Biomaterial strategies for generating therapeutic immune responses

Unraveling and Harnessing the Immune Response at the Cell-Biomaterial Interface for Tissue Engineering Purposes

Biomaterials are defined as "engineered materials" and include a range of natural and synthetic products, designed for their introduction into and interaction with living tissues. Biomaterials are considered prominent tools in regenerative medicine that support the restoration of tissue defects and retain physiologic functionality. Although commonly used in the medical field, these constructs are inherently foreign toward the host and induce an immune response at the material-tissue interface, defined as the foreign body response (FBR). A strong connection between the foreign body response and tissue regeneration is suggested, in which an appropriate amount of immune response and macrophage polarization is necessary to trigger autologous tissue formation. Recent developments in this field have led to the characterization of immunomodulatory traits that optimizes bioactivity, the integration of biomaterials and determines the fate of tissue regeneration. This review addresses a variety of aspects that are involved in steering the inflammatory response, including immune cell interactions, physical characteristics, biochemical cues, and metabolomics. Harnessing the advancing knowledge of the FBR allows for the optimization of biomaterial-based implants, aiming to prevent damage of the implant, improve natural regeneration, and provide the tools for an efficient and successful in vivo implantation.

Investigating Immunomodulatory Biomaterials for Preventing the Foreign Body Response

Implantable biomaterials represent the forefront of regenerative medicine, providing platforms and vessels for delivering a creative range of therapeutic benefits in diverse disease contexts. However, the chronic damage resulting from implant rejection tends to outweigh the intended healing benefits, presenting a considerable challenge when implementing treatment-based biomaterials. In response to implant rejection, proinflammatory macrophages and activated fibroblasts contribute to a synergistically destructive process of uncontrolled inflammation and excessive fibrosis. Understanding the complex biomaterial-host cell interactions that occur within the tissue microenvironment is crucial for the development of therapeutic biomaterials that promote tissue integration and minimize the foreign body response. Recent modifications of specific material properties enhance the immunomodulatory capabilities of the biomaterial and actively aid in taming the immune response by tuning interactions with the surrounding microenvironment either directly or indirectly. By incorporating modifications that amplify anti-inflammatory and pro-regenerative mechanisms, biomaterials can be optimized to maximize their healing benefits in harmony with the host immune system.

Nano-immunotherapy: overcoming delivery challenge of immune checkpoint therapy

Immune checkpoint (ICP) molecules expressed on tumor cells can suppress immune responses against tumors. ICP therapy promotes anti-tumor immune responses by targeting inhibitory and stimulatory pathways of immune cells like T cells and dendritic cells (DC). The investigation into the combination therapies through novel immune checkpoint inhibitors (ICIs) has been limited due to immune-related adverse events (irAEs), low response rate, and lack of optimal strategy for combinatorial cancer immunotherapy (IMT). Nanoparticles (NPs) have emerged as powerful tools to promote multidisciplinary cooperation. The feasibility and efficacy of targeted delivery of ICIs using NPs overcome the primary barrier, improve therapeutic efficacy, and provide a rationale for more clinical investigations. Likewise, NPs can conjugate or encapsulate ICIs, including antibodies, RNAs, and small molecule inhibitors. Therefore, combining the drug delivery system (DDS) with ICP therapy could provide a profitable immunotherapeutic strategy for cancer treatment. This article reviews the significant NPs with controlled DDS using current data from clinical and pre-clinical trials on mono- and combination IMT to overcome ICP therapeutic limitations.

Latest advances on MXenes in biomedical research and health care

The unique combination of physical and chemical properties of MXenes has propelled a growing number of applications in biomedicine and healthcare. The expanding library of MXenes with tunable properties is paving the way for high-performance, application-specific MXene-based sensing and therapeutic platforms. In this article, we highlight the emerging biomedical applications of MXenes with specific emphasis on bioelectronics, biosensors, tissue engineering, and therapeutics. We present examples of MXenes and their composites enabling novel technological platforms and therapeutic strategies, and elucidate potential avenues for further developments. Finally, we discuss the materials, manufacturing, and regulatory challenges that need to be synergistically addressed for the clinical translation of MXene-based biomedical technologies.

