Biomaterial-assisted scalable cell production for cell therapy

Biomaterials for Cell Manufacturing

Cell therapies, potent populations of cells used to treat disease and injury, can be strategically manufactured with biomaterial intervention to improve clinical translation. In this viewpoint, we discuss biomaterial design and integration into cell manufacturing steps to achieve three main goals: scale-up, phenotype control, and selection of potent cells. Material properties can be engineered to influence the cell-biomaterial interface and, therefore, impart desirable cell behavior such as growth, secretory activity, and differentiation. Future directions for the field should capitalize on the combinatorial design of biomaterial properties to yield highly specific and potent cell populations. Furthermore, future biomaterials could contribute to novel high-throughput cell separation technologies that can individually select the most therapeutically relevant cells within a produced batch.

Bioprinting of Cells, Organoids and Organs-on-a-Chip Together with Hydrogels Improves Structural and Mechanical Cues

The 3D bioprinting technique has made enormous progress in tissue engineering, regenerative medicine and research into diseases such as cancer. Apart from individual cells, a collection of cells, such as organoids, can be printed in combination with various hydrogels. It can be hypothesized that 3D bioprinting will even become a promising tool for mechanobiological analyses of cells, organoids and their matrix environments in highly defined and precisely structured 3D environments, in which the mechanical properties of the cell environment can be individually adjusted. Mechanical obstacles or bead markers can be integrated into bioprinted samples to analyze mechanical deformations and forces within these bioprinted constructs, such as 3D organoids, and to perform biophysical analysis in complex 3D systems, which are still not standard techniques. The review highlights the advances of 3D and 4D printing technologies in integrating mechanobiological cues so that the next step will be a detailed analysis of key future biophysical research directions in organoid generation for the development of disease model systems, tissue regeneration and drug testing from a biophysical perspective. Finally, the review highlights the combination of bioprinted hydrogels, such as pure natural or synthetic hydrogels and mixtures, with organoids, organoid-cell co-cultures, organ-on-a-chip systems and organoid-organ-on-a chip combinations and introduces the use of assembloids to determine the mutual interactions of different cell types and cell-matrix interferences in specific biological and mechanical environments.

Triple-Hybrid BioScaffold Based on Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates: Preparation, Characterization of Physiochemical and Biopharmaceutical Properties

Bioscaffolds, which promote cell regeneration and restore tissues' functions, have emerged as significant need in clinic. The hybrid of several biomaterials in a bioscaffold renders clinically advanced and relevant properties for applications yet add challenges in cost efficiency, production, and clinical investigation. This study proposes a facile and sustainable method to formulate a triple-hybrid bioscaffold based on Vietnamese cocoon origin Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates (nano-BCP) that can be easily molded, has high porosity (55-80%), and swelling capacity that facilitates cell proliferation and nutrient diffusion. Notably, their mechanical properties, in particular compressive strength, can easily be tuned in a range from 50 - 200 kPa by changing the amount of nano-BCP addition, which is comparable to the successful precedents for productive cell regeneration. The latter parts investigate the biopharmaceutical properties of a representative bioscaffold, including drug loading and release studies with two kinds of active compounds, salmon calcitonin and methylprednisolone. Furthermore, the bioscaffold is highly biocompatible as the results of hemocompatibility and hemostasis tests, as well as ovo chick chorioallantoic membrane investigation. The findings of the study suggest the triple-hybrid scaffold as a promising platform for multi-functional drug delivery and bone defect repair.

Advances, challenges, and future directions in the clinical translation of ECM biomaterials for regenerative medicine applications

Extracellular Matrix (ECM) scaffolds and biomaterials have been widely used for decades across a variety of diverse clinical applications and have been implanted in millions of patients worldwide. ECM-based biomaterials have been especially successful in soft tissue repair applications but their utility in other clinical applications such as for regeneration of bone or neural tissue is less well understood. The beneficial healing outcome with the use of ECM biomaterials is the result of their biocompatibility, their biophysical properties and their ability to modify cell behavior after injury. As a consequence of successful clinical outcomes, there has been motivation for the development of next-generation formulations of ECM materials ranging from hydrogels, bioinks, powders, to whole organ or tissue scaffolds. The continued development of novel ECM formulations as well as active research interest in these materials ensures a wealth of possibilities for future clinical translation and innovation in regenerative medicine. The clinical translation of next generation formulations ECM scaffolds faces predictable challenges such as manufacturing, manageable regulatory pathways, surgical implantation, and the cost required to address these challenges. The current status of ECM-based biomaterials, including clinical translation, novel formulations and therapies currently under development, and the challenges that limit clinical translation of ECM biomaterials are reviewed herein.

