Inflammatory cytokines presented from polymer matrices differentially generate and activate DCs in situ

Enhancing pancreatic cancer immunotherapy: Leveraging localized delivery strategies through the use of implantable devices and scaffolds

Pancreatic cancer (PC) remains the predominant type of upper gastrointestinal tract cancer, associated with heightened morbidity and a survival rate below 12%. While immunotherapy has brought about transformative changes in the standards of care for most solid tumors, its application in PC is hindered by the ''cold tumor'' microenvironment, marked by the presence of immunosuppressive cells. Modest response rates in PC are attributed, in part to, the fibrotic stroma that obstructs the delivery of systemic immunotherapy. Furthermore, the occurrence of immune-related adverse events (iRAEs) often necessitates the use of sub-therapeutic doses or treatment discontinuation. In the pursuit of innovative approaches to enhance the effectiveness of immunotherapy for PC, implantable drug delivery devices and scaffolds emerge as promising strategies. These technologies offer the potential for sustained drug delivery directly to the tumor site, overcoming stromal barriers, immunosuppression, T cell exclusion, immunotherapy resistance, optimizing drug dosage, and mitigating systemic toxicity. This review offers a comprehensive exploration of pancreatic ductal adenocarcinoma (PDAC), the most common and aggressive form of PC, accompanied by a critical analysis of the challenges the microenvironment presents to the development of successful combinational immunotherapy approaches. Despite efforts, these approaches have thus far fallen short in enhancing treatment outcomes for PDAC. The review will subsequently delve into the imperative need for refining delivery strategies, providing an examination of past and ongoing studies in the field of localized immunotherapy for PDAC. Addressing these issues will lay the groundwork for the development of effective new therapies, thereby enhancing treatment response, patient survival, and overall quality of life for individuals diagnosed with PDAC.

Targeting lymph nodes for enhanced cancer vaccination: From nanotechnology to tissue engineering

Lymph nodes (LNs) occupy a critical position in initiating and augmenting immune responses, both spatially and functionally. In cancer immunotherapy, tumor-specific vaccines are blooming as a powerful tool to suppress the growth of existing tumors, as well as provide preventative efficacy against tumorigenesis. Delivering these vaccines more efficiently to LNs, where antigen-presenting cells (APCs) and T cells abundantly reside, is under extensive exploration. Formulating vaccines into nanomedicines, optimizing their physiochemical properties, and surface modification to specifically bind molecules expressed on LNs or APCs, are common routes and have brought encouraging outcomes. Alternatively, porous scaffolds can be engineered to attract APCs and provide an environment for them to mature, proliferate and migrate to LNs. A relatively new research direction is inducing the formation of LN-like organoids, which have shown positive relevance to tumor prognosis. Cutting-edge advances in these directions and discussions from a future perspective are given here, from which the up-to-date pattern of cancer vaccination will be drawn to hopefully provide basic guidance to future studies.

Engineering customized nanovaccines for enhanced cancer immunotherapy

Nanovaccines have gathered significant attention for their potential to elicit tumor-specific immunological responses. Despite notable progress in tumor immunotherapy, nanovaccines still encounter considerable challenges such as low delivery efficiency, limited targeting ability, and suboptimal efficacy. With an aim of addressing these issues, engineering customized nanovaccines through modification or functionalization has emerged as a promising approach. These tailored nanovaccines not only enhance antigen presentation, but also effectively modulate immunosuppression within the tumor microenvironment. Specifically, they are distinguished by their diverse sizes, shapes, charges, structures, and unique physicochemical properties, along with targeting ligands. These features of nanovaccines facilitate lymph node accumulation and activation/regulation of immune cells. This overview of bespoke nanovaccines underscores their potential in both prophylactic and therapeutic applications, offering insights into their future development and role in cancer immunotherapy.

Adoptive T cell transfer and host antigen-presenting cell recruitment with cryogel scaffolds promotes long-term protection against solid tumors

Although adoptive T cell therapy provides the T cell pool needed for immediate tumor debulking, the infused T cells generally have a narrow repertoire for antigen recognition and limited ability for long-term protection. Here, we present a hydrogel that locally delivers adoptively transferred T cells to the tumor site while recruiting and activating host antigen-presenting cells with GMCSF or FLT3L and CpG, respectively. T cells alone loaded into these localized cell depots provided significantly better control of subcutaneous B16-F10 tumors than T cells delivered through direct peritumoral injection or intravenous infusion. T cell delivery combined with biomaterial-driven accumulation and activation of host immune cells prolonged the activation of the delivered T cells, minimized host T cell exhaustion, and enabled long-term tumor control. These findings highlight how this integrated approach provide both immediate tumor debulking and long-term protection against solid tumors, including against tumor antigen escape.

Future regenerative medicine developments and their therapeutic applications

Although the currently available pharmacological assays can cure most pathological disorders, they have limited therapeutic value in relieving certain disorders like myocardial infarct, peripheral vascular disease, amputated limbs, or organ failure (e.g. renal failure). Pilot studies to overcome such problems using regenerative medicine (RM) delivered promising data. Comprehensive investigations of RM in zebrafish or reptilians are necessary for better understanding. However, the precise mechanisms remain poorly understood despite the tremendous amount of data obtained using the zebrafish model investigating the exact mechanisms behind their regenerative capability. Indeed, understanding such mechanisms and their application to humans can save millions of lives from dying due to potentially life-threatening events. Recent studies have launched a revolution in replacing damaged human organs via different approaches in the last few decades. The newly established branch of medicine (known as Regenerative Medicine aims to enhance natural repair mechanisms. This can be done through the application of several advanced broad-spectrum technologies such as organ transplantation, tissue engineering, and application of Scaffolds technology (support vascularization using an extracellular matrix), stem cell therapy, miRNA treatment, development of 3D mini-organs (organoids), and the construction of artificial tissues using nanomedicine and 3D bio-printers. Moreover, in the next few decades, revolutionary approaches in regenerative medicine will be applied based on artificial intelligence and wireless data exchange, soft intelligence biomaterials, nanorobotics, and even living robotics capable of self-repair. The present work presents a comprehensive overview that summarizes the new and future advances in the field of RM.

