Hydrogel matrices based on elastin and alginate for tissue engineering applications

Design and evaluation of a bilayered dermal/hypodermal 3D model using a biomimetic hydrogel formulation

Due to the limitations of the current skin wound treatments, it is highly valuable to have a wound healing formulation that mimics the extracellular matrix (ECM) and mechanical properties of natural skin tissue. Here, a novel biomimetic hydrogel formulation has been developed based on a mixture of Agarose-Collagen Type I (AC) combined with skin ECM-related components: Dermatan sulfate (DS), Hyaluronic acid (HA), and Elastin (EL) for its application in skin tissue engineering (TE). Different formulations were designed by combining AC hydrogels with DS, HA, and EL. Cell viability, hemocompatibility, physicochemical, mechanical, and wound healing properties were investigated. Finally, a bilayered hydrogel loaded with fibroblasts and mesenchymal stromal cells was developed using the Ag-Col I-DS-HA-EL (ACDHE) formulation. The ACDHE hydrogel displayed the best in vitro results and acceptable physicochemical properties. Also, it behaved mechanically close to human native skin and exhibited good cytocompatibility. Environmental scanning electron microscopy (ESEM) analysis revealed a porous microstructure that allows the maintenance of cell growth and ECM-like structure production. These findings demonstrate the potential of the ACDHE hydrogel formulation for applications such as an injectable hydrogel or a bioink to create cell-laden structures for skin TE.

A new strategy for intervertebral disc regeneration: The synergistic potential of mesenchymal stem cells and their extracellular vesicles with hydrogel scaffolds

Intervertebral disc degeneration (IDD) is a disease that severely affects spinal health and is prevalent worldwide. Mesenchymal stem cells (MSCs) and their derived extracellular vesicles (EVs) have regenerative potential and have emerged as promising therapeutic tools for treating degenerative discs. However, challenges such as the harsh microenvironment of degenerated intervertebral discs and EVs' limited stability and efficacy have hindered their clinical application. In recent years, hydrogels have attracted much attention in the field of IDD therapy because they can mimic the physiologic microenvironment of the disc and provide a potential solution by providing a suitable growth environment for MSCs and EVs. This review introduced the biological properties of MSCs and their derived EVs, summarized the research on the application of MSCs and EVs in IDD, summarized the current clinical trial studies of MSCs and EVs, and also explored the mechanism of action of MSCs and EVs in intervertebral discs. In addition, plenty of research elaborated on the mechanism of action of different classified hydrogels in tissue engineering, the synergistic effect of MSCs and EVs in promoting intervertebral disc regeneration, and their wide application in treating IDD. Finally, the challenges and problems still faced by hydrogel-loaded MSCs and EVs in the treatment of IDD are summarized, and potential solutions are proposed. This paper outlines the synergistic effects of MSCs and EVs in treating IDD in combination with hydrogels and aims to provide theoretical references for future related studies.

Directly coaxial bioprinting of 3D vascularized tissue using novel bioink based on decellularized human amniotic membrane

Despite several progressions in the biofabrication of large-scale engineered tissues, direct biopri nting of perfusable three-dimensional (3D) vasculature remained unaddressed. Developing a feasible method to generate cell-laden thick tissue with an effective vasculature network to deliver oxygen and nutrient is crucial for preventing the formation of necrotic spots and tissue death. In this study, we developed a novel technique to directly bioprint 3D cell-laden prevascularized construct. We developed a novel bioink by mixing decellularized human amniotic membrane (dHAM) and alginate (Alg) in various ratios. The bioink with encapsulated human vein endothelial cells (HUVECs) and a crosslinker, CaCl2, were extruded via sheath and core nozzle respectively to directly bioprint a perfusable 3D vasculature construct. The various concentration of bioink was assessed from several aspects like biocompatibility, porosity, swelling, degradation, and mechanical characteristics, and accordingly, optimized concentration was selected (Alg 4 %w/v - dHAM 0.6 %w/v). Then, the crosslinked bioink without microchannel and the 3D bioprinted construct with various microchannel distances (0, 1.5 mm, 3 mm) were compared. The 3D bioprinted construct with a 1.5 mm microchannels distance demonstrated superiority owing to its 492 ± 18.8 % cell viability within 14 days, excellent tubulogenesis, remarkable expression of VEGFR-2 which play a crucial role in endothelial cell proliferation, migration, and more importantly angiogenesis, and neovascularization. This perfusable bioprinted construct also possess appropriate mechanical stability (32.35 ± 5 kPa Young's modulus) for soft tissue. Taking these advantages into the account, our new bioprinting method possesses a prominent potential for the fabrication of large-scale prevascularized tissue to serve for regenerative medicine applications like implantation, drug-screening platform, and the study of mutation disease.

