Engineered Human Ferritin Nanoparticles for Direct Delivery of Tumor Antigens to Lymph Node and Cancer Immunotherapy

Design and application of ferritin-based nanomedicine for targeted cancer therapy

Owing to its unique structure and favorable biocompatibility, ferritin has been widely studied as a promising drug carrier over the past two decades. Since the identification of its inherent tumor-targeting property due to unique recognition ablity of the transferrin receptor 1 (TfR1), ferritin-based nanomedicine has attracted widespread attention and triggered a research surge in the field of targeted cancer therapy. Along with progress in structure studies and modification technology, diverse strategies have been carried out to equip ferritin with on-demand functions, further improving the antitumor efficacy and in vivo safety of ferritin-based cancer therapy. In this review, we highlight the structure-based rational design of ferritin and summarize the design strategies in detail from two main perspectives: multifunctional modification and drug loading. In particular, the critical issues that need attention in the design are discussed in depth. Furthermore, we provide an overview of the latest advances in the application of ferritin-based nanomedicines in chemotherapy, phototherapy and immunotherapy, with particular emphasis on emerging therapeutic approaches among these therapies.

Neoantigen-Displaying Protein Nanoparticles as a Therapeutic Cancer Vaccine Against Melanoma

Although interest in peptide-based cancer vaccines has surged in the era of personalized immunotherapy enabled by the discovery of neoantigens, the effective generation of neoantigen-specific T cell responses has been limited. Here, a Brucella BP26 protein-based nanoparticle displaying the MHC class II-restricted melanoma neoantigen, M30, is reported for use as a therapeutic cancer vaccine. Genetic engineering of 10 tandem repeats of the M30 neoepitope to a BP26 monomer results in the self-assembled, neoantigen-displaying protein nanoparticles (BP26-M30 NPs). Subcutaneous immunization of mice with BP26-M30 NPs/CpG adjuvant leads to the activation and maturation of antigen-presenting cells in draining local lymph nodes and elicits M30-specific CD4+ T cell immune responses and immunological memory. In a mouse model of aggressive B16-F10 melanoma, immunization with BP26-M30 NPs/CpG significantly inhibits the growth of established tumors. These findings suggest that the BP26-based self-assembled protein nanoparticle has the potential to be used as a cancer vaccine platform for personalized cancer immunotherapy.

Optimization of Conditions for Expression of Dengue Serotype 2 EDIII Protein in Escherichia coli and Immune Responses of Adjuvant-Free EDIII Ferritin Nanoparticles Against Dengue Virus in BALB/c Mice

Self-assembling ferritin nanoparticle technology is a widely used vaccine development platform for enhancing the efficacy of subunit vaccines by displaying multiple antigens on nanocages. The dengue virus (DENV) envelope domain III (EDIII) protein, the most promising antigen for DENV, has been applied in vaccine development, and it is essential to evaluate the relative immunogenicity of the EDIII protein and EDIII-conjugated ferritin to show the efficiency of the ferritin delivery system compared with EDIII. In this study, we optimized the conditions for the expression of the EDIII protein in E. coli, protein purification, and refolding, and these optimization techniques were applied for the purification of EDIII ferritin nanoparticles. Thus, purified DENV2 EDIII and EDIII human ferritin heavy chain nanoparticles were immunized intramuscularly into BALB/c mice without an adjuvant, and the immunogenicity was analyzed using IgG ELISA and a serum-neutralizing assay. Purified, properly refolded, aggregate-free EDIII and EDIII ferritin proteins were obtained, and ferritin nanoparticles were identified using an electron microscope. By analyzing the immunogenicity of mouse serum, EDIII ferritin generated significantly higher IgG responses and neutralizing activity than EDIII-immunized mice. The IgG ELISA results confirmed that EDIII ferritin can induce a significantly higher IgG titer (O.D.:1.8) than EDIII (O.D.:0.05). Furthermore, EDIII ferritin produced a neutralizing titer of 1:68, whereas EDIII protein produced an average titer of 1:16, which is the serum dilution that inhibited 90% of the viruses. The longevity of the immune responses was analyzed using the serum obtained 2 months after the final immunization, and the results confirmed that EDIII ferritin induced constant immunity throughout the period.

Nano- and Micro-Platforms in Therapeutic Proteins Delivery for Cancer Therapy: Materials and Strategies

Proteins have emerged as promising therapeutics in oncology due to their great specificity. Many treatment strategies are developed based on protein biologics, such as immunotherapy, starvation therapy, and pro-apoptosis therapy, while some protein biologics have entered the clinics. However, clinical translation is severely impeded by instability, short circulation time, poor transmembrane transportation, and immunogenicity. Micro- and nano-particles-based drug delivery platforms are designed to solve those problems and enhance protein therapeutic efficacy. This review first summarizes the different types of therapeutic proteins in clinical and research stages, highlighting their administration limitations. Next, various types of micro- and nano-particles are described to demonstrate how they can overcome those limitations. The potential of micro- and nano-particles are then explored to enhance the therapeutic efficacy of proteins by combinational therapies. Finally, the challenges and future directions of protein biologics carriers are discussed for optimized protein delivery.

Recombinant ferritin-based nanoparticles as neoantigen carriers significantly inhibit tumor growth and metastasis

BACKGROUND

Tumor neoantigen peptide-based vaccines, systemic immunotherapies that enhance antitumor immunity by activating and expanding antigen-specific T cells, have achieved remarkable results in the treatment of a variety of solid tumors. However, how to effectively deliver neoantigens to induce robust antitumor immune responses remains a major obstacle.

RESULTS

Here, we developed a safe and effective neoantigen peptide delivery system (neoantigen-ferritin nanoparticles, neoantigen-FNs) that successfully achieved effective lymph node targeting and induced robust antitumor immune responses. The genetically engineered self-assembled particles neoantigen-FNs with a size of 12 nm were obtained by fusing a neoantigen with optimized ferritin, which rapidly drainage to and continuously accumulate in lymph nodes. The neoantigen-FNs vaccine induced a greater quantity and quality of antigen-specific CD8+ T cells and resulted in significant growth control of multiple tumors, dramatic inhibition of melanoma metastasis and regression of established tumors. In addition, no obvious toxic side effects were detected in the various models, indicating the high safety of optimized ferritin as a vaccine carrier.

CONCLUSIONS

Homogeneous and safe neoantigen-FNs could be a very promising system for neoantigen peptide delivery because of their ability to efficiently drainage to lymph nodes and induce efficient antitumor immune responses.

