Engineering self-assembled materials to study and direct immune function

Self-Assembled Nanobiomaterials for Combination Immunotherapy

Nanotechnological interventions for cancer immunotherapy are a rapidly evolving paradigm with immense potential. Self-assembled nanobiomaterials present safer alternatives to their nondegradable counterparts and pose better functionalities in terms of controlled drug delivery and phototherapy to activate immunogenic cell death. In this Review, we discuss several classes of self-assembled nanobiomaterials based on polymers, lipids, peptides, hydrogel, metal organic frameworks, and covalent-organic frameworks with the ability to activate systemic immune response and convert a "cold" immunosuppressive tumor mass to a "hot" antitumor immune cell rich microenvironment. The unique aspects of these materials are underpinned, and their mechanisms of combinatorial immunotherapeutic action are discussed. Future challenges associated with their clinical translation are also highlighted.

Multivalent Scaffolds to Promote B cell Tolerance

Autoimmune diseases are characterized by aberrant immune responses toward self-antigens. Current treatments lack specificity, promoting adverse effects by broadly suppressing the immune system. Therapies that specifically target the immune cells responsible for disease are a compelling strategy to mitigate adverse effects. Multivalent formats that display numerous binding epitopes off a single scaffold may enable selective immunomodulation by eliciting signals through pathways unique to the targeted immune cells. However, the architecture of multivalent immunotherapies can vary widely, and there is limited clinical data with which to evaluate their efficacy. Here, we set forth to review the architectural properties and functional mechanisms afforded by multivalent ligands and evaluate four multivalent scaffolds that address autoimmunity by altering B cell signaling pathways. First, we address both synthetic and natural polymer backbones functionalized with a variety of small molecule, peptide, and protein ligands for probing the effects of valency and costimulation. Then, we review nanoparticles composed entirely from immune signals which have been shown to be efficacious. Lastly, we outline multivalent liposomal nanoparticles capable of displaying high numbers of protein antigens. Taken together, these examples highlight the versatility and desirability of multivalent ligands for immunomodulation and illuminate strengths and weaknesses of multivalent scaffolds for treating autoimmunity.

Role of dendritic cells in MYD88-mediated immune recognition and osteoinduction initiated by the implantation of biomaterials

Bone substitute material implantation has become an important treatment strategy for the repair of oral and maxillofacial bone defects. Recent studies have shown that appropriate inflammatory and immune cells are essential factors in the process of osteoinduction of bone substitute materials. Previous studies have mainly focused on innate immune cells such as macrophages. In our previous work, we found that T lymphocytes, as adaptive immune cells, are also essential in the osteoinduction procedure. As the most important antigen-presenting cell, whether dendritic cells (DCs) can recognize non-antigen biomaterials and participate in osteoinduction was still unclear. In this study, we found that surgical trauma associated with materials implantation induces necrocytosis, and this causes the release of high mobility group protein-1 (HMGB1), which is adsorbed on the surface of bone substitute materials. Subsequently, HMGB1-adsorbed materials were recognized by the TLR4-MYD88-NFκB signal axis of dendritic cells, and the inflammatory response was activated. Finally, activated DCs release regeneration-related chemokines, recruit mesenchymal stem cells, and initiate the osteoinduction process. This study sheds light on the immune-regeneration process after bone substitute materials implantation, points out a potential direction for the development of bone substitute materials, and provides guidance for the development of clinical surgical methods.

Harnessing Biomaterials to Study and Direct Antigen-Specific Immunotherapy

Immunotherapies are an evolving treatment paradigm for addressing cancer, autoimmunity, and infection. While exciting, most of the existing therapies are limited by their specificity─unable to differentiate between healthy and diseased cells at an antigen-specific level. Biomaterials are a powerful tool that enable the development of next-generation immunotherapies due to their tunable synthesis properties. Our lab harnesses biomaterials as tools to study antigen-specific immunity and as technologies to enable new therapeutic vaccines and immunotherapies to combat cancer, autoimmunity, and infections. Our efforts have spanned the study of intrinsic immune profiles of biomaterials, development of novel nanotechnologies assembled entirely from immune cues, manipulation of innate immune signaling, and advanced technologies to direct and control specialized immune niches such as skin and lymph nodes.

Self-assembled nanoparticles: A new platform for revolutionizing therapeutic cancer vaccines

Cancer vaccines have had some success in the past decade. Based on in-depth analysis of tumor antigen genomics, many therapeutic vaccines have already entered clinical trials for multiple cancers, including melanoma, lung cancer, and head and neck squamous cell carcinoma, which have demonstrated impressive tumor immunogenicity and antitumor activity. Recently, vaccines based on self-assembled nanoparticles are being actively developed as cancer treatment, and their feasibility has been confirmed in both mice and humans. In this review, we summarize recent therapeutic cancer vaccines based on self-assembled nanoparticles. We describe the basic ingredients for self-assembled nanoparticles, and how they enhance vaccine immunogenicity. We also discuss the novel design method for self-assembled nanoparticles that pose as a promising delivery platform for cancer vaccines, and the potential in combination with multiple therapeutic approaches.