Immune evaluation of granulocyte-macrophage colony stimulating factor loaded hierarchically 3D nanofiber scaffolds in a humanized mice model

Background: Immune evaluation of biomaterials for tissue regeneration is a critical preclinical evaluation. The current evaluation criterion (ISO 10993-1 or GB/T 16886) uses rodents to perform the immune evaluation. However, the immune system of rodents is different from humans, the obtained results may not be reliable, which could lead directly to the failure of clinical trials. Granulocyte-macrophage colony-stimulating factor (GM-CSF) shows a great potential application in tissue regeneration by regulating local immune responses. The presented work combines the advantages of GM-CSF (immunoregulation) and hierarchically 3D nanofiber scaffolds (tissue regeneration). Methods: Firstly, we fabricated GM-CSF loaded 3D radially aligned nanofiber scaffolds, and then subcutaneous implantation was performed in humanized mice. The whole scaffold and surrounding tissue were harvested at each indicated time point. Finally, the cell infiltration and local immune responses were detected by histological observations, including H&E and Masson staining and immunochemistry. Results: We found significant cell migration and extracellular matrix deposition within the 3D radially aligned nanofiber scaffold after subcutaneous implantation. The locally released GM-CSF could accelerate the expression of human dendritic cells (CD11c) only 3 days after subcutaneous implantation. Moreover, higher expression of human cytotoxic T cells (CD3⁺/CD8⁺), M1 macrophages (CD68/CCR7) was detected within GM-CSF loaded radially aligned nanofiber scaffolds and their surrounding tissues. Conclusions: The 3D radially aligned scaffold can accelerate cell migration from surrounding tissues to regenerate the wound area. And the locally released GM-CSF enhances dendritic cell recruitment and activation of cytotoxic T cells and M1 macrophages. Taken together, the GM-CSF loaded 3D radially aligned nanofiber scaffolds have a promising potential for achieving tissue regeneration.

In Situ Dendritic Cell Recruitment and T Cell Activation for Cancer Immunotherapy

Cancer immunotherapy has shifted the paradigm for cancer treatment in the past decade, but new immunotherapies enabling the effective treatment of solid tumors are still greatly demanded. Here we report a pore-forming hydrogel-based immunotherapy that enables simultaneous recruitment of dendritic cells and in situ activation of T cells, for reshaping the immunosuppressive tumor microenvironment and amplifying cytotoxic T lymphocyte response. The injectable pore-forming hydrogel composed of porogen-dispersed alginate network can form a macroporous structure upon injection into mice, and enables controlled release of granulocyte-macrophage colony-stimulating factor (GM-CSF), a chemoattractant for recruiting dendritic cells, and epacadostat, an inhibitor of indoleamine 2, 3-dioxygenase for activating T cells. We show that gels loaded with GM-CSF and epacadostat, after peritumoral injection, can recruit massive dendritic cells in situ and activate effector T cells in the tumor tissues, resulting in enhanced frequency and activation status of dendritic cells, reduced numbers of regulatory T (Treg) cells, and increased CD8⁺/Treg ratios in the tumor microenvironment. This hydrogel-based immunotherapy holds great promise for treating poorly-immunogenic solid tumors.

Emerging biomaterial-based strategies for personalized therapeutic in situ cancer vaccines

Landmark successes in oncoimmunology have led to development of therapeutics boosting the host immune system to eradicate local and distant tumors with impactful tumor reduction in a subset of patients. However, current immunotherapy modalities often demonstrate limited success when involving immunologically cold tumors and solid tumors. Here, we describe the role of various biomaterials to formulate cancer vaccines as a form of cancer immunotherapy, seeking to utilize the host immune system to activate and expand tumor-specific T cells. Biomaterial-based cancer vaccines enhance the cancer-immunity cycle by harnessing cellular recruitment and activation against tumor-specific antigens. In this review, we discuss biomaterial-based vaccine strategies to induce lymphocytic responses necessary to mediate anti-tumor immunity. We focus on strategies that selectively attract dendritic cells via immunostimulatory gradients, activate them against presented tumor-specific antigens, and induce effective cross-presentation to T cells in secondary lymphoid organs, thereby generating immunity. We posit that personalized cancer vaccines are promising targets to generate long-term systemic immunity against patient- and tumor-specific antigens to ensure long-term cancer remission.

Bioinspired and Biomimetic Delivery Platforms for Cancer Vaccines

Cancer vaccines aim at eliciting tumor-specific responses for the immune system to identify and eradicate malignant tumor cells while sparing the normal tissues. Furthermore, cancer vaccines can potentially induce long-term immunological memory for antitumor responses, preventing metastasis and cancer recurrence, thus presenting an attractive treatment option in cancer immunotherapy. However, clinical efficacy of cancer vaccines has remained low due to longstanding challenges, such as poor immunogenicity, immunosuppressive tumor microenvironment, tumor heterogeneity, inappropriate immune tolerance, and systemic toxicity. Recently, bioinspired materials and biomimetic technologies have emerged to play a part in reshaping the field of cancer nanomedicine. By mimicking desirable chemical and biological properties in nature, bioinspired engineering of cancer vaccine delivery platforms can effectively transport therapeutic cargos to tumor sites, amplify antigen and adjuvant bioactivities, and enable spatiotemporal control and on-demand immunoactivation. As such, integration of biomimetic designs into delivery platforms for cancer vaccines can enhance efficacy while retaining good safety profiles, which contributes to expediting the clinical translation of cancer vaccines. Recent advances in bioinspired delivery platforms for cancer vaccines, existing obstacles faced, as well as insights and future directions for the field are discussed here.

Translational Applications of Hydrogels

Advances in hydrogel technology have unlocked unique and valuable capabilities that are being applied to a diverse set of translational applications. Hydrogels perform functions relevant to a range of biomedical purposes-they can deliver drugs or cells, regenerate hard and soft tissues, adhere to wet tissues, prevent bleeding, provide contrast during imaging, protect tissues or organs during radiotherapy, and improve the biocompatibility of medical implants. These capabilities make hydrogels useful for many distinct and pressing diseases and medical conditions and even for less conventional areas such as environmental engineering. In this review, we cover the major capabilities of hydrogels, with a focus on the novel benefits of injectable hydrogels, and how they relate to translational applications in medicine and the environment. We pay close attention to how the development of contemporary hydrogels requires extensive interdisciplinary collaboration to accomplish highly specific and complex biological tasks that range from cancer immunotherapy to tissue engineering to vaccination. We complement our discussion of preclinical and clinical development of hydrogels with mechanical design considerations needed for scaling injectable hydrogel technologies for clinical application. We anticipate that readers will gain a more complete picture of the expansive possibilities for hydrogels to make practical and impactful differences across numerous fields and biomedical applications.

Biomaterial vaccines capturing pathogen-associated molecular patterns protect against bacterial infections and septic shock

Most bacterial vaccines work for a subset of bacterial strains or require the modification of the antigen or isolation of the pathogen before vaccine development. Here we report injectable biomaterial vaccines that trigger potent humoral and T-cell responses to bacterial antigens by recruiting, reprogramming and releasing dendritic cells. The vaccines are assembled from regulatorily approved products and consist of a scaffold with absorbed granulocyte-macrophage colony-stimulating factor and CpG-rich oligonucleotides incorporating superparamagnetic microbeads coated with the broad-spectrum opsonin Fc-mannose-binding lectin for the magnetic capture of pathogen-associated molecular patterns from inactivated bacterial-cell-wall lysates. The vaccines protect mice against skin infection with methicillin-resistant Staphylococcus aureus, mice and pigs against septic shock from a lethal Escherichia coli challenge and, when loaded with pathogen-associated molecular patterns isolated from infected animals, uninfected animals against a challenge with different E. coli serotypes. The strong immunogenicity and low incidence of adverse events, a modular manufacturing process, and the use of components compatible with current good manufacturing practice could make this vaccine technology suitable for responding to bacterial pandemics and biothreats.

