Biomaterial technology for tissue engineering applications

Viscoelastic Behavior of Cellular Biomaterials Based on Octet-Truss and Tetrahedron Topologies

Cellular biomaterials offer unique properties for diverse biomedical applications. However, their complex viscoelastic behavior requires careful consideration for design optimization. This study explores the effective viscoelastic response of two promising unit cell designs (tetrahedron-based and octet-truss) suitable for high porosity and strong mechanics. The asymptotic homogenization (AH) method was employed to determine effective longitudinal and shear moduli, as well as Poisson's ratio, across various relative densities. Finite element simulations (ABAQUS) validated the AH results, demonstrating good agreement (<10% discrepancies). Additionally, analytical models and compression tests on 3D-printed lattice structures supported the theoretical predictions. The study revealed a strong correlation between relative density and the effective modulus of both designs. Notably, the tetrahedron-based design exhibited superior modulus, making it favorable for high loading levels, particularly when used as a high-density configuration. Both designs demonstrated minimal time-dependent elastic modulus changes and a near-constant Poisson's ratio (0.34-0.349 for octet-truss, 0.316-0.326 for tetrahedron) across a 5-50% relative density range. While minimal, time-dependent modulus reduction needs to be considered in longer-term simulations (t>107 s). This study provides valuable insights into the viscoelastic behavior of these unit cells using the homogenization method, with potential applications in various biomedical fields.

Hydrogels and Their Functionalization-Analysis of the Possibility of Their Application in Post-Fire Water Treatment Processes

Increasingly intense changes in climatic conditions and the use of modified materials are causing fires, the consequences of which are increasingly serious for the environment. On one hand, there is the issue of access to water resources. On the other hand, there is the problem of post-fire wastewater, which often contains a mixture of simple inorganic compounds and complex organic molecules, making the removal of pollutants a difficult task requiring innovative approaches. Among these solutions, hydrogels stand out as a promising class of sorption materials. Depending on their synthesis or functionalization, hydrogels can effectively capture contaminants and facilitate the reduction or removal of specific pollutants. This study explores the functionalization of polymeric materials, specifically hydrogels, using microorganisms or bioactive substances to create materials capable of treating water contaminated with hazardous substances generated during firefighting incidents. The possibility of wastewater capture was also taken into account to retain pretreated water at the place of pollutant generation. The analysis covered the potential, conditions, and limitations of using hydrogels in post-fire operations for the effective management of contaminated waters. It was shown that hydrogels, depending on the modification, have the potential to capture wastewater and purify it from both organic and inorganic substances specific to post-fire wastewater. However, it is not possible for a given hydrogel to meet all desired expectations at the same time. Furthermore, modifications that facilitate the optimal performance of certain functionalities may render the others ineffective.

Enhancing Cartilage Repair: Surgical Approaches, Orthobiologics, and the Promise of Exosomes

Treating cartilage damage is challenging as its ability for self-regeneration is limited. Left untreated, it can progress to osteoarthritis (OA), a joint disorder characterized by the deterioration of articular cartilage and other joint tissues. Surgical options, such as microfracture and cell/tissue transplantation, have shown promise as techniques to harness the body's endogenous regenerative capabilities to promote cartilage repair. Nonetheless, these techniques have been scrutinized due to reported inconsistencies in long-term outcomes and the tendency for the defects to regenerate as fibrocartilage instead of the smooth hyaline cartilage native to joint surfaces. Orthobiologics are medical therapies that utilize biologically derived substances to augment musculoskeletal healing. These treatments are rising in popularity because of their potential to enhance surgical standards of care. More recent developments in orthobiologics have focused on the role of exosomes in articular cartilage repair. Exosomes are nano-sized extracellular vesicles containing cargo such as proteins, lipids, and nucleic acids, and are known to facilitate intercellular communication, though their regenerative potential still needs to be fully understood. This review aims to demonstrate the advancements in cartilage regeneration, highlight surgical and biological treatment options, and discuss the recent strides in understanding the precise mechanisms of action involved.

Trends in sustainable chitosan-based hydrogel technology for circular biomedical engineering: A review

Eco-friendly materials have emerged in biomedical engineering, driving major advances in chitosan-based hydrogels. These hydrogels offer a promising green alternative to conventional polymers due to their non-toxicity, biodegradability, biocompatibility, environmental friendliness, affordability, and easy accessibility. Known for their remarkable properties such as drug encapsulation, delivery capabilities, biosensing, functional scaffolding, and antimicrobial behavior, chitosan hydrogels are at the forefront of biomedical research. This paper explores the fabrication and modification methods of chitosan hydrogels for diverse applications, highlighting their role in advancing climate-neutral healthcare technologies. It reviews significant scientific advancements and trends chitosan hydrogels focusing on cancer diagnosis, drug delivery, and wound care. Additionally, it addresses current challenges and green synthesis practices that support a circular economy, enhancing biomedical sustainability. By providing an in-depth analysis of the latest evidence on climate-neutral management, this review aims to facilitate informed decision-making and foster the development of sustainable strategies leveraging chitosan hydrogel technology. The insights from this comprehensive examination are pivotal for steering future research and applications in sustainable biomedical solutions.

Surgical Management of Myelomeningocele

Myelomeningocele (MMC) is one of the most common abnormalities of the central nervous system that causes significant neurological impairment. Traditionally, treatment consisted of postnatal closure with the management of the complications, such as ventricular shunting. MMC is a plausible candidate for in-utero surgery because of the mechanism of neurologic damage that begins with abnormal neurulation and continues throughout gestation. Researchers discussed the benefits of in-utero closure prior to the publication of the prospective randomized multicenter Management of Myelomeningocele Study (MOMS trial). Compared to postnatal repair with maternal complications and prematurity as trade-offs, prenatal repair reduced shunting, reversed hindbrain herniation, and improved neurological function. This article discusses the diagnosis, evaluation, long-term follow-up, surgical options, and innovative treatment for fetal myelomeningocele.

Cellulose-Based Metallogels-Part 1: Raw Materials and Preparation

Metallogels are a class of materials produced by the complexation of polymer gels with metal ions that can form coordination bonds with the functional groups of the gel. Hydrogels with metal phases attract special attention due to the numerous possibilities for functionalization. Cellulose is preferable for the production of hydrogels from economic, ecological, physical, chemical, and biological points of view since it is inexpensive, renewable, versatile, non-toxic, reveals high mechanical and thermal stability, has a porous structure, an imposing number of reactive OH groups, and good biocompatibility. Due to the poor solubility of natural cellulose, the hydrogels are commonly produced from cellulose derivatives that require multiple chemical manipulations. However, there is a number of techniques of hydrogel preparation via dissolution and regeneration of non-derivatized cellulose of various origins. Thus, hydrogels can be produced from plant-derived cellulose, lignocellulose and cellulose wastes, including agricultural, food and paper wastes. The advantages and limitations of using solvents are discussed in this review with regard to the possibility of industrial scaling up. Metallogels are often formed on the basis of ready-made hydrogels, which is why the choice of an adequate solvent is important for obtaining desirable results. The methods of the preparation of cellulose metallogels with d-transition metals in the present state of the art are reviewed.