Converging bioprinting and organoids to better recapitulate the tumor microenvironment

Bioprinting shows excellent potential for preclinical tumor modeling, with significant advantages over 2D cell cultures in replicating the tumor microenvironment (TME). Recently, the use of tumor organoids in bioprinting models has emerged as a groundbreaking approach to simulate volumetric tumor tissues. This synergetic fabrication method leverages the advantages of the spatial and geometric control of bioprinting to assemble heterogeneous TME components, while tumor organoids maintain collective cell behaviors. In this review, we provide a landscape of the latest progress on the convergence of 3D bioprinting and tumor organoids. Furthermore, we discuss the potential to incorporate organ-on-a-chip with bioprinting tumor organoids to improve the biomimicry and predictability of therapeutic performance. Lastly, we address the challenges to personalized medicine and predictive clinical integration.

In vitro encapsulation and expansion of T and CAR-T cells using 3D synthetic thermo-responsive matrices

Suspension cell culture and rigid commercial substrates are the most common methods to clinically manufacture therapeutic CAR-T cells ex vivo. However, suspension culture and nano/micro-scale commercial substrates poorly mimic the microenvironment where T cells naturally develop, leading to profound impacts on cell proliferation and phenotype. To overcome this major challenge, macro-scale substrates can be used to emulate that environment with higher precision. This work employed a biocompatible thermo-responsive material with tailored mechanical properties as a potential synthetic macro-scale scaffold to support T cell encapsulation and culture. Cell viability, expansion, and phenotype changes were assessed to study the effect of two thermo-responsive hydrogel materials with stiffnesses of 0.5 and 17 kPa. Encapsulated Pan-T and CAR-T cells were able to grow and physically behave similar to the suspension control. Furthermore, matrix stiffness influenced T cell behavior. In the softer polymer, T cells had higher activation, differentiation, and maturation after encapsulation obtaining significant cell numbers. Even when terpolymer encapsulation affected the CAR-T cell viability and expansion, CAR T cells expressed favorable phenotypical profiles, which was supported with cytokines and lactate production. These results confirmed the biocompatibility of the thermo-responsive hydrogels and their feasibility as a promising 3D macro-scale scaffold for in vitro T cell expansion that could potentially be used for cell manufacturing process.

Neural stem cell therapies for spinal cord injury repair: an update on recent preclinical and clinical advances

Traumatic spinal cord injury (SCI) is a leading cause of lifelong disabilities. Permanent sensory, motor and autonomic impairments after SCI are substantially attributed to degeneration of spinal cord neurons and axons, and disintegration of neural network. To date, minimal regenerative treatments are available for SCI with an unmet need for new therapies to reconstruct the damaged spinal cord neuron-glia network and restore connectivity with the supraspinal pathways. Multipotent neural precursor cells (NPCs) have a unique capacity to generate neurons, oligodendrocytes and astrocytes. Due to this capacity, NPCs have been an attractive cell source for cellular therapies for SCI. Transplantation of NPCs has been extensively tested in preclinical models of SCI in the past two decades. These studies have identified opportunities and challenges associated with NPC therapies. While NPCs have the potential to promote neuroregeneration through various mechanisms, their low long-term survival and integration within the host injured spinal cord limit the functional benefits of NPC-based therapies for SCI. To address this challenge, combinatorial strategies have been developed to optimize the outcomes of NPC therapies by enriching SCI microenvironment through biomaterials, genetic and pharmacological therapies. In this review, we will provide an in-depth discussion on recent advances in preclinical NPC-based therapies for SCI. We will discuss modes of actions and mechanism by which engrafted NPCs contribute to the repair process and functional recovery. We will also provide an update on current clinical trials and new technologies that have facilitated preparation of medical-grade human NPCs suitable for transplantation in clinical studies.