Graphical abstract

Development of functional nanomedicines for tumor associated macrophages-focused cancer immunotherapy

Clinical cancer immunotherapies are usually impeded by tumor immunosuppression driven by tumor associated macrophages (TAMs). Thus, TAMs can be considered as a promising therapeutic target for improved immunotherapy, and TAMs-focused molecular targeting agents have made ideal progress in clinical practice. Even so, most TAMs-targeting agents still cannot cover up their own shortcomings as free drugs. The emergence of multifunctional nanomaterials can expectedly endow these therapeutic cargoes with high solubility, favorable pharmacokinetic distribution, cell-specific delivery, and controlled release. Here, the underlying mechanisms of tumor immunosuppression caused by TAMs are first emphatically elucidated, and then the basic design of TAMs-focused immune-nanomedicines are discussed, mainly including diverse categories of nanomaterials, targeted and stimulus-responsive modifications, and TAM imaging in nanomedicines. A summary of current TAMs-targeting immunotherapeutic mechanisms based on functional nanomedicines for TAMs elimination and/or repolarization is further presented. Lastly, some severe challenges related to functional nanomedicines for TAMs-focused cancer immunotherapy are proposed, and some feasible perspectives on clinical translation of TAMs-associated anticancer immunonanomedicines are provided. It is hoped that, with rapid development of nanomedicine in cancer immunotherapy, TAMs-focused therapeutic strategies may be anticipated to become an emerging immunotherapeutic modality for future clinical cancer treatment.

Three-dimensional (3D) scaffolds as powerful weapons for tumor immunotherapy

Though increasing understanding and remarkable clinical successes have been made, enormous challenges remain to be solved in the field of cancer immunotherapy. In this context, biomaterial-based immunomodulatory strategies are being developed to boost antitumor immunity. For the local immunotherapy, macroscale biomaterial scaffolds with 3D network structures show great superiority in the following aspects: facilitating the encapsulation, localized delivery, and controlled release of immunotherapeutic agents and even immunocytes for more efficient immunomodulation. The concentrating immunomodulation in situ could minimize systemic toxicities, but still exert abscopal effects to harness the power of overall anticancer immune response for eradicating malignancy. To promote such promising immunotherapies, the design requirements of macroscale 3D scaffolds should comprehensively consider their physicochemical and biological properties, such as porosity, stiffness, surface modification, cargo release kinetics, biocompatibility, biodegradability, and delivery modes. To date, increasing studies have focused on the relationships between these parameters and the biosystems which will guide/assist the 3D biomaterial scaffolds to achieve the desired immunotherapeutic outcomes. In this review, by highlighting some recent achievements, we summarized the latest advances in the development of various 3D scaffolds as niches for cancer immunotherapy. We also discussed opportunities, challenges, current trends, and future perspectives in 3D macroscale biomaterial scaffold-assisted local treatment strategies. More importantly, this review put more efforts to illustrate how the 3D biomaterial systems affect to modulate antitumor immune activities, where we discussed how significant the roles and behaviours of 3D macroscale scaffolds towards in situ cancer immunotherapy in order to direct the design of 3D immunotherapeutic.

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Macroscale biomaterial scaffolds with 3D network structures show great superiority for enhanced tumor immunotherapy.

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More focuses have been put on the relationships between the properties of 3D scaffolds and the biosystem when immunotherapy.

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The most recent remarkable 3D cancer immunotherapeutic platforms are summarized for future clinical transformation.