Recent advances in regenerative medicine strategies for cancer treatment

Cancer stands as one of the most leading causes of death worldwide, while one of the most significant challenges in treating it is revealing novel alternatives to predict, diagnose, and eradicate tumor cell growth. Although various methods, such as surgery, chemotherapy, and radiation therapy, are used today to treat cancer, its mortality rate is still high due to the numerous shortcomings of each approach. Regenerative medicine field, including tissue engineering, cell therapy, gene therapy, participate in cancer treatment and development of cancer models to improve the understanding of cancer biology. The final intention is to convey fundamental and laboratory research to effective clinical treatments, from the bench to the bedside. Proper interpretation of research attempts helps to lessen the burden of treatment and illness for patients. The purpose of this review is to investigate the role of regenerative medicine in accelerating and improving cancer treatment. This study examines the capabilities of regenerative medicine in providing novel cancer treatments and the effectiveness of these treatments to clarify this path as much as possible and promote advanced future research in this field.

Nanotechnology synergized immunoengineering for cancer

Novel strategies modulating the immune system yielded enhanced anticancer responses and improved cancer survival. Nevertheless, the success rate of immunotherapy in cancer treatment has been below expectation(s) due to unpredictable efficacy and off-target effects from systemic dosing of immunotherapeutic(s). As a result, there is an unmet clinical need for improving conventional immunotherapy. Nanotechnology offers several new strategies, multimodality, and multiplex biological targeting advantage to overcome many of these challenges. These efforts enable programming the pharmacodynamics, pharmacokinetics, and delivery of immunomodulatory agents/co-delivery of compounds to prime at the tumor sites for improved therapeutic benefits. This review provides an overview of the design and clinical principles of biomaterials driven nanotechnology and their potential use in personalized nanomedicines, vaccines, localized tumor modulation, and delivery strategies for cancer immunotherapy. In this review, we also summarize the latest highlights and recent advances in combinatorial therapies availed in the treatment of cold and complicated tumors. It also presents key steps and parameters implemented for clinical success. Finally, we analyse, discuss, and provide clinical perspectives on the integrated opportunities of nanotechnology and immunology to achieve synergistic and durable responses in cancer treatment.

Hitchhiking on Controlled-Release Drug Delivery Systems: Opportunities and Challenges for Cancer Vaccines

Cancer vaccines represent among the most promising strategies in the battle against cancers. However, the clinical efficacy of current cancer vaccines is largely limited by the lack of optimized delivery systems to generate strong and persistent antitumor immune responses. Moreover, most cancer vaccines require multiple injections to boost the immune responses, leading to poor patient compliance. Controlled-release drug delivery systems are able to address these issues by presenting drugs in a controlled spatiotemporal manner, which allows co-delivery of multiple drugs, reduction of dosing frequency and avoidance of significant systemic toxicities. In this review, we outline the recent progress in cancer vaccines including subunit vaccines, genetic vaccines, dendritic cell-based vaccines, tumor cell-based vaccines and in situ vaccines. Furthermore, we highlight the efforts and challenges of controlled or sustained release drug delivery systems (e.g., microparticles, scaffolds, injectable gels, and microneedles) in ameliorating the safety, effectiveness and operability of cancer vaccines. Finally, we briefly discuss the correlations of vaccine release kinetics and the immune responses to enlighten the rational design of the next-generation platforms for cancer therapy.

Aliphatic Polyester-Based Materials for Enhanced Cancer Immunotherapy

Poly(lactic acid) (PLA) and its copolymer, poly(lactic-co-glycolic acid) (PLGA), based aliphatic polyesters have been extensively used for biomedical applications, such as drug delivery system and tissue engineering, thanks to their biodegradability, benign toxicity, renewability, and adjustable mechanical properties. A rapidly growing field of cancer research, the development of therapeutic cancer vaccines or treatment modalities is aimed to deliver immunomodulatory signals that control the quality of immune responses against tumors. Herein, the progress and applications of PLA and PLGA are reviewed in delivering immunotherapeutics to treat cancers.

Sendai virus-based immunoadjuvant in hydrogel vaccine intensity-modulated dendritic cells activation for suppressing tumorigenesis

The conventional immunoadjuvants in vaccine have weak effect on stimulating antigen presentation and activating anti-tumor immunity. Unexpectedly, we discovered that non-pathogenic Sendai virus (SeV) could activate antigen-presenting cells (APCs) represented by dendritic cells (DCs). Here, we designed an injectable SeV-based hydrogel vaccine (SHV) to execute multi-channel recruitment and stimulation of DCs for boosting the specific immune response against tumors. After the release of the NIR-triggered antigens from tumor cells, dendritic cells around the vaccine efficiently transport the antigens to lymph nodes and present them to T lymphocytes, thereby inducing systemic anti-tumor immune memory. Our findings demonstrated that the SHV with excellent universality, convenience and flexibility has achieved better immune protection effects in inhibiting the occurrence of melanoma and breast cancer. In conclusion, the SHV system might serve as the next generation of personalized anti-tumor vaccines with enhanced features over standard vaccination regimens, and represented an alternative way to suppress tumorigenesis.

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SeV served as immuneadjuvant can activate APCs through TLR7/8 and TLR3 pathways.

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Non-pathogenic SeV in the injectable hydrogel vaccine recruit and activate DCs.

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Tumor cells acted as an “antigen library” to release all antigens by NIR-trigger.

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Fragmented DNA from tumor cells after photothermal damage activated STING pathway.

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The synergy effect of SHV and aOX40 greatly enhanced anti-tumor immune memory.

Immunostimulatory biomaterials to boost tumor immunogenicity

Cancer immunotherapy is exhibiting great promise as a new therapeutic modality for cancer treatment. However, immunotherapies are limited by the inability of some tumors to provoke an immune response. These tumors with a 'cold' immunological phenotype are characterized by low numbers of tumor-infiltrating lymphocytes, high numbers of immunosuppressive leukocytes (e.g. regulatory T cells, tumor-associated macrophages), and high production of immune-dampening signals (e.g. IL-10, TGF-β, IDO-1). Strategies to boost the aptitude of tumors to initiate an immune response (i.e. boost tumor immunogenicity) will turn 'cold' tumors 'hot' and augment the anti-tumor efficacy of current immunotherapies. Approaches to boost tumor immunogenicity already show promise; however, multifaceted delivery and immunobiology challenges exist. For instance, systemic delivery of many immune-stimulating agents causes off-target toxicity and/or the development of autoimmunity, limiting the administrable dose below the threshold needed to achieve efficacy. Moreover, once administered in vivo, molecules such as the nucleic acid-based agonists for many pattern recognition receptors are either rapidly cleared or degraded, and don't efficiently traffic to the intracellular compartments where the receptors are located. Thus, these nucleic acid-based drugs are ineffective without a delivery system. Biomaterials-based approaches aim to enhance current strategies to boost tumor immunogenicity, enable novel strategies, and spare dose-limiting toxicities. Here, we review recent progress to improve cancer immunotherapies by boosting immunogenicity within tumors using immunostimulatory biomaterials.