Recent progresses in natural based therapeutic materials for Alzheimer's disease

Alzheimer's disease is a neurological disorder that causes increased memory loss, mood swings, behavioral disorders, and disruptions in daily activities. Polymer scaffolds for the brain have been grown under laboratory, physiological, and pathological circumstances because of the limitations of conventional treatments for patients with central nervous system diseases. The blood-brain barrier prevents medications from entering the brain, challenging AD treatment. Numerous biomaterials such as biomolecules, polymers, inorganic metals, and metal oxide nanoparticles have been used to transport therapeutic medicines into the nervous system. Incorporating biocompatible materials that support neurogenesis through a combination of topographical, pharmacological, and mechanical stimuli has also shown promise for the transfer of cells to replenish dopaminergic neurons. Components made of naturally occurring biodegradable polymers are appropriate for the regeneration of nerve tissue. The ability of natural-based materials (biomaterials) has been shown to promote endogenous cell development after implantation. Also, strategic functionalization of polymeric nanocarriers could be employed for treating AD. In particular, nanoparticles could resolve Aβ aggregation and thus help cure Alzheimer's disease. Drug moieties can be effectively directed to the brain by utilizing nano-based systems and diverse colloidal carriers, including hydrogels and biodegradable scaffolds. Notably, early investigations employing neural stem cells have yielded promising results, further emphasizing the potential advancements in this field. Few studies have fully leveraged the combination of cells with cutting-edge biomaterials. This study provides a comprehensive overview of prior research, highlighting the pivotal role of biomaterials as sophisticated drug carriers. It delves into various intelligent drug delivery systems, encompassing pH and thermo-triggered mechanisms, polymeric and lipid carriers, inorganic nanoparticles, and other vectors. The discussion synthesizes existing knowledge and underscores the transformative impact of these biomaterials in devising innovative strategies, augmenting current therapeutic methodologies, and shaping new paradigms in the realm of Alzheimer's disease treatment.

Enhancing regenerative medicine: the crucial role of stem cell therapy

Stem cells offer new therapeutic avenues for the repair and replacement of damaged tissues and organs owing to their self-renewal and multipotent differentiation capabilities. In this paper, we conduct a systematic review of the characteristics of various types of stem cells and offer insights into their potential applications in both cellular and cell-free therapies. In addition, we provide a comprehensive summary of the technical routes of stem cell therapy and discuss in detail current challenges, including safety issues and differentiation control. Although some issues remain, stem cell therapy demonstrates excellent potential in the field of regenerative medicine and provides novel tactics and methodologies for managing a wider spectrum of illnesses and traumas.

Emerging advances in hydrogel-based therapeutic strategies for tissue regeneration

Significant developments in cell therapy and biomaterial science have broadened the therapeutic landscape of tissue regeneration. Tissue damage is a complex biological process in which different types of cells play a specific role in repairing damaged tissues and growth factors strictly regulate the activity of these cells. Hydrogels have become promising biomaterials for tissue regeneration if appropriate materials are selected and the hydrogel properties are well-regulated. Importantly, they can be used as carriers for living cells and growth factors due to the high water-holding capacity, high permeability, and good biocompatibility of hydrogels. Cell-loaded hydrogels can play an essential role in treating damaged tissues and open new avenues for cell therapy. There is ample evidence substantiating the ability of hydrogels to facilitate the delivery of cells (stem cell, macrophage, chondrocyte, and osteoblast) and growth factors (bone morphogenetic protein, transforming growth factor, vascular endothelial growth factor and fibroblast growth factor). This paper reviewed the latest advances in hydrogels loaded with cells or growth factors to promote the reconstruction of tissues. Furthermore, we discussed the shortcomings of the application of hydrogels in tissue engineering to promote their further development.