New theoretical ISM-K2 Bayesian network model for evaluating vaccination effectiveness

Aiming at the difficulty in obtaining a complete Bayesian network (BN) structure directly through search-scoring algorithms, authors attempted to incorporate expert judgment and historical data to construct an interpretive structural model with an ISM-K2 algorithm for evaluating vaccination effectiveness (VE). By analyzing the influenza vaccine data provided by Hunan Provincial Center for Disease Control and Prevention, risk factors influencing VE in each link in the process of "Transportation-Storage-Distribution-Inoculation" were systematically investigated. Subsequently, an evaluation index system of VE and an ISM-K2 BN model were developed. Findings include: (1) The comprehensive quality of the staff handling vaccines has a significant impact on VE; (2) Predictive inference and diagnostic reasoning through the ISM-K2 BN model are stable, effective, and highly interpretable, and consequently, the post-production supervision of vaccines is enhanced. The study provides a theoretical basis for evaluating VE and a scientific tool for tracking the responsibility of adverse events of ineffective vaccines, which has the value of promotion in improving VE and reducing the transmission rate of infectious diseases.

Recent advancements in nanoparticle-mediated approaches for restoration of multiple sclerosis

Multiple Sclerosis (MS) is an autoimmune disease with complicated immunopathology which necessitates considering multifactorial aspects for its management. Nano-sized pharmaceutical carriers named nanoparticles (NPs) can support impressive management of disease not only in early detection and prognosis level but also in a therapeutic manner. The most prominent initiator of MS is the domination of cellular immunity to humoral immunity and increment of inflammatory cytokines. The administration of several platforms of NPs for MS management holds great promise so far. The efforts for MS management through in vitro and in vivo (experimental animal models) evaluations, pave a new way to a highly efficient therapeutic means and aiding its translation to the clinic in the near future.

Peptide-based supramolecular vaccine systems

Currently approved replication-competent and inactivated vaccines are limited by excessive reactogenicity and poor safety profiles, while subunit vaccines are often insufficiently immunogenic without co-administering exogenous adjuvants. Self-assembling peptide-, peptidomimetic-, and protein-based biomaterials offer a means to overcome these challenges through their inherent modularity, multivalency, and biocompatibility. As these scaffolds are biologically derived and present antigenic arrays reminiscent of natural viruses, they are prone to immune recognition and are uniquely capable of functioning as self-adjuvanting vaccine delivery vehicles that improve humoral and cellular responses. Beyond this intrinsic immunological advantage, the wide range of available amino acids allows for facile de novo design or straightforward modifications to existing sequences. This has permitted the development of vaccines and immunotherapies tailored to specific disease models, as well as generalizable platforms that have been successfully applied to prevent or treat numerous infectious and non-infectious diseases. In this review, we briefly introduce the immune system, discuss the structural determinants of coiled coils, β-sheets, peptide amphiphiles, and protein subunit nanoparticles, and highlight the utility of these materials using notable examples of their innate and adaptive immunomodulatory capacity.

Dynamic nanoassembly-based drug delivery system (DNDDS): Learning from nature

Dynamic nanoassembly-based drug delivery system (DNDDS) has evolved from being a mere curiosity to emerging as a promising strategy for high-performance diagnosis and/or therapy of various diseases. However, dynamic nano-bio interaction between DNDDS and biological systems remains poorly understood, which can be critical for precise spatiotemporal and functional control of DNDDS in vivo. To deepen the understanding for fine control over DNDDS, we aim to explore natural systems as the root of inspiration for researchers from various fields. This review highlights ingenious designs, nano-bio interactions, and controllable functionalities of state-of-the-art DNDDS under endogenous or exogenous stimuli, by learning from nature at the molecular, subcellular, and cellular levels. Furthermore, the assembly strategies and response mechanisms of tailor-made DNDDS based on the characteristics of various diseased microenvironments are intensively discussed. Finally, the current challenges and future perspectives of DNDDS are briefly commented.

Peptide-based supramolecular hydrogels for local drug delivery

Peptide-based supramolecular hydrogels have shown great promise as drug delivery systems (DDSs) because of their excellent biocompatibility, biodegradability, biological function, synthetic feasibility, and responsiveness to external stimuli. Self-assembling peptide molecules are able rationally designed into specific nanoarchitectures in response to the different environmental factors under different circumstances. Among all stimuli that have been investigated, utilizing inherent biological microenvironment, such as metal ions, enzymes and endogenous redox species, to trigger self-assembly endows such systems spatiotemporal controllability to transport therapeutics more accurately. Materials formed by weak non-covalent interactions result in the shear-thinning and immediate recovery behavior. Thus, they are injectable via a syringe or catheter, making them the ideal vehicles to deliver drugs. Based on the above merits, self-assembling peptide-based DDSs have been applied to treat various diseases via direct administration at the lesion site. Herein, in this review, we outline the triggers for inducing peptide-based hydrogels formation and serving as DDSs. We also described the advancements of peptide-based supramolecular hydrogels for local drug delivery, including intratumoral, subcutaneous, ischemia-related tissue (intramyocardial, intrarenal, and ischemic hind limb), and ocular administration. Finally, we give a brief perspective about the prospects and challenges in this field.

CATCH Peptides Coassemble into Structurally Heterogeneous β-Sheet Nanofibers with Little Preference to β-Strand Alignment

Coassembling peptides offer an additional degree of freedom in the design of nanostructured biomaterials when compared to analogous self-assembling peptides. Yet, our understanding of how amino acid sequences encodes coassembled nanofiber structure is limited. Prior work on a charge-complementary pair, CATCH+ and CATCH- peptides, detected like-peptide nearest neighbors (CATCH+:CATCH+ and CATCH-:CATCH-) within coassembled β-sheet nanofibers; these self-associated peptide pairs marked a departure from an "ideal" coassembled structure. In this work, we employ solid-state NMR, isotope-edited FTIR, and coarse-grained molecular dynamics simulations to evaluate the alignment of β-strands within CATCH peptide nanofibers. Both experimental and computational results suggest that CATCH molecules coassemble into structurally heterogeneous nanofibers, which is consistent with our observations in another coassembling system, the King-Webb peptides. Within β-sheet nanofibers, β-strands were found to have nearest neighbors aligned in-register parallel, in-register antiparallel, and out-of-register. In comparison to the King-Webb peptides, CATCH nanofibers exhibit a greater degree of structural heterogeneity. By comparing the amino acid sequences of CATCH and King-Webb peptides, we can begin to unravel sequence-to-structure relationships, which may encode more precise coassembled β-sheet nanostructures.