Endogenous capsid-forming protein ARC for self-assembling nanoparticle vaccines

The application of nanoscale scaffolds has become a promising strategy in vaccine design, with protein-based nanoparticles offering desirable avenues for the biocompatible and efficient delivery of antigens. Here, we presented a novel endogenous capsid-forming protein, activated-regulated cytoskeleton-associated protein (ARC), which could be engineered through the plug-and-play strategy (SpyCatcher3/SpyTag3) for multivalent display of antigens. Combined with the self-assembly capacity and flexible modularity of ARC, ARC-based vaccines elicited robust immune responses against Mpox or SARS-CoV-2, comparable to those induced by ferritin-based vaccines. Additionally, ARC-based nanoparticles functioned as immunostimulants, efficiently stimulating dendritic cells and facilitating germinal center responses. Even without adjuvants, ARC-based vaccines generated protective immune responses in a lethal challenge model. Hence, this study showed the feasibility of ARC as a novel protein-based nanocarrier for multivalent surface display of pathogenic antigens and demonstrated the potential of exploiting recombinant mammalian retrovirus-like protein as a delivery vehicle for bioactive molecules.

Advanced Strategies for Strengthening the Immune Activation Effect of Traditional Antitumor Therapies

The utilization of traditional therapies (TTS), such as chemotherapy, reactive oxygen species-based therapy, and thermotherapy, to induce immunogenic cell death (ICD) in tumor cells has emerged as a promising strategy for the activation of the antitumor immune response. However, the limited effectiveness of most TTS in inducing the ICD effect of tumors hinders their applications in combination with immunotherapy. To address this challenge, various intelligent strategies have been proposed to strengthen the immune activation effect of these TTS, and then achieve synergistic antitumor efficacy with immunotherapy. These strategies primarily focus on augmenting the tumor ICD effect or facilitating the antigen (released by the ICD tumor cells) presentation process during TTS, and they are systematically summarized in this review. Finally, the existing bottlenecks and prospects of TTS in the application of tumor immune regulation are also discussed.

Single Ferritin Nanocages Expressing SARS-CoV-2 Spike Variants to Receptor and Antibodies

SARS-CoV-2 virus variants of concern (VOCs) have rapidly changed their transmissibility and pathogenicity primarily through mutations in the structural proteins. Herein, we present molecular details with dynamics of the ferritin nanocages stitched with synthetic chimeras displaying the Spike receptor binding domains (RBDs). Our findings demonstrated the potential usage of ferritin-based vaccines that may effectively inhibit viral entry by blocking the Spike-ACE2 network and may induce cross-protective antibody responses. Taking the nanocage constructs into consideration, we evaluated the effects of variants on the docked interface of the SARS-CoV-2 Spike RBD with the ACE2 (angiotensin-converting enzyme 2) host cell receptor and neutralizing antibodies (Abs). Investigating the VOCs revealed that most of the mutations reported a possibly reduced structural stability within the Spike RBD domain. Point mutations have moderate or no effect for VVH-72, CR3022, and S309 Abs when bound with the Spike RBD, whereas a significant effect was observed for B38, CB6, and m396 over the surface of the H-ferritin nanocage. In addition to providing useful therapeutic approaches against COVID-19 (coronavirus disease 2019), these structural details can also be used to fight future coronavirus outbreaks.

Impact of doxorubicin-loaded ferritin nanocages (FerOX) vs. free doxorubicin on T lymphocytes: a translational clinical study on breast cancer patients undergoing neoadjuvant chemotherapy

Despite the advent of numerous targeted therapies in clinical practice, anthracyclines, including doxorubicin (DOX), continue to play a pivotal role in breast cancer (BC) treatment. DOX directly disrupts DNA replication, demonstrating remarkable efficacy against BC cells. However, its non-specificity toward cancer cells leads to significant side effects, limiting its clinical utility. Interestingly, DOX can also enhance the antitumor immune response by promoting immunogenic cell death in BC cells, thereby facilitating the presentation of tumor antigens to the adaptive immune system. However, the generation of an adaptive immune response involves highly proliferative processes, which may be adversely affected by DOX-induced cytotoxicity. Therefore, understanding the impact of DOX on dividing T cells becomes crucial, to deepen our understanding and potentially devise strategies to shield anti-tumor immunity from DOX-induced toxicity. Our investigation focused on studying DOX uptake and its effects on human lymphocytes. We collected lymphocytes from healthy donors and BC patients undergoing neoadjuvant chemotherapy (NAC). Notably, patient-derived peripheral blood mononuclear cells (PBMC) promptly internalized DOX when incubated in vitro or isolated immediately after NAC. These DOX-treated PBMCs exhibited significant proliferative impairment compared to untreated cells or those isolated before treatment initiation. Intriguingly, among diverse lymphocyte sub-populations, CD8 + T cells exhibited the highest uptake of DOX. To address this concern, we explored a novel DOX formulation encapsulated in ferritin nanocages (FerOX). FerOX specifically targets tumors and effectively eradicates BC both in vitro and in vivo. Remarkably, only T cells treated with FerOX exhibited reduced DOX internalization, potentially minimizing cytotoxic effects on adaptive immunity.Our findings underscore the importance of optimizing DOX delivery to enhance its antitumor efficacy while minimizing adverse effects, highlighting the pivotal role played by FerOX in mitigating DOX-induced toxicity towards T-cells, thereby positioning it as a promising DOX formulation. This study contributes valuable insights to modern cancer therapy and immunomodulation.

Nanovaccine-based strategies for lymph node targeted delivery and imaging in tumor immunotherapy

Therapeutic tumor vaccines have attracted considerable attention in the past decade; they can induce tumor regression, eradicate minimal residual disease, establish lasting immune memory and avoid non-specific and adverse side effects. However, the challenge in the field of therapeutic tumor vaccines is ensuring the delivery of immune components to the lymph nodes (LNs) to activate immune cells. The clinical response rate of traditional therapeutic tumor vaccines falls short of expectations due to inadequate lymph node delivery. With the rapid development of nanotechnology, a large number of nanoplatform-based LN-targeting nanovaccines have been exploited for optimizing tumor immunotherapies. In addition, some nanovaccines possess non-invasive visualization performance, which is benefit for understanding the kinetics of nanovaccine exposure in LNs. Herein, we present the parameters of nanoplatforms, such as size, surface modification, shape, and deformability, which affect the LN-targeting functions of nanovaccines. The recent advances in nanoplatforms with different components promoting LN-targeting are also summarized. Furthermore, emerging LNs-targeting nanoplatform-mediated imaging strategies to both improve targeting performance and enhance the quality of LN imaging are discussed. Finally, we summarize the prospects and challenges of nanoplatform-based LN-targeting and /or imaging strategies, which optimize the clinical efficacy of nanovaccines in tumor immunotherapies.