Potential effects of biomaterials on macrophage function and their signalling pathways

The use of biomaterials in biomedicine and healthcare has increased in recent years. Macrophages are the primary immune cells that induce inflammation and tissue repair after implantation of biomaterials. Given that macrophages exhibit high heterogeneity and plasticity, the influence of biomaterials on macrophage phenotype should be considered a crucial evaluation criterion during the development of novel biomaterials. This review provides a comprehensive summary of the physicochemical, biological, and dynamic characteristics of biomaterials that drive the regulation of immune responses in macrophages. The mechanisms involved in the interaction between macrophages and biomaterials, including endocytosis, receptors, signalling pathways, integrins, inflammasomes and long non-coding RNAs, are summarised in this review. In addition, research prospects of the interaction between macrophages and biomaterials are discussed. An in-depth understanding of mechanisms underlying the spatiotemporal changes in macrophage phenotype induced by biomaterials and their impact on macrophage polarization can facilitate the identification and development of novel biomaterials with superior performance. These biomaterials may be used for tissue repair and regeneration, vaccine or drug delivery and immunotherapy.

A BMP-2-triggered in vivo osteo-organoid for cell therapy

Cell therapies and regenerative medicine interventions require an adequate source of therapeutic cells. Here, we demonstrate that constructing in vivo osteo-organoids by implanting bone morphogenetic protein-2-loaded scaffolds into the internal muscle pocket near the femur of mice supports the growth and subsequent harvest of therapeutically useful cells including hematopoietic stem/progenitor cells (HSPCs), mesenchymal stem cells (MSCs), lymphocytes, and myeloid cells. Profiling of the in vivo osteo-organoid maturation process delineated three stages-fibroproliferation, osteochondral differentiation, and marrow generation-each of which entailed obvious changes in the organoid structure and cell type distribution. The MSCs harvested from the osteochondral differentiation stage mitigated carbon tetrachloride (CCl₄)-induced chronic liver fibrosis in mice, while HSPCs and immune cells harvested during the marrow generation stage rapidly and effectively reconstituted the impaired peripheral and solid immune organs of irradiated mice. These findings demonstrate the therapeutic potentials of in vivo osteo-organoid-derived cells in cell therapies.

Targeted therapy in Coronavirus disease 2019 (COVID-19): Implication from cell and gene therapy to immunotherapy and vaccine

Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is a highly pathogenic and transmissible virus. Infection caused by SARS-CoV-2 known as Coronavirus disease 2019 (COVID-19) can be severe, especially among high risk populations affected of underlying medical conditions. COVID-19 is characterized by the severe acute respiratory syndrome, a hyper inflammatory syndrome, vascular injury, microangiopathy and thrombosis. Antiviral drugs and immune modulating methods has been evaluated. So far, a particular therapeutic option has not been approved for COVID-19 and a variety of treatments have been studied for COVID-19 including, current treatment such as oxygen therapy, corticosteroids, antiviral agents until targeted therapy and vaccines which are diverse in each patient and have various outcomes. According to the findings of different in vitro and in vivo studies, some novel approach such as gene editing, cell based therapy, and immunotherapy may have significant potential in the treatment of COVID-19. Based on these findings, this paper aims to review the different strategies of treatment against COVID-19 and provide a summary from traditional and newer methods in curing COVID-19.

Nonmulberry silk fibroin-based biomaterials: Impact on cell behavior regulation and tissue regeneration

Silk fibroin (SF) is a promising biomaterial due to its good biocompatibility, easy availability, and high mechanical properties. Compared with mulberry silk fibroin (MSF), nonmulberry silk fibroin (NSF) isolated from typical nonmulberry silkworm silk exhibits unique arginine-glycine-aspartic acid (RGD) sequences with favorable cell adhesion enhancing effect. This inherent property probably makes the NSF more suitable for cell culture and tissue regeneration-related applications. Accordingly, various types of NSF-based biomaterials, such as particles, films, fiber mats, and 3D scaffolds, are constructed and their application potential in different biomedical fields is extensively investigated. Based on these promising NSF biomaterials, this review firstly makes a systematical comparison between the molecular structure and properties of MSF and typical NSF and highlights the unique properties of NSF. In addition, we summarize the effective fabrication strategies from degummed nonmulberry silk fibers to regenerated NSF-based biomaterials with controllable formats and their recent application progresses in cell behavior regulation and tissue regeneration. Finally, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials are discussed. Related research and perspectives may provide valuable references for designing and modifying effective NSF-based and other natural biomaterials. STATEMENT OF SIGNIFICANCE: There exist many reviews about mulberry silk fibroin (MSF) biomaterials and their biomedical applications, while that about nonmulberry silk fibroin (NSF) biomaterials is scarce. Compared with MSF, NSF exhibits unique arginine-glycine-aspartic acid sequences with promising cell adhesion enhancing effect, which makes NSF more suitable for cell culture and tissue regeneration related applications. Focusing on these advanced NSF biomaterials, this review has systematically compared the structure and properties of MSF and NSF, and emphasized the unique properties of NSF. Following that, the effective construction strategies for NSF-based biomaterials are summarized, and their recent applications in cell behavior regulations and tissue regenerations are highlighted. Furthermore, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials were discussed.