Advances in nanomaterial vaccine strategies to address infectious diseases impacting global health

Despite the overwhelming success of vaccines in preventing infectious diseases, there remain numerous globally devastating diseases without fully protective vaccines, particularly human immunodeficiency virus (HIV), malaria and tuberculosis. Nanotechnology approaches are being developed both to design new vaccines against these diseases as well as to facilitate their global implementation. The reasons why a given pathogen may present difficulties for vaccine design are unique and tied to the co-evolutionary history of the pathogen and humans, but there are common challenges that nanotechnology is beginning to help address. In each case, a successful vaccine will need to raise immune responses that differ from the immune responses raised by normal infection. Nanomaterials, with their defined compositions, commonly modular construction, and length scales allowing the engagement of key immune pathways, collectively facilitate the iterative design process necessary to identify such protective immune responses and achieve them reliably. Nanomaterials also provide strategies for engineering the trafficking and delivery of vaccine components to key immune cells and lymphoid tissues, and they can be highly multivalent, improving their engagement with the immune system. This Review will discuss these aspects along with recent nanomaterial advances towards vaccines against infectious disease, with a particular emphasis on HIV/AIDS, malaria and tuberculosis.

Novel approaches for vaccine development

Vaccines are critical tools for maintaining global health. Traditional vaccine technologies have been used across a wide range of bacterial and viral pathogens, yet there are a number of examples where they have not been successful, such as for persistent infections, rapidly evolving pathogens with high sequence variability, complex viral antigens, and emerging pathogens. Novel technologies such as nucleic acid and viral vector vaccines offer the potential to revolutionize vaccine development as they are well-suited to address existing technology limitations. In this review, we discuss the current state of RNA vaccines, recombinant adenovirus vector-based vaccines, and advances from biomaterials and engineering that address these important public health challenges.

Biocompatibility of nanomaterials and their immunological properties

Nanomaterials (NMs) have revolutionized multiple aspects of medicine by enabling novel sensing, diagnostic, and therapeutic approaches. Advancements in processing and fabrication have also allowed significant expansion in the applications of the major classes of NMs based on polymer, metal/metal oxide, carbon, liposome, or multi-scale macro-nano bulk materials. Concomitantly, concerns regarding the nanotoxicity and overall biocompatibility of NMs have been raised. These involve putative negative effects on both patients and those subjected to occupational exposure during manufacturing. In this review, we describe the current state of testing of NMs including those that are in clinical use, in clinical trials, or under development. We also discuss the cellular and molecular interactions that dictate their toxicity and biocompatibility. Specifically, we focus on the reciprocal interactions between NMs and host proteins, lipids, and sugars and how these induce responses in immune and other cell types leading to topical and/or systemic effects.

10-hydroxy-2-decenoic acid a bio-immunomodulator in tissue engineering; generates tolerogenic dendritic cells by blocking the toll-like receptor4

Dendritic cells (DCs), in response to the biomaterials, utilize toll-like receptors (TLRs) to become mature or tolerogenic through TLRs-dependent signaling pathways, especially TLR4. Regarding the physicochemical properties of biomaterials, some of such signaling pathways are activated. Unsaturated fatty acids have been explored as an antagonist for TLRs and lead to the tolerogenic phenotype of DCs. Here we showed that, although cultured DCs on both chitosan and Alginate-polyethyleneimine (Alg-PEI) films became fully mature, 10-hydroxy-2-decanoic acid (10-HDA), an unsaturated fatty acid found in royal jelly, led to the tolerogenic immunophenotype of DCs on both films. The cultured cells on the films possessed iDCs-like morphology in the presence of 10-HDA. Moreover, 10-HDA expressed lower levels of CD80, CD83, CD86, and HLA-DR, a higher level of IL-10, and lower level of IL-12 in the cultured DCs on both films. Furthermore, HEK293T cells expressing only TLR4 (HEK-TLR4 cells) were co-cultured with LPS, a specific agonist for TLR4, and 10-HDA. The 10-HDA significantly reduced the expression of tumor necrosis factor-a (TNF-α) in the HEK-TLR4 cells compared to treated only with LPS. These findings indicate that the 10-HDA acts as an antagonist of TLR4; therefore, potentially can be used in autoimmune diseases and preventing the rejection of biomaterials implantation and allograft transplantation.

Histatin 5 variant reduces Candida albicans biofilm viability and inhibits biofilm formation

Candida albicans is a commensal organism and opportunistic pathogen that can form biofilms that colonize surfaces of medical devices, such as implants, catheters, and dentures. Compared to planktonic C. albicans cells, cells in biofilms exhibit increased resistance to treatment. Histatin 5 (Hst-5) is an antimicrobial peptide that is natively secreted by human salivary glands and has strong antifungal activity against C. albicans. However, C. albicans produces secreted aspartic proteases (Saps) that can cleave and inactivate Hst-5, limiting its antifungal properties. We previously showed that residue substitutions K11R and K17R within Hst-5 improve its antifungal activity and prevent proteolytic degradation by Saps when treating planktonic C. albicans. Here, we investigated the use of the K11R-K17R peptide as an alternative therapeutic against C. albicans biofilms by assessing its ability to reduce viability of pre-formed biofilms and to inhibit the formation of biofilms and showed that K11R-K17R had improved activity compared to Hst-5. Based on these results, we incorporated K11R-K17R and Hst-5 into polyelectrolyte multilayer (PEM) surface coatings and demonstrated that films functionalized with K11R-K17R reduced the formation of C. albicans biofilms. Our results demonstrate the therapeutic potential of the K11R-K17R Hst-5 variant in preventing and treating biofilms.