Sustainable Approach of Functional Biomaterials-Tissue Engineering for Skin Burn Treatment: A Comprehensive Review

Burns are a widespread global public health traumatic injury affecting many people worldwide. Non-fatal burn injuries are a leading cause of morbidity, resulting in prolonged hospitalization, disfigurement, and disability, often with resulting stigma and rejection. The treatment of burns is aimed at controlling pain, removing dead tissue, preventing infection, reducing scarring risk, and tissue regeneration. Traditional burn wound treatment methods include the use of synthetic materials such as petroleum-based ointments and plastic films. However, these materials can be associated with negative environmental impacts and may not be biocompatible with the human body. Tissue engineering has emerged as a promising approach to treating burns, and sustainable biomaterials have been developed as an alternative treatment option. Green biomaterials such as collagen, cellulose, chitosan, and others are biocompatible, biodegradable, environment-friendly, and cost-effective, which reduces the environmental impact of their production and disposal. They are effective in promoting wound healing and reducing the risk of infection and have other benefits such as reducing inflammation and promoting angiogenesis. This comprehensive review focuses on the use of multifunctional green biomaterials that have the potential to revolutionize the way we treat skin burns, promoting faster and more efficient healing while minimizing scarring and tissue damage.

Tissue-mimetic culture enhances mesenchymal stem cell secretome capacity to improve regenerative activity of keratinocytes and fibroblasts in vitro

Mesenchymal stem/stromal cells (MSCs) are a heterogenous population of multipotent and highly secretory cells currently being investigated in the field of wound healing for their ability to augment tissue responses. The adaptive response of MSC populations to the rigid substrate of current 2D culture systems has been considered to result in a deterioration of regenerative 'stem-like' properties. In this study, we characterise how the improved culture of adipose-derived mesenchymal stem cells (ASCs) within a tissue-mimetic 3D hydrogel system, that is mechanically similar to native adipose tissue, enhances their regenerative capabilities. Notably, the hydrogel system contains a porous microarchitecture that permits mass transport, enabling efficient collection of secreted cellular compounds. By utilising this 3D system, ASCs retained a significantly higher expression of ASC 'stem-like' markers while demonstrating a significant reduction in senescent populations, relative to 2D. Additionally, culture of ASCs within the 3D system resulted in enhanced secretory activity with significant increases in the secretion of proteinaceous factors, antioxidants and extracellular vesicles (EVs) within the conditioned media (CM) fraction. Lastly, treatment of wound healing cells, keratinocytes (KCs) and fibroblasts (FBs), with ASC-CM from the 2D and 3D systems resulted in augmented functional regenerative activity, with ASC-CM from the 3D system significantly increasing KC and FB metabolic, proliferative and migratory activity. This study demonstrates the potential beneficial role of MSC culture within a tissue-mimetic 3D hydrogel system that more closely mimics native tissue mechanics, and subsequently how the improved phenotype augments secretory activity and potential wound healing capabilities of the MSC secretome.

Microfluidic Organ-on-A-chip: A Guide to Biomaterial Choice and Fabrication

Organ-on-A-chip (OoAC) devices are miniaturized, functional, in vitro constructs that aim to recapitulate the in vivo physiology of an organ using different cell types and extracellular matrix, while maintaining the chemical and mechanical properties of the surrounding microenvironments. From an end-point perspective, the success of a microfluidic OoAC relies mainly on the type of biomaterial and the fabrication strategy employed. Certain biomaterials, such as PDMS (polydimethylsiloxane), are preferred over others due to their ease of fabrication and proven success in modelling complex organ systems. However, the inherent nature of human microtissues to respond differently to surrounding stimulations has led to the combination of biomaterials ranging from simple PDMS chips to 3D-printed polymers coated with natural and synthetic materials, including hydrogels. In addition, recent advances in 3D printing and bioprinting techniques have led to the powerful combination of utilizing these materials to develop microfluidic OoAC devices. In this narrative review, we evaluate the different materials used to fabricate microfluidic OoAC devices while outlining their pros and cons in different organ systems. A note on combining the advances made in additive manufacturing (AM) techniques for the microfabrication of these complex systems is also discussed.

Fabrication and Bioactivity of Peptide-Conjugated Biomaterial Tissue Engineering Constructs

Tissue engineering combines materials engineering, cells and biochemical factors to improve, restore or replace various types of biological tissues. A nearly limitless combination of these strategies can be combined, providing a means to augment the function of a number of biological tissues such as skin tissue, neural tissue, bones, and cartilage. Compounds such as small molecule therapeutics, proteins, and even living cells have been incorporated into tissue engineering constructs to influence biological processes at the site of implantation. Peptides have been conjugated to tissue engineering constructs to circumvent limitations associated with conjugation of proteins or incorporation of cells. This review highlights various contemporary examples in which peptide conjugation is used to overcome the disadvantages associated with the inclusion of other bioactive compounds. This review covers several peptides that are commonly used in the literature as well as those that do not appear as frequently to provide a broad scope of the utility of the peptide conjugation technique for designing constructs capable of influencing the repair and regeneration of various bodily tissues. Additionally, a brief description of the construct fabrication techniques encountered in the covered examples and their advantages in various tissue engineering applications is provided.

Cell delivery devices for cancer immunotherapy

Adoptive cell therapy (ACT) that leverages allogeneic or autologous immune cells holds vast promise in targeted cancer therapy. Despite the tremendous success of ACT in treating hematopoietic malignancies, its efficacy is limited in eradicating solid tumors via intravenous infusion of immune cells. With the extending technology of cancer immunotherapy, novel delivery strategies have been explored to improve the therapeutic potency of adoptively transferred cells for solid tumor treatment by innovating the administration route, maintaining the cell viability, and normalizing the tumor microenvironment. In this review, a variety of devices for cell delivery are summarized. Perspectives and challenges of cell delivery devices for cancer immunotherapy are also discussed.

Polysaccharide-Based Adhesive Antibacterial and Self-Healing Hydrogel for Sealing Hemostasis

Adhesive hydrogels have been considered as one of the most ideal materials for wound dressing. However, most existing adhesive hydrogels still have disadvantages such as low mechanical properties, poor biological activity (antibacterial and hemostatic ability), and low biocompatibility, which largely limit their application. Thus, it is highly desired to prepare a hydrogel-based wound dressing with good self-healing, ideal adhesive properties, rapid hemostasis, and excellent wound infection prevention activity. In this study, a simple method was presented to prepare a PAM-Lignin-CS-Laponite-SA hydrogel for wound dressing. The obtained hydrogel displayed excellent self-healing ability and repeatable adhesive performance, benefiting from the introduction of hydrogen bonding and electrostatic interactions inside the hydrogel network. In addition, the PAM-Lignin-CS-Laponite-SA hydrogel also exhibited low cell cytotoxicity, good antibacterial activity, and outstanding hemostatic properties. In conclusion, the PAM-Lignin-CS-Laponite-SA hydrogel demonstrated good tissue adhesion, excellent self-healing ability, effective bleeding control, and good antibacterial activity to prevent wound infection, which provides a new idea for developing a multifunctional hydrogel-based tissue adhesive hemostatic dressing.

