Controlled Delivery of Immunomodulators from a Biomaterial Scaffold Niche to Induce a Tolerogenic Phenotype in Human Dendritic Cells

Drug polymer conjugates: Average release time from thin films

The reaction-diffusion problem describing the release of drugs conjugated through labile bonds to polymeric thin films has a known analytical solution, when the reaction kinetics is of first order. Using this solution, an exact formula is derived for the average release time of the system. This simple expression provides the characteristic time of release tav as the sum of the corresponding average diffusion time plus the inverse reaction rate constant: tav=(1/12)⋅(L2/D)+(1/k), where L is the slab thickness, D the diffusion coefficient, and k the reaction rate constant. The former term dominates in a diffusion-controlled release, while the latter one in a reaction-controlled delivery. The crossover regime is exactly described by their sum. The obtained result for the average release time is verified by direct numerical integration through the drug release profiles of the analytical solution. The value of fractional drug release at the characteristic average time is between 60-64%. These results can be used for the design of polymer-drug conjugates with a desired delivery time scale, as well as for the experimental determination of the values of microscopic parameters D and k in a conjugated system of interest.

Recent Advancements in Bone Tissue Engineering: Integrating Smart Scaffold Technologies and Bio-Responsive Systems for Enhanced Regeneration

In exploring the challenges of bone repair and regeneration, this review evaluates the potential of bone tissue engineering (BTE) as a viable alternative to traditional methods, such as autografts and allografts. Key developments in biomaterials and scaffold fabrication techniques, such as additive manufacturing and cell and bioactive molecule-laden scaffolds, are discussed, along with the integration of bio-responsive scaffolds, which can respond to physical and chemical stimuli. These advancements collectively aim to mimic the natural microenvironment of bone, thereby enhancing osteogenesis and facilitating the formation of new tissue. Through a comprehensive combination of in vitro and in vivo studies, we scrutinize the biocompatibility, osteoinductivity, and osteoconductivity of these engineered scaffolds, as well as their interactions with critical cellular players in bone healing processes. Findings from scaffold fabrication techniques and bio-responsive scaffolds indicate that incorporating nanostructured materials and bioactive compounds is particularly effective in promoting the recruitment and differentiation of osteoprogenitor cells. The therapeutic potential of these advanced biomaterials in clinical settings is widely recognized and the paper advocates continued research into multi-responsive scaffold systems.

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.

Recent advances in biomaterial-assisted cell therapy

With the outstanding achievement of chimeric antigen receptor (CAR)-T cell therapy in the clinic, cell-based medicines have attracted considerable attention for biomedical applications and thus generated encouraging progress. As the basic construction unit of organisms, cells harbor low immunogenicity, desirable compatibility, and a strong capability of crossing various biological barriers. However, there is still a long way to go to fix significant bottlenecks for their clinical translation, such as facile preparation, strict stability requirements, scale-up manufacturing, off-target toxicity, and affordability. The rapid development of biotechnology and engineering approaches in materials sciences has provided an ideal platform to assist cell-based therapeutics for wide application in disease treatments by overcoming these issues. Herein, we survey the most recent advances of various cells as bioactive ingredients and outline the roles of biomaterials in developing cell-based therapeutics. Besides, a perspective of cell therapies is offered with a particular focus on biomaterial-involved development of cell-based biopharmaceuticals.

Immune-instructive materials as new tools for immunotherapy

Immune instructive materials, are materials with the ability to modulate or mimic the function of immune cells, provide exciting opportunities for developing new therapies in many areas including medical devices, chronic inflammation, cancer, and autoimmune diseases. In this review we highlight some of the latest research involving material-based strategies for modulating macrophage phenotype and dendritic cell function, as well as a brief description on biomaterial use in T cell and natural killer cell engineering. We highlight studies on material topography, size, shape and surface chemistry to reduce inflammation, along with scaffold and hydrogel delivery systems that are used for modulating DC phenotype and influencing T cell polarization. Artificial antigen presenting cells are also reviewed as a promising approach to cancer immunotherapy.