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.

Bioartificial livers: a review of their design and manufacture

Acute liver failure (ALF) is a rapidly progressive disease with high morbidity and mortality rates. Liver transplantation and artificial liver support systems, such as artificial livers (ALs) and bioartificial livers (BALs), are the two major therapies for ALF. Compared to ALs, BALs are composed of functional hepatocytes that provide essential liver functions, including detoxification, metabolite synthesis, and biotransformation. Furthermore, BALs can potentially provide effective support as a form of bridging therapy to liver transplantation or spontaneous recovery for patients with ALF. In this review, we systematically discussed the currently available state-of-the-art designs and manufacturing processes for BAL support systems. Specifically, we classified the cell sources and bioreactors that are applied in BALs, highlighted the advanced technologies of hepatocyte culturing and bioreactor fabrication, and discussed the current challenges and future trends in developing next generation BALs for large scale clinical applications.

The Intracellular and Extracellular Microenvironment of Tumor Site: The Trigger of Stimuli-Responsive Drug Delivery Systems

The tumor microenvironment (TME), including intracellular and extracellular microenvironment, contains many biochemical indicators (such as acidity/alkalinity, oxygen content, and enzymatic activity) that are different from the normal physiological environment. These abnormal biochemical indicators can accelerate the heterogeneity of tumors, but on the other hand, they also provide opportunities for the design of intelligent drug delivery systems (DDSs). The TME-responsive DDSs have shown great potential in reducing the side effects of chemotherapy and improving the curative effect of tumors. In this review, the abnormal biochemical indicators of TME are introduced in detail from both the extracellular and intracellular aspects. In view of the various physiological barriers encountered during drug delivery, the strategy of constructing TME-responsive DDSs is discussed. By summarizing the typical research progress, the authors prospect the development of TME-responsive DDS in the future.

Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells Hold Lower Heterogeneity and Great Promise in Biological Research and Clinical Applications

Mesenchymal stem cells (MSC) isolated from different tissue sources exhibit multiple biological effects and have shown promising therapeutic effects in a broad range of diseases. In order to fulfill their clinical applications in context of precision medicine, however, more detailed molecular characterization of diverse subgroups and standardized scalable production of certain functional subgroups would be highly desired. Thus far, the generation of induced pluripotent stem cell (iPSC)-derived MSC (iMSC) seems to provide the unique opportunity to solve most obstacles that currently exist to prevent the broad application of MSC as an advanced medicinal product. The features of iMSC include their single cell clone origins, and defined and controllable cultural conditions for their derivation and proliferation. Still, comprehensive research of the molecular and functional heterogeneity of iMSC, just like MSC from any other tissue types, would be required. Furthered on previous efforts on iMSC differentiation and expansion platform and transcriptomic studies, advantages of single cell multi-omics analysis and other up-to-dated technologies would be taken in order to elucidate the molecular origin and regulation of heterogeneity and to obtain iMSC subgroups homogeneous enough for particular clinical conditions. In this perspective, the current obstacles in MSC applications, the advantages of iMSC over MSC and their implications for biological research and clinical applications will be discussed.