Self-Assembly as a Molecular Strategy to Improve Immunotherapy

Immunotherapies harness an individual's immune system to battle diseases such as cancer and autoimmunity. During cancer, the immune system often fails to detect and destroy cancerous cells, whereas during autoimmune disease, the immune system mistakenly attacks self-tissue. Immunotherapies can help guide more effective responses in these settings, as evidenced by recent advances with monoclonal antibodies and adoptive cell therapies. However, despite the transformative gains of immunotherapies for patients, many therapies are not curative, work only for a small subset of patients, and lack specificity in distinguishing between healthy and diseased cells, which can cause severe side effects. From this perspective, self-assembled biomaterials are promising technologies that could help address some of the limitations facing immunotherapies. For example, self-assembly allows precision control over the combination and relative concentration of immune cues and directed cargo display densities. These capabilities support selectivity and potency that could decrease off-target effects and enable modular or personalized immunotherapies. The underlying forces driving self-assembly of most systems in aqueous solution result from hydrophobic interactions or charge polarity. In this Account, we highlight how these forces are being used to self-assemble immunotherapies for cancer and autoimmune disease.Hydrophobic interactions can create a range of intricate structures, including peptide nanofibers, nanogels, micelle-like particles, and in vivo assemblies with protein carriers. Certain nanofibers with hydrophobic domains uniquely benefit from the ability to elicit immune responses without additional stimulatory signals. This feature can reduce nonspecific inflammation but may also limit the nanofiber's application because of their inherent stimulatory properties. Micelle-like particles have been developed with the ability to incorporate a range of tumor-specific antigens for immunotherapies in mouse models of cancer. Key observations have revealed that both the total dose of antigen and display density of antigen per particle can impact immune response and efficacy of immunotherapies. These developments are promising benchmarks that could reveal design principles for engineering more specific and personalized immunotherapies.There has also been extensive work to develop platforms using electrostatic interactions to drive assembly of oppositely charged immune signals. These strategies benefit from the ability to tune biophysical interactions between components by altering the ratio of cationic to anionic charge during formulation, or the density of charge. Using a layer-by-layer assembly method, our lab developed hollow capsules composed entirely of immune signals for therapies in cancer and autoimmune disease models. This platform allowed for 100% of the immunotherapy to be composed of immune signals and completely prevents the onset of disease in a mouse model of multiple sclerosis. Layer-by-layer assembly has also been used to coat microneedle patches to target signals to immune cells in the dermal layer. As an alternative to layer-by-layer assembly, one step assembly can be achieved by mixing cationic and anionic components in solution. Additional approaches have created molecular structures that leverage hydrogen bonding for self-assembly. The creativity of engineered self-assembly has led to key insights that could benefit future immunotherapies and revealed aspects that require further study. The challenge now remains to utilize these insights to push development of new immunotherapeutics into clinical settings.

Self-Assembled Nanoparticles: Exciting Platforms for Vaccination

Vaccination is successfully advanced to control several fatal diseases and improve human life expectancy. However, additional innovations are required in this field because there are no effective vaccines to prevent some infectious diseases. The shift from the attenuated or inactivated pathogens to safer but less immunogenic protein or peptide antigens has led to a search for effective antigen delivery carriers that can function as both antigen vehicles and intrinsic adjuvants. Among these carriers, self-assembled nanoparticles (SANPs) have shown great potential to be the best representative. For the nanoscale and multiple presentation of antigens, with accurate control over size, geometry, and functionality, these nanoparticles are assembled spontaneously and mimic pathogens, resulting in enhanced antigen presentation and increased cellular and humoral immunity responses. In addition, they may be applied through needle-free routes due to their adhesive ability, which gives them a great future in vaccination applications. This review provides an overview of various SANPs and their applications in prophylactic vaccines.

Biomaterials as Tools to Decode Immunity

The immune system has remarkable capabilities to combat disease with exquisite selectivity. This feature has enabled vaccines that provide protection for decades and, more recently, advances in immunotherapies that can cure some cancers. Greater control over how immune signals are presented, delivered, and processed will help drive even more powerful options that are also safe. Such advances will be underpinned by new tools that probe how immune signals are integrated by immune cells and tissues. Biomaterials are valuable resources to support this goal, offering robust, tunable properties. The growing role of biomaterials as tools to dissect immune function in fundamental and translational contexts is highlighted. These technologies can serve as tools to understand the immune system across molecular, cellular, and tissue length scales. A common theme is exploiting biomaterial features to rationally direct how specific immune cells or organs encounter a signal. This precision strategy, enabled by distinct material properties, allows isolation of immunological parameters or processes in a way that is challenging with conventional approaches. The utility of these capabilities is demonstrated through examples in vaccines for infectious disease and cancer immunotherapy, as well as settings of immune regulation that include autoimmunity and transplantation.