Clickable Biomaterials for Modulating Neuroinflammation

Crosstalk between the nervous and immune systems in the context of trauma or disease can lead to a state of neuroinflammation or excessive recruitment and activation of peripheral and central immune cells. Neuroinflammation is an underlying and contributing factor to myriad neuropathologies including neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease; autoimmune diseases like multiple sclerosis; peripheral and central nervous system infections; and ischemic and traumatic neural injuries. Therapeutic modulation of immune cell function is an emerging strategy to quell neuroinflammation and promote tissue homeostasis and/or repair. One such branch of ‘immunomodulation’ leverages the versatility of biomaterials to regulate immune cell phenotypes through direct cell-material interactions or targeted release of therapeutic payloads. In this regard, a growing trend in biomaterial science is the functionalization of materials using chemistries that do not interfere with biological processes, so-called ‘click’ or bioorthogonal reactions. Bioorthogonal chemistries such as Michael-type additions, thiol-ene reactions, and Diels-Alder reactions are highly specific and can be used in the presence of live cells for material crosslinking, decoration, protein or cell targeting, and spatiotemporal modification. Hence, click-based biomaterials can be highly bioactive and instruct a variety of cellular functions, even within the context of neuroinflammation. This manuscript will review recent advances in the application of click-based biomaterials for treating neuroinflammation and promoting neural tissue repair.

Engineering immunomodulatory nanoplatforms from commensal bacteria-derived polysaccharide A

Capsular zwitterionic polysaccharides (CZPs), typically found on the surfaces of commensal gut bacteria, are important immunomodulatory molecules due to their ability to produce a T-cell dependent immune response upon processing...

Interaction of monodispersed strontium containing bioactive glass nanoparticles with macrophages

The cellular response of murine primary macrophages to monodisperse strontium containing bioactive glass nanoparticles (SrBGNPs), with diameters of 90 ± 10 nm and a composition (mol%) of 88.8 SiO₂-1.8CaO-9.4SrO (9.4% Sr-BGNPs) was investigated for the first time. Macrophage response is critical as applications of bioactive nanoparticles will involve the nanoparticles circulating in the blood stream and macrophages will be the first cells to encounter the particles, as part of inflammatory response mechanisms. Macrophage viability and total DNA measurements were not decreased by particle concentrations of up to 250 μg/mL. The Sr-BGNPs were actively internalised by the macrophages via formation of endosome/lysosome-like vesicles bordered by a membrane inside the cells. The Sr-BGNPs degraded inside the cells, with the Ca and Sr maintained inside the silica network. When RAW264.7 cells were incubated with Sr-BGNPs, the cells were polarised towards the pro-regenerative M2 population rather than the pro-inflammatory M1 population. Sr-BGNPs are potential biocompatible vehicles for therapeutic cation delivery for applications in bone regeneration.

Biomaterial and Therapeutic Approaches for the Manipulation of Macrophage Phenotype in Peripheral and Central Nerve Repair

Injury to the peripheral or central nervous systems often results in extensive loss of motor and sensory function that can greatly diminish quality of life. In both cases, macrophage infiltration into the injury site plays an integral role in the host tissue inflammatory response. In particular, the temporally related transition of macrophage phenotype between the M1/M2 inflammatory/repair states is critical for successful tissue repair. In recent years, biomaterial implants have emerged as a novel approach to bridge lesion sites and provide a growth-inductive environment for regenerating axons. This has more recently seen these two areas of research increasingly intersecting in the creation of 'immune-modulatory' biomaterials. These synthetic or naturally derived materials are fabricated to drive macrophages towards a pro-repair phenotype. This review considers the macrophage-mediated inflammatory events that occur following nervous tissue injury and outlines the latest developments in biomaterial-based strategies to influence macrophage phenotype and enhance repair.

Cancer treatment evolution from traditional methods to stem cells and gene therapy

BACKGROUND

Cancer, a malignant tumor, is caused by the failure of the mechanism that controls cell growth and proliferation. Late clinical symptoms often manifest as lumps, pain, ulcers, and bleeding. Systemic symptoms include weight loss, fatigue, and loss of appetite. It is a major disease that threatens human life and health. How to treat cancer is a long-standing problem that needs to be overcome in the history of medicine.