Vaccine adjuvants: mechanisms and platforms

Adjuvants are indispensable components of vaccines. Despite being widely used in vaccines, their action mechanisms are not yet clear. With a greater understanding of the mechanisms by which the innate immune response controls the antigen-specific response, the adjuvants' action mechanisms are beginning to be elucidated. Adjuvants can be categorized as immunostimulants and delivery systems. Immunostimulants are danger signal molecules that lead to the maturation and activation of antigen-presenting cells (APCs) by targeting Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) to promote the production of antigen signals and co-stimulatory signals, which in turn enhance the adaptive immune responses. On the other hand, delivery systems are carrier materials that facilitate antigen presentation by prolonging the bioavailability of the loaded antigens, as well as targeting antigens to lymph nodes or APCs. The adjuvants' action mechanisms are systematically summarized at the beginning of this review. This is followed by an introduction of the mechanisms, properties, and progress of classical vaccine adjuvants. Furthermore, since some of the adjuvants under investigation exhibit greater immune activation potency than classical adjuvants, which could compensate for the deficiencies of classical adjuvants, a summary of the adjuvant platforms under investigation is subsequently presented. Notably, we highlight the different action mechanisms and immunological properties of these adjuvant platforms, which will provide a wide range of options for the rational design of different vaccines. On this basis, this review points out the development prospects of vaccine adjuvants and the problems that should be paid attention to in the future.

Instigation of the epoch of nanovaccines in cancer immunotherapy

Cancer is an unprecedented proliferation of cells leading to abnormalities in differentiation and maturation. Treatment of primary and metastatic cancer is challenging. In addition to surgery, chemotherapy and radiation therapies have been conventionally used; however, they suffer from severe toxicity and non-specificity. Immunotherapy, the science of programming the body's own defense system against cancer has gained tremendous attention in the last few decades. However, partial immunogenic stimulation, premature degradation and inability to activate dendritic and helper T cells has resulted in limited clinical success. The era of nanomedicine has brought about several breakthroughs in various pharmaceutical and biomedical fields. Hereby, we review and discuss the interplay of tumor microenvironment (TME) and the immunological cascade and how they can be employed to develop nanoparticle-based cancer vaccines and immunotherapies. Nanoparticles composed of lipids, polymers and inorganic materials contain useful properties suitable for vaccine development. Proteinaceous vaccines derived from mammalian viruses, bacteriophages and plant viruses also have unique advantages due to their immunomodulation capabilities. This review accounts for all such considerations. Additionally, we explore how attributes of nanotechnology can be utilized to develop successful nanomedicine-based vaccines for cancer therapy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Protein Nanoparticle-Mediated Delivery of Recombinant Influenza Hemagglutinin Enhances Immunogenicity and Breadth of the Antibody Response

The vast majority of seasonal influenza vaccines administered each year are derived from virus propagated in eggs using technology that has changed little since the 1930s. The immunogenicity, durability, and breadth of response would likely benefit from a recombinant nanoparticle-based approach. Although the E2 protein nanoparticle (NP) platform has been previously shown to promote effective cell-mediated responses to peptide epitopes, it has not yet been reported to deliver whole protein antigens. In this study, we synthesized a novel maleimido tris-nitrilotriacetic acid (NTA) linker to couple protein hemagglutinin (HA) from H1N1 influenza virus to the E2 NP, and we evaluated the HA-specific antibody responses using protein microarrays. We found that recombinant H1 protein alone is immunogenic in mice but requires two boosts for IgG to be detected and is strongly IgG1 (Th2) polarized. When conjugated to E2 NPs, IgG2c is produced leading to a more balanced Th1/Th2 response. Inclusion of the Toll-like receptor 4 agonist monophosphoryl lipid A (MPLA) significantly enhances the immunogenicity of H1-E2 NPs while retaining the Th1/Th2 balance. Interestingly, broader homo- and heterosubtypic cross-reactivity is also observed for conjugated H1-E2 with MPLA, compared to unconjugated H1 with or without MPLA. These results highlight the potential of an NP-based delivery of HA for tuning the immunogenicity, breadth, and Th1/Th2 balance generated by recombinant HA-based vaccination. Furthermore, the modularity of this protein-protein conjugation strategy may have utility for future vaccine development against other human pathogens.

Ferritin-based nanomedicine for disease treatment

Ferritin is an endogenous protein which is self-assembled by 24 subunits into a highly uniform nanocage structure. Due to the drug-encapsulating ability in the hollow inner cavity and abundant modification sites on the outer surface, ferritin nanocage has been demonstrated great potential to become a multi-functional nanomedicine platform. Its good biocompatibility, low toxicity and immunogenicity, intrinsic tumor-targeting ability, high stability, low cost and massive production, together make ferritin nanocage stand out from other nanocarriers. In this review, we summarized ferritin-based nanomedicine in field of disease diagnosis, treatment and prevention. The different types of drugs to be loaded in ferritin, as well as drug-loading methods were classified. The strategies for site-specific and non-specific functional modification of ferritin were investigated, then the application of ferritin for disease imaging, drug delivery and vaccine development were discussed. Finally, the challenges restricting the clinical translation of ferritin-based nanomedicines were analyzed.

Protein-based nanocages for vaccine development

Protein nanocages have attracted considerable attention in various fields of nanomedicine due to their intrinsic properties, including biocompatibility, biodegradability, high structural stability, and ease of modification of their surfaces and inner cavities. In vaccine development, these protein nanocages are suited for efficient targeting to and retention in the lymph nodes and can enhance immunogenicity through various mechanisms, including excellent uptake by antigen-presenting cells and crosslinking with multiple B cell receptors. This review highlights the superiority of protein nanocages as antigen delivery carriers based on their physiological and immunological properties such as biodistribution, immunogenicity, stability, and multifunctionality. With a focus on design, we discuss the utilization and efficacy of protein nanocages such as virus-like particles, caged proteins, and artificial caged proteins against cancer and infectious diseases such as coronavirus disease 2019 (COVID-19). In addition, we summarize available knowledge on the protein nanocages that are currently used in clinical trials and provide a general outlook on conventional distribution techniques and hurdles faced, particularly for therapeutic cancer vaccines.

Locoregional Lymphatic Delivery Systems Using Nanoparticles and Hydrogels for Anticancer Immunotherapy

The lymphatic system has gained significant interest as a target tissue to control cancer progress, which highlights its central role in adaptive immune response. Numerous mechanistic studies have revealed the benefits of nano-sized materials in the transport of various cargos to lymph nodes, overcoming barriers associated with lymphatic physiology. The potential of sustained drug delivery systems in improving the therapeutic index of various immune modulating agents is also being actively discussed. Herein, we aim to discuss design rationales and principles of locoregional lymphatic drug delivery systems for invigorating adaptive immune response for efficient antitumor immunotherapy and provide examples of various advanced nanoparticle- and hydrogel-based formulations.