Materials for Immunotherapy

Breakthroughs in materials engineering have accelerated the progress of immunotherapy in preclinical studies. The interplay of chemistry and materials has resulted in improved loading, targeting, and release of immunomodulatory agents. An overview of the materials that are used to enable or improve the success of immunotherapies in preclinical studies is presented, from immunosuppressive to proinflammatory strategies, with particular emphasis on technologies poised for clinical translation. The materials are organized based on their characteristic length scale, whereby the enabling feature of each technology is organized by the structure of that material. For example, the mechanisms by which i) nanoscale materials can improve targeting and infiltration of immunomodulatory payloads into tissues and cells, ii) microscale materials can facilitate cell-mediated transport and serve as artificial antigen-presenting cells, and iii) macroscale materials can form the basis of artificial microenvironments to promote cell infiltration and reprogramming are discussed. As a step toward establishing a set of design rules for future immunotherapies, materials that intrinsically activate or suppress the immune system are reviewed. Finally, a brief outlook on the trajectory of these systems and how they may be improved to address unsolved challenges in cancer, infectious diseases, and autoimmunity is presented.

Molecular complementarity and structural heterogeneity within co-assembled peptide β-sheet nanofibers

Self-assembling peptides have garnered an increasing amount of interest as a functional biomaterial for medical and biotechnological applications. Recently, β-sheet peptide designs utilizing complementary pairs of peptides composed of charged amino acids positioned to impart co-assembly behavior have expanded the portfolio of peptide aggregate structures. Structural characterization of these charge-complementary peptide co-assemblies has been limited. Thus, it is not known how the complementary peptides organize on the molecular level. Through a combination of solid-state NMR measurements and discontinuous molecular dynamics simulations, we investigate the molecular organization of King-Webb peptide nanofibers. KW+ and KW- peptides co-assemble into near stoichiometric two-component β-sheet structures as observed by computational simulations and ¹³C-¹³C dipolar couplings. A majority of β-strands are aligned with antiparallel nearest neighbors within the β-sheet as previously suggested by Fourier transform infrared spectroscopy measurements. Surprisingly, however, a significant proportion of β-strand neighbors are parallel. While charge-complementary peptides were previously assumed to organize in an ideal (AB)_n pattern, dipolar recoupling measurements on isotopically diluted nanofiber samples reveal a non-negligible amount of self-associated (AA and BB) pairs. Furthermore, computational simulations predict these different structures can coexist within the same nanofiber. Our results highlight structural disorder at the molecular level in a charge-complementary peptide system with implications on co-assembling peptide designs.

Integrating Biomaterials and Immunology to Improve Vaccines Against Infectious Diseases

Despite the success of vaccines in preventing many infectious diseases, effective vaccines against pathogens with ongoing challenges - such as HIV, malaria, and tuberculosis - remain unavailable. The emergence of new pathogen variants, the continued prevalence of existing pathogens, and the resurgence of yet other infectious agents motivate the need for new, interdisciplinary approaches to direct immune responses. Many current and candidate vaccines, for example, are poorly immunogenic, provide only transient protection, or create risks of regaining pathogenicity in certain immune-compromised conditions. Recent advances in biomaterials research are creating new potential to overcome these challenges through improved formulation, delivery, and control of immune signaling. At the same time, many of these materials systems - such as polymers, lipids, and self-assembly technologies - may achieve this goal while maintaining favorable safety profiles. This review highlights ways in which biomaterials can advance existing vaccines to safer, more efficacious technologies, and support new vaccines for pathogens that do not yet have vaccines. Biomaterials that have not yet been applied to vaccines for infectious disease are also discussed, and their potential in this area is highlighted.

Recent progress in supramolecular peptide assemblies as virus mimics for cancer immunotherapy

Supramolecular peptide assemblies can mimic natural viruses and serve as well-defined, dynamic and multifunctional nanoplatforms for cancer immunotherapy, where the peptide segments act as antigens, adjuvants and carriers.

Biomaterials for topical and transdermal drug delivery in reconstructive transplantation

Lifelong systemic immunosuppression remains the biggest challenge in vascularized composite allotransplantation (VCA) due to the adverse effects it causes. Since VCA is a life-enhancing procedure as compared with solid organ transplant which is life-saving; one needs to weigh the benefits and risks carefully. Thus, there is a huge unmet clinical need to design biomaterial-based vehicles that can deliver drugs more efficiently, topically and locally to eliminate adverse effects of systemic immune suppression. This review discusses several biomaterial-based systems that have been carefully designed, conceived and attempted to make VCA a more patient compliant approach. Variety of promising preclinical studies has shown the feasibility of the approaches, and clinical trials are required to bridge the gap. Several challenges for the future and new approaches have been discussed.

Designing inorganic nanomaterials for vaccines and immunotherapies

Vaccines and immunotherapies have changed the face of health care. Biomaterials offer the ability to improve upon these medical technologies through increased control of the types and concentrations of immune signals delivered. Further, these carriers enable targeting, stability, and delivery of poorly soluble cargos. Inorganic nanomaterials possess unique optical, electric, and magnetic properties, as well as defined chemistry, high surface-to-volume- ratio, and high avidity display that make this class of materials particularly advantageous for vaccine design, cancer immunotherapy, and autoimmune treatments. In this review we focus on this understudied area by highlighting recent work with inorganic materials - including gold nanoparticles, carbon nanotubes, and quantum dots. We discuss the intrinsic features of these materials that impact the interactions with immune cells and tissue, as well as recent reports using inorganic materials across a range of emerging immunological applications.