Dendritic cells support a proliferative antigen-specific T-cell response in the presence of poly(lactic-co-glycolic acid)

Biomaterials are known to modulate immune cell functions, which subsequently determine the host inflammatory and immune responses. Poly(lactic-co-glycolic acid) or PLGA, a biodegradable and biocompatible biomaterial, induces a pro-inflammatory, mature phenotype in antigen presentation cells, namely dendritic cells (DCs) in vitro. In vivo, PLGA can boost the humoral immune response to a co-delivered model antigen, a phenomenon known as the PLGA-adjuvant effect. This study elucidates the link between PLGA's effect on the DC phenotype in vitro and its adjuvant effect in vivo using the CD11c-DTR mouse model. These mice undergo conditional ablation of DCs upon treatment with diphtheria toxin. To measure immune activation, the mice were first given ovalbumin (OVA)-reactive T cells from OT-II/OT-I mice. Later, the same mice received subcutaneous OVA-loaded PLGA scaffold implants. In response to the scaffold implants, OVA-reactive OT-II CD4+ T cells showed decreased proliferation in the absence of CD11c+ DCs, indicating an attenuation of the PLGA-adjuvant effect. Furthermore, PLGA may also influence the antigen cross-presentation function of DCs, as evident with the lowered OVA-reactive OT-I CD8+ T-cell response. Understanding the immunomodulatory ability of biomaterials in the context of DCs will aid in designing improved DC-based immunotherapies against infectious diseases and cancer.

Local delivery strategies to restore immune homeostasis in the context of inflammation

Immune homeostasis is maintained by a precise balance between effector immune cells and regulatory immune cells. Chronic deviations from immune homeostasis, driven by a greater ratio of effector to regulatory cues, can promote the development and propagation of inflammatory diseases/conditions (i.e., autoimmune diseases, transplant rejection, etc.). Current methods to treat chronic inflammation rely upon systemic administration of non-specific small molecules, resulting in broad immunosuppression with unwanted side effects. Consequently, recent studies have developed more localized and specific immunomodulatory approaches to treat inflammation through the use of local biomaterial-based delivery systems. In particular, this review focuses on (1) local biomaterial-based delivery systems, (2) common materials used for polymeric-delivery systems and (3) emerging immunomodulatory trends used to treat inflammation with increased specificity.

Current knowledge of immunomodulation strategies for chronic skin wound repair

In orchestrating the wound healing process, the immune system plays a critical role. Hence, controlling the immune system to repair skin defects is an attractive approach. The highly complex immune system includes the coordinated actions of several immune cells, which can produce various inflammatory and antiinflammatory cytokines and affect the healing of skin wounds. This process can be optimized using biomaterials, bioactive molecules, and cell delivery. The present review discusses various immunomodulation strategies for supporting the healing of chronic wounds. In this regard, following the evolution of the immune system and its role in the wound healing mechanism, the interaction between the extracellular mechanism and immune cells for acceleration wound healing will be firstly investigated. Consequently, the immune-based chronic wounds will be briefly examined and the mechanism of progression, and conventional methods of their treatment are evaluated. In the following, various biomaterials-based immunomodulation strategies are introduced to stimulate and control the immune system to treat and regenerate skin defects. Other effective methods of controlling the immune system in wound healing which is the release of bioactive agents (such as antiinflammatory, antigens, and immunomodulators) and stem cell therapy at the site of injury are reviewed.

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Engineering Strategies for Allogeneic Solid Tissue Acceptance

Advances in allogeneic transplantation of solid organs and tissues depend on our understanding of mechanisms that mediate the prevention of graft rejection. For the past decades, clinical practice has established guidelines to prevent allograft rejection, which mostly rely on the intake of nontargeted immunosuppressants as the gold standard. However, such lifelong regimens have been reported to trigger severe morbidities and commonly fail in preventing late allograft loss. In this review, the biology of allogeneic rejection and self-tolerance is analyzed, as well as the mechanisms of cellular-based therapeutics driving suppression and/or tolerance. Bioinspired engineering strategies that take advantage of cells, biomaterials, or combinations thereof to prevent allograft rejection are addressed, as well as biological mechanisms that drive their efficacy.