METHOD

Traditional tumor treatment methods are poorly targeted, and the side effects of treatment seriously damage the physical and mental health of patients. In recent years, with the advancement of medical science and technology, the research on gene combined with mesenchymal stem cells to treat tumors has been intensified. Mesenchymal stem cells carry genes to target cancer cells, which can achieve better therapeutic effects.

DISCUSSION

In the text, we systematically review the cancer treatment evolution from traditional methods to novel approaches that include immunotherapy, nanotherapy, stem cell theapy, and gene therapy. We provide the latest review of the application status, clinical trials and development prospects of mesenchymal stem cells and gene therapy for cancer, as well as their integration in cancer treatment. Mesenchymal stem cells are effective carriers carrying genes and provide new clinical ideas for tumor treatment.

CONCLUSION

This review focuses on the current status, application prospects and challenges of mesenchymal stem cell combined gene therapy for cancer, and provides new ideas for clinical research.

Endometrial SUSD2+ Mesenchymal Stem/Stromal Cells in Tissue Engineering: Advances in Novel Cellular Constructs for Pelvic Organ Prolapse

Cellular therapy is an emerging field in clinical and personalised medicine. Many adult mesenchymal stem/progenitor cells (MSC) or pluripotent derivatives are being assessed simultaneously in preclinical trials for their potential treatment applications in chronic and degenerative human diseases. Endometrial mesenchymal stem/progenitor cells (eMSC) have been identified as clonogenic cells that exist in unique perivascular niches within the uterine endometrium. Compared with MSC isolated from other tissue sources, such as bone marrow and adipose tissue, eMSC can be extracted through less invasive methods of tissue sampling, and they exhibit improvements in potency, proliferative capacity, and control of culture-induced differentiation. In this review, we summarize the potential cell therapy and tissue engineering applications of eMSC in pelvic organ prolapse (POP), emphasising their ability to exert angiogenic and strong immunomodulatory responses that improve tissue integration of novel surgical constructs for POP and promote vaginal tissue healing.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

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.

Injectable Hydrogels as Three-Dimensional Network Reservoirs for Osteoporosis Treatment

Despite tremendous progresses made in the field of tissue engineering over the past several decades, it remains a significant challenge for the treatment of osteoporosis (OP) due to the lack of appropriate carriers to improve the bioavailability of therapeutic agents and the unavailability of artificial bone matrix with desired properties for the replacement of damaged bone regions. Encouragingly, the development of injectable hydrogels for the treatment of OP has attracted increasing attention in recent years because they can serve either as a reservoir for various therapeutic species or as a perfect filler for bone injuries with irregular shapes. However, the relationship between the complicated pathological mechanism of OP and the properties of diverse polymeric materials lacks elucidation, which clearly hampers the clinical application of injectable hydrogels for the efficient treatment of OP. To clarify this relationship, this article summarized both localized and systematic treatment of OP using an injectable hydrogel-based strategy. Specifically, the pathogenesis of OP and the limitations of current treatment approaches were first analyzed. We further focused on the use of hydrogels loaded with various therapeutic substances following a classification standard of the encapsulated cargoes for OP treatment with an emphasis on the application and precautions of each category. A concluding remark on existing challenges and future directions of this rapidly developing research area was finally made. Impact statement Effective osteoporosis (OP) treatment remains a significant challenge due substantially to the unavailability of appropriate drug carriers and artificial matrices with desired properties to promote bone repair and replace damaged regions. For this purpose, this review focused on the development of diverse injectable hydrogel systems for the delivery of various therapeutic agents, including drugs, stem cells, and nucleic acids, for effective increase in bone mass and favorable osteogenesis. The summarized important guidelines are believed to promote clinical development and translation of hydrogels for the efficient treatment of OP and OP-related bone damages toward improved life quality of millions of patients.