Harnessing the layer-by-layer assembly technique to design biomaterials vaccines for immune modulation in translational applications

The existence of challenging diseases such as cancers, HIV and Zika requires developing new vaccines that can generate tunable and robust immune responses against the diseases. Biomaterials-based techniques have been broadly explored for designing vaccines that can produce controllable and potent immunity. Among the existing biomaterials-based strategies, the layer-by-layer (LbL) assembly technique is remarkably attractive in vaccine design due to its unique features such as programmed and versatile cargo loading, cargo protection, co-delivery, juxtaposing of immune signals, etc. In this work, we reviewed the existing LbL-based vaccine design techniques for translational applications. Specifically, we discussed nanovaccines constructed by coating polyelectrolyte multilayers (PEMs) on nanoparticles, microcapsule vaccines assembled from PEMs, polyplex/complex vaccines condensed from charged materials and microneedle vaccines deposited with PEMs, highlighting the employment of these techniques to promote immunity against diseases ranging from cancers to infectious and autoimmune diseases (i.e., HIV, influenza, multiple sclerosis, etc.). Additionally, the review specifically emphasized using LbL-based vaccine technologies for tuning the cellular and molecular pathways, demonstrating the unique advantages presented by these vaccination strategies. These studies showed the versatility and potency of using LbL-based techniques for designing the next generation of biomaterials vaccines for translational purposes.

Induction of anti-cancer T cell immunity by in situ vaccination using systemically administered nanomedicines

Patients with inadequate anti-cancer T cell responses experience limited benefit from immune checkpoint inhibitors and other immunotherapies that require T cells. Therefore, treatments that induce de novo anti-cancer T cell immunity are needed. One strategy - referred to as in situ vaccination - is to deliver chemotherapeutic or immunostimulatory drugs into tumors to promote cancer cell death and provide a stimulatory environment for priming T cells against antigens already present in the tumor. However, achieving sufficient drug concentrations in tumors without causing dose-limiting toxicities remains a major challenge. To address this challenge, nanomedicines based on nano-sized carriers ('nanocarriers') of chemotherapeutics and immunostimulants are being developed to improve drug accumulation in tumors following systemic (intravenous) administration. Herein, we present the rationale for using systemically administrable nanomedicines to induce anti-cancer T cell immunity via in situ vaccination and provide an overview of synthetic nanomedicines currently used clinically. We also describe general strategies for improving nanomedicine design to increase tumor uptake, including use of micelle- and star polymer-based nanocarriers. We conclude with perspectives for how nanomedicine properties, host factors and treatment combinations can be leveraged to maximize efficacy.

Tailored Polymers with Complement Activation Ability To Improve Antitumor Immunity

The complement system plays an important role in host innate immunity, and its activation can be exploited as a potential strategy for vaccine adjuvants. Herein, a pH-responsive micellar vaccine platform (COOH-NPs) was developed using a carboxyl-modified diblock copolymer of poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (COOH-PEOz-PLA). The copolymer self-assembled into micelles with hydroxyl groups shielding on the surface, which activated the complement system for the enhanced immune responses. Compared with the control nanoparticles (OCH₃-NPs), COOH-NPs significantly enhanced lymph node-resident dendritic cell maturation, antigen-specific IgG production, antigen-specific CD4⁺ and CD8⁺ T-cell activation, and the amount of memory T-cell generation in vivo. Furthermore, immunization with COOH-NPs/OVA in E.G7-OVA tumor-bearing mice not only remarkably inhibited tumor growth but also prolonged the survival of tumor-bearing mice. These results indicated that COOH-NPs with the capability of complement activation efficiently boosted the immune responses for the antitumor effect. The study demonstrated the significance of taking advantage of a complement-activating vaccine platform for cancer immunotherapy.

Engineering Biomaterials to Direct Innate Immunity

Small alterations during early stages of innate immune response can drive large changes in how adaptive immune cells develop and function during protective immunity or disease. Controlling these events creates exciting potential in development of immune engineered vaccines and therapeutics. This progress report discusses recent biomaterial technologies exploiting innate immunity to dissect immune function and to design new vaccines and immunotherapies for infectious diseases, cancer, and autoimmunity. Across these examples, an important idea is the possibility to co-opt innate immune mechanisms to enhance immunity during infection and cancer. During inflammatory or autoimmune disease, some of these same innate immune mechanisms can be manipulated in different ways to control excess inflammation by promotion of immunological tolerance.

Single-Step Self-Assembly and Physical Crosslinking of PEGylated Chitosan Nanoparticles by Tannic Acid

Chitosan-based nanoparticles are promising materials for potential biomedical applications. We used Flash NanoPrecipitation as a rapid, scalable, single-step method to achieve self-assembly of crosslinked chitosan nanoparticles. Self-assembly was driven by electrostatic interactions, hydrogen bonding, and hydrophobic interactions; tannic acid served to precipitate chitosan to seed nanoparticle formation and crosslink the chitosan to stabilize the resulting particles. The size of the nanoparticles can be tuned by varying formulation parameters including the total solids concentration and block copolymer to core mass ratio. We demonstrated that hydrophobic moieties can be incorporated into the nanoparticle using a lipophilic fluorescent dye as a model system.

Directing toll-like receptor signaling in macrophages to enhance tumor immunotherapy

A key challenge facing immunotherapy is poor infiltration of T cells into tumors, along with suppression of cells reaching these sites. However, macrophages make up a majority of immune cell infiltrates into tumors, creating natural targets for immunotherapies able to direct macrophages away from tumor-supportive functions and toward anti-tumor phenotypes. Recent studies demonstrate that toll-like receptors (TLRs) - pathways that quickly trigger early immune responses - play an important role in polarizing macrophages. Here, we present emerging ways in which TLR signaling is being manipulated in macrophages to create new opportunities for cancer immunotherapy. In particular, we discuss approaches to deliver TLR agonists, to leverage biomaterials in these therapies, and to couple TLR-based approaches with other frontline treatments as combination cancer therapies.

