasts and dopaminergic neurons. Administration of apo-Tf, which scavenges free iron, has been explored for various clinical conditions including atransferrinemia, iron overload, and tissue ischemia. Apo-Tf has also been shown to ameliorate anemia in animal models of β-thalassemia. In this review, I provide an update and summary on our knowledge of mammalian Tf and its receptors.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Disulfide-mediated conversion of 8-mer bowl-like protein architecture into three different nanocages

Constructing different protein nanostructures with high-order discrete architectures by using one single building block remains a challenge. Here, we present a simple, effective disulfide-mediated approach to prepare a set of protein nanocages with different geometries from single building block. By genetically deleting an inherent intra-subunit disulfide bond, we can render the conversion of an 8-mer bowl-like protein architecture (NF-8) into a 24-mer ferritin-like nanocage in solution, while selective insertion of an inter-subunit disulfide bond into NF-8 triggers its conversion into a 16-mer lenticular nanocage. Deletion of the same intra-subunit disulfide bond and insertion of the inter-subunit disulfide bond results in the conversion of NF-8 into a 48-mer protein nanocage in solution. Thus, in the laboratory, simple mutation of one protein building block can generate three different protein nanocages in a manner that is highly reminiscent of natural pentamer building block originating from viral capsids that self-assemble into protein assemblies with different symmetries.

Positive magnetic resonance angiography using ultrafine ferritin-based iron oxide nanoparticles

Iron oxide nanoparticles with good biocompatibility can serve as safe magnetic resonance imaging contrast agents. Herein, we report that ultrafine ferritin-based iron oxide (hematite/maghemite) nanoparticles synthesized by controlled biomimetic mineralization using genetically recombinant human H chain ferritin can be used as a positive contrast agent in magnetic resonance angiography. The synthesized magnetoferritin with an averaged core size of 2.2 ± 0.7 nm (hereafter named M-HFn-2.2) shows a r1 value of 0.86 mM-1 s-1 and a r2/r1 ratio of 25.1 at a 7 T magnetic field. Blood pool imaging on mice using the M-HFn-2.2 nanoparticles that were injected through a tail vein by single injection at a dose of 0.54 mM Fe per kg mouse body weight enabled detecting detailed vascular nets at 3 minutes post-injection; the MR signal intensity continuously enhanced up to 2 hours post-injection, which is much longer than that of the commercial magnevist (Gd-DTPA) contrast. Moreover, biodistribution examination indicates that organs such as liver, spleen and kidney safely cleared the injected nanoparticles within one day after the injection, demonstrating no risk of iron overload in test mice. Therefore, this study sheds light on developing high-performance gadolinium free positive magnetic resonance contrast agents for biomedical applications.

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.

Development of novel apoferritin formulations for antitumour benzothiazoles

BACKGROUND

The benzothiazole structure is important in medicinal chemistry, and 5-fluoro-2-(3,4-dimethoxyphenyl) benzothiazole (GW 610) is of particular interest as it shows outstanding anticancer activity in sensitive breast and colorectal carcinoma cell lines via generation of lethal DNA adducts in sensitive cancer cells. Despite promising activity, poor water solubility limits its applications. The apoferritin (AFt) protein cage has been proposed as a robust and biocompatible drug delivery vehicle.

AIMS

Here, we aim to enhance solubility of GW 610 by developing amino acid prodrug conjugates and utilizing the AFt capsule as drug delivery vessel.

METHODS AND RESULTS

The potent experimental antitumour agent, GW 610, has been successfully encapsulated within AFt with more than 190 molecules per AFt cage. The AFt-GW 610 complex exhibits dose-dependent growth inhibition and is more potent than GW 610 alone in 5/7 cancer cell lines. To enhance both aqueous solubility and encapsulation efficiency, a series of amino acid esters of GW 608 prodrug were synthesized via N,N'-dicyclohexylcarbodiimide ester coupling to produce molecules with different polarity. A dramatic increase in encapsulation efficiency was achieved, with more than 380 molecules of GW 608-Lys molecules per AFt cage. Release studies show sustained release of the cargo over 12 hours at physiologically relevant pH. The AFt-encapsulated amino acid modified GW 608 complexes are sequestered more rapidly and exhibit more potent anticancer activity than unencapsulated agent.

CONCLUSION

These results indicate that AFt-encapsulation of GW 610 prodrug provides a biocompatible delivery option for this potent, selective experimental antitumour agent and for amino acid-modified GW 608. Of particular interest is the encapsulation efficiency and in vitro antitumour activity of AFt-GW 608-Lys, which warrants further preclinical evaluation.