Functional Gadofullerene Nanoparticles Trigger Robust Cancer Immunotherapy Based on Rebuilding an Immunosuppressive Tumor Microenvironment

Cancer immunotherapy as a novel cancer therapeutic strategy has shown enormous promise. However, the immunosuppressive tumor microenvironment (ITM) is a primary obstacle. Tumor-associated macrophages (TAMs) as a major component of immune cells in a tumor microenvironment are generally polarized to the M2 phenotype that not only accelerates tumor growth but also influences the infiltration of lymphocytes and leads to immunosuppression. Thus, rebuilding ITM by re-educating TAMs and increasing infiltration of lymphocytes is a promising strategy. Herein, gadofullerene (GF-Ala) nanoparticles are demonstrated to reprogram TAMs to M1-like and increase the infiltration of cytotoxic T lymphocytes (CTLs), achieving effective inhibition of tumor growth. Notably, the modulation of ITM by GF-Ala promotes the anticancer efficacy of anti-PD-L1 immune checkpoint inhibitor, achieving superior synergistic treatment. Additionally, GF-Ala nanoparticles can be mostly excreted from the body and cause no obvious toxicity. Together, this study provides an effective immunomodulation strategy using gadofullerene nanoparticles by rebuilding ITM and synergizing immune checkpoint blockade therapy.

Emerging Nano/Micro-Structured Degradable Polymeric Meshes for Pelvic Floor Reconstruction

Pelvic organ prolapse (POP) is a hidden women's health disorder that impacts 1 in 4 women across all age groups. Surgical intervention has been the only treatment option, often involving non-degradable meshes, with variable results. However, recent reports have highlighted the adverse effects of meshes in the long term, which involve unacceptable rates of erosion, chronic infection and severe pain related to mesh shrinkage. Therefore, there is an urgent unmet need to fabricate of new class of biocompatible meshes for the treatment of POP. This review focuses on the causes for the downfall of commercial meshes, and discusses the use of emerging technologies such as electrospinning and 3D printing to design new meshes. Furthermore, we discuss the impact and advantage of nano-/microstructured alternative meshes over commercial meshes with respect to their tissue integration performance. Considering the key challenges of current meshes, we discuss the potential of cell-based tissue engineering strategies to augment the new class of meshes to improve biocompatibility and immunomodulation. Finally, this review highlights the future direction in designing the new class of mesh to overcome the hurdles of foreign body rejection faced by the traditional meshes, in order to have safe and effective treatment for women in the long term.

Engineered biomaterials for cancer immunotherapy

Although cancer immunotherapy is showing tremendous promise and has progressed to the clinic, it has only achieved sporadic efficacy, with only a fraction of patients benefitting from the therapy and with undesirable side effects due to poor selectivity and high doses. Localized delivery of immunomodulators to activate anticancer immunity in situ avoids overactivation of the systemic immune system and reduces side effects. Engineered biomaterials-implantable, injectable, or transdermal-fabricated into drug delivery devices are critical components for the development of localized cancer immunotherapies. In this review, we briefly summarize progress in the application of engineered biomaterials to the localized delivery of cancer immunotherapy.