Pathophysiology and Therapeutic Approaches for Spinal Cord Injury

Spinal cord injury (SCI) is a disabling condition that disrupts motor, sensory, and autonomic functions. Despite extensive research in the last decades, SCI continues to be a global health priority affecting thousands of individuals every year. The lack of effective therapeutic strategies for patients with SCI reflects its complex pathophysiology that leads to the point of no return in its function repair and regeneration capacity. Recently, however, several studies started to uncover the intricate network of mechanisms involved in SCI leading to the development of new therapeutic approaches. In this work, we present a detailed description of the physiology and anatomy of the spinal cord and the pathophysiology of SCI. Additionally, we provide an overview of different molecular strategies that demonstrate promising potential in the modulation of the secondary injury events that promote neuroprotection or neuroregeneration. We also briefly discuss other emerging therapies, including cell-based therapies, biomaterials, and epidural electric stimulation. A successful therapy might target different pathologic events to control the progression of secondary damage of SCI and promote regeneration leading to functional recovery.

Discussing the final size and shape of the reconstructed tissues in tissue engineering

Tissue engineering (TE) has made a revolution in repairing, replacing, or regenerating tissues or organs, but it has still a long way ahead. The mechanical properties along with suitable physicochemical and biological characteristics are the initial criteria for scaffolds in TE that should be fulfilled. This research will provide another point of view toward TE challenges concerning the morphological and geometrical aspects of the reconstructed tissue and which parameters may affect it. Based on our survey, there is a high possibility that the final reconstructed tissue may be different in size and shape compared to the original design scaffold. Thereby, the 3D-printed scaffold might not guarantee an accurate tissue reconstruction. The main justification for this is the unpredicted behavior of cells, specifically in the outer layer of the scaffold. It can also be a concern when the scaffold is implanted while cell migration cannot be controlled through the in vivo signaling pathways, which might cause cancer challenges. To sum up, it is concluded that more studies are necessary to focus on the size and geometry of the final reconstructed tissue.

Polymer-Based Hydrogels Enriched with Essential Oils: A Promising Approach for the Treatment of Infected Wounds

Among the factors that delay the wound healing process in chronic wounds, bacterial infections are a common cause of acute wounds becoming chronic. Various therapeutic agents, such as antibiotics, metallic nanoparticles, and essential oils have been employed to treat infected wounds and also prevent the wounds from bacterial invasion. Essential oils are promising therapeutic agents with excellent wound healing, anti-inflammatory and antimicrobial activities, and good soothing effects. Some essential oils become chemically unstable when exposed to light, heat, oxygen, and moisture. The stability and biological activity of essential oil can be preserved via loading into hydrogels. The polymer-based hydrogels loaded with bioactive agents are regarded as ideal wound dressings with unique features, such as controlled and sustained drug release mechanisms, good antibacterial activity, non-toxicity, excellent cytocompatibility, good porosity, moderate water vapour transmission rate, etc. This review addresses the pre-clinical outcomes of hydrogels loaded with essential oils in the treatment of infected wounds.

Long-Term Examination of Degradation and In Vivo Biocompatibility of Some Mg-0.5Ca-xY Alloys in Sprague Dawley Rats

The medical field has undergone constant development in recent years, and a segment of this development is occupied by biodegradable alloys. The most common alloys in this field are those based on Mg, their main advantage being the ability to degrade gradually, without affecting the patient, and also their ability to be fully absorbed by the human body. One of their most important conditions is the regeneration and replacement of human tissue. Tissue can be engineered in different ways, one being tissue regeneration in vivo, which can serve as a template. In vivo remodeling aims to restore tissue or organs. The key processes of tissue formation and maturation are: proliferation (sorting and differentiation of cells), proliferation and organization of the extracellular matrix, biodegradation of the scaffold-remodeling, and potential tissue growth. In the present paper, the design of the alloys in the Mg-Ca-Y system is formed from the beginning using high-purity components, Mg-98.5%, master-alloys: Mg-Y (70 wt.%-30 wt.%) and Mg-Ca (85 wt.%-15 wt.%). After 8 weeks of implantation, the degradation of the implanted material is observed, and only small remaining fragments are found. At the site of implantation, no inflammatory reaction is observed, but it is observed that the process of integration and reabsorption, over time, accentuates the prosaic surface of the material. The aim of the work is to test the biocompatibility of magnesium-based alloys on laboratory rats in order to use these alloys in medical applications. The innovative parts of these analyses are the chemical composition of the alloys used and the tests performed on laboratory animals.

Additive Manufacturing of Biomaterials-Design Principles and Their Implementation

Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented.

Multifunctional and Smart Wound Dressings—A Review on Recent Research Advancements in Skin Regenerative Medicine

The healing of wounds is a dynamic function that necessitates coordination among multiple cell types and an optimal extracellular milieu. Much of the research focused on finding new techniques to improve and manage dermal injuries, chronic injuries, burn injuries, and sepsis, which are frequent medical concerns. A new research strategy involves developing multifunctional dressings to aid innate healing and combat numerous issues that trouble incompletely healed injuries, such as extreme inflammation, ischemic damage, scarring, and wound infection. Natural origin-based compounds offer distinct characteristics, such as excellent biocompatibility, cost-effectiveness, and low toxicity. Researchers have developed biopolymer-based wound dressings with drugs, biomacromolecules, and cells that are cytocompatible, hemostatic, initiate skin rejuvenation and rapid healing, and possess anti-inflammatory and antimicrobial activity. The main goal would be to mimic characteristics of fetal tissue regeneration in the adult healing phase, including complete hair and glandular restoration without delay or scarring. Emerging treatments based on biomaterials, nanoparticles, and biomimetic proteases have the keys to improving wound care and will be a vital addition to the therapeutic toolkit for slow-healing wounds. This study focuses on recent discoveries of several dressings that have undergone extensive pre-clinical development or are now undergoing fundamental research.

The Role of Alginate Hydrogels as a Potential Treatment Modality for Spinal Cord Injury: A Comprehensive Review of the Literature

Objective

To comprehensively characterize the utilization of alginate hydrogels as an alternative treatment modality for spinal cord injury (SCI).

Methods

An extensive review of the published literature on studies using alginate hydrogels to treat SCI was performed. The review of the literature was performed using electronic databases such as PubMed, EMBASE, and OVID MEDLINE electronic databases. The keywords used were “alginate,” “spinal cord injury,” “biomaterial,” and “hydrogel.”

Results

In the literature, we identified a total of 555 rat models that were treated with alginate scaffolds for regenerative biomarkers. Alginate hydrogels were found to be efficient and promising substrates for tissue engineering, drug delivery, neural regeneration, and cellbased therapies for SCI repair. With its ability to act as a pro-regenerative and antidegenerative agent, the alginate hydrogel has the potential to improve clinical outcomes.

Conclusion

The emerging developments of alginate hydrogels as treatment modalities may support current and future tissue regenerative strategies for SCI.