Engineering release kinetics with polyelectrolyte multilayers to modulate TLR signaling and promote immune tolerance

Autoimmune disorders, such as multiple sclerosis and type 1 diabetes, occur when immune cells fail to recognize "self" molecules. Recently, studies have revealed aberrant inflammatory signaling through pathogen sensing pathways, such as toll-like receptors (TLRs), during autoimmune disease. Therapeutic inhibition of these pathways might attenuate disease development, skewing disease-causing inflammatory cells towards cell types that promote tolerance. Delivering antagonistic ligands to a TLR upstream of an inflammatory signaling cascade, TLR9, has demonstrated exciting potential in a mouse model of MS; however, strategies that enable sustained delivery could reduce the need for repeated administration or enhance therapeutic efficacy. We hypothesized that GpG - an oligonucleotide TLR9 antagonist - which is inherently anionic, could be self-assembled into polyelectrolyte multilayers (PEMs) with a cationic, degradable poly(β-amino ester) (Poly1). We hypothesized that degradable Poly1/GpG PEMs could promote sustained release of GpG and modulate inflammatory immune cell functions. Here we demonstrate layer-by-layer assembly of degradable PEMs, as well as subsequent degradation and release of GpG. Following assembly and release, GpG maintains the ability to reduce dendritic cell activation and inflammatory cytokine secretion, restrain TLR9 signaling, and polarize myelin specific T cells towards regulatory phenotypes and functions in primarily immune cells. These results indicate that degradable PEMs may be able to promote tolerogenic immune function in the context of autoimmunity.

Advanced manufacturing of microdisk vaccines for uniform control of material properties and immune cell function

The continued challenges facing vaccines in infectious disease and cancer highlight a need for better control over the features of vaccines and the responses they generate. Biomaterials offer unique advantages to achieve this goal through features such as controlled release and co-delivery of antigens and adjuvants. However, many synthesis strategies lead to particles with heterogeneity in diameter, shape, loading level, or other properties. In contrast, advanced manufacturing techniques allow precision control of material properties at the micro- and nano-scale. These capabilities in vaccines and immunotherapies could allow more rational design to speed efficient design and clinical translation. Here we employed soft lithography to generate polymer microdisk vaccines with uniform structures and tunable compositions of vaccine antigens and toll like receptor agonists (TLRas) that serve as molecular adjuvants. Compared to conventional PLGA particles formed by emulsion, microdisks provided a dramatic improvement in the consistency of properties such as diameter. During culture with primary dendritic cells (DCs) from mice, microdisks were internalized by the cells without toxicity, while promoting co-delivery of antigen and TLRa to the same cell. Analysis of DC surface activation markers by flow cytometry revealed microdisk vaccines activated dendritic cells in a manner that depended on the level of TLRa, while antigen processing and presentation depended on the amount of antigen in the microdisks. Together, this work demonstrates the use of advanced manufacturing techniques to produce uniform vaccines that direct DC function depending on the composition in the disks.

Designing natural and synthetic immune tissues

Vaccines and immunotherapies have provided enormous improvements for public health, but there are fundamental disconnects between where most studies are performed-in cell culture and animal models-and the ultimate application in humans. Engineering immune tissues and organs, such as bone marrow, thymus, lymph nodes and spleen, could be instrumental in overcoming these hurdles. Fundamentally, designed immune tissues could serve as in vitro tools to more accurately study human immune function and disease, while immune tissues engineered for implantation as next-generation vaccines or immunotherapies could enable direct, on-demand control over generation and regulation of immune function. In this Review, we discuss recent interdisciplinary strategies that are merging materials science and immunology to create engineered immune tissues in vitro and in vivo. We also highlight the hurdles facing these approaches and the need for comparison to existing clinical options, relevant animal models, and other emerging technologies.

Progress Toward the Clinical Translation of Bioinspired Peptide and Protein Assemblies

Supramolecular materials composed of proteins and peptides have been receiving considerable attention toward a range of diseases and conditions from vaccines to drug delivery. Owing to the relative newness of this class of materials, the bulk of work to date has been preclinical. However, examples of approved treatments particularly in vaccines, dentistry, and hemostasis demonstrate the translational potential of supramolecular polypeptides. Critical milestones in the clinical development of this class of materials and currently approved supramolecular polypeptide therapies are described in this study. Additional examples of not-yet-approved materials that are steadily advancing toward clinical use are also featured. Spherical assemblies such as virus-like particles, designed protein nanoparticles, and spherical peptide amphiphiles are highlighted, followed by fiber-forming systems such as fibrillizing peptides, fiber-forming peptide-amphiphiles, and filamentous bacteriophages.

A poly(beta-amino ester) activates macrophages independent of NF-κB signaling

Nucleic acid delivery vehicles are poised to play an important role in delivering gene therapy for vaccines and immunotherapies, and in delivering nucleic acid based adjuvants. A number of common polymeric delivery vehicles used in nucleic acid delivery have recently been shown to interact with immune cells and directly stimulate immunogenic responses, particularly in particle form. Poly(beta-amino esters) were designed for nucleic acid delivery and have demonstrated promising performance in a number of vaccine and therapeutic studies. Yet, little work has characterized the mechanisms by which these polymers activate immune cells. Here we demonstrate that a poly(beta-amino ester) activates antigen presenting cells in soluble and particulate forms, and that these effects are independent of TLR signaling pathways. Moreover, we show the polymers induce activation independent of NF-κB signaling, but do activate IRF, an important innate inflammatory pathway. New knowledge linking physicochemical features of poly(beta-amino esters) or other polymeric carriers to inflammatory mechanisms could support more rational design approaches for vaccines and immunotherapies harnessing these materials.