Biomaterials as Local Niches for Immunomodulation

A major function of the immune system is to detect threat from foreign invaders, tissue damage, or cancer and to mount a counter response that resolves the threat, restores homeostasis, and supplies immunological memory to prevent a second assault. Our increasing understanding of the immune system has opened up numerous avenues for modulating immune responses against infections, cancer, and autoimmunity. However, agents used for immunomodulation have been traditionally administered systemically via bolus injection, leading to unintended consequences by disrupting homeostasis at nontarget sites. Consequently, systemic hyperactivation and hypoactivation can result from bolus administration of immune-activators and immunosuppressants, respectively. Macroscale biomaterial scaffolds can instead be placed at the intended target site to provide both localized, controlled release of immunomodulatory agents and control over local immune cell trafficking and function, potentially maximizing therapeutic efficacy and limiting systemic exposure. These scaffolds have found utility in the area of cancer immunotherapy, especially in situ cancer vaccination where controlled release of factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and the local presentation of tumor antigen and danger signals lead to the recruitment of immature dendritic cells and facilitate their activation and antigen presentation. These cells eventually migrate into secondary lymphoid organs where they prime tumor specific T cells for downstream tumor clearance. Scaffolds can also be used in adoptive T cell therapy to generate large numbers of potent antigen specific T cells or chimeric antigen receptor (CAR) T cells in vitro for subsequent delivery to patients. Macroscale biomaterial scaffolds have also found utility beyond cancer immunotherapy and have been developed to promote immune tolerance by regulatory T cell induction and to expedite tissue regeneration. The design of these macroscale biomaterial scaffolds considers their biocompatibility, biodegradability, mode of delivery, porosity, and kinetics of therapeutic cargo release. Consequently, the numerous approaches that have been developed to fabricate biomaterial scaffolds are aimed at tuning these parameters to achieve the desired therapeutic outcome. This Account will discuss the use of biomaterial scaffolds as niches for immunomodulation and will focus on (1) approaches that have been used to fabricate various biomaterial systems being employed as niches for immunomodulation and (2) how these biomaterial systems have been used to modulate immune responses, specifically in area of cancer immunotherapy, where we will discuss the role of macroscale biomaterial scaffolds for in situ vaccination and in vitro T cell expansion. We will also briefly discuss the utility of biomaterial scaffolds beyond cancer, drawing examples from tolerance and tissue regeneration.

Drug-loading three-dimensional scaffolds based on hydroxyapatite-sodium alginate for bone regeneration

Bone tissue engineering is a promising approach for tackling clinical challenges. Osteoprogenitor cells, osteogenic factors, and osteoinductive/osteoconductive scaffolds are employed in bone tissue engineering. However, scaffold materials remain limited due to their source, low biocompatibility, and so on. In this study, a composite hydrogel scaffold composed of hydroxyapatite (HA) and sodium alginate (SA) was manufactured using three-dimensional printing. Naringin (NG) and calcitonin-gene-related peptide (CGRP) were used as osteogenic factors in the fabrication of drug-loaded scaffolds. Investigation using animal experiments, as well as scanning electron microscopy, cell counting kit-8 testing, alkaline phosphatase staining, and alizarin red-D staining of bone marrow mesenchymal stem cell culture showed that the three scaffolds displayed similar physicochemical properties and that the HA/SA/NG and HA/SA/CGRP scaffolds displayed better osteogenesis than that of the HA/SA scaffold. Thus, the HA/SA scaffold could be a biocompatible material with potential applications in bone regeneration. Meanwhile, NG and CGRP doping could result in better and more positive proliferation and differentiation.

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.

Glyco-Modification of Mucin Hydrogels to Investigate Their Immune Activity

Mucins are multifunctional glycosylated proteins that are increasingly investigated as building blocks of novel biomaterials. An attractive feature is their ability to modulate the immune response, in part by engaging with sialic acid binding receptors on immune cells. Once assembled into hydrogels, bovine submaxillary mucins (Muc gels) were shown to modulate the recruitment and activation of immune cells and avoid fibrous encapsulation in vivo. However, nothing is known about the early immune response to Muc gels. This study characterizes the response of macrophages, important orchestrators of the material-mediated immune response, over the first 7 days in contact with Muc gels. The role of mucin-bound sialic acid sugar residues was investigated by first enzymatically cleaving the sugar and then assembling the mucin variants into covalently cross-linked hydrogels with rheological and surface nanomechanical properties similar to nonmodified Muc gels. Results with THP-1 and human primary peripheral blood monocytes derived macrophages showed that Muc gels transiently activate the expression of both pro-inflammatory and anti-inflammatory cytokines and cell surface markers, for most makers with a maximum on the first day and loss of the effect after 7 days. The activation was sialic acid-dependent for a majority of the markers followed. The pattern of gene expression, protein expression, and functional measurements did not strictly correspond to M1 or M2 macrophage phenotypes. This study highlights the complex early events in macrophage activation in contact with mucin materials and the importance of sialic acid residues in such a response. The enzymatic glyco-modulation of Muc gels appears as a useful tool to help understand the biological functions of specific glycans on mucins which can further inform on their use in various biomedical applications.

Targeted drug delivery therapies inspired by natural taxes

A taxis is the movement responding to a stimulus of an organism. This behavior helps organisms to migrate, to find food or to avoid dangers. By mimicking and using natural taxes, many bio-inspired and bio-hybrid drug delivery systems have been synthesized. Under the guidance of physical and chemical stimuli, drug-loaded carriers are led to a target, for example tumors, then locally release the drug, inducing a therapeutic effect without influencing other parts of the body. On the other hand, for moving targets, for example metastasis cancer cells or bacteria, taking advantage of their taxes behavior is a solution to capture and to eliminate them. For instance, several traps and ecological niches have been fabricated to attract cancer cells by releasing chemokines. Cancer cells are then eliminated by drug loaded inside the trap, by radiotherapy focusing on the trap location or by simply removing the trap. Further research is needed to deeply understand the taxis behavior of organisms, which is essential to ameliorate the performance of taxes-inspired drug delivery application.