Ovalbumin and Poly(i:c) Encapsulated Dendritic Cell-Targeted Nanoparticles for Immune Activation in the Small Intestinal Lymphatic System

Here, antigen and adjuvant encapsulated dendritic cell-targeted nanoparticles for immune activation in the small intestinal lymphatic system to inhibit melanoma development are described. This strategy is demonstrated using chondroitin sulfate-coated nanoparticles (OPGMN) grafted with glycocholic acid and mannose for cationic liposomes encapsulated with ovalbumin as an antigen and polyinosine-polycytidylic acid as a cancer-specific adjuvant. OPGMN is absorbed in the gastrointestinal tract and delivered to the lymph nodes when orally administered. Oral delivery of OPGMN induces increased dendritic cell maturation compared to the intradermal route in the lymph node and induces T helper type 1 and type 2 responses, such as immunoglobulin G1 and G2c, interferon-gamma, and interleukin-2, in the blood. Repeated oral administration of OPGMN increases the population of CD3+ CD8+ T cells, CD44high CD62Llow memory T cells, and CD11b+ CD27+ natural killer cells in the blood. OPGMN completely prevents melanoma development in the B16F10-bearing C57BL/6 mouse model by reducing the population of CD4+ CD25+ Foxp3+ regulatory T cells in the blood. This strategy is expected to prevent the recurrence of tumors after various cancer treatments.

Ferritin - a multifaceted protein scaffold for biotherapeutics

The ferritin nanocage is an endogenous protein that exists in almost all mammals. Its hollow spherical structure that naturally stores iron ions has been diversely exploited by researchers in biotherapeutics. Ferritin has excellent biosafety profiles, and the nanosized particles exhibit rapid dispersion and controlled/sustained release pharmacokinetics. Moreover, the large surface-to-volume ratio and the disassembly/reassembly behavior of the 24 monomer subunits into a sphere allow diverse modifications by chemical and genetic methods on the surface and inner cage of ferritin. Here, we critically review ferritin and its applications. We (i) introduce the application of ferritin in drug delivery; (ii) present an overview of the use of ferritin in imaging and diagnosis for biomedical purposes; (iii) discuss ferritin-based vaccines; and (iv) review ferritin-based agents currently in clinical trials. Although there are no currently approved drugs based on ferritin, this multifunctional protein scaffold shows immense potential in drug development in diverse categories, and ferritin-based drugs have recently entered phase I clinical trials. This golden shortlist of recent developments will be of immediate benefit and interest to researchers studying ferritin and other protein-based biotherapeutics.

Engineered Design of the E-Helix Structure on Ferritin Nanoparticles

Insertion of an immunogenic epitope at the C-terminus of ferritin has shown the potential to produce a stable and efficacious vaccine. There is however limited understanding of how C-terminus insertion affects ferritin protein stability. The E-helix at the C-terminus has attracted interest because there are contradictory reports as to whether it has a role in protein stabilization. Here, we report, for the first time, combining molecular dynamics simulation (MDS) with experiment to engineer the design of the E-helix at the C-terminus of engineered human ferritin heavy chain (F₁) inserted with Epstein-Barr nuclear antigen 1 (EBNA1, E₁) and flexible linker (L₃) residues (to afford F₁L₃E₁). Hot spots on the E-helix of the C-terminus were predicted by MDS at aa 167 (Glu) and aa 171 (Asp). Five (5) variants of F₁L₃E₁ were constructed by considering hot spots and alteration of electrostatic or hydrophobic interfaces, namely, (1) C1, hot spots substituted with noncharged residue Gln; (2) C2, hot spots substituted with positively charged residue Arg; (3) C3, hydrophobic residues substituted with the most hydrophobic residues Val and Ile; (4) C4, hydrophobic residues substituted with the most hydrophilic residues Gln and Asn; and (5) C5, a heptad repeat structure in the E-helix disrupted by substituting "a" and "d" heptad residues with noncharged polar residue Gln. It was found that the E-helix is essential to maintain integrated protein stability and that changing the hydrophobic interface (C3 and C4) had more significant effects on protein folding and stability than changing the electrostatic interface (C1 and C2). It was confirmed by both MDS and experiment that variants C1, C2, and C5 were able to fold to form stable conformational structures with protein surface hydrophobicity similar to that of F₁L₃E₁. However, they are less thermally stable than F₁L₃E₁. Significant changes in hydrophobicity drove significant protein aggregation for variants C3 and C4. It is concluded that the molecular design of the C-terminus in engineered ferritin, especially the E-helix, is important to ensure the epitope-based chimeric vaccine is safe (aggregate free) and efficacious.

A Multivalent Vaccine Based on Ferritin Nanocage Elicits Potent Protective Immune Responses against SARS-CoV-2 Mutations

The SARS-CoV-2 pandemic has created a global public crisis and heavily affected personal lives, healthcare systems, and global economies. Virus variants are continuously emerging, and, thus, the pandemic has been ongoing for over two years. Vaccines were rapidly developed based on the original SARS-CoV-2 (Wuhan-Hu-1) to build immunity against the coronavirus disease. However, they had a very low effect on the virus' variants due to their low cross-reactivity. In this study, a multivalent SARS-CoV-2 vaccine was developed using ferritin nanocages, which display the spike protein from the Wuhan-Hu-1, B.1.351, or B.1.429 SARS-CoV-2 on their surfaces. We show that the mixture of three SARS-CoV-2 spike-protein-displaying nanocages elicits CD4+ and CD8+ T cells and B-cell immunity successfully in vivo. Furthermore, they generate a more consistent antibody response against the B.1.351 and B.1.429 variants than a monovalent vaccine. This leads us to believe that the proposed ferritin-nanocage-based multivalent vaccine platform will provide strong protection against emerging SARS-CoV-2 variants of concern (VOCs).

Rational design of engineered H-ferritin nanoparticles with improved siRNA delivery efficacy across an in vitro model of the mouse BBB

Gene therapy holds tremendous potential for the treatment of incurable brain diseases including Alzheimer's disease (AD), stroke, glioma, and Parkinson's disease. The main challenge is the lack of effective gene delivery systems traversing the blood-brain barrier (BBB), due to the complex microvessels present in the brain which restrict substances from the circulating blood passing through. Recently, increasing efforts have been made to develop promising gene carriers for brain-related disease therapies. One such development is the self-assembled heavy chain ferritin (HFn) nanoparticles (NPs). HFn NPs have a unique hollow spherical structure that can encapsulate nucleic acid drugs (NADs) and specifically bind to cancer cells and BBB endothelial cells (BBB ECs) via interactions with the transferrin receptor 1 (TfR1) overexpressed on their surfaces, which increases uptake through the BBB. However, the gene-loading capacity of HFn is restricted by its limited interior volume and negatively charged inner surface; therefore, these drawbacks have prompted the demand for strategies to remould the structure of HFn. In this work, we analyzed the three-dimensional (3D) structure of HFn using Chimera software (v 1.14) and developed a class of internally cationic HFn variants (HFn+ NPs) through arginine mutation on the lumenal surface of HFn. These HFn+ NPs presented powerful electrostatic forces in their cavities, and exhibited higher gene encapsulation efficacy than naive HFn. The top-performing candidate, HFn2, effectively delivered siRNA to glioma cells after traversing the BBB and achieved the highest silencing efficacy among HFn+ NPs. Overall, our findings demonstrate that HFn+ NPs obtained by this genetic engineering method provide critical insights into the future development of nucleic acid delivery carriers with BBB-crossing ability.