Hydrogel Application in Urban Farming: Potentials and Limitations—A Review

Urban agriculture plays a vital role in ensuring the self-sufficiency of a great variety of fresh vegetables and nutrients. It promotes a sustainable food system as well as reducing the dependency on imports for the growing population. Urban farming has made it possible for agriculture practices to be implemented anywhere at any time in a sophisticated way. Hydrogel has been introduced in urban agriculture in the past few decades. However, the application of hydrogel in urban agriculture is still being explored in terms of hydrogel types, structure, physical and chemical properties, change due to external factors, and its suitability for different plant species. This review discusses the potentials and limitations of hydrogel in different application conditions. We present the state of knowledge on hydrogel production and crosslinking methods, hydrogel characteristics, water absorption and release mechanisms of hydrogel, hydrogel advantages and limitations, and current and future applications in urban farming.

Application of neurotrophic and proangiogenic factors as therapy after peripheral nervous system injury

The intrinsic ability of peripheral nerves to regenerate after injury is extremely limited, especially in case of severe injury. This often leads to poor motor function and permanent disability. Existing approaches for the treatment of injured nerves do not provide appropriate conditions to support survival and growth of nerve cells. This drawback can be compensated by the use of gene therapy and cell therapy-based drugs that locally provide an increase in the key regulators of nerve growth, including neurotrophic factors and extracellular matrix proteins. Each growth factor plays its own specific angiotrophic or neurotrophic role. Currently, growth factors are widely studied as accelerators of nerve regeneration. Particularly noteworthy is synergy between various growth factors, that is essential for both angiogenesis and neurogenesis. Fibroblast growth factor 2 and vascular endothelial growth factor are widely known for their proangiogenic effects. At the same time, fibroblast growth factor 2 and vascular endothelial growth factor stimulate neural cell growth and play an important role in neurodegenerative diseases of the peripheral nervous system. Taken together, their neurotrophic and angiogenic properties have positive effect on the regeneration process. In this review we provide an in-depth overview of the role of fibroblast growth factor 2 and vascular endothelial growth factor in the regeneration of peripheral nerves, thus demonstrating their neurotherapeutic efficacy in improving neuron survival in the peripheral nervous system.

Strategies to Improve the Potency of Oxazolidinones towards Bacterial Biofilms

Biofilms are part of the natural lifecycle of bacteria and are known to cause chronic infections that are difficult to treat. Most antibiotics are developed and tested against bacteria in the planktonic state and are ineffective against bacterial biofilms. The oxazolidinones, including the last resort drug linezolid, are one of the main classes of synthetic antibiotics progressed to clinical use in the last 50 years. They have a unique mechanism of action and only develop low levels of resistance in the clinical setting. With the aim of providing insight into strategies to design more potent antibiotic compounds with activity against bacterial biofilms, we review the biofilm activity of clinically approved oxazolidinones and report on structural modifications to oxazolidinones and their delivery systems which lead to enhanced anti-biofilm activity.

Progress in Gelatin as Biomaterial for Tissue Engineering

Tissue engineering has become a medical alternative in this society with an ever-increasing lifespan. Advances in the areas of technology and biomaterials have facilitated the use of engineered constructs for medical issues. This review discusses on-going concerns and the latest developments in a widely employed biomaterial in the field of tissue engineering: gelatin. Emerging techniques including 3D bioprinting and gelatin functionalization have demonstrated better mimicking of native tissue by reinforcing gelatin-based systems, among others. This breakthrough facilitates, on the one hand, the manufacturing process when it comes to practicality and cost-effectiveness, which plays a key role in the transition towards clinical application. On the other hand, it can be concluded that gelatin could be considered as one of the promising biomaterials in future trends, in which the focus might be on the detection and diagnosis of diseases rather than treatment.

Biomechanically and biochemically functional scaffold for recruitment of endogenous stem cells to promote tendon regeneration

Tendon regeneration highly relies on biomechanical and biochemical cues in the repair microenvironment. Herein, we combined the decellularized bovine tendon sheet (DBTS) with extracellular matrix (ECM) from tendon-derived stem cells (TDSCs) to fabricate a biomechanically and biochemically functional scaffold (tECM-DBTS), to provide a functional and stem cell ECM-based microenvironment for tendon regeneration. Our prior study showed that DBTS was biomechanically suitable to tendon repair. In this study, the biological function of tECM-DBTS was examined in vitro, and the efficiency of the scaffold for Achilles tendon repair was evaluated using immunofluorescence staining, histological staining, stem cell tracking, biomechanical and functional analyses. It was found that tECM-DBTS increased the content of bioactive factors and had a better performance for the proliferation, migration and tenogenic differentiation of bone marrow-derived stem cells (BMSCs) than DBTS. Furthermore, our results demonstrated that tECM-DBTS promoted tendon regeneration and improved the biomechanical properties of regenerated Achilles tendons in rats by recruiting endogenous stem cells and participating in the functionalization of these stem cells. As a whole, the results of this study demonstrated that the tECM-DBTS can provide a bionic microenvironment for recruiting endogenous stem cells and facilitating in situ regeneration of tendons.

Peptide-Grafted Microspheres for Mesenchymal Stem Cell Sorting and Expansion by Selective Adhesion

Mesenchymal stem cells (MSCs) have considerable value in regenerative medicine because of their unique properties such as pluripotency, self-renewal ability, and low immunogenicity. Isolation and purification are prerequisites for various biomedical applications of MSCs, and traditional sorting methods are often expensive, complicated, and difficult to apply on a large scale. In addition to purification, the requirement for expansion of cells also limits the further application of MSCs. The purpose of this study was to develop a unique magnetic sorting microsphere to obtain relatively pure and high-yield MSCs in an economical and effective way, that can also be used for the expansion of MSCs. Poly (ethylene glycol) (PEG)-based anti-adhesive treatment of the prepared oleic acid grafted Fe3O4-poly (lactic-co-glycolic acid) magnetic microspheres was performed, and then E7 peptide was covalently grafted onto the treated microspheres. Upon a series of characterization, the magnetic microspheres were of uniform size, and cells were unable to adhere to the PEG-treated surface. E7 grafting significantly improved cell adhesion and proliferation. The results obtained from separate culture of various cell types as well as static or dynamic co-culture showed that selective adhesion of MSCs was observed on the magnetic sorting microspheres. Furthermore, the cells expanded on the microspheres maintained their phenotype and typical differentiation potentials. The magnetic properties of the microspheres enabled sampling, distribution, and transfer of cells without the usage of trypsin digestion. And it facilitated the separation of cells and microspheres for harvesting of MSCs after digestion. These findings have promising prospects for MSC research and clinical applications.

A critical review of fibrous polyurethane-based vascular tissue engineering scaffolds

Certain polymeric materials such as polyurethanes (PUs) are the most prevalent class of used biomaterials in regenerative medicine and have been widely explored as vascular substitutes in several animal models. It is thought that PU-based biomaterials possess suitable hemo-compatibility with comparable performance related to the normal blood vessels. Despite these advantages, the possibility of thrombus formation and restenosis limits their application as artificial functional vessels. In this regard, various surface modification approaches have been developed to enhance both hemo-compatibility and prolong patency. While critically reviewing the recent advances in vascular tissue engineering, mainly PU grafts, this paper summarizes the application of preferred cell sources to vascular regeneration, physicochemical properties, and some possible degradation mechanisms of PU to provide a more extensive perspective for future research.