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.

Biomaterial-based platforms for in situ dendritic cell programming and their use in antitumor immunotherapy

Dendritic cells (DCs) are central players in the immune system, with an exquisite capacity to initiate and modulate immune responses. These functional characteristics have led to intense research on the development of DC-based immunotherapies, particularly for oncologic diseases. During recent decades, DC-based vaccines have generated very promising results in animal studies, and more than 300 clinical assays have demonstrated the safety profile of this approach. However, clinical data are inconsistent, and clear evidence of meaningful efficacy is still lacking. One of the reasons for this lack of evidence is the limited functional abilities of the used ex vivo-differentiated DCs. Therefore, alternative approaches for targeting and modulating endogenous DC subpopulations have emerged as an attractive concept. Here, we sought to revise the evolution of several strategies for the in situ mobilization and modulation of DCs. The first approaches using chemokine-secreting irradiated tumor cells are addressed, and special attention is given to the cutting-edge injectable bioengineered platforms, programmed to release chemoattractants, tumor antigens and DC maturating agents. Finally, we discuss how our increasing knowledge of DC biology, the use of neoantigens and their combination with immune checkpoint inhibitors can leverage the refinement of these polymeric vaccines to boost their antitumor efficacy.

Mesoporous Silica as a Versatile Platform for Cancer Immunotherapy

Immunotherapy has been recognized for decades as a promising therapeutic method for cancer treatment. To enhance host immune responses against cancer, antigen-presenting cells (APCs; e.g., dendritic cells) or T cells are educated using immunomodulatory agents including tumor-associated antigens and adjuvants, and manipulated to induce a cascading adaptive immune response targeting tumor cells. Mesoporous silica materials are promising candidates to improve cancer immunotherapy based on their attractive properties that include high porosity, high biocompatibility, facile surface modification, and self-adjuvanticity. Here, the recent progress on mesoporous-silica-based immunotherapies based on two material forms is summarized: 1) mesoporous silica nanoparticles (MSNs), which can be internalized into APCs, and 2) micrometer-sized mesoporous silica rods (MSRs) that can form a 3D space to recruit APCs. Subcutaneously injected MSN-based cancer vaccines can be taken up by peripheral APCs or by APCs in lymphoid organs to educate the immune system against cancer cells. MSR cancer vaccines can recruit immune cells into the MSR scaffold to induce cancer-specific immunity. Both vaccine systems successfully stimulate the adaptive immune response to eradicate cancer in vivo. Thus, mesoporous silica has potential value as a material platform for the treatment of cancer or infectious diseases.

Advances in immunotherapy delivery from implantable and injectable biomaterials

Macroscale biomaterials, such as preformed implantable scaffolds and injectable soft materials, possess powerful synergies with anti-cancer immunotherapies. Immunotherapies on their own typically have poor delivery properties, and often require repeated high-dose injections that result in serious off-tumor effects and/or limited efficacy. Rationally designed biomaterials allow for discrete localization and controlled release of immunotherapeutic agents, and have been shown in a large number of applications to improve outcomes in the treatment of cancers via immunotherapy. Among various strategies, macroscale biomaterial delivery systems can take the form of robust tablet-like scaffolds that are surgically implanted into a tumor resection site, releasing programmed immune cells or immunoregulatory agents. Alternatively they can be developed as soft gel-like materials that are injected into solid tumors or sites of resection to stimulate a potent anti-tumor immune response. Biomaterials synthesized from diverse components such as polymers and peptides can be combined with any immunotherapy in the modern toolbox, from checkpoint inhibitors and stimulatory adjuvants, to cancer antigens and adoptive T cells, resulting in unique synergies and improved therapeutic efficacy. The field is growing rapidly in size as publications continue to appear in the literature, and biomaterial-based immunotherapies are entering clinical trials and human patients. It is unarguably an exciting time for cancer immunotherapy and biomaterial researchers, and further work seeks to understand the most critical design considerations in the development of the next-generation of immunotherapeutic biomaterials. This review will discuss recent advances in the delivery of immunotherapies from localized biomaterials, focusing on macroscale implantable and injectable systems. STATEMENT OF SIGNIFICANCE: Anti-cancer immunotherapies have shown exciting clinical results in the past few decades, yet they suffer from a few distinct limitations, such as poor delivery kinetics, narrow patient response profiles, and systemic side effects. Biomaterial systems are now being developed that can overcome many of these problems, allowing for localized adjuvant delivery, focused dose concentrations, and extended therapy presentation. The field of biocompatible carrier materials is uniquely suited to be combined with immunotherapy, promising to yield significant improvements in treatment outcomes and clinical care. In this review, the first pioneering efforts and most recent advances in biomaterials for immunotherapeutic applications are explored, with a specific focus on implantable and injectable biomaterials such as porous scaffolds, cryogels, and hydrogels.

Delivery technologies for cancer immunotherapy

Immunotherapy has become a powerful clinical strategy for treating cancer. The number of immunotherapy drug approvals has been increasing, with numerous treatments in clinical and preclinical development. However, a key challenge in the broad implementation of immunotherapies for cancer remains the controlled modulation of the immune system, as these therapeutics have serious adverse effects including autoimmunity and nonspecific inflammation. Understanding how to increase the response rates to various classes of immunotherapy is key to improving efficacy and controlling these adverse effects. Advanced biomaterials and drug delivery systems, such as nanoparticles and the use of T cells to deliver therapies, could effectively harness immunotherapies and improve their potency while reducing toxic side effects. Here, we discuss these research advances, as well as the opportunities and challenges for integrating delivery technologies into cancer immunotherapy, and we critically analyse the outlook for these emerging areas.

Local biomaterials-assisted cancer immunotherapy to trigger systemic antitumor responses

Cancer immunotherapy by educating or stimulating patients’ own immune systems to attack cancer cells has demonstrated promising therapeutic responses in the clinic.