Redox-responsive degradable prodrug nanogels for intracellular drug delivery by crosslinking of amine-functionalized poly(N-vinylpyrrolidone) copolymers

HYPOTHESIS

Facile approaches for the development of new tailored drug carriers are of high importance for the controlled administration of drugs. Herein we report a method for the synthesis of water-soluble reactive copolymers with well-defined architectures for fabrication of redox-sensitive degradable prodrug nanogels for intracellular drug release.

EXPERIMENTS

Primary amine-functionalized statistical copolymers were obtained by hydrolysis of poly(N-vinylpyrrolidone-co-N-vinylformamide) copolymers which were synthesized via Reversible Addition-Fragmentation chain-Transfer (RAFT) polymerization. Redox-sensitive degradable nanogels with varying crosslinking densities were synthesized with a redox-sensitive cross-linker. Doxorubicin (DOX) was loaded to form prodrug nanogels (DNG) with hydrodynamic radius from 142 nm to 240 nm.

FINDINGS

The nanogels demonstrated slower degradation and retarded drug release rate with increased crosslinking density in the presence of 10 mM reduced glutathione (GSH) at 37 °C. The in vitro release studies revealed that maximum 85% DOX was released in 24 h under a reductive environment. Intracellular drug release profiles in HeLa cells indicated that the DOX delivery rate was tunable via varying crosslinking density of the nanogels. Cell viability assay demonstrated that the blank nanogels were biocompatible in wide concentrations up to 0.5 mg/mL while the DOX-loaded nanogels displayed medium antitumor activity with IC50 (half-maximal inhibitory concentration) of 1.80 μg/mL, 2.57 μg/mL, 3.01 μg/mL for DNG5, DNG10 and DNG15 respectively.

Iron as a Central Player and Promising Target in Cancer Progression

Iron is an essential element for virtually all organisms. On the one hand, it facilitates cell proliferation and growth. On the other hand, iron may be detrimental due to its redox abilities, thereby contributing to free radical formation, which in turn may provoke oxidative stress and DNA damage. Iron also plays a crucial role in tumor progression and metastasis due to its major function in tumor cell survival and reprogramming of the tumor microenvironment. Therefore, pathways of iron acquisition, export, and storage are often perturbed in cancers, suggesting that targeting iron metabolic pathways might represent opportunities towards innovative approaches in cancer treatment. Recent evidence points to a crucial role of tumor-associated macrophages (TAMs) as a source of iron within the tumor microenvironment, implying that specifically targeting the TAM iron pool might add to the efficacy of tumor therapy. Here, we provide a brief summary of tumor cell iron metabolism and updated molecular mechanisms that regulate cellular and systemic iron homeostasis with regard to the development of cancer. Since iron adds to shaping major hallmarks of cancer, we emphasize innovative therapeutic strategies to address the iron pool of tumor cells or cells of the tumor microenvironment for the treatment of cancer.

Emerging blood–brain-barrier-crossing nanotechnology for brain cancer theranostics

The advancements, perspectives, and challenges in blood–brain-barrier (BBB)-crossing nanotechnology for effective brain tumor delivery and highly efficient brain cancer theranostics.

Disulfide-mediated reversible two-dimensional self-assembly of protein nanocages

Disulfide-mediated 2D protein self-assembly was achieved by single point mutation of hot spots at the C₄ interface of ferritin.

Nanoparticle ferritin-bound erastin and rapamycin: a nanodrug combining autophagy and ferroptosis for anticancer therapy

The intracellular autophagy-mediated ferroptosis-induction process by the NFER nanodrug assembled by ferritin, erastin, and rapamycin.

Thermostability of protein nanocages: the effect of natural extra peptide on the exterior surface

Protein nanocages have been used as functional bio-templates for the synthesis or organization of nanomaterials. However, the stability of these protein nanocages is nonideal, which limits their applications. Herein, we characterized the high thermal stability of plant ferritin, soybean seed H-2 ferritin (SSFH-2), the melting point (T_m) of which is 106 °C. We demonstrated that the hyperthermostability of SSFH-2 is derived from extra peptides (EP) located on its outer surface. Indeed, removal of the EP domains resulted in a dramatic decrease in T_m to 88 °C. Similar to EP-deleted plant ferritin, human H-chain ferritin (HuHF) has a T_m of 82 °C. Excitingly, the graft of the EP domain on the exterior surface of HuHF pronouncedly improved its T_m to 103 °C, which represents a simple, efficient approach to the construction of protein architectures with high stability. The remarkable stability of protein nanocages will greatly facilitate their application as robust biotemplates in the field of nanoscience.