Drug Delivery Strategies and Biomedical Significance of Hydrogels: Translational Considerations

Hydrogels are a promising and attractive option as polymeric gel networks, which have immensely fascinated researchers across the globe because of their outstanding characteristics such as elevated swellability, the permeability of oxygen at a high rate, good biocompatibility, easy loading, and drug release. Hydrogels have been extensively used for several purposes in the biomedical sector using versatile polymers of synthetic and natural origin. This review focuses on functional polymeric materials for the fabrication of hydrogels, evaluation of different parameters of biocompatibility and stability, and their application as carriers for drugs delivery, tissue engineering and other therapeutic purposes. The outcome of various studies on the use of hydrogels in different segments and how they have been appropriately altered in numerous ways to attain the desired targeted delivery of therapeutic agents is summarized. Patents and clinical trials conducted on hydrogel-based products, along with scale-up translation, are also mentioned in detail. Finally, the potential of the hydrogel in the biomedical sector is discussed, along with its further possibilities for improvement for the development of sophisticated smart hydrogels with pivotal biomedical functions.

Engineering Hydrogels for the Development of Three-Dimensional In Vitro Models

The superiority of in vitro 3D cultures over conventional 2D cell cultures is well recognized by the scientific community for its relevance in mimicking the native tissue architecture and functionality. The recent paradigm shift in the field of tissue engineering toward the development of 3D in vitro models can be realized with its myriad of applications, including drug screening, developing alternative diagnostics, and regenerative medicine. Hydrogels are considered the most suitable biomaterial for developing an in vitro model owing to their similarity in features to the extracellular microenvironment of native tissue. In this review article, recent progress in the use of hydrogel-based biomaterial for the development of 3D in vitro biomimetic tissue models is highlighted. Discussions of hydrogel sources and the latest hybrid system with different combinations of biopolymers are also presented. The hydrogel crosslinking mechanism and design consideration are summarized, followed by different types of available hydrogel module systems along with recent microfabrication technologies. We also present the latest developments in engineering hydrogel-based 3D in vitro models targeting specific tissues. Finally, we discuss the challenges surrounding current in vitro platforms and 3D models in the light of future perspectives for an improved biomimetic in vitro organ system.

Recent Progress in Biopolymer-Based Hydrogel Materials for Biomedical Applications

Hydrogels from biopolymers are readily synthesized, can possess various characteristics for different applications, and have been widely used in biomedicine to help with patient treatments and outcomes. Polysaccharides, polypeptides, and nucleic acids can be produced into hydrogels, each for unique purposes depending on their qualities. Examples of polypeptide hydrogels include collagen, gelatin, and elastin, and polysaccharide hydrogels include alginate, cellulose, and glycosaminoglycan. Many different theories have been formulated to research hydrogels, which include Flory-Rehner theory, Rubber Elasticity Theory, and the calculation of porosity and pore size. All these theories take into consideration enthalpy, entropy, and other thermodynamic variables so that the structure and pore sizes of hydrogels can be formulated. Hydrogels can be fabricated in a straightforward process using a homogeneous mixture of different chemicals, depending on the intended purpose of the gel. Different types of hydrogels exist which include pH-sensitive gels, thermogels, electro-sensitive gels, and light-sensitive gels and each has its unique biomedical applications including structural capabilities, regenerative repair, or drug delivery. Major biopolymer-based hydrogels used for cell delivery include encapsulated skeletal muscle cells, osteochondral muscle cells, and stem cells being delivered to desired locations for tissue regeneration. Some examples of hydrogels used for drug and biomolecule delivery include insulin encapsulated hydrogels and hydrogels that encompass cancer drugs for desired controlled release. This review summarizes these newly developed biopolymer-based hydrogel materials that have been mainly made since 2015 and have shown to work and present more avenues for advanced medical applications.

Development of a Bone-Mimetic 3D Printed Ti6Al4V Scaffold to Enhance Osteoblast-Derived Extracellular Vesicles' Therapeutic Efficacy for Bone Regeneration

Extracellular Vesicles (EVs) are considered promising nanoscale therapeutics for bone regeneration. To date, EVs are typically procured from cells on 2D tissue culture plastic, an artificial environment that limits cell growth and does not replicate in situ biochemical or biophysical conditions. This study investigated the potential of 3D printed titanium scaffolds coated with hydroxyapatite to promote the therapeutic efficacy of osteoblast-derived EVs. Ti6Al4V titanium scaffolds with different pore sizes (500 and 1000 µm) and shapes (square and triangle) were fabricated by selective laser melting. A bone-mimetic nano-needle hydroxyapatite (nnHA) coating was then applied. EVs were procured from scaffold-cultured osteoblasts over 2 weeks and vesicle concentration was determined using the CD63 ELISA. Osteogenic differentiation of human bone marrow stromal cells (hBMSCs) following treatment with primed EVs was evaluated by assessing alkaline phosphatase activity, collagen production and calcium deposition. Triangle pore scaffolds significantly increased osteoblast mineralisation (1.5-fold) when compared to square architectures (P ≤ 0.001). Interestingly, EV yield was also significantly enhanced on these higher permeability structures (P ≤ 0.001), in particular (2.2-fold) for the larger pore structures (1000 µm). Furthermore osteoblast-derived EVs isolated from triangular pore scaffolds significantly increased hBMSCs mineralisation when compared to EVs acquired from square pore scaffolds (1.7-fold) and 2D culture (2.2-fold) (P ≤ 0.001). Coating with nnHA significantly improved osteoblast mineralisation (>2.6-fold) and EV production (4.5-fold) when compared to uncoated scaffolds (P ≤ 0.001). Together, these findings demonstrate the potential of harnessing bone-mimetic culture platforms to enhance the production of pro-regenerative EVs as an acellular tool for bone repair.

Zinc Chloride: Time-Dependent Cytotoxicity, Proliferation and Promotion of Glycoprotein Synthesis and Antioxidant Gene Expression in Human Keratinocytes

The use of ionic metals such as zinc (Zn2+) is providing promising results in regenerative medicine. In this study, human keratinocytes (HaCaT cells) were treated with different concentrations of zinc chloride (ZnCl2), ranging from 1 to 800 µg/mL, for 3, 12 and 24 h. The results showed a time-concentration dependence with three non-cytotoxic concentrations (10, 5 and 1 µg/mL) and a median effective concentration value of 13.5 µg/mL at a cell exposure to ZnCl2 of 24 h. However, the zinc treatment with 5 or 1 µg/mL had no effect on cell proliferation in HaCaT cells in relation to the control sample at 72 h. The effects of the Zn2+ treatment on the expression of several genes related to glycoprotein synthesis, oxidative stress, proliferation and differentiation were assessed at the two lowest non-cytotoxic concentrations after 24 h of treatment. Out of 13 analyzed genes (superoxide dismutase 1 (SOD1), catalase (CAT), matrix metallopeptidase 1 (MMP1), transforming growth factor beta 1 (TGFB1), glutathione peroxidase 1 (GPX1), fibronectin 1 (FN1), hyaluronan synthase 2 (HAS2), laminin subunit beta 1 (LAMB1), lumican (LUM), cadherin 1 (CDH1), collagen type IV alpha (COL4A1), fibrillin (FBN) and versican (VCAN)), Zn2+ was able to upregulate SOD1, CAT, TGFB1, GPX1, LUM, CDH1, FBN and VCAN, with relative expression levels of at least 1.9-fold with respect to controls. We found that ZnCl2 promoted glycoprotein synthesis and antioxidant gene expression, thus confirming its great potential in biomedicine.