SIGNIFICANCE STATEMENT

The last several years have brought exciting work exploring biomaterials as delivery vehicles for immunotherapies, vaccines, and gene therapies. However, a gap remains between the striking finding that many biomaterials exhibit intrinsic immunogenic features, and the specific structural properties that drive these responses. The results in the current study indicate PBAEs cause macrophage activation by pathways that are distinct from pathways activated by common vaccine and immunotherapies components, such as toll-like receptor agonists. Thus, the work reveals new mechanistic details that can be exploited in investigating other materials, and to support more rational design of future biomaterial vaccines and immunotherapy carriers.

Nanoparticles for the Induction of Antigen-Specific Immunological Tolerance

Antigen-specific immune tolerance has been a long-standing goal for immunotherapy for the treatment of autoimmune diseases and allergies and for the prevention of allograft rejection and anti-drug antibodies directed against biologic therapies. Nanoparticles have emerged as powerful tools to initiate and modulate immune responses due to their inherent capacity to target antigen-presenting cells (APCs) and deliver coordinated signals that can elicit an antigen-specific immune response. A wide range of strategies have been described to create tolerogenic nanoparticles (tNPs) that fall into three broad categories. One strategy includes tNPs that provide antigen alone to harness natural tolerogenic processes and environments, such as presentation of antigen in the absence of costimulatory signals, oral tolerance, the tolerogenic environment of the liver, and apoptotic cell death. A second strategy includes tNPs that carry antigen and simultaneously target tolerogenic receptors, such as pro-tolerogenic cytokine receptors, aryl hydrocarbon receptor, FAS receptor, and the CD22 inhibitory receptor. A third strategy includes tNPs that carry a payload of tolerogenic pharmacological agents that can “lock” APCs into a developmental or metabolic state that favors tolerogenic presentation of antigens. These diverse strategies have led to the development of tNPs that are capable of inducing antigen-specific immunological tolerance, not just immunosuppression, in animal models. These novel tNP technologies herald a promising approach to specifically prevent and treat unwanted immune reactions in humans. The first tNP, SEL-212, a biodegradable synthetic vaccine particle encapsulating rapamycin, has reached the clinic and is currently in Phase 2 clinical trials.

Self-assembled nanomaterials for synergistic antitumour therapy

Recent progress on self-assembled nanodrugs for anticancer treatment was discussed.

Designing biomaterials with immunomodulatory properties for tissue engineering and regenerative medicine

Recent research in the vaccine and immunotherapy fields has revealed that biomaterials have the ability to activate immune pathways, even in the absence of other immune-stimulating signals. Intriguingly, new studies reveal these responses are influenced by the physicochemical properties of the material. Nearly all of this work has been done in the vaccine and immunotherapy fields, but there is tremendous opportunity to apply this same knowledge to tissue engineering and regenerative medicine. This review discusses recent findings that reveal how material properties-size, shape, chemical functionality-impact immune response, and links these changes to emerging opportunities in tissue engineering and regenerative medicine. We begin by discussing what has been learned from studies conducted in the contexts of vaccines and immunotherapies. Next, research is highlighted that elucidates the properties of materials that polarize innate immune cells, including macrophages and dendritic cells, toward either inflammatory or wound healing phenotypes. We also discuss recent studies demonstrating that scaffolds used in tissue engineering applications can influence cells of the adaptive immune system-B and T cell lymphocytes-to promote regenerative tissue microenvironments. Through greater study of the intrinsic immunogenic features of implantable materials and scaffolds, new translational opportunities will arise to better control tissue engineering and regenerative medicine applications.

Controlled Release of Second Generation mTOR Inhibitors to Restrain Inflammation in Primary Immune Cells

Autoimmune disease occurs when the immune system incorrectly targets the body's own tissue. Inflammatory CD4⁺ T cell phenotypes, such as T_H1 and T_H17, are key drivers of this attack. Recent studies demonstrate treatment with rapamycin-a key inhibitor of the mTOR pathway-can skew T cell development, moving T cell responses away from inflammatory phenotypes and toward regulatory T cells (T_REGS). T_REGS are important in inducing and maintaining tolerance to self-antigens, creating new potential to treat autoimmune diseases more effectively and specifically. Next generation analogs of rapamycin, such as everolimus and temsirolimus, confer increased potency with reduced toxicity, but are understudied in the context of autoimmunity. Further, these drugs are still broadly-acting and require frequent treatment due to short half-lives. Thus, there is strong interest in harnessing the unique properties of biomaterials-controlled drug release and targeting, for example, to improve autoimmune therapies. Using second generation mTOR inhibitors and rapamycin, we prepared sets of degradable polymer particles from poly(lactide-co-glycolide). We then used these materials to assess physicochemical properties and the ability to control autoimmune inflammation in a primary cell co-culture model. Treatment with particle formulations resulted in significant dose-dependent decreases in dendritic cell activation, T cell proliferation, inflammatory cytokines, and frequencies of inflammatory T_H1 phenotypes. Considering the current limitations of rapamycin, and the potential of next-generation analogs, this work provides a screening platform for biomaterials and sets the stage for in vivo evaluation, where delivery kinetics, stability, and targeting could improve autoimmune therapies through biomaterial-enabled delivery.