Enabling sublingual peptide immunization with molecular self-assemblies

Short peptides are poorly immunogenic when delivered sublingually - under the tongue. Nanomaterial delivery of peptides could be utilized to improve immunogenicity towards designed sublingual vaccines, but nanomaterials have not been widely successful in sublingual vaccines owing to the challenges of transport through the sublingual mucosa. Here, we report that the sublingual immunogenicity of peptides is negligible, even in the presence of sublingual adjuvants or when PEGylated, but can be dramatically enhanced by assembly into supramolecular polymer-peptide nanofibers bearing low-molecular weight PEG, optimally between 2000 and 3000 Da. Neither PEGylation nor a sublingual adjuvant were capable of rendering peptides immunogenic without assembly into nanofibers. We found that PEG decreased nanofiber interactions with mucin and promoted longer residence time at the sublingual immunization site. Parallel investigations with shortened nanofibers indicated that the size of the assemblies had a surprisingly negligible influence over sublingual immunogenicity. In mice, optimized formulations were capable of raising strong and highly durable systemic antibody responses, antibodies in the upper respiratory and reproductive tracts, and systemic antigen-specific T-cell responses. These nanofiber-based sublingual vaccines were effective with both protein and nucleotide adjuvants and raised responses against both a model peptide epitope and a peptide epitope from M. tuberculosis. Further, PASylation (modification of nanofibers with peptide sequences rich in Pro, Ala, and Ser) could be substituted for PEGylation to also achieve sublingual immunogenicity. These findings indicated that surface properties supersede nanomaterial size in modulating sublingual nanomaterial immunogenicity, having important implications for the design of synthetic sublingual vaccines.

Dendritic Cells as Targets for Biomaterial-Based Immunomodulation

Various subtypes of immunocytes react against implanted biomaterials to eliminate the foreign body object from the host's body. Among these cells, dendritic cells (DCs) play a key role in early immune response, later engaging lymphocytes through antigens presentation. Due to their capability to induce tolerogenic or immunogenic responses, DCs have been considered as key therapeutic targets for immunomodulatory products. For instance, tolerogenic DCs are applied in the treatment of autoimmune diseases, rejection of allograft transplantation, and implanted biomaterial. Due to the emerging importance of DCs in immunomodulatory biomaterials, this Review summarizes DCs' responses-such as adhesion, migration, and maturation-to biomaterials. We also review some examples of key molecules and their applications in DCs' immunoengineering. These evaluations would pave the way for designing advanced biomaterials and nanomaterials to modulate the immune system, applicable in tissue engineering, transplantation, and drug delivery technologies.

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.

Direct Microscopic Observation of Human Neutrophil-Staphylococcus aureus Interaction In Vitro Suggests a Potential Mechanism for Initiation of Biofilm Infection on an Implanted Medical Device

The ability of human neutrophils to clear newly attached Staphylococcus aureus bacteria from a serum-coated glass surface was examined in vitro using time-lapse confocal scanning laser microscopy. Quantitative image analysis was used to measure the temporal change in bacterial biomass, neutrophil motility, and fraction of the surface area policed by neutrophils. In control experiments in which the surface was inoculated with bacteria but no neutrophils were added, prolific bacterial growth was observed. Neutrophils were able to control bacterial growth but only consistently when the neutrophil/bacterium number ratio exceeded approximately 1. When preattached bacteria were given a head start and allowed to grow for 3 h prior to neutrophil addition, neutrophils were unable to maintain control of the nascent biofilm. In these head-start experiments, aggregates of bacterial biofilm with areas of 50 μm² or larger formed, and the growth of such aggregates continued even when multiple neutrophils attacked a cluster. These results suggest a model for the initiation of a biofilm infection in which a delay in neutrophil recruitment to an abiotic surface allows surface-attached bacteria time to grow and form aggregates that become protected from neutrophil clearance. Results from a computational model of the neutrophil-biofilm surface contest supported this conceptual model and highlighted the stochastic nature of the interaction. Additionally, we observed that both neutrophil motility and clearance of bacteria were impaired when oxygen tension was reduced to 0% or 2% O₂.