Potential of Ferritin-Based Platforms for Tumor Immunotherapy

Ferritin is an iron storage protein that plays a key role in iron homeostasis and cellular antioxidant activity. Ferritin has many advantages as a tumor immunotherapy platform, including a small particle size that allows for penetration into tumor-draining lymph nodes or tumor tissue, a unique structure consisting of 24 self-assembled subunits, cavities that can encapsulate drugs, natural targeting functions, and a modifiable outer surface. In this review, we summarize related research applying ferritin as a tumor immune vaccine or a nanocarrier for immunomodulator drugs based on different targeting mechanisms (including dendritic cells, tumor-associated macrophages, tumor-associated fibroblasts, and tumor cells). In addition, a ferritin-based tumor vaccine expected to protect against a wide range of coronaviruses by targeting multiple variants of SARS-CoV-2 has entered phase I clinical trials, and its efficacy is described in this review. Although ferritin is already on the road to transformation, there are still many difficulties to overcome. Therefore, three barriers (drug loading, modification sites, and animal models) are also discussed in this paper. Notwithstanding, the ferritin-based nanoplatform has great potential for tumor immunotherapy, with greater possibility of clinical transformation.

Animal protein-plant protein composite nanospheres for dual-drug loading and synergistic cancer therapy

The co-delivery of multiple drugs using one drug carrier is a viable strategy to optimize drug dosage and reduce the side effects in chemotherapy. Herein, a hydrophilic animal protein (silk fibroin) and a hydrophobic plant protein (zein) were selected for preparing a composite drug carrier. Adapting our previously developed method for the preparation of regenerated silk fibroin (RSF) nanospheres, we prepared RSF/zein nanospheres that displayed an interesting structure including a single central hole. The particle size of the RSF/zein nanospheres was regulated from 150 to 460 nm by varying the preparation conditions, implying that such a drug carrier is suitable for both intravenous administration and lymphatic chemotherapy. Two anti-cancer drugs with different target sites, paclitaxel (PTX) and curcumin (CUR), were selected for the preparation of dual-drug-loaded CUR/PTX@RSF/zein nanospheres. Both drugs achieved a high loading capacity in the RSF/zein nanospheres, i.e., 8.2% for PTX and 12.1% for CUR. Subsequently, the encapsulated PTX and CUR were released from the RSF/zein nanospheres in a sustained manner for at least 7 days. Importantly, these dual-drug-loaded RSF/zein nanospheres exhibited a considerable synergistic therapeutic effect, showing more efficient suppression of in vitro cancer cell growth than free PTX or CUR, a combination of free PTX and CUR, or single-drug-loaded nanospheres. Therefore, the CUR/PTX@RSF/zein nanospheres developed in this study hold great potential for combination chemotherapy in future clinical applications.

Protein Cages: From Fundamentals to Advanced Applications

Proteins that self-assemble into polyhedral shell-like structures are useful molecular containers both in nature and in the laboratory. Here we review efforts to repurpose diverse protein cages, including viral capsids, ferritins, bacterial microcompartments, and designed capsules, as vaccines, drug delivery vehicles, targeted imaging agents, nanoreactors, templates for controlled materials synthesis, building blocks for higher-order architectures, and more. A deep understanding of the principles underlying the construction, function, and evolution of natural systems has been key to tailoring selective cargo encapsulation and interactions with both biological systems and synthetic materials through protein engineering and directed evolution. The ability to adapt and design increasingly sophisticated capsid structures and functions stands to benefit the fields of catalysis, materials science, and medicine.

Utilization of metal or non-metal-based functional materials as efficient composites in cancer therapies

There has been great progress in cancer treatment through traditional approaches, even though some of them are still trapped in relative complications such as certain side effects and prospective chances of full recovery. As a conventional method, the immunotherapy approach is regarded as an effective approach to cure cancer. It is mainly promoted by immune checkpoint blocking and adoptive cell therapy, which can utilize the human immune system to attack tumor cells and make them necrose completely or stop proliferating cancer cells. Currently however, immunotherapy shows limited success due to the limitation of real applicable cases of targeted tumor environments and immune systems. Considering the urgent need to construct suitable strategies towards cancer therapy, metallic materials can be used as delivery systems for immunotherapeutic agents in the human body. Metallic materials exhibit a high degree of specificity, effectiveness, diagnostic ability, imaging ability and therapeutic effects with different biomolecules or polymers, which is an effective option for cancer treatment. In addition, these modified metallic materials contain immune-modulators, which can activate immune cells to regulate tumor microenvironments and enhance anti-cancer immunity. Additionally, they can be used as adjuvants with immunomodulatory activities, or as carriers for molecular transport to specific targets, which results in the loading of specific ligands to facilitate specific uptake. Here, we provide an overview of the different types of metallic materials used as efficient composites in cancer immunotherapy. We elaborate on the advancements using metallic materials with functional agents as effective composites in synergistic cancer treatment. Some nonmetallic functional composites also appear as a common phenomenon. Ascribed to the design of the composites themselves, the materials' surface structural characteristics are introduced as the drug-loading substrate. The physical and chemical properties of the functional materials emphasize that further research is required to fully characterize their mechanism, showing appropriate relevance for material toxicology and biomedical applications.

Protein-Based Nanoparticles for the Imaging and Treatment of Solid Tumors: The Case of Ferritin Nanocages, a Narrative Review

Protein nanocages have been studied extensively, due to their unique architecture, exceptional biocompatibility and highly customization capabilities. In particular, ferritin nanocages (FNs) have been employed for the delivery of a vast array of molecules, ranging from chemotherapeutics to imaging agents, among others. One of the main favorable characteristics of FNs is their intrinsic targeting efficiency toward the Transferrin Receptor 1, which is overexpressed in many tumors. Furthermore, genetic manipulation can be employed to introduce novel variants that are able to improve the loading capacity, targeting capabilities and bio-availability of this versatile drug delivery system. In this review, we discuss the main characteristics of FN and the most recent applications of this promising nanotechnology in the field of oncology with a particular emphasis on the imaging and treatment of solid tumors.

Innovations in lymph node targeting nanocarriers

Lymph nodes are secondary lymphoid tissues in the body that facilitate the co-mingling of immune cells to enable and regulate the adaptive immune response. They are also tissues implicated in a variety of diseases, including but not limited to malignancy. The ability to access lymph nodes is thus attractive for a variety of therapeutic and diagnostic applications. As nanotechnologies are now well established for their potential in translational biomedical applications, their high relevance to applications that involve lymph nodes is highlighted. Herein, established paradigms of nanocarrier design to enable delivery to lymph nodes are discussed, considering the unique lymph node tissue structure as well as lymphatic system physiology. The influence of delivery mechanism on how nanocarrier systems distribute to different compartments and cells that reside within lymph nodes is also elaborated. Finally, current advanced nanoparticle technologies that have been developed to enable lymph node delivery are discussed.