Strategies for Anisotropic Fibrillar Hydrogels: Design, Cell Alignment, and Applications in Tissue Engineering

Efficient cellular alignment in biomaterials presents a considerable challenge, demanding the refinement of appropriate material morphologies, while ensuring effective cell-surface interactions. To address this, biomaterials are continuously researched with diverse coatings, hydrogels, and polymeric surfaces. In this context, we investigate the influence of physicochemical parameters on the architecture of fibrillar hydrogels that significantly orient the topography of flexible hydrogel substrates, thereby fostering cellular adhesion and spatial organization. Our Review comprehensively assesses various techniques for aligning polymer fibrils within hydrogels, specifically interventions applied during and after the cross-linking process. These methodologies include mechanical strains, precise temperature modulation, controlled fluidic dynamics, and chemical modulators, as well as the use of magnetic and electric fields. We highlight the intrinsic appeal of these methodologies in fabricating cell-aligning interfaces and discuss their potential implications within the fields of biomaterials and tissue engineering, particularly concerning the pursuit of optimal cellular alignment.

Natural Polymer-Based Hydrogels: From Polymer to Biomedical Applications

Hydrogels prepared from natural polymer have attracted extensive attention in biomedical fields such as drug delivery, wound healing, and regenerative medicine due to their good biocompatibility, degradability, and flexibility. This review outlines the commonly used natural polymer in hydrogel preparation, including cellulose, chitosan, collagen/gelatin, alginate, hyaluronic acid, starch, guar gum, agarose, and dextran. The polymeric structure and process/synthesis of natural polymers are illustrated, and natural polymer-based hydrogels including the hydrogel formation and properties are elaborated. Subsequently, the biomedical applications of hydrogels based on natural polymer in drug delivery, tissue regeneration, wound healing, and other biomedical fields are summarized. Finally, the future perspectives of natural polymers and hydrogels based on them are discussed. For natural polymers, novel technologies such as enzymatic and biological methods have been developed to improve their structural properties, and the development of new natural-based polymers or natural polymer derivatives with high performance is still very important and challenging. For natural polymer-based hydrogels, novel hydrogel materials, like double-network hydrogel, multifunctional composite hydrogels, and hydrogel microrobots have been designed to meet the advanced requirements in biomedical applications, and new strategies such as dual-cross-linking, microfluidic chip, micropatterning, and 3D/4D bioprinting have been explored to fabricate advanced hydrogel materials with designed properties for biomedical applications. Overall, natural polymeric hydrogels have attracted increasing interest in biomedical applications, and the development of novel natural polymer-based materials and new strategies/methods for hydrogel fabrication are highly desirable and still challenging.

Double network structure via ionic bond and covalent bond of carboxymethyl chitosan and poly(ethylene glycol): Factors affecting hydrogel formation

The factors were studied that affect the formation of DN hydrogel, which was prepared using a water-based, environmental-friendly system. The DN hydrogel was designed and prepared based on a cross-linked, polysaccharide-based, polymer carboxymethyl chitosan (CMCS) via an ionic crosslinking reaction for the first network structure. UV irradiation created a radical crosslinking reaction of poly(ethylene glycol) from a double bond at the chain end for the second network structure. It was found that the optimum hydrogel was produced using 9.5 %v/v of 1000PEGGMA, CMCS 5%w/v, and CaCl₂ 3%w/v. The results showed the highest percentage of the gel fraction was 87.84 % and the hydrogel was stable based on its rheological properties. Factors affecting the hydrogel formation were the concentration and molecular weight of PEGGMA and the concentrations of CMCS and calcium chloride (CaCl₂). The DN hydrogel had bioactivity due to its octacalcium phosphate (OCP) hydroxyapatite crystal form. In addition, the composite DN scaffold with a conductive polymer of chitosan-grafted-polyaniline (CS-g-PANI) had conduction of 2.33 × 10^-5 S/cm when the concentration of CS-g-PANI was 3 mg/ml, confirming the semi-conductive nature of the material. All the results indicated that DN hydrogel could be a candidate to apply in tissue-engineering applications.