Bioscaffold-Induced Brain Tissue Regeneration

Brain tissue lost after a stroke is not regenerated, although a repair response associated with neurogenesis does occur. A failure to regenerate functional brain tissue is not caused by the lack of available neural cells, but rather the absence of structural support to permit a repopulation of the lesion cavity. Inductive bioscaffolds can provide this support and promote the invasion of host cells into the tissue void. The putative mechanisms of bioscaffold degradation and its pivotal role to permit invasion of neural cells are reviewed and discussed in comparison to peripheral wound healing. Key differences between regenerating and non-regenerating tissues are contrasted in an evolutionary context, with a special focus on the neurogenic response as a conditio sine qua non for brain regeneration. The pivotal role of the immune system in biodegradation and the formation of a neovasculature are contextualized with regeneration of peripheral soft tissues. The application of rehabilitation to integrate newly forming brain tissue is suggested as necessary to develop functional tissue that can alleviate behavioral impairments. Pertinent aspects of brain tissue development are considered to provide guidance to produce a metabolically and functionally integrated de novo tissue. Although little is currently known about mechanisms involved in brain tissue regeneration, this review outlines the various components and their interplay to provide a framework for ongoing and future studies. It is envisaged that a better understanding of the mechanisms involved in brain tissue regeneration will improve the design of biomaterials and the methods used for implantation, as well as rehabilitation strategies that support the restoration of behavioral functions.

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.

Mesenchymal stem cell-based bioengineered constructs: foreign body response, cross-talk with macrophages and impact of biomaterial design strategies for pelvic floor disorders

An excessive foreign body response (FBR) has contributed to the adverse events associated with polypropylene mesh usage for augmenting pelvic organ prolapse surgery. Consequently, current biomaterial research considers the critical role of the FBR and now focuses on developing better biocompatible biomaterials rather than using inert implants to improve the clinical outcomes of their use. Tissue engineering approaches using mesenchymal stem cells (MSCs) have improved outcomes over traditional implants in other biological systems through their interaction with macrophages, the main cellular player in the FBR. The unique angiogenic, immunomodulatory and regenerative properties of MSCs have a direct impact on the FBR following biomaterial implantation. In this review, we focus on key aspects of the FBR to tissue-engineered MSC-based implants for supporting pelvic organs and beyond. We also discuss the immunomodulatory effects of the recently discovered endometrial MSCs on the macrophage response to new biomaterials designed for use in pelvic floor reconstructive surgery. We conclude with a focus on considerations in biomaterial design that take into account the FBR and will likely influence the development of the next generation of biomaterials for gynaecological applications.

Tailoring Nanomaterials for Targeting Tumor-Associated Macrophages

Advances in the field of nanotechnology together with an increase understanding of tumor immunology have paved the way for the development of more personalized cancer immuno-nanomedicines. Nanovehicles, due to their specific physicochemical properties, are emerging as key translational moieties in tackling tumor-promoting, M2-like tumor-associated macrophages (TAMs). Cancer immuno-nanomedicines target TAMs primarily by blocking M2-like TAM survival or affecting their signaling cascades, restricting macrophage recruitment to tumors and re-educating tumor-promoting M2-like TAMs to the tumoricidal, M1-like phenotype. Here, the TAM effector mechanisms and strategies for targeting TAMs are summarized, followed by a focus on the mechanistic considerations in the development of novel immuno-nanomedicines. Furthermore, imaging TAMs with nanoparticles so as to forecast a patient's clinical outcome, describing treatment options, and observing therapy responses is also discussed. At present, strategies that target TAMs are being investigated not only at the basic research level but also in early clinical trials. The significance of TAM-targeting biomaterials is highlighted, with the goal of facilitating future clinical translation.

Heating up cancer vaccines

A microneedle patch containing melanin promotes systemic antitumor response upon photothermal irradiation.

Injectable hydrogels of optimized acellular nerve for injection in the injured spinal cord

OBJECTIVE

Spinal cord injury (SCI) affects a quarter million individuals in the United States, and there is currently no clinical treatment. Both fresh and acellular peripheral nerve grafts can induce spinal axon regeneration and support functional recovery in experimental injury models. Nonetheless, a scaffold that can be injected into a spinal contusion would be far less invasive to apply. We aimed to develop the first injectable acellular nerve graft for promoting repair after contusion SCI.

APPROACH

We report a method to enzymatically solubilize optimized acellular (OA) nerve-a decellularized peripheral nerve graft developed in our laboratory and currently used clinically-to obtain an injectable solution that undergoes thermal gelation under physiological conditions. We quantified multiple physical and compositional properties of this novel material as well as tested its efficacy at acute and chronic time points following cervical contusion SCI.