Combined therapy of platelet-rich plasma and basic fibroblast growth factor using gelatin-hydrogel sheet for rotator cuff healing in rat models

Introduction

Excellent outcomes of arthroscopic rotator cuff repair for small and medium tears have been recently reported. However, re-tears after surgery have been a common complication after surgical repair of large and massive rotator cuff tears and often occur in early postoperative phase. It was previously reported that basic fibroblast growth factor and platelet-rich plasma enhanced rotator cuff tear healing. We hypothesized that this combined therapy could enhance rotator cuff healing after rotator cuff repair in a rat model. This study aimed to evaluate the efficacy of combined therapy of platelet-rich plasma and basic fibroblast growth factor with gelatin-hydrogel sheet.

Methods

To create a rotator cuff defect, the infraspinatus tendon of Sprague Dawley rat was resected from the greater tuberosity. The infraspinatus tendons were repaired and covered with gelatin-hydrogel sheet impregnated with PBS (control group), basic fibroblast growth factor (bFGF group), platelet-rich plasma (PRP group), or both basic fibroblast growth factor and platelet-rich plasma (combined group). Histological examinations were conducted using hematoxylin and eosin, safranin O, and immunofluorescence staining, such as Isolectin B4, type II collagen at 2 weeks postoperatively. For mechanical analysis, ultimate failure load of the tendon-humeral head complex was evaluated at 6 weeks postoperatively.

Results

In the hematoxylin and eosin staining, the tendon maturing score of the combined group was higher than that of the control group at postoperative 2 weeks. In the safranin O staining, stronger proteoglycan staining was observed in the combined group compared with the other groups at postoperative 2 weeks. Vascular staining with isolectin B4 in 3 treatment groups was significantly higher than that in the control group. Type II collagen expression in the combined group was significantly higher than those in the other groups. The ultimate failure load of the combined group was significantly higher than that of the control group.

Conclusion

Combined therapy of basic fibroblast growth factor and platelet-rich plasma promoted angiogenesis, tendon maturing and fibrocartilage regeneration at the enthesis, which could enhance the mechanical strength. It was suggested that combined basic fibroblast growth factor and platelet-rich plasma might enhance both tendon and bone–tendon junction healing, and basic fibroblast growth factor and platelet-rich plasma might be synergistic.

Engineering Bioactive Scaffolds for Skin Regeneration

Large skin wounds pose a major clinical challenge. Scarcity of donor site and postsurgical scarring contribute to the incomplete or partial loss of function and aesthetic concerns in skin wound patients. Currently, a wide variety of skin grafts are being applied in clinical settings. Scaffolds are used to overcome the issues related to the misaligned architecture of the repaired skin tissues. The current review summarizes the contribution of biomaterials to wound healing and skin regeneration and addresses the existing limitations in skin grafting. Then, the clinically approved biologic and synthetic skin substitutes are extensively reviewed. Next, the techniques for modification of skin grafts aiming for enhanced tissue regeneration are outlined, and a summary of different growth factor delivery systems using biomaterials is presented. Considering the significant progress in biomaterial science and manufacturing technologies, the idea of biomaterial-based skin grafts with the ability for scarless wound healing and reconstructing full skin organ is more achievable than ever.

A Pilot Investigation Generating an Alternative Therapeutic Strategy Combining Deproteinized Bovine Bone and Gelatin Sponge for a Novel Implant Material in Sinus Floor Elevation Operation

Background

Implant placement in the posterior maxilla is typically complicated by a shortage of bone. Gelatin sponge could be combined with an appropriate material to enhance mechanical strength and maintain stability of an implant. This study aimed to evaluate the clinical application of bone grafting with bovine bone mixed with gelatin sponge.

Material/Methods

Fifty-four patients were divided into a control group (deproteinized bovine bone, n=26) and a test group (deproteinized bovine bone combined with gelatin sponge, n=28). Implants were placed in patients simultaneously after surgery (operation). Cone-beam computed tomography examination was carried out immediately and 6 months after surgery. Space with grafting materials was measured with Mimics software (version 16.0).

Results

No remarkable differences were found for simultaneous placement, height of residual bone, delayed placement, width of residual bone, graft volume immediately after surgery (V₁), graft volume 6 months after surgery (V₂), or volumetric change rate between the test group and the control group (P>0.05). Graft volume V₂ was remarkably decreased compared with V₁ in the control and test groups (P=0.01). There were no significant differences for bone height immediately after surgery (H₁) and bone height at 6 months after surgery (H₂) between the 2 groups. Bone height H₂ was markedly decreased compared with H₁ (P<0.05). At 1 year after implantation, there was 1 implant loss in the control group and 2 in the test group. The implant survival rate in the control group was 97.62% and 95.24% in the test group.

Conclusions

Absorbable gelatin sponge combined with bovine bone particles was an effective and economical material for use in routine sinus floor elevation surgery.

Endothelial Progenitor Cell-Derived Extracellular Vesicles: Potential Therapeutic Application in Tissue Repair and Regeneration

Recently, many studies investigated the role of a specific type of stem cell named the endothelial progenitor cell (EPC) in tissue regeneration and repair. EPCs represent a heterogeneous population of mononuclear cells resident in the adult bone marrow. EPCs can migrate and differentiate in injured sites or act in a paracrine way. Among the EPCs’ secretome, extracellular vesicles (EVs) gained relevance due to their possible use for cell-free biological therapy. They are more biocompatible, less immunogenic, and present a lower oncological risk compared to cell-based options. EVs can efficiently pass the pulmonary filter and deliver to target tissues different molecules, such as micro-RNA, growth factors, cytokines, chemokines, and non-coding RNAs. Their effects are often analogous to their cellular counterparts, and EPC-derived EVs have been tested in vitro and on animal models to treat several medical conditions, including ischemic stroke, myocardial infarction, diabetes, and acute kidney injury. EPC-derived EVs have also been studied for bone, brain, and lung regeneration and as carriers for drug delivery. This review will discuss the pre-clinical evidence regarding EPC-derived EVs in the different disease models and regenerative settings. Moreover, we will discuss the translation of their use into clinical practice and the possible limitations of this process.