Ferritin nanocage exhibits hyperthermostability with EP domain located on its outer surface.

Self-Assembly of Ferritin: Structure, Biological Function and Potential Applications in Nanotechnology

Protein cages are normally formed by the self-assembly of multiple protein subunits and ferritin is a typical example of a protein cage structure. Ferritin is a ubiquitous multi-subunit iron storage protein formed by 24 polypeptide chains that self-assemble into a hollow, roughly spherical protein cage. Ferritin has external and internal diameters of approximately 12 nm and 8 nm, respectively. Functionally, ferritin performs iron sequestration and is highly conserved in evolution. The interior cavity of ferritin provides a unique reaction vessel to carry out reactions separated from the exterior environment. In nature, the cavity is utilized for sequestration of iron and bio-mineralization as a mechanism to render iron inert and safe from the external environment. Material scientists have been inspired by this system and exploited a range of ferritin superfamily proteins as supramolecular templates to encapsulate different carrier molecules ranging from cancer drugs to therapeutic proteins, in addition to using ferritin proteins as well-defined building blocks for fabrication. Besides the interior cavity, the exterior surface and sub-unit interface of ferritin can be modified without affecting ferritin assembly.

Apoferritin encapsulation of cysteine protease inhibitors for cathepsin L inhibition in cancer cells

Cysteine proteases play a key role in tumorigenesis causing protein degradation and promoting invasive tumour growth. Cathepsin L is overexpressed in cancer cells and could provide a specific target for delivery of anticancer agents. We encapsulated novel dipeptidyl nitrile based cysteine protease inhibitors (Neq0551, Neq0554 and Neq0568) into biocompatible apoferritin (AFt) protein nanocages to achieve specific delivery to tumours and pH-induced drug release. AFt-encapsulated Neq0554 demonstrated ∼3-fold enhanced in vitro activity (GI₅₀ = 79 μM) compared to naked agent against MiaPaCa-2 pancreatic carcinoma cells. Selectivity for cancer cells was confirmed by comparing their activity to non-tumourigenic human fibroblasts (GI₅₀ > 200 μM). Transferrin receptor (TfR-1) expression, detected only in lysates prepared from carcinoma cells, may contribute to the cancer-selectivity. The G₁ cell cycle arrest caused by AFt-Neq0554 resulting in cytostasis was corroborated by clonogenic assays. Superior and more persistent inhibition of cathepsin L up to 80% was achieved with AFt-encapsulated agent in HCT-116 cells following 6 h exposure to 50 μM agent. The selective anticancer activity of AFt-encapsulated cysteine protease inhibitor Neq0554 reported here warrants further preclinical in vivo evaluation.

Novel apoferritin encapsulated cysteine protease inhibitors are developed with enhanced and selective uptake by cancer cells, and sustained pH-induced release of the agent. The persistent inhibition of cathepsin L is demonstrated in vitro.

Peptide-directed encapsulation of inorganic nanoparticles into protein containers

Biomolecules can be combined with inorganic compounds to unite biological features with the chemical and physical properties of abiotic materials. In particular, protein containers, with their inherent ability to encapsulate cargo molecules, are perfect platforms for the generation of multifunctional assemblies. However, encapsulation of foreign cargo is immensely challenging due to the lack of specific interactions between cargo and container. Here, we demonstrate that the highly specific cargo-loading mechanism of the bacterial nanocompartment encapsulin can be employed for encapsulation of artificial cargo like inorganic nanoparticles. For this purpose, container-filling gold nanoparticles were decorated with a small number of encapsulin cargo-loading peptides. By lock-and-key interaction between the peptides and the peptide-binding pockets on the inner container surface, the nanoparticles are encapsulated into encapsulin with extremely high efficiency. Most notably, peptide binding is independent from external factors such as ionic strength. Cargo-loading peptides may serve as generally applicable tool for efficient and specific encapsulation of cargo molecules into a proteinaceous compartment.

Preparation, structure, cytotoxicity and mechanism of action of ferritin-Pt(II) terpyridine compound nanocomposites

AIM

A Pt(II)-terpyridine compound, bearing two piperidine substituents at positions 2 and 2' of the terpyridine ligand (1), is highly cytotoxic and shows a mechanism of action distinct from cisplatin. 1 has been incorporated within the ferritin nanocage (AFt).