Magnetic Control and Real-Time Monitoring of Stem Cell Differentiation by the Ligand Nanoassembly

Native extracellular matrix (ECM) exhibits dynamic change in the ligand position. Herein, the ECM-emulating control and real-time monitoring of stem cell differentiation are demonstrated by ligand nanoassembly. The density of gold nanoassembly presenting cell-adhesive Arg-Gly-Asp (RGD) ligand on Fe₃ O₄ (magnetite) nanoparticle in nanostructures flexibly grafted to material is changed while keeping macroscale ligand density invariant. The ligand nanoassembly on the Fe₃ O₄ can be magnetically attracted to mediate rising and falling ligand movements via linker stretching and compression, respectively. High ligand nanoassembly density stimulates integrin ligation to activate the mechanosensing-assisted stem cell differentiation, which is monitored via in situ real-time electrochemical sensing. Magnetic control of rising and falling ligand movements hinders and promotes the adhesion-mediated mechanotransduction and differentiation of stem cells, respectively. These rising and falling ligand states yield the difference in the farthest distance (≈34.6 nm) of the RGD from material surface, thereby dynamically mimicking static long and short flexible linkers, which hinder and promote cell adhesion, respectively. Design of cytocompatible ligand nanoassemblies can be made with combinations of dimensions, shapes, and biomimetic ligands for remotely regulating stem cells for offering novel methodologies to advance regenerative therapies.

Thermoresponsive Hydrogels as Microniches for Growth and Controlled Release of Induced Pluripotent Stem Cells

The recently emerging stem‐cell artificial niche engineering in induced pluripotent stem cell (iPSCs) 3D cultures has provided enormous opportunities to fully utilize the potential of these cells in biomedical applications. Although a fully chemically defined niche environment can supply cells with desirable safety for clinical use, establishing an artificial degradable niche environment for the controlled release of proliferated cells under mild conditions is still a big challenge. Here, an advanced controlled releasable iPSC 3D artificial niche is reported based on dendritic polyglycerol and poly(N‐isopropylacrylamide)‐co‐polyethylene glycol polymers via a physical–chemical cogelation strategy. Benefiting from the chemically defined synthetic materials and their precise cooperation by covalent cross‐linking and physical phase transition, the cogelation‐based artificial niche system can be adjusted with optimal parameters and owns high cell biocompatibility to support the robust production of high quality iPSCs with an excellent expansion efficiency. Moreover, the expanded cells can be released out of their niche environment controllably only by adjusting the temperature. Overall, this controlled release hydrogel scaffold shows great promise in iPSC 3D culture for downstream applications.

Establishment of Babesia bovis In Vitro Culture Using Medium Free of Animal Products

Babesia bovis, an etiological agent of bovine babesiosis, causes a significant burden to the cattle industry worldwide. The most efficient method to mitigate bovine babesiosis is a live vaccine produced by serial passage in splenectomized cattle. However, there are several concerns regarding live vaccine production, including variation between batches and the use of many animals. In this study, we report a B. bovis-SF strain continuously cultured in a medium free of components of animal origin enriched with a chemically defined lipid mixture (CD lipid mixture) and the use of a perfusion bioreactor to harvest a large amount of B. bovis. Six culture media were compared, including VP-SFM, CD-CHO, CD-Hydrolyzed, CD-CHO, SFM, and ADMEM/F12. We found that the VP-SFM medium performed the best for B. bovis growth, with a maximum percentage of parasitized erythrocytes (PPE) of 8.6%. The effect of six dilutions of a commercial mixture of CD lipids added to VP-SFM showed that the CD lipid mixture at a dilution of 1:100 had the best B. bovis growth curve, with a maximum PPE of 13.9%. Propagation of the in vitro B. bovis culture was scaled up in a perfusion bioreactor using VP-SFM with a CD lipid mixture, and the PPE reached over 32%. The continuous in vitro B. bovis culture in a medium free of animal origin components could potentially reduce and replace the use of animals to produce a reagent for diagnostics and live vaccines to control bovine babesiosis.