In vitro Toxico-genomics of Etoposide Loaded Gelatin Nanoparticles and Its in-vivo Therapeutic Potential: Pharmacokinetics, Biodistribution and Tumor Regression in Ehrlich Ascites Carcinoma (EAC) Mice Model

Globally, breast cancer is the foremost cause of mortality among women detected with cancer, with 21% diagnosed in India alone. Etoposide loaded gelatin nanoparticles (EGNP) were prepared and its physical characterization (size:150nm±0.241; zeta potential −29.32 mV) was done along with in-vitro studies to assess biotoxicity, intracellular ROS, cell cycle arrest and death caused by EGNPs. We report the molecular pathways induced by EGNP in-vitro, pharmacokinetics, biodistribution and tumor regression in-vivo in Balb/c mice.Gene expression profiling of Bax, Bcl2, p53, Caspase-3, RIPK1, RIPK3 and ß-actin as internal control were done by RT-PCR wherein Etoposide and EGNP treated MCF-7 cells showed higher expressions of apoptotic genes-Bax, p53, caspase-3, lower expression of anti-apoptotic gene-Bcl2 when compared to control. Enhanced expression of necroptosis-RIPK1 were observed, while RIPK3 was insignificant. Since, RIPK1 regulates necroptosis and apoptosis, expression of apoptotic markers confirmed apoptotic molecular mechanisms. Negligible hemolysis of Gelatin nanoparticles (GNP), and EGNP at selected dosages confirmed biocompatibility. In vivo pharmacokinetics and biodistribution were done by 99Tc-labelled nanoparticles indicating increased circulation of EGNPs, allowing accumulation at the tumor site by Enhanced permeability and retention (EPR) phenomena. Tumor regression indicates the efficacy of EGNP by reducing the tumor burden when compared to void GNP and Etop per se, resulting in increased life span. High biocompatibility and bio-efficacy of EGNPs prove their therapeutic potential in cancer treatment.

Synthesis of nanohydroxyapatite/collagen-loaded fucoidan-based composite hydrogel for drug delivery to gastrointestinal cancer cells

The present study aims to evaluate the synthesis of nanohydroxyapatite/collagen-loaded fucoidan-based composite hydrogel and characterized its physico-chemical properties for targeted drug delivery to gastrointestinal cancer cells. The nanomaterial is fabricated and characterized as small spherical nanosheets with a high thermal stability by using Fourier transform infrared (FTIR) analysis, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), UV-vis spectrophotometry (UV-vis), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). in vitro cytotoxicity, BrdU cell proliferation, and scratch assays demonstrate that the nanohydroxyapatite/collagen-loaded fucoidan-based nanomaterial exhibits non-toxicity and increases cell proliferation and migration. in vitro free radical scavenging assays confirm that the fabricated nanomaterial inhibits reactive oxygen species and generates singlet oxygen radicals in the gastrointestinal cancer cells by. The current findings suggest that the proposed nanomaterial can be a potential carrier for the targeted drug delivery to the gastrointestinal cancer cells.

Prenatal Neural Tube Anomalies: A Decade of Intrauterine Stem Cell Transplantation Using Advanced Tissue Engineering Methods

Neural tube defects (NTDs) are among the most common congenital defects during neurulation. Spina bifida is a type of NTD that can occur in different forms. Since myelomeningocele (MMC) is the most severe form of spina bifida, finding a satisfactory treatment for MMC is a gold standard for the treatment of spina bifida. The Management of Myelomeningocele Study (MOMS) demonstrated that intrauterine treatment of spina bifida could ameliorate the complications associated with spina bifida and would also reduce the placement of ventriculoperitoneal (VP) shunt by 50%. Recently developed tissue engineering (TE) approaches using scaffolds, stem cells, and growth factors allow treatment of the fetus with minimally invasive methods and promising outcomes. The application of novel patches with appropriate stem cells and growth factors leads to better coverage of the defect with fewer complications. These approaches with less invasive surgical procedures, even in animal models with similar characteristics as the human MMC defect, paves the way for the modern application of less invasive surgical methods. Significantly, the early detection of these problems and applying these approaches can increase the potential efficacy of MMC treatment with fewer complications. However, further studies should be conducted to find the most suitable scaffolds and stem cells, and their application should be evaluated in animal models. This review intends to discuss advanced TE methods for treating MMC and recent successes in increasing the efficacy of the treatment.

A Bibliometric Analysis of the Global Trend of Using Alginate, Gelatine, and Hydroxyapatite for Bone Tissue Regeneration Applications

Collecting information from previous investigations and expressing it in a scientometrics study can be a priceless guide to getting a complete overview of a specific research area. The aim of this study is to explore the interrelated connection between alginate, gelatine, and hydroxyapatite within the scope of bone tissue and scaffold. A review of traditional literature with data mining procedures using bibliometric analyses was considered to identify the evolution of the selected research area between 2009 and 2019. Bibliometric methods and knowledge visualization technologies were implemented to investigate diverse publications based on the following indicators: year of publication, document type, language, country, institution, author, journal, keyword, and number of citations. An analysis using a bibliometric study found that 7446 papers were located with the keywords "bone tissue" and "scaffold", and 1767 (alginate), 185 (gelatine), 5658 (hydroxyapatite) papers with those specific sub keywords. The number of publications that relate to "tissue engineering" and bone more than doubled between 2009 (1352) and 2019 (2839). China, the United States and India are the most productive countries, while Sichuan University and the Chinese Academy of Science from China are the most important institutions related to bone tissue scaffold. Materials Science and Engineering C is the most productive journal, followed by the Journal of Biomedical Materials Research Part A. This paper is a starting point, providing the first bibliometric analysis study of bone tissue and scaffold considering alginate, gelatine and hydroxyapatite. A bibliometric analysis would greatly assist in giving a scientific insight to support desired future research work, not only associated with bone tissue engineering applications. It is expected that the analysis of alginate, gelatine and hydroxyapatite in terms of 3D bioprinting, clinical outcomes, scaffold architecture, and the regenerative medicine approach will enhance the research into bone tissue engineering in the near future. Continued studies into these research fields are highly recommended.

Beneficial Roles of Cellulose Patch-Mediated Cell Therapy in Myocardial Infarction: A Preclinical Study

Biological scaffolds have become an attractive approach for repairing the infarcted myocardium and have been shown to facilitate constructive remodeling in injured tissues. This study aimed to investigate the possible utilization of bacterial cellulose (BC) membrane patches containing cocultured cells to limit myocardial postinfarction pathology. Myocardial infarction (MI) was induced by ligating the left anterior descending coronary artery in 45 Wistar rats, and patches with or without cells were attached to the hearts. After one week, the animals underwent echocardiography to assess for ejection fraction and left ventricular end-diastolic and end-systolic volumes. Following patch formation, the cocultured cells retained viability of >90% over 14 days in culture. The patch was applied to the myocardial surface of the infarcted area after staying 14 days in culture. Interestingly, the BC membrane without cellular treatment showed higher preservation of cardiac dimensions; however, we did not observe improvement in the left ventricular ejection fraction of this group compared to coculture-treated membranes. Our results demonstrated an important role for BC in supporting cells known to produce cardioprotective soluble factors and may thus provide effective future therapeutic outcomes for patients suffering from ischemic heart disease.