Direct Ink Writing of Carbon-Doped Polymeric Composite Ink: A Review on Its Requirements and Applications

Direct Ink Writing (DIW) opens new possibilities in three-dimensional (3D) printing of carbon-based polymeric ink. This is due to its ability in design flexibility, structural complexity, and environmental sustainability. This area requires exhaustive study because of its wide application in different manufacturing sectors. The present article is related to the variant emerging 3D printing techniques and DIW of carbonaceous materials. Carbon-based materials, extensively used for various applications in 3D printing, possess impressive chemical stability, strength, and flexible nanostructure. Fine printable inks consist predominantly of uniform solutions of carbon materials, such as graphene, graphene oxide (GO), carbon fibers (CFs), carbon nanotubes (CNTs), and solvents. It also contains compatible polymers and suitable additives. This review article elaborately discusses the fundamental requirements of DIW in structuring carbon-doped polymeric inks viz. ink formulation, required ink rheology, extrusion parameters, print fidelity prediction, layer bonding examination, substrate selection, and curing method to achieve fine functional composites. A detailed description of its application in the fields of electronics, medical, and mechanical segments have also been focused in this study.

Biocompatible and bioactive hydrogels of recombinant fusion elastin with low transition temperature for improved healing of UV-irradiated skin

Prolonged exposure to UV radiation can cause severe photodamage to the skin, leading to abnormal fragmentation of elastin fibers. As one of the main protein components of the dermal extracellular matrix, elastin plays a critical role in the mechanical behavior and physiological function of the skin. Animal-derived elastin has attracted extensive attention in tissue engineering, however it suffers from severe drawbacks such as a risk of virus transmission, ready degradation, and challenging quality control. Herein, we have for the first time developed a novel recombinant fusion elastin (RFE) and its cross-linked hydrogel for improved healing efficacy for UV-irradiated skin. RFE showed temperature-sensitive aggregation behavior similar to natural elastin. Compared with recombinant elastin without the fusion V-foldon domain, RFE showed a much more ordered secondary structure and lower transition temperature. Furthermore, Native-PAGE results indicated that the addition of the V-foldon domain triggered the formation of remarkable oligomers in RFE, which may result in a more ordered conformation. Tetrakis Hydroxymethyl Phosphonium Chloride (THPC) cross-linking of RFE led to the production of a fibrous hydrogel with uniform three-dimensional porous nanostructures and excellent mechanical strength. The RFE hydrogel showed superior cellular activity, significantly promoting the survival and proliferation of human foreskin fibroblast-1 (HFF-1). Studies of mice models of UV-irradiated skin demonstrated that the RFE hydrogel pronouncedly accelerated their healing process by inhibiting epidermal hyperplasia as well as boosting the regeneration of collagen and elastin fibers. The highly biocompatible and bioactive recombinant fusion elastin and its cross-linked hydrogel provide a potent treatment for photodamaged skin, which may have promising applications in dermatology and tissue engineering.

Modification, 3D printing process and application of sodium alginate based hydrogels in soft tissue engineering: A review

Sodium alginate (SA) is an inexpensive and biocompatible biomaterial with fast and gentle crosslinking that has been widely used in biological soft tissue repair/regeneration. Especially with the advent of 3D bioprinting technology, SA hydrogels have been applied more deeply in tissue engineering due to their excellent printability. Currently, the research on material modification, molding process and application of SA-based composite hydrogels has become a hot topic in tissue engineering, and a lot of fruitful results have been achieved. To better help readers have a comprehensive understanding of the development status of SA based hydrogels and their molding process in tissue engineering, in this review, we summarized SA modification methods, and provided a comparative analysis of the characteristics of various SA based hydrogels. Secondly, various molding methods of SA based hydrogels were introduced, the processing characteristics and the applications of different molding methods were analyzed and compared. Finally, the applications of SA based hydrogels in tissue engineering were reviewed, the challenges in their applications were also analyzed, and the future research directions were prospected. We believe this review is of great helpful for the researchers working in biomedical and tissue engineering.