Co-delivery of RNAi and chemokine by polyarginine nanocapsules enables the modulation of myeloid-derived suppressor cells

Myeloid-Derived Suppressor Cells (MDSCs), immunosuppressive cells that promote tumor growth, represent an attractive target in cancer immunotherapy. However, the clinical success of this strategy is limited by the lack of efficient drug delivery vehicles targeting this cell compartment. The objective of this work was to develop a delivery carrier, multilayer polymer nanocapsules, with the capacity to co-encapsulate two types of immunomodulatory drugs, a chemokine and an RNAi sequence, aimed at reverting MDSC-mediated immunosuppression. The chemokine CCL2, intended to attract monocyte-macrophage MDSCs, was encapsulated within the L2 inverse micellar aqueous domains of the lipid core of these nanocapsules. On the other hand, two different RNAi sequences that modulate the CCAAT/enhancer-binding protein beta (C/EBPβ) pathway, shC/EBPβ and miR 142-3p, were successfully associated to their polymer shell. These RNAi sequences were covered by subsequent layers of polyarginine and hyaluronic acid, thereby creating multi-layered assemblies that protected them and facilitated their targeted delivery. The in vitro studies performed in primary MDSCs cultures showed the capacity of miR 142-3p-loaded nanocapsules to reduce the highly immunosuppressive monocyte-macrophage subset. Additionally, the encapsulation of CCL2 within the nanocapsules induced a potent monocyte-macrophage chemoattraction that could be used to direct the therapy to these cell subsets. Finally, in vitro and in vivo studies showed the capacity of shC/EBPβ-loaded nanocapsules to downregulate C/EBPβ levels in MDSCs and to reduce monocyte differentiation into tumor-associated macrophages in an MCA-203 fibrosarcoma mice model. In conclusion, the multilayer polymer nanocapsules described here are efficient vehicles for the co-delivery of proteins and RNA, and are potential candidates as nanomedicines for the modulation of MDSCs.

Prevention of Type 1 Diabetes with Acetalated Dextran Microparticles Containing Rapamycin and Pancreatic Peptide P31

Type 1 diabetes (T1D) is a common autoimmune disease with no cure. T1D subjects are dependent on daily exogenous insulin administration, due to the loss of functional insulin-producing β cells. Needed are immunotherapies that prevent and/or treat T1D. One approach of immunotherapy is to administer an autoantigen to selectively tolerize diabetogenic effector T cells without global immunosuppression. To date, however, strategies of antigen-specific immunotherapy are largely ineffective in the clinic. Using an antigen-specific approach, a biodegradable polymeric delivery vehicle, acetalated dextran microparticles (Ace-DEX MPs), is applied and T1D development is prevented through coadministration of the immunosuppressant rapamycin and the diabetogenic peptide P31 (Rapa/P31/MPs), via alterations of both innate and adaptive immunity. Ex vivo, adoptively transferred CD4⁺ T cells exhibit reduced proliferation and an increased ratio of FoxP3⁺ to IFNγ⁺ T cells. In vitro analysis indicates dendritic cells exhibit a less mature phenotype following coculture with Rapa/P31/MPs, which results in reduced CD4⁺ T cell proliferation and proinflammatory cytokine production (IFNγ and IL-2), but promotes PD-1 expression. Together these results demonstrate Ace-DEX MP-based antigen-specific therapy effectively tolerizes diabetogenic CD4⁺ T cells to prevent T1D, thereby demonstrating one of the first successful attempts of T1D prevention using a single-formulation particulate delivery platform.

Injectable Hydrogels Coencapsulating Granulocyte-Macrophage Colony-Stimulating Factor and Ovalbumin Nanoparticles to Enhance Antigen Uptake Efficiency

The combination of an antigen and adjuvant has synergistic effects on an immune response. Coadministration of an antigen and a granulocyte-macrophage colony-stimulating factor (GM-CSF) hydrogel delivery system will afford a novel strategy for enhancement of an immune response because of the dual role of the hydrogel as a vaccine carrier with a sustained release and a platform for recruiting dendritic cells (DCs). Herein, an injectable poly(caprolactone)-poly(ethylene glycol)-poly(caprolactone) thermosensitive hydrogel coencapsulating GM-CSF and ovalbumin nanoparticles was developed to enhance antigen uptake efficiency. The GM-CSF released from the hydrogel ensured accumulation of DCs; this effect improved the antigen uptake efficiency with the targeted delivery to antigen-presenting cells. Furthermore, the dual delivery system induced a stronger immune effect, including higher CD8⁺ T proportion, interferon γ secretion, and a greater cytotoxic T lymphocyte response, which may benefit from the recruitment of DCs, increasing antigen residence time, and the controllable antigen release owing to the combined effect of the hydrogel and nanoparticles. Meanwhile, the real-time antigen delivery process in vivo was revealed by a noninvasive fluorescence imaging method. All of the results indicated that the visible dual delivery system may have a greater potential for the efficient and trackable vaccine delivery.

Lymph Node-Targeting Nanovaccine through Antigen-CpG Self-Assembly Potentiates Cytotoxic T Cell Activation

Therapeutic vaccines that arouse the cytotoxic T cell immune response to reject infected cells have been investigated extensively for treating disease. Due to the large amounts of resident antigen-presenting cells (APCs) and T cells in lymph nodes, great efforts have been made to explore the strategy of targeting lymph nodes directly with nanovaccines to activate T cells. However, these nanovaccines still have several problems, such as a low loading efficiency and compromised activity of antigens and adjuvants derived from traditional complicated preparation. There are also safety concerns about materials synthesized without FDA approval. Herein, we construct an assembled nanoparticle composed of an antigen (ovalbumin, OVA) and adjuvant (CpG) to ensure its safety and high loading efficiency. The activity of both components was well preserved due to the mild self-assembly process. The small size, narrow distribution, negative charge, and good stability of the nanoparticle endow these nanovaccines with superior capacity for lymph node targeting. Correspondingly, the accumulation at lymph nodes can be improved by 10-fold. Subsequently, due to the sufficient APC internalization and maturation in lymph nodes, ~60% of T cells are stimulated to proliferate and over 70% of target cells are specifically killed. Based on the effective and quick cellular immune response, the assembled nanoparticles exhibit great potential as therapeutic vaccines.

Improving the clinical impact of biomaterials in cancer immunotherapy

Immunotherapies for cancer have progressed enormously over the past few decades, and hold great promise for the future. The successes of these therapies, with some patients showing durable and complete remission, demonstrate the power of harnessing the immune system to eradicate tumors. However, the effectiveness of current immunotherapies is limited by hurdles ranging from immunosuppressive strategies employed by tumors, to inadequate specificity of existing therapies, to heterogeneity of disease. Further, the vast majority of approved immunotherapies employ systemic delivery of immunomodulators or cells that make addressing some of these challenges more difficult. Natural and synthetic biomaterials–such as biocompatible polymers, self-assembled lipid particles, and implantable biodegradable devices–offer unique potential to address these hurdles by harnessing the benefits of therapeutic targeting, tissue engineering, co-delivery, controlled release, and sensing. However, despite the enormous investment in new materials and nanotechnology, translation of these ideas to the clinic is still an uncommon outcome. Here we review the major challenges facing immunotherapies and discuss how the newest biomaterials and nanotechnologies could help overcome these challenges to create new clinical options for patients.