Regeneration using endogenous neural stem cells following neonatal brain injury

Despite recent advancements in perinatal care, the incidence of neonatal brain injury has not decreased. No therapies are currently available to repair injured brain tissues. In the postnatal brain, neural stem cells reside in the ventricular-subventricular zone (V-SVZ) and continuously generate new immature neurons (neuroblasts). After brain injury in rodents, V-SVZ-derived neuroblasts migrate toward the injured area using blood vessels as a scaffold. Notably, the neonatal V-SVZ has a remarkable neurogenic capacity. Furthermore, compared with the adult brain, after neonatal brain injury, larger numbers of neuroblasts migrate toward the lesion, raising the possibility that the V-SVZ could be a source for endogenous neuronal regeneration after neonatal brain injury. We recently demonstrated that efficient migration of V-SVZ-derived neuroblasts toward a lesion is supported by neonatal radial glia via neural cadherin (N-cadherin)-mediated neuron-fiber contact, which promotes RhoA activity. Moreover, providing blood vessel- and radial glia-mimetic scaffolds for migrating neuroblasts promotes neuronal migration and improves functional gait behaviors after neonatal brain injury. In the V-SVZ, oligodendrocyte progenitor cells (OPCs) are also generated and migrate toward the surrounding white matter, where they differentiate and form myelin. After white matter injury in rodents, the production and subsequent migration of V-SVZ-derived OPCs are enhanced. In the neonatal period, administration of growth factors at a specific time promotes oligodendrocyte regeneration and functional recovery after brain injury. These findings suggest that activating the high regenerative capacity that is specific to the neonatal period could lead to the development of new therapeutic strategies for neonatal brain injury.

Chitosan and Cellulose-Based Hydrogels for Wound Management

Wound management remains a challenge worldwide, although there are several developed wound dressing materials for the management of acute and chronic wounds. The wound dressings that are currently used include hydrogels, films, wafers, nanofibers, foams, topical formulations, transdermal patches, sponges, and bandages. Hydrogels exhibit unique features which make them suitable wound dressings such as providing a moist environment for wound healing, exhibiting high moisture content, or creating a barrier against bacterial infections, and are suitable for the management of exuding and granulating wounds. Biopolymers have been utilized for their development due to their non-toxic, biodegradable, and biocompatible properties. Hydrogels have been prepared from biopolymers such as cellulose and chitosan by crosslinking with selected synthetic polymers resulting in improved mechanical, biological, and physicochemical properties. They were useful by accelerating wound re-epithelialization and also mimic skin structure, inducing skin regeneration. Loading antibacterial agents into them prevented bacterial invasion of wounds. This review article is focused on hydrogels formulated from two biopolymers-chitosan and cellulose-for improved wound management.

Carbonaceous Nanomaterials-Mediated Defense Against Oxidative Stress

The concept of nanoscale materials and their applications in industrial technologies, consumer goods, as well as in novel medical therapies has rapidly escalated in the last several years. Consequently, there is a critical need to understand the mechanisms that drive nanomaterials biocompatibility or toxicity to human cells and tissues. The ability of nanomaterials to initiate cellular pathways resulting in oxidative stress has emerged as a leading hypothesis in nanotoxicology. Nevertheless, there are a few examples revealing another face of nanomaterials - they can alleviate oxidative stress via decreasing the level of reactive oxygen species. The fundamental structural and physicochemical properties of carbonaceous nanomaterials that govern these anti-oxidative effects are discussed in this article. The signaling pathways influenced by these unique nanomaterials, as well as examples of their applications in the biomedical field, e.g. cell culture, cell-based therapies or drug delivery, are presented. We anticipate this emerging knowledge of intrinsic anti-oxidative properties of carbon nanomaterials to facilitate the use of tailored nanoparticles in vivo.

Addition of glycerol enhances the flexibility of gelatin hydrogel sheets; application for in utero tissue engineering

Gelatin hydrogels are naturally derived scaffolds useful for tissue engineering because of their cytocompatibility and controllable degradability. However, they are brittle and inflexible when dry, which limits their use for in utero tissue engineering in large animal models. Therefore, in this study, we attempted to generate flexible gelatin sheets by adding various plasticizers with different molecular weights (MW). We systematically evaluated the flexibility, sustainability, and potential clinical utility of the resulting flexible gelatin sheets. Gelatin sheets with low-MW plasticizers, such as monosaccharides or sugar alcohols, showed a reduced tensile modulus in dynamic viscoelasticity, which reflected their actual flexibility. Wet gelatin sheets containing plasticizers showed higher tensile strength than the nonplasticizer control, although wet gelatin sheets under all conditions had a much lower tensile strength than dry gelatin sheets. In a functional study, gelatin sheets containing glycerol, which has the lowest MW among sugar alcohols, showed encouraging results, such as good fit to the curvature of the experimental animal, biocompatibility, and suitability for endoscopic approaches. The findings of this study should enable the expansion of future applications for flexible gelatin sheets.

Engineered Extracellular Vesicles: Tailored-Made Nanomaterials for Medical Applications

Extracellular vesicles (EVs) are emerging as promising nanoscale therapeutics due to their intrinsic role as mediators of intercellular communication, regulating tissue development and homeostasis. The low immunogenicity and natural cell-targeting capabilities of EVs has led to extensive research investigating their potential as novel acellular tools for tissue regeneration or for the diagnosis of pathological conditions. However, the clinical use of EVs has been hindered by issues with yield and heterogeneity. From the modification of parental cells and naturally-derived vesicles to the development of artificial biomimetic nanoparticles or the functionalisation of biomaterials, a multitude of techniques have been employed to augment EVs therapeutic efficacy. This review will explore various engineering strategies that could promote EVs scalability and therapeutic effectiveness beyond their native utility. Herein, we highlight the current state-of-the-art EV-engineering techniques with discussion of opportunities and obstacles for each. This is synthesised into a guide for selecting a suitable strategy to maximise the potential efficacy of EVs as nanoscale therapeutics.

Cell Biological Techniques and Cell-Biomaterial Interactions

Biomaterials play a key role in modern tissue engineering and regenerative medicine. They are expected to take over the function of a damaged tissue in the long term, trigger the self-healing potential of the body, and biodegrade at an appropriate rate. To meet these requirements, it is imperative to understand the cell-biomaterial interactions and develop new cell biotechnologies. The collection of this Special Issue brings together a number of studies portraying the underlying mechanisms of cell-biomaterial interactions.

Cell attachment effects of collagen nanoparticles on crosslinked electrospun nanofibers

Since collagen is naturally a main extracellular matrix protein, it has been applied widely in skin's tissue engineering scaffolds to mimics the characteristics of extracellular matrix for proper transplantation of living cells. However, there are challenges that come with application of this natural polymer such as high solubility in aqueous environments which requires further consideration such as chemically cross-linking in order to stabilization. But these treatments also affect its functionality and finally cellular behaviors on scaffold. In this research we evaluated the suitability of collagen nanofibers versus collagen nanoparticles for cell adhesion and viability on glutaraldehyde cross-linked scaffolds. Appling a dual-pump electrospining machine a blend PCL-Gelatin from one side and collagen nanofibers or collagen nanoparticles from the other side were collected on the collector. The fabricated scaffolds were characterized by scanning electron microscopy, contact angle, and mechanical analysis. The cell viability, adhesion and morphology were studied respectively using MTT assay, hoechst staining and scanning electron microscopy. The results indicated significantly improvement of cell viability, adhesion and better spreading on scaffolds with collagen nanoparticles than collagen nanofibers. It seems changes in surface morphology, viscoelastic moduli and swelling ability following cross-linking with glutaraldehyde in scaffold with collagen nanoparticles are still favorable for cellular proliferation. Based on these results, in the case of glutaraldehyde cross-linking, application of collagen nanoparticles rather than collagen nanofibers in tissue regeneration scaffolds will better mimic the extracellular matrix characteristics; and preserve the viability and adhesion of seeded cells.