Pullulan-Based Hydrogels in Wound Healing and Skin Tissue Engineering Applications: A Review

Wound healing is a complex process of overlapping phases with the primary aim of the creation of new tissues and restoring their anatomical functions. Wound dressings are fabricated to protect the wound and accelerate the healing process. Biomaterials used to design dressing of wounds could be natural or synthetic as well as the combination of both materials. Polysaccharide polymers have been used to fabricate wound dressings. The applications of biopolymers, such as chitin, gelatin, pullulan, and chitosan, have greatly expanded in the biomedical field due to their non-toxic, antibacterial, biocompatible, hemostatic, and nonimmunogenic properties. Most of these polymers have been used in the form of foams, films, sponges, and fibers in drug carrier devices, skin tissue scaffolds, and wound dressings. Currently, special focus has been directed towards the fabrication of wound dressings based on synthesized hydrogels using natural polymers. The high-water retention capacity of hydrogels makes them potent candidates for wound dressings as they provide a moist environment in the wound and remove excess wound fluid, thereby accelerating wound healing. The incorporation of pullulan with different, naturally occurring polymers, such as chitosan, in wound dressings is currently attracting much attention due to the antimicrobial, antioxidant and nonimmunogenic properties. Despite the valuable properties of pullulan, it also has some limitations, such as poor mechanical properties and high cost. However, these properties are improved by blending it with different polymers. Additionally, more investigations are required to obtain pullulan derivatives with suitable properties in high quality wound dressings and tissue engineering applications. This review summarizes the properties and wound dressing applications of naturally occurring pullulan, then examines it in combination with other biocompatible polymers, such chitosan and gelatin, and discusses the facile approaches for oxidative modification of pullulan.

Development of Scaffolds from Bio-Based Natural Materials for Tissue Regeneration Applications: A Review

Tissue damage and organ failure are major problems that many people face worldwide. Most of them benefit from treatment related to modern technology's tissue regeneration process. Tissue engineering is one of the booming fields widely used to replace damaged tissue. Scaffold is a base material in which cells and growth factors are embedded to construct a substitute tissue. Various materials have been used to develop scaffolds. Bio-based natural materials are biocompatible, safe, and do not release toxic compounds during biodegradation. Therefore, it is highly recommendable to fabricate scaffolds using such materials. To date, there have been no singular materials that fulfill all the features of the scaffold. Hence, combining two or more materials is encouraged to obtain the desired characteristics. To design a reliable scaffold by combining different materials, there is a need to choose a good fabrication technique. In this review article, the bio-based natural materials and fine fabrication techniques that are currently used in developing scaffolds for tissue regeneration applications, along with the number of articles published on each material, are briefly discussed. It is envisaged to gain explicit knowledge of developing scaffolds from bio-based natural materials for tissue regeneration applications.

Application of Collagen-Based Scaffolds for the Treatment of Spinal Cord Injuries in Animal Models: A Literature Update

SCI is regarded as one of the most devastating central nervous system (CNS) injuries, exhibiting an alarmingly rising incidence rate, indirectly connected with the expansion of the global economy. The consequences of SCI are multidimensional: SCI injuries may result in permanent voluntary motor dysfunction and loss of sensation while incurring heavy economic and psychological burdens as part of the treatment. Thus, it is crucial to develop effective and suitable SCI treatment strategies. Collagen-based scaffold application is one of the most promising methods of SCI treatment.

This review compiles newer bibliographical data regarding the application of collagen scaffolds for the treatment of Spinal cord injury (SCI) in animal models. Recently, several relevant studies have been carried out using carefully selected animals with similar pathophysiology to humans. In mouse, rat and canine models that have undergone transection or hemisection, the stump connection, the transplanted cell differentiation, and the elimination of glial scar are promising. Also, encouraging results have been found regarding the increased neuronal growth, the decreased collagen deposition, the behavioral recovery, the improved electrophysiology, and the enhanced axonal regeneration. 