Administration of signalling molecules dictates stem cell homing for in situ regeneration

Ex vivo-expanded stem cells have long been a cornerstone of biotherapeutics and have attracted increasing attention for treating intractable diseases and improving tissue regeneration. However, using exogenous cellular materials to develop restorative treatments for large numbers of patients has become a major concern for both economic and safety reasons. Advances in cell biological research over the past two decades have expanded the potential for using endogenous stem cells during wound healing processes, and in particular, recent insight into stem cell movement and homing has prompted regenerative research and therapy based on recruiting endogenous cells. Inspired by the natural healing process, artificial administration of specific chemokines as signals systemically or at the injury site, typically using biomaterials as vehicles, is a state-of-the-art strategy that potentiates stem cell homing and recreates an anti-inflammatory and immunomodulatory microenvironment to enhance in situ tissue regeneration. However, pharmacologically coaxing endogenous stem cells to act as therapeutics in the field of biomedicine remains in the early stages; its efficacy is limited by the lack of innovative methodologies for chemokine presentation and release. This review describes how to direct the homing of endogenous stem cells via the administration of specific signals, with a particular emphasis on targeted signalling molecules that regulate this homing process, to enhance in situ tissue regeneration. We also provide an outlook on and critical considerations for future investigations to enhance stem cell recruitment and harness the reparative potential of these recruited cells as a clinically relevant cell therapy.

Functional and Biomimetic Materials for Engineering of the Three-Dimensional Cell Microenvironment

The cell microenvironment has emerged as a key determinant of cell behavior and function in development, physiology, and pathophysiology. The extracellular matrix (ECM) within the cell microenvironment serves not only as a structural foundation for cells but also as a source of three-dimensional (3D) biochemical and biophysical cues that trigger and regulate cell behaviors. Increasing evidence suggests that the 3D character of the microenvironment is required for development of many critical cell responses observed in vivo, fueling a surge in the development of functional and biomimetic materials for engineering the 3D cell microenvironment. Progress in the design of such materials has improved control of cell behaviors in 3D and advanced the fields of tissue regeneration, in vitro tissue models, large-scale cell differentiation, immunotherapy, and gene therapy. However, the field is still in its infancy, and discoveries about the nature of cell-microenvironment interactions continue to overturn much early progress in the field. Key challenges continue to be dissecting the roles of chemistry, structure, mechanics, and electrophysiology in the cell microenvironment, and understanding and harnessing the roles of periodicity and drift in these factors. This review encapsulates where recent advances appear to leave the ever-shifting state of the art, and it highlights areas in which substantial potential and uncertainty remain.

Synthetic immune niches for cancer immunotherapy

Cancer immunotherapy can successfully promote long-term anticancer immune responses, although there is still only a limited number of patients who benefit from such treatment, and it can sometimes have severe treatment-associated adverse events. Compared with systemic immunomodulation, local immunomodulation may enable more effective treatment at lower doses and, at the same time, prevent systemic toxicity. Local delivery of engineered three-dimensional scaffolds may fulfil this role by acting as synthetic immune niches that boost anticancer immunity. In this Opinion article, we highlight the potential of scaffold-based adoptive cell transfer and scaffold-based cancer vaccines that, although applied locally, can promote systemic antitumour immunity. Furthermore, we discuss how scaffold-based cancer immunotherapy may contribute to the development of the next generation of cancer treatments.

Bioengineering of Artificial Antigen Presenting Cells and Lymphoid Organs

The immune system protects the body against a wide range of infectious diseases and cancer by leveraging the efficiency of immune cells and lymphoid organs. Over the past decade, immune cell/organ therapies based on the manipulation, infusion, and implantation of autologous or allogeneic immune cells/organs into patients have been widely tested and have made great progress in clinical applications. Despite these advances, therapy with natural immune cells or lymphoid organs is relatively expensive and time-consuming. Alternatively, biomimetic materials and strategies have been applied to develop artificial immune cells and lymphoid organs, which have attracted considerable attentions. In this review, we survey the latest studies on engineering biomimetic materials for immunotherapy, focusing on the perspectives of bioengineering artificial antigen presenting cells and lymphoid organs. The opportunities and challenges of this field are also discussed.

Tailoring Biomaterials for Cancer Immunotherapy: Emerging Trends and Future Outlook

Cancer immunotherapy, as a paradigm shift in cancer treatment, has recently received tremendous attention. The active cancer vaccination, immune checkpoint blockage (ICB) and chimeric antigen receptor (CAR) for T-cell-based adoptive cell transfer are among these developments that have achieved a significant increase in patient survival in clinical trials. Despite these advancements, emerging research at the interdisciplinary interface of cancer biology, immunology, bioengineering, and materials science is important to further enhance the therapeutic benefits and reduce side effects. Here, an overview of the latest studies on engineering biomaterials for the enhancement of anticancer immunity is given, including the perspectives of delivery of immunomodulatory therapeutics, engineering immune cells, and constructing immune-modulating scaffolds. The opportunities and challenges in this field are also discussed.

Emerging Trends in Micro- and Nanoscale Technologies in Medicine: From Basic Discoveries to Translation

We discuss the state of the art and innovative micro- and nanoscale technologies that are finding niches and opening up new opportunities in medicine, particularly in diagnostic and therapeutic applications. We take the design of point-of-care applications and the capture of circulating tumor cells as illustrative examples of the integration of micro- and nanotechnologies into solutions of diagnostic challenges. We describe several novel nanotechnologies that enable imaging cellular structures and molecular events. In therapeutics, we describe the utilization of micro- and nanotechnologies in applications including drug delivery, tissue engineering, and pharmaceutical development/testing. In addition, we discuss relevant challenges that micro- and nanotechnologies face in achieving cost-effective and widespread clinical implementation as well as forecasted applications of micro- and nanotechnologies in medicine.

Mimicking biological functionality with polymers for biomedical applications

The vast opportunities for biomaterials design and functionality enabled by mimicking nature continue to stretch the limits of imagination. As both biological understanding and engineering capabilities develop, more sophisticated biomedical materials can be synthesized that have multifaceted chemical, biological and physical characteristics designed to achieve specific therapeutic goals. Mimicry is being used in the design of polymers for biomedical applications that are required locally in tissues, systemically throughout the body, and at the interface with tissues.

Proteomic composition and immunomodulatory properties of urinary bladder matrix scaffolds in homeostasis and injury

Urinary bladder matrix (UBM) is used clinically for management of wounds and reinforcement of surgical soft tissue repair, among other applications. UBM consists of the lamina propria and basal lamina of the porcine urinary bladder, and is decellularized as part of the process to manufacture the medical device. UBM is composed mainly of Collagen I, but also contains a wide variety of fibrillar and basement membrane collagens, glycoproteins, proteoglycans and ECM-associated factors. Upon application of the biomaterial in a traumatic or non-traumatic setting in a mouse model, there is a cascade of immune cells that respond to the damaged tissue and biomaterial. Here, through the use of multicolor flow cytometry, we describe the various cells that infiltrate the UBM scaffold in a subcutaneous and volumetric muscle injury model. A wide variety of immune cells are found in the UBM scaffold immune microenvironment (SIM) including F4/80⁺ macrophages, CD11c⁺ dendritic cells, CD3⁺ T cells and CD19⁺ B cells. A systemic IL-4 upregulation and a local M2-macrophage response were observed in the proximity of the implanted UBM. The recruitment and activation of these cells is dependent upon signals from the scaffold and communication between the different cell types present.