Functionalizing Ferritin Nanoparticles for Vaccine Development

In the last decade, the interest in ferritin-based vaccines has been increasing due to their safety and immunogenicity. Candidates against a wide range of pathogens are now on Phase I clinical trials namely for influenza, Epstein-Barr, and SARS-CoV-2 viruses. Manufacturing challenges related to particle heterogeneity, improper folding of fused antigens, and antigen interference with intersubunit interactions still need to be overcome. In addition, protocols need to be standardized so that the production bioprocess becomes reproducible, allowing ferritin-based therapeutics to become readily available. In this review, the building blocks that enable the formulation of ferritin-based vaccines at an experimental stage, including design, production, and purification are presented. Novel bioengineering strategies of functionalizing ferritin nanoparticles based on modular assembly, allowing the challenges associated with genetic fusion to be circumvented, are discussed. Distinct up/down-stream approaches to produce ferritin-based vaccines and their impact on production yield and vaccine efficacy are compared. Finally, ferritin nanoparticles currently used in vaccine development and clinical trials are summarized.

Development of purification process for dual-function recombinant human heavy-chain ferritin by the investigation of genetic modification impact on conformation

Ferritin is a promising drug delivery platform and has been functionalized through genetic modifications. This work has designed and expressed a dual-functional engineered human heavy-chain ferritin (HFn) with the inserted functional peptide PAS and RGDK to extend half-life and improve tumor targeted drug delivery. A facile and cost-effective two-step purification pathway for recombinant HFn was developed. The genetic modification was found to affect HFn conformation, and therefore varied the purification performance. Heat-acid precipitation followed by butyl fast flow hydrophobic interaction chromatography (HIC) has been developed to purify HFn and modified HFns. Nucleic acid removal reached above 99.8% for HFn and modified HFns. However, HFn purity reached above 95% and recovery yield (overall) above 90%, compared with modified HFns purity above 82% and recovery yield (overall) above 58%. It is interesting to find that the inserted functional peptides significantly changed the molecule conformation, where a putative turnover of the E-helix with the inserted functional peptides formed a "flop" conformation, in contrast with the "flip" conformation of HFn. It could be the cause of fragile stability of modified HFns, and therefore less tolerant to heat and acid condition, observed by the lower recovery yield in heat-acid precipitation.

Nanocages displaying SIRP gamma clusters combined with prophagocytic stimulus of phagocytes potentiate anti-tumor immunity

Antigen-presenting cells (APCs), including macrophages and dendritic cells (DCs), play a crucial role in bridging innate and adaptive immunity; thereby, innate immune checkpoint blockade-based therapy is an attractive approach for the induction of sustainable tumor-specific immunity. The interaction between the cluster of differentiation 47 (CD47) on tumor and signal-regulatory protein alpha (SIRPα) on phagocytic cells inhibits the phagocytic function of APCs, acting as a "don't eat me" signal. Accordingly, CD47 blockade is known to increase tumor cell phagocytosis, eliciting tumor-specific CD8⁺ T-cell immunity. Here, we introduced a nature-derived nanocage to deliver SIRPγ for blocking of antiphagocytic signaling through binding to CD47 and combined it with prophagocytic stimuli using a metabolic reprogramming reagent for APCs (CpG-oligodeoxynucleotides). Upon delivering the clustered SIRPγ variant, the nanocage showed enhanced CD47 binding profiles on tumor cells, thereby promoting active engulfment by phagocytes. Moreover, combination with CpG potentiated the prophagocytic ability, leading to the establishment of antitumorigenic surroundings. This combination treatment could competently inhibit tumor growth by invigorating APCs and CD8⁺ T-cells in TMEs in B16F10 orthotopic tumor models, known to be resistant to CD47-targeting therapeutics. Collectively, enhanced delivery of an innate immune checkpoint antagonist with metabolic modulation stimuli of immune cells could be a promising strategy for arousing immune responses against cancer.

Bioengineered Ferritin Nanocarriers for Cancer Therapy

Ferritin naturally exists in most organisms and can specifically recognize the transferrin 1 receptor (TfR1), which is generally highly expressed on various types of tumor cells. The pH dependent reversible assembling and disassembling property of ferritin renders it as a suitable candidate for encapsulating a variety of anticancer drugs and imaging probes. Ferritins external surface is chemically and genetically modifiable which can serve as attachment site for tumor specific targeting peptides or moieties. Moreover, the biological origin of these protein cages makes it a biocompatible nanocarrier that stabilizes and protects the enclosed particles from the external environment without provoking any toxic or immunogenic responses. Recent studies, further establish ferritin as a multifunctional nanocarrier for targeted cancer chemotherapy and phototherapy. In this review, we introduce the favorable characteristics of ferritin drug carriers, the specific targeted surface modification and a multifunctional nanocarriers combined chemotherapy with phototherapy for tumor treatment. Taken together, ferritin is a potential ideal base of engineered nanoparticles for tumor therapy and still needs to explore more on its way.

Design and Synthesis of Piperazine-Based Compounds Conjugated to Humanized Ferritin as Delivery System of siRNA in Cancer Cells

Gene expression regulation by small interfering RNA (siRNA) holds promise in treating a wide range of diseases through selective gene silencing. However, successful clinical application of nucleic acid-based therapy requires novel delivery options. Herein, to achieve efficient delivery of negatively charged siRNA duplexes, the internal cavity of "humanized" chimeric Archaeal ferritin (HumAfFt) was specifically decorated with novel cationic piperazine-based compounds (PAs). By coupling these rigid-rod-like amines with thiol-reactive reagents, chemoselective conjugation was efficiently afforded on topologically selected cysteine residues properly located inside HumAfFt. The capability of PAs-HumAfFt to host and deliver siRNA molecules through human transferrin receptor (TfR1), overexpressed in many cancer cells, was explored. These systems allowed siRNA delivery into HeLa, HepG2, and MCF-7 cancer cells with improved silencing effect on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression with respect to traditional transfection methodologies and provided a promising TfR1-targeting system for multifunctional siRNA delivery to therapeutic applications.

Self-assembled peptide and protein nanostructures for anti-cancer therapy: Targeted delivery, stimuli-responsive devices and immunotherapy

Self-assembled peptides and proteins possess tremendous potential as targeted drug delivery systems and key applications of these well-defined nanostructures reside in anti-cancer therapy. Peptides and proteins can self-assemble into nanostructures of diverse sizes and shapes in response to changing environmental conditions such as pH, temperature, ionic strength, as well as host and guest molecular interactions; their countless benefits include good biocompatibility and high loading capacity for hydrophobic and hydrophilic drugs. These self-assembled nanomaterials can be adorned with functional moieties to specifically target tumor cells. Stimuli-responsive features can also be incorporated with respect to the tumor microenvironment. This review sheds light on the growing interest in self-assembled peptides and proteins and their burgeoning applications in cancer treatment and immunotherapy.