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

Milestones and current achievements in development of multifunctional bioscaffolds for medical application

Tissue engineering (TE) is a rapidly growing interdisciplinary field, which aims to restore or improve lost tissue function. Despite that TE was introduced more than 20 years ago, innovative and more sophisticated trends and technologies point to new challenges and development. Current challenges involve the demand for multifunctional bioscaffolds which can stimulate tissue regrowth by biochemical curves, biomimetic patterns, active agents and proper cell types. For those purposes especially promising are carefully chosen primary cells or stem cells due to its high proliferative and differentiation potential. This review summarized a variety of recently reported advanced bioscaffolds which present new functions by combining polymers, nanomaterials, bioactive agents and cells depending on its desired application. In particular necessity of study biomaterial-cell interactions with in vitro cell culture models, and studies using animals with in vivo systems were discuss to permit the analysis of full material biocompatibility. Although these bioscaffolds have shown a significant therapeutic effect in nervous, cardiovascular and muscle, tissue engineering, there are still many remaining unsolved challenges for scaffolds improvement.

Mechanical properties of cell- and microgel bead-laden oxidized alginate-gelatin hydrogels

3D-printing technologies, such as biofabrication, capitalize on the homogeneous distribution and growth of cells inside biomaterial hydrogels, ultimately aiming to allow for cell differentiation, matrix remodeling, and functional tissue analogues. However, commonly, only the mechanical properties of the bioinks or matrix materials are assessed, while the detailed influence of cells on the resulting mechanical properties of hydrogels remains insufficiently understood. Here, we investigate the properties of hydrogels containing cells and spherical PAAm microgel beads through multi-modal complex mechanical analyses in the small- and large-strain regimes. We evaluate the individual contributions of different filler concentrations and a non-fibrous oxidized alginate-gelatin hydrogel matrix on the overall mechanical behavior in compression, tension, and shear. Through material modeling, we quantify parameters that describe the highly nonlinear mechanical response of soft composite materials. Our results show that the stiffness significantly drops for cell- and bead concentrations exceeding four million per milliliter hydrogel. In addition, hydrogels with high cell concentrations (≥6 mio ml^-1) show more pronounced material nonlinearity for larger strains and faster stress relaxation. Our findings highlight cell concentration as a crucial parameter influencing the final hydrogel mechanics, with implications for microgel bead drug carrier-laden hydrogels, biofabrication, and tissue engineering.

Differential Responses to Bioink-Induced Oxidative Stress in Endothelial Cells and Fibroblasts

A hydrogel system based on oxidized alginate covalently crosslinked with gelatin (ADA-GEL) has been utilized for different biofabrication approaches to design constructs, in which cell growth, proliferation and migration have been observed. However, cell-bioink interactions are not completely understood and the potential effects of free aldehyde groups on the living cells have not been investigated. In this study, alginate, ADA and ADA-GEL were characterized via FTIR and NMR, and their effect on cell viability was investigated. In the tested cell lines, there was a concentration-dependent effect of oxidation degree on cell viability, with the strongest cytotoxicity observed after 72 h of culture. Subsequently, primary human cells, namely fibroblasts and endothelial cells (ECs) were grown in ADA and ADA-GEL hydrogels to investigate the molecular effects of oxidized material. In ADA, an extremely strong ROS generation resulting in a rapid depletion of cellular thiols was observed in ECs, leading to rapid necrotic cell death. In contrast, less pronounced cytotoxic effects of ADA were noted on human fibroblasts. Human fibroblasts had higher cellular thiol content than primary ECs and entered apoptosis under strong oxidative stress. The presence of gelatin in the hydrogel improved the primary cell survival, likely by reducing the oxidative stress via binding to the CHO groups. Consequently, ADA-GEL was better tolerated than ADA alone. Fibroblasts were able to survive the oxidative stress in ADA-GEL and re-entered the proliferative phase. To the best of our knowledge, this is the first report that shows in detail the relationship between oxidative stress-induced intracellular processes and alginate di-aldehyde-based bioinks.

Progress in Modern Marine Biomaterials Research

The growing demand for new, sophisticated, multifunctional materials has brought natural structural composites into focus, since they underwent a substantial optimization during long evolutionary selection pressure and adaptation processes. Marine biological materials are the most important sources of both inspiration for biomimetics and of raw materials for practical applications in technology and biomedicine. The use of marine natural products as multifunctional biomaterials is currently undergoing a renaissance in the modern materials science. The diversity of marine biomaterials, their forms and fields of application are highlighted in this review. We will discuss the challenges, solutions, and future directions of modern marine biomaterialogy using a thorough analysis of scientific sources over the past ten years.