MATERIALS & METHODS

Spectroscopic and crystallographic data of the Pt(II)-AFt nanocomposite have been collected and in vitro anticancer activity has been explored using cancer cells.

RESULTS

Pt(II)-containing fragments bind His49, His114 and His132. Pt(II)-AFt nanocomposite is less cytotoxic than 1, but it is more toxic than cisplatin at high concentrations. The Pt(II)-AFt nanocomposite triggers necrosis in cancer cells, as free 1 does.

CONCLUSION

Pt(II)-AFt nanocomposites are promising vehicles to deliver Pt-based drugs to cancer cells.

Deep Tumor-Penetrated Nanocages Improve Accessibility to Cancer Stem Cells for Photothermal-Chemotherapy of Breast Cancer Metastasis

Cancer stem cells (CSCs) are proposed to account for the initiation of cancer metastasis, but their accessibility remains a great challenge. This study reports deep tumor-penetrated biomimetic nanocages to augment the accessibility to CSCs fractions in tumor for anti-metastasis therapy. The nanocages can load photothermal agent of 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DBN) and chemotherapeutic epirubicin (EBN) to eradicate CSCs for photothermal-chemotherapy of breast cancer metastasis. In metastatic 4T1-indcued tumor model, both DBN and EBN can efficiently accumulate in tumor sites and feasibly permeate throughout the tumor mass. These biomimetic nanosystems can be preferentially internalized by cancer cells and effectively accessed to CSCs fractions in tumor. The DBN+laser/EBN treatment produces considerable depression of primary tumor growth, drastically eradicates around 80% of CSCs fractions in primary tumor, and results in 95.2% inhibition of lung metastasis. Thus, the biomimetic nanocages can be a promising delivery nanovehicle with preferential CSCs-accessibility for effective anti-metastasis therapy.

On-Axis Alignment of Protein Nanocage Assemblies from 2D to 3D through the Aromatic Stacking Interactions of Amino Acid Residues

Aromatic-aromatic interactions between natural aromatic amino acids Phe, Tyr, and Trp play crucial roles in protein-protein recognition and protein folding. However, the function of such interactions in the preparation of different dimensional, ordered protein superstructures has not been recognized. Herein, by a combination of the directionality of the symmetry axes of protein building blocks and the strength of the aromatic-aromatic interactions coming from a group of aromatic amino acid residues, we built an engineering strategy to construct protein superlattices. Based on this strategy, substitution of single amino acid residue Glu162 around the C₄ rotation axes near the outer surface of 24-mer ferritin nanocage with Phe, Tyr, and Trp, respectively, resulted in 2D and 3D protein superlattices where protein cages are aligned along the C₄ axes, imposing a fixed disposition of neighboring ferritins. The self-assembly of these superlattices is reversible, which can be tuned by external stimuli (salt concentration or pH). Moreover, these superlattices can serve as biotemplates for the fabrication of 2D and 3D inorganic nanoparticle arrays.

Emerging and Dynamic Biomedical Uses of Ferritin

Ferritin, a ubiquitously expressed protein, has classically been considered the main iron cellular storage molecule in the body. Owing to the ferroxidase activity of the H-subunit and the nucleation ability of the L-subunit, ferritin can store a large amount of iron within its mineral core. However, recent evidence has demonstrated a range of abilities of ferritin that extends well beyond the scope of iron storage. This review aims to discuss novel functions and biomedical uses of ferritin in the processes of iron delivery, delivery of biologics such as chemotherapies and contrast agents, and the utility of ferritin as a biomarker in a number of neurological diseases.

Supramolecular chemotherapy based on host-guest molecular recognition: a novel strategy in the battle against cancer with a bright future

Chemotherapy is currently one of the most effective ways to treat cancer. However, traditional chemotherapy faces several obstacles to clinical trials, such as poor solubility/stability, non-targeting capability and uncontrollable release of the drugs, greatly limiting their anticancer efficacy and causing severe side effects towards normal tissues. Supramolecular chemotherapy integrating non-covalent interactions and traditional chemotherapy is a highly promising candidate in this regard and can be appropriately used for targeted drug delivery. By taking advantage of supramolecular chemistry, some limitations impeding traditional chemotherapy for clinical applications can be solved effectively. Therefore, we present here a review summarizing the progress of supramolecular chemotherapy in cancer treatment based on host-guest recognition and provide guidance on the design of new targeting supramolecular chemotherapy combining diagnostic and therapeutic functions. Based on a large number of state-of-the-art studies, our review will advance supramolecular chemotherapy on the basis of host-guest recognition and promote translational clinical applications.