Chemical Conjugation Strategies for the Development of Protein-Based Subunit Nanovaccines

The production of subunit nanovaccines relies heavily on the development of a vaccine delivery system that is safe and efficient at delivering antigens to the target site. Nanoparticles have been extensively investigated for vaccine delivery over the years, as they often possess self-adjuvanting properties. The conjugation of antigens to nanoparticles by covalent bonds ensures co-delivery of these components to the same subset of immune cells in order to trigger the desired immune responses. Herein, we review covalent conjugation strategies for grafting protein or peptide antigens onto other molecules or nanoparticles to obtain subunit nanovaccines. We also discuss the advantages of chemical conjugation in developing these vaccines.

Design of PD-1-decorated nanocages targeting tumor-draining lymph node for promoting T cell activation

Targeted delivery of immunomodulatory molecules to the lymph nodes is an attractive means of improving the efficacy of anti-cancer immunotherapy. In this study, to improve the efficacy of PD-1 blockade-based therapy, nanocages were designed by surface engineering to decorate a programmed cell death protein 1 (PD-1) that is capable of binding against programmed death-ligand 1 (PD-L1) and -ligand 2 (PD-L2). This nanocage-mediated multivalent interaction remarkably increases the binding affinity and improves the antagonistic activity compared to free soluble PD-1. In addition, with the desirable nanocage size for optimal tumor-draining lymph node (TDLN) targeting (approximately 20 nm), rapid draining and increased accumulation into the TDLNs were observed. Moreover, the interference of the PD-1/PD-L axis with ultra-high affinity in the tumor microenvironment (effector phase) and the TDLNs (cognitive phase) significantly enhances the dendritic cell-mediated tumor-specific T cell activation. This characteristic successfully inhibited tumor growth and induced complete tumor eradication in some mice. Thus, the delivery of immunomodulatory molecules with nanocages can be a highly efficient strategy to achieve stronger anti-tumor immunity.

Tumor Accumulation and Off-Target Biodistribution of an Indocyanine-Green Fluorescent Nanotracer: An Ex Vivo Study on an Orthotopic Murine Model of Breast Cancer

Indocyanine green (ICG) is a near infrared fluorescent tracer used in image-guided surgery to assist surgeons during resection. Despite appearing as a very promising tool for surgical oncology, its employment in this area is limited to lymph node mapping or to laparoscopic surgery, as it lacks tumor targeting specificity. Recently, a nanoformulation of this dye has been proposed with the aim toward tumor targeting specificity in order to expand its employment in surgical oncology. This nanosystem is constituted by 24 monomers of H-Ferritin (HFn), which self-assemble into a spherical cage structure enclosing the indocyanine green fluorescent tracer. These HFn nanocages were demonstrated to display tumor homing due to the specific interaction between the HFn nanocage and transferrin receptor 1, which is overexpressed in most tumor tissues. Here, we provide an ex vivo detailed comparison between the biodistribution of this nanotracer and free ICG, combining the results obtained with the Karl Storz endoscope that is currently used in clinical practice and the quantification of the ICG signal derived from the fluorescence imaging system IVIS Lumina II. These insights demonstrate the suitability of this novel HFn-based nanosystem in fluorescence-guided oncological surgery.

One-step construction of ferritin encapsulation drugs for cancer chemotherapy

Conventionally, a disassembly and reassembly method has been used for encapsulation of drug molecules in ferritin protein nano-cages. However, clinical applications of ferritin have been greatly restricted by its limited drug-loading capacity and process complexity. Here, we establish a simple high yield process for preparing high drug-loaded ferritin nanomedicine for industrial production. A complex of ferritin and a target drug was obtained by incubating the mixture at an appropriate pH. An electrostatic charge potential and small ferritin cavity facilitates the passage of drug molecules through the pores, traversing the ferritin shell and enabling deposition of the drug in the ferritin cavity. Compared to the disassembly/reassembly method, the loading capacity of a doxorubicin-loaded ferritin heavy chain (DOX-FTH), constructed by our novel method, was over 3-fold higher, while doxorubicin recovery was 10-fold higher. Results of transmission electron microscopy, size exclusion chromatography, dynamic light scattering, and zeta potential indicate that DOX-FTH exhibits the same physicochemical characteristics of natural apo-ferritin. Moreover, DOX-FTH can be taken up and induce apoptosis of cancer cells overexpressing TfR1. Here, we have demonstrated the successful introduction of more than ten drug molecule types into ferritin nano-cages using a novel method. These results demonstrate that this one-step method is a powerful production process to construct a drug-loading ferritin drug delivery system carrier.

Broad Neutralization Responses Against Oncogenic Human Papillomaviruses Induced by a Minor Capsid L2 Polytope Genetically Incorporated Into Bacterial Ferritin Nanoparticles

Cervical cancer remains a global health burden despite the introduction of highly effective vaccines for the prophylaxis of causative human papillomavirus infection (HPV). Current efforts to eradicate cervical cancer focus on the development of broadly protective, cost-effective approaches. HPV minor capsid protein L2 is being recognized as a promising alternative to the major capsid protein L1 because of its ability to induce responses against a wider range of different HPV types. However, a major limitation of L2 as a source of cross-neutralizing epitopes is its lower immunogenicity compared to L1 when assembled into VLPs. Various approaches have been proposed to overcome this limitation, we developed and tested ferritin-based bio-nanoparticles displaying tandemly repeated L2 epitopes from eight different HPV types grafted onto the surface of Pyrococcus furiosus thioredoxin (Pf Trx). Genetic fusion of the Pf Trx-L2(8x) module to P. furiosus ferritin (Pf Fe) did not interfere with ferritin self-assembly into an octahedral structure composed by 24 protomers. In guinea pigs and mice, the ferritin super-scaffolded, L2 antigen induced a broadly neutralizing antibody response covering 14 oncogenic and two non-oncogenic HPV types. Immune-responsiveness lasted for at least one year and the resulting antibodies also conferred protection in a cervico-vaginal mouse model of HPV infection. Given the broad organism distribution of thioredoxin and ferritin, we also verified the lack of cross-reactivity of the antibodies elicited against the scaffolds with human thioredoxin or ferritin. Altogether, the results of this study point to P. furiosus ferritin nanoparticles as a robust platform for the construction of peptide-epitope-based HPV vaccines.