MAIN RESULTS

This injectable optimized acellular (iOA) nerve graft retains native chemical cues such as collagens and glycosaminoglycans. By varying hydrogel concentration, the rheological properties and compressive modulus of iOA were similar to that previous reported for rat central nervous tissue. iOA solution was compatible with rat Schwann cells in culture, and hydrogel injection into a rat cervical contusion model significantly reduced the ratio of M1:M2 macrophages after one week, favoring regenerative phenotypes (p < 0.05). Furthermore, while iOA treatment did not affect locomotor or respiratory recovery over an eight week period, the percentage of axonal coverage increased at the distal tissue interface (p < 0.05), suggesting enhanced axonal extension within this region.

SIGNIFICANCE

Our data indicate that this novel injectable form of acellular nerve grafts is amenable for use after contusion SCI and may bolster a simultaneous therapy by acutely modulating the inflammatory milieu and supporting axonal growth.

Nanoparticles for dendritic cell-based immunotherapy

Crosstalk among immune cells has attracted considerable attention with the advent of immunotherapy as a novel therapeutic approach for challenging diseases, especially cancer, which is the leading cause of mortality worldwide. Dendritic cells-the key antigen-presenting cells-play a pivotal role in immunological response by presenting exogenous epitopes to T cells, which induces the self-defense mechanisms of the body. Furthermore, nanotechnology has provided promising ways for diagnosing and treating cancer in the last decade. The progress in nanoparticle drug carrier development, combined with enhanced understanding of the immune system, has enabled harnessing of anti-tumor immunity. This review focuses on the recent advances in nanotechnology that have improved the therapeutic efficacy of immunotherapies, with emphasis on dendritic cell physiology and its role in presenting antigens and eliciting therapeutic T cell response.

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.

Injectable network biomaterials via molecular or colloidal self-assembly

Self-assembly is a powerful tool to create functional materials. A specific application for which self-assembled materials are ideally suited is in creating injectable biomaterials. Contrasting with traditional biomaterials that are implanted through surgical means, injecting biomaterials through the skin offers numerous advantages, expanding the scope and impact for biomaterials in medicine. In particular, self-assembled biomaterials prepared from molecular or colloidal interactions have been frequently explored. The strategies to create these materials are varied, taking advantage of engineered oligopeptides, proteins, and nanoparticles as well as affinity-mediated crosslinking of synthetic precursors. Self-assembled materials typically facilitate injectability through two different mechanisms: i) in situ self-assembly, whereby materials would be administered in a monomeric or oligomeric form and self-assemble in response to some physiologic stimulus, or ii) self-assembled materials that, by virtue of their dynamic, non-covalent interactions, shear-thin to facilitate flow within a syringe and subsequently self-heal into its reassembled material form at the injection site. Indeed, many classes of materials are capable of being injected using a combination of these two mechanisms. Particular utility has been noted for self-assembled biomaterials in the context of tissue engineering, regenerative medicine, drug delivery, and immunoengineering. Given the controlled and multifunctional nature of many self-assembled materials demonstrated to date, we project a future where injectable self-assembled biomaterials afford improved practice in advancing healthcare.

Bioengineering strategies for inducing tolerance in autoimmune diabetes

Type 1 diabetes is an autoimmune disease marked by the destruction of insulin-producing beta cells in the pancreatic islets. Strategies to delay onset or prevent the autoimmune recognition of beta cell antigens or T cell-mediated killing of beta cells have mainly focused on systemic immunomodulation and antigen-specific immunotherapy. To bridge the fields of type 1 diabetes immunology and biomaterials engineering, this article will review recent trends in the etiology of type 1 diabetes immunopathology and will focus on the contributions of emerging bioengineered strategies in the fight against beta cell autoimmunity in type 1 diabetes.