Adjuvant-Loaded Subcellular Vesicles Derived From Disrupted Cancer Cells for Cancer Vaccination

Targeted subunit vaccines for cancer immunotherapy do not capture tumor antigenic complexity, and approaches employing tumor lysate are often limited by inefficient antigen uptake and presentation, and low immunogenicity. Here, whole cancer cells are processed to generate antigen-rich, membrane-enclosed subcellular particles, termed "reduced cancer cells", that reflect the diversity and breadth of the parent cancer cell antigen repertoire, and can be loaded with disparate adjuvant payloads. These vesicular particles enhance the uptake of the adjuvant payload, and potentiate the activation of primary dendritic cells in vitro. Similarly, reduced cancer cell-associated antigens are more efficiently presented by primary dendritic cells in vitro than their soluble counterparts or lysate control. In mice, vaccination using adjuvant-loaded reduced cancer cells facilitates the induction of antigen-specific cellular and humoral immune responses. Taken together, these observations demonstrate that adjuvant-loaded reduced cancer cells could be utilized in cancer vaccines as an alternative to lysate.

Developing a pro-regenerative biomaterial scaffold microenvironment requires T helper 2 cells

Immune-mediated tissue regeneration driven by a biomaterial scaffold is emerging as an innovative regenerative strategy to repair damaged tissues. We investigated how biomaterial scaffolds shape the immune microenvironment in traumatic muscle wounds to improve tissue regeneration. The scaffolds induced a pro-regenerative response, characterized by an mTOR/Rictor-dependent T helper 2 pathway that guides interleukin-4-dependent macrophage polarization, which is critical for functional muscle recovery. Manipulating the adaptive immune system using biomaterials engineering may support the development of therapies that promote both systemic and local pro-regenerative immune responses, ultimately stimulating tissue repair.

Biomaterials for enhancing anti-cancer immunity

Cancer immunotherapy is becoming a standard approach to treat many cancers. However, shortcomings of current methods limit therapeutic benefit in many patients. Rationally designed biomaterial strategies to deliver immune modulatory drugs can potentially show improved safety profiles, while providing multifunctional and spatiotemporally controlled signals to immune cells to improve their anti-cancer activity. This brief review describes biomaterials-based strategies that enhance immune cell function at various tissue sites to improve anti-cancer immunity. Continued collaboration between bioengineers, immunologists, industry, and clinicians is required for biomaterial-based immunotherapy strategies to continue moving to the clinic.

The effect of surface modification of mesoporous silica micro-rod scaffold on immune cell activation and infiltration

Biomaterial scaffold based vaccines show significant potential in generating potent antigen-specific immunity. However, the role of the scaffold surface chemistry in initiating and modulating the immune response is not well understood. In this study, a mesoporous silica micro-rod (MSR) scaffold was modified with PEG, PEG-RGD and PEG-RDG groups. PEG modification significantly enhanced BMDC activation marker up-regulation and IL-1β production in vitro, and innate immune cell infiltration in vivo. PEG-RGD MSRs and PEG-RDG MSRs displayed decreased inflammation compared to PEG MSRs, and the effect was not RGD specific. Finally, the Nlrp3 inflammasome was found to be necessary for MSR stimulated IL-1β production in vitro and played a key role in regulating immune cell infiltration in vivo. These findings suggest that simply modulating the surface chemistry of a scaffold can regulate its immune cell infiltration profile and have implications for the design and development of new material based vaccines.

Biomaterials and emerging anticancer therapeutics: engineering the microenvironment

The microenvironment is increasingly recognized to have key roles in cancer, and biomaterials provide a means to engineer microenvironments both in vitro and in vivo to study and manipulate cancer. In vitro cancer models using 3D matrices recapitulate key elements of the tumour microenvironment and have revealed new aspects of cancer biology. Cancer vaccines based on some of the same biomaterials have, in parallel, allowed for the engineering of durable prophylactic and therapeutic anticancer activity in preclinical studies, and some of these vaccines have moved to clinical trials. The impact of biomaterials engineering on cancer treatment is expected to further increase in importance in the years to come.

Injectable, Pore-Forming Hydrogels for In Vivo Enrichment of Immature Dendritic Cells

Biomaterials-based vaccines have emerged as a powerful method to evoke potent immune responses directly in vivo, without the need for ex vivo cell manipulation, and modulating dendritic cell (DC) responses in a noninflammatory context could enable the development of tolerogenic vaccines to treat autoimmunity. This study describes the development of a noninflammatory, injectable hydrogel system to locally enrich DCs in vivo without inducing their maturation or activation, as a first step toward this goal. Alginate hydrogels that form pores in situ are characterized and used as a physical scaffold for cell infiltration. These gels are also adapted to control the release of granulocyte-macrophage colony stimulating factor (GM-CSF), a potent inducer of DC recruitment and proliferation. In vivo, sustained release of GM-CSF from the pore-forming gels leads to the accumulation of millions of cells in the material. These cells are highly enriched in CD11b(+) CD11c(+) DCs, and further analysis of cell surface marker expression indicates these DCs are immature. This study demonstrates that a polymeric delivery system can mediate the accumulation of a high number and percentage of immature DCs, and may provide the basis for further development of materials-based, therapeutic vaccines.

Engineered Materials for Cancer Immunotherapy

Immunotherapy is a promising treatment modality for cancer as it can promote specific and durable anti-cancer responses. However, limitations to current approaches remain. Therapeutics administered as soluble injections often require high doses and frequent re-dosing, which can result in systemic toxicities. Soluble bolus-based vaccine formulations typically elicit weak cellular immune responses, limiting their use for cancer. Current methods for ex vivo T cell expansion for adoptive T cell therapies are suboptimal, and achieving high T cell persistence and sustained functionality with limited systemic toxicity following transfer remains challenging. Biomaterials can play important roles in addressing some of these limitations. For example, nanomaterials can be employed as vehicles to deliver immune modulating payloads to specific tissues, cells, and cellular compartments with minimal off-target toxicity, or to co-deliver antigen and danger signal in therapeutic vaccine formulations. Alternatively, micro-to macroscale materials can be employed as devices for controlled molecular and cellular delivery, or as engineered microenvironments for recruiting and programming immune cells in situ. Recent work has demonstrated the potential for combining cancer immunotherapy and biomaterials, and the application of biomaterials to cancer immunotherapy is likely to enable the development of effective next-generation platforms. This review discusses the application of engineered materials for the delivery of immune modulating agents to the tumor microenvironment, therapeutic cancer vaccination, and adoptive T cell therapy.