Engineering in vitro human neural tissue analogs by 3D bioprinting and electrostimulation

There is a fundamental need for clinically relevant, reproducible, and standardized in vitro human neural tissue models, not least of all to study heterogenic and complex human-specific neurological (such as neuropsychiatric) disorders. Construction of three-dimensional (3D) bioprinted neural tissues from native human-derived stem cells (e.g., neural stem cells) and human pluripotent stem cells (e.g., induced pluripotent) in particular is appreciably impacting research and conceivably clinical translation. Given the ability to artificially and favorably regulate a cell's survival and behavior by manipulating its biophysical environment, careful consideration of the printing technique, supporting biomaterial and specific exogenously delivered stimuli, is both required and advantageous. By doing so, there exists an opportunity, more than ever before, to engineer advanced and precise tissue analogs that closely recapitulate the morphological and functional elements of natural tissues (healthy or diseased). Importantly, the application of electrical stimulation as a method of enhancing printed tissue development in vitro, including neuritogenesis, synaptogenesis, and cellular maturation, has the added advantage of modeling both traditional and new stimulation platforms, toward improved understanding of efficacy and innovative electroceutical development and application.

Covalently Crosslinked Hydrogels via Step-Growth Reactions: Crosslinking Chemistries, Polymers, and Clinical Impact

Hydrogels are an important class of biomaterials with the unique property of high-water content in a crosslinked polymer network. In particular, chemically crosslinked hydrogels have made a great clinical impact in past years because of their desirable mechanical properties and tunability of structural and chemical properties. Various polymers and step-growth crosslinking chemistries are harnessed for fabricating such covalently crosslinked hydrogels for translational research. However, selecting appropriate crosslinking chemistries and polymers for the intended clinical application is time-consuming and challenging. It requires the integration of polymer chemistry knowledge with thoughtful crosslinking reaction design. This task becomes even more challenging when other factors such as the biological mechanisms of the pathology, practical administration routes, and regulatory requirements add additional constraints. In this review, key features of crosslinking chemistries and polymers commonly used for preparing translatable hydrogels are outlined and their performance in biological systems is summarized. The examples of effective polymer/crosslinking chemistry combinations that have yielded clinically approved hydrogel products are specifically highlighted. These hydrogel design parameters in the context of the regulatory process and clinical translation barriers, providing a guideline for the rational selection of polymer/crosslinking chemistry combinations to construct hydrogels with high translational potential are further considered.

Rose petal topography mimicked poly(dimethylsiloxane) substrates for enhanced corneal endothelial cell behavior

Low proliferation capacity of corneal endothelial cells (CECs) and worldwide limitations in transplantable donor tissues reveal the critical need of a robust approach for in vitro CEC growth. However, preservation of CEC-specific phenotype with increased proliferation has been a great challenge. Here we offer a biomimetic cell substrate design, by optimizing mechanical, topographical and biochemical characteristics of materials with CEC microenvironment. We showed the surprising similarity between topographical features of white rose petals and corneal endothelium due to hexagonal cell shapes and physiologically relevant cell density (≈ 2000 cells/mm²). Polydimethylsiloxane (PDMS) substrates with replica of white rose petal topography and cornea-friendly Young's modulus (211.85 ± 74.9 kPa) were functionalized with two of the important corneal extracellular matrix (ECM) components, collagen IV (COL 4) and hyaluronic acid (HA). White rose petal patterned and COL 4 modified PDMS with optimized stiffness provided enhanced bovine CEC response with higher density monolayers and increased phenotypic marker expression. This biomimetic approach demonstrates a successful platform to improve in vitro cell substrate properties of PDMS for corneal applications, suggesting an alternative environment for CEC-based therapies, drug toxicity investigations, microfluidics and organ-on-chip applications.