Lymphatic immunomodulation using engineered drug delivery systems for cancer immunotherapy

Though immunotherapy has revolutionized the treatment of cancer to improve disease outcomes, an array of challenges remain that limit wider clinical success, including low rate of response and immune-related adverse events. Targeting immunomodulatory drugs to therapeutically relevant tissues offers a way to overcome these challenges by potentially enabling enhanced therapeutic efficacy and decreased incidence of side effects. Research highlighting the importance of lymphatic tissues in the response to immunotherapy has increased interest in the application of engineered drug delivery systems (DDSs) to enable specific targeting of immunomodulators to lymphatic tissues and cells that they house. To this end, a variety of DDS platforms have been developed that enable more efficient uptake into lymphatic vessels and lymph nodes to provide targeted modulation of the immune response to cancer. This can occur either by delivery of immunotherapeutics to lymphatics tissues or by direct modulation of the lymphatic vasculature itself due to their direct involvement in tumor immune processes. This review will highlight DDS platforms that, by enabling the activities of cancer vaccines, chemotherapeutics, immune checkpoint blockade (ICB) antibodies, and anti- or pro-lymphangiogenic factors to lymphatic tissues through directed delivery and controlled release, augment cancer immunotherapy.

Targeted cancer cell delivery of arsenate as a reductively activated prodrug

Nanoformulations, prodrugs, and targeted therapies are among the most intensively investigated approaches to new cancer therapeutics. Human ferritin has been used extensively as a nanocarrier for the delivery of drugs and imaging agents to cancerous tumor cells both in vitro and in vivo. We report exploitation of the native properties of ferritin, which can be co-loaded with simple forms of iron (FeOOH) and arsenic (arsenate) in place of the native phosphate. The As(III) form arsenic trioxide has been successfully used to treat one blood cancer, but has so far proven too systemically toxic for use on solid tumors in the clinic. The As(V) form, arsenate, on the other hand, while much less systemically toxic upon bolus injection has also proven ineffective for cancer therapy. We extended the C-terminal ends of the human ferritin subunits with a tumor cell receptor targeting peptide and loaded this modified ferritin with ~ 800 arsenates and ~ 1100 irons. Our results demonstrate targeting and uptake of the iron, arsenate-loaded modified human ferritin by breast cancer cells. At the same arsenic levels, the cytotoxicity of the iron, arsenate-loaded human ferritin was equivalent to that of free arsenic trioxide and much greater than that of free arsenate. The iron-only loaded human ferritin was not cytotoxic at the highest achievable doses. The results are consistent with the receptor-targeted human ferritin delivering arsenate as a reductively activated 'prodrug'. This targeted delivery could be readily adapted to treat other types of solid tumor cancers.

Functionalization of Nanomaterials and Their Application in Melanoma Cancer Theranostics

Treatment and cure for melanoma, the most aggressive subcategory of skin cancer, still remains a daunting challenge to be circumvented. When metastasized, it requires radiotherapy, chemotherapy, targeted therapy, immunotherapy, etc. as its treatment, although it can be removed by surgical intervention if detected in its early stage. Development of upgraded therapeutic modalities for melanoma facilitating early diagnosis with subsequent excision before metastasis is, therefore, an urgent need. As we witnessed, nanotechnology has become instrumental with its far-reaching ramifications both in diagnosis and treatment of melanoma. In this review we are going to summarize the encouraging developments made in recent times for functionalization of nanoparticles (including liposomes, polymeric, metal, viral, protein nanoparticles) to create numerous theranostics (therapy plus diagnostics) for melanoma. We will also reflect on the melanoma statistics, molecular biology, conventional therapies, ongoing clinical trials, and future outlook.

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.

Addressing barriers to effective cancer immunotherapy with nanotechnology: achievements, challenges, and roadmap to the next generation of nanoimmunotherapeutics

Cancer is a complex systemic disorder that affects many organs and tissues and arises from the altered function of multiple cellular and molecular mechanisms. One of the systems malfunctioning in cancer is the immune system. Restoring and improving the ability of the immune system to effectively recognize and eradicate cancer is the main focus of immunotherapy, a topic which has garnered recent and significant interest. The initial excitement about immunotherapy, however, has been challenged by its limited efficacy in certain patient populations and the development of adverse effects such as therapeutic resistance and autoimmunity. At the same time, a number of advances in the field of nanotechnology have sought to address the challenges faced by modern immunotherapeutics and allow these therapeutic strategies to realize their full potential. This endeavour requires an understanding of not only the immunological barriers in cancer but also the mechanisms by which modern technologies and immunotherapeutics modulate the function of the immune system. Herein, we summarize the major barriers relevant to cancer immunotherapy and review current progress in addressing these obstacles using various approaches and clinically approved therapies. We then discuss the remaining challenges and how they can be addressed by nanotechnology. We lay out translational considerations relevant to the therapies described and propose a framework for the development of next-generation nanotechnology-enabled immunotherapies.

Protein-based nanoparticles in cancer vaccine development

Peptide and protein-based cancer vaccines usually fail to elicit efficient immune responses against tumors. However, delivery of these peptides and proteins as components within caged protein nanoparticles has shown promising improvements in vaccine efficacy. Advantages of protein nanoparticles over other vaccine platforms include their highly organized structures and symmetry, biodegradability, ability to be specifically functionalized at three different interfaces (inside and outside the protein cage, and between subunits in macromolecular assembly), and ideal size for vaccine delivery. In this review, we discuss different classes of virus-like particles and caged protein nanoparticles that have been used as vehicles to transport and increase the interaction of cancer vaccine components with the immune system. We review the effectiveness of these protein nanoparticles towards inducing and elevating specific immune responses, which are needed to overcome the low immunogenicity of the tumor microenvironment.

Enhanced Immune Responses Conferring Cross-Protection by Skin Vaccination With a Tri-Component Influenza Vaccine Using a Microneedle Patch

Skin vaccination using biodegradable microneedle patch (MNP) technology in vaccine delivery is a promising strategy showing significant advantages over conventional flu shots. In this study, we developed an MNP encapsulating a 4M2e-tFliC fusion protein and two types of whole inactivated influenza virus vaccines (H1N1 and H3N2) as a universal vaccine candidate. We demonstrated that mice receiving this tri-component influenza vaccine via MNP acquired improved IgG1 antibody responses with more balanced IgG1/IgG2a antibody responses and enhanced cellular immune responses, including increased populations of IL-4 and IFN-γ producing cells and higher frequencies of antigen-specific plasma cells compared with intramuscular injection. In addition, stronger germinal center reactions, increased numbers of Langerin-positive migratory dendritic cells, and increased cytokine secretion were observed in the skin-draining lymph nodes after immunization with the tri-component influenza MNP vaccine. The MNP-immunized group also possessed enhanced protection against a heterologous reassortant A/Shanghai/2013 H7N9 (rSH) influenza virus infection. Furthermore, the sera collected from 4M2e-tFliC MNP-immunized mice were demonstrated to have antiviral efficacy against reassortant A/Vietnam/1203/2004 H5N1 (rVet) and A/Shanghai/2013 H7N9 (rSH) virus challenges. The immunological advantages of skin vaccination with this tri-component MNP vaccine could offer a promising approach to develop an easily applicable and broadly protective universal influenza vaccine.