Integrating biomaterials and food biopolymers for cultured meat production

Cultured meat has recently achieved mainstream prominence due to the emergence of societal and industrial interest. In contrast to animal-based production of traditional meat, the cultured meat approach entails laboratory cultivation of engineered muscle tissue. However, bioengineers have hitherto engineered tissues to fulfil biomedical endpoints, and have had limited experience in engineering muscle tissue for its post-mortem traits, which broadly govern consumer definitions of meat quality. Furthermore, existing tissue engineering approaches face fundamental challenges in technical feasibility and industrial scalability for cultured meat production. This review discusses how animal-based meat production variables influence meat properties at both the molecular and functional level, and whether current cultured meat approaches recapitulate these properties. In addition, this review considers how conventional meat producers employ exogenous biopolymer-based meat ingredients and processing techniques to mimic desirable meat properties in meat products. Finally, current biomaterial strategies for engineering muscle and adipose tissue are surveyed in the context of emerging constraints that pertain to cultured meat production, such as edibility, sustainability and scalability, and potential areas for integrating biomaterials and food biopolymer approaches to address these constraints are discussed. STATEMENT OF SIGNIFICANCE: Laboratory-grown or cultured meat has gained increasing interest from industry and the public, but currently faces significant impediment to market feasibility. This is due to fundamental knowledge gaps in producing realistic meat tissues via conventional tissue engineering approaches, as well as translational challenges in scaling up these approaches in an efficient, sustainable and high-volume manner. By defining the molecular basis for desirable meat quality attributes, such as taste and texture, and introducing the fundamental roles of food biopolymers in mimicking these properties in conventional meat products, this review aims to bridge the historically disparate fields of meat science and biomaterials engineering in order to inspire potentially synergistic strategies that address some of these challenges.

Bioactive potential of natural biomaterials: identification, retention and assessment of biological properties

Biomaterials have had an increasingly important role in recent decades, in biomedical device design and the development of tissue engineering solutions for cell delivery, drug delivery, device integration, tissue replacement, and more. There is an increasing trend in tissue engineering to use natural substrates, such as macromolecules native to plants and animals to improve the biocompatibility and biodegradability of delivered materials. At the same time, these materials have favourable mechanical properties and often considered to be biologically inert. More importantly, these macromolecules possess innate functions and properties due to their unique chemical composition and structure, which increase their bioactivity and therapeutic potential in a wide range of applications. While much focus has been on integrating these materials into these devices via a spectrum of cross-linking mechanisms, little attention is drawn to residual bioactivity that is often hampered during isolation, purification, and production processes. Herein, we discuss methods of initial material characterisation to determine innate bioactivity, means of material processing including cross-linking, decellularisation, and purification techniques and finally, a biological assessment of retained bioactivity of a final product. This review aims to address considerations for biomaterials design from natural polymers, through the optimisation and preservation of bioactive components that maximise the inherent bioactive potency of the substrate to promote tissue regeneration.

Engineering liver microtissues for disease modeling and regenerative medicine

The burden of liver diseases is increasing worldwide, accounting for two million deaths annually. In the past decade, tremendous progress has been made in the basic and translational research of liver tissue engineering. Liver microtissues are small, three-dimensional hepatocyte cultures that recapitulate liver physiology and have been used in biomedical research and regenerative medicine. This review summarizes recent advances, challenges, and future directions in liver microtissue research. Cellular engineering approaches are used to sustain primary hepatocytes or produce hepatocytes derived from pluripotent stem cells and other adult tissues. Three-dimensional microtissues are generated by scaffold-free assembly or scaffold-assisted methods such as macroencapsulation, droplet microfluidics, and bioprinting. Optimization of the hepatic microenvironment entails incorporating the appropriate cell composition for enhanced cell-cell interactions and niche-specific signals, and creating scaffolds with desired chemical, mechanical and physical properties. Perfusion-based culture systems such as bioreactors and microfluidic systems are used to achieve efficient exchange of nutrients and soluble factors. Taken together, systematic optimization of liver microtissues is a multidisciplinary effort focused on creating liver cultures and on-chip models with greater structural complexity and physiological relevance for use in liver disease research, therapeutic development, and regenerative medicine.

Stem cell therapy: old challenges and new solutions

Stem cell therapy (SCT), born as therapeutic revolution to replace pharmacological treatments, remains a hope and not yet an effective solution. Accordingly, stem cells cannot be conceivable as a "canonical" drug, because of their unique biological properties. A new reorientation in this field is emerging, based on a better understanding of stem cell biology and use of cutting-edge technologies and innovative disciplines. This will permit to solve the gaps, failures, and long-term needs, such as the retention, survival and integration of stem cells, by employing pharmacology, genetic manipulation, biological or material incorporation. Consequently, the clinical applicability of SCT for chronic human diseases will be extended, as well as its effectiveness and success, leading to long-awaited medical revolution. Here, some of these aspects are summarized, reviewing and discussing recent advances in this rapidly developing research field.