Bone-derived dECM/alginate bioink for fabricating a 3D cell-laden mesh structure for bone tissue engineering

Alginate bioink has been widely employed to fabricate 3D cell-laden structures because of its low toxicity, appropriate biocompatibility, and easy/fast cross-linking ability. However, the low bioactivity of the hydrogel is a main shortcoming, so that physical or chemical modification with bioactive components is a promising strategy to efficiently increase the biological activity of alginate hydrogel. The present study proposes a new method to obtain bioactive alginate-based bioink by supplementing it with methacrylated (Ma)-decellularized extracellular matrix (dECM) derived from bone tissues. We demonstrate that the appropriate processing conditions and concentration of Ma-dECM in the bioink offer not only reasonable printability for fabricating 3D cell-laden structures, but also meaningful cell viability of the printed cell-laden construct. Moreover, the biologically improved microenvironment of alginate-based cell-laden structures formed using our method demonstrated a substantial effect on the osteogenic differentiation of the human adipose derived stem cells that were laden in the bioink.

Biomedical Applications of Hemicellulose-Based Hydrogels

Background:

Hydrogel has a three-dimensional network structure that is able to absorb a large amount of water/liquid and maintain its original structure. Hemicellulose (HC) is the second most abundant polysaccharide after cellulose in plants and a heterogeneous polysaccharide consisting of various saccharide units. The unique physical and chemical properties of hemicellulose make it a promising material for hydrogels.

Methods:

This review first summarizes the three research hotspots on the hemicellulose-based hydrogels: intelligence, biodegradability and biocompatibility. It also overviews the progress in the fabrication and applications of hemicellulose hydrogels in the drug delivery system and tissue engineering (articular cartilage, cell immobilization, and wound dressing).

Results:

Hemicellulose-based hydrogels have many unique properties, such as stimuliresponsibility, biodegradability and biocompatibility. Interpenetrating networking can endow appropriate mechanical properties to hydrogels. These properties make the hemicellulose-based hydrogels promising materials in biomedical applications such as drug delivery systems and tissue engineering (articular cartilage, cell immobilization, and wound dressing).

Conclusion:

Hydrogels have been widely used in biomedicine and tissue engineering areas, such as tissue fillers, drug release agents, enzyme encapsulation, protein electrophoresis, contact lenses, artificial plasma, artificial skin, and tissue engineering scaffold materials. This article reviews the recent progress in the fabrication and applications of hemicellulose-based hydrogels in the biomedical field.

Development of NSAID-loaded nano-composite scaffolds for skin tissue engineering applications

Scar free healing together with pain management is one of the major considerations in full thickness wound healing. Extensive wounds take longer to heal without any clinical intervention and, hence, need natural or artificial extracellular matrix support for quick skin regeneration. To address these issues, medicated 3D porous biomimetic scaffolds were developed with a unique combination of biopolymers, that is, chitosan, sodium alginate, and elastin, supplemented with a non-steroidal anti-inflammatory drug (NSAID). Scaffolds were physically characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), swelling ratio analysis, and degradation studies. Findings of the performed analyses proved that these skin substitutes suitable for skin tissue engineering applications attributable to their nano-microporous structures (pore size in range of 0.085-256 μm) allowing cell infiltration and high-water absorption capacity for management of wound exudates. Optimal dose of the loaded ibuprofen was estimated by evaluating effect of variable concentrations of ibuprofen (control, ILM-10, ILM-15, and ILM-20) on adipose tissue-derived mesenchymal stem cells (ASCs) proliferation rate. Out of all experimental groups, ILM-20 constructs were found to accelerate the proliferation rate of seeded ASCs confirming their non-cytotoxic characteristics as well potential to be used for translational scaffold-based therapies.

Biodegradable Polymers as the Pivotal Player in the Design of Tissue Engineering Scaffolds

Biodegradable polymers play a pivotal role in in situ tissue engineering. Utilizing various technologies, researchers have been able to fabricate 3D tissue engineering scaffolds using biodegradable polymers. They serve as temporary templates, providing physical and biochemical signals to the cells and determining the successful outcome of tissue remodeling. Furthermore, a biodegradable scaffold also presents the fourth dimension for tissue engineering, namely time. The properties of the biodegradable polymer change over time, presenting continuously changing features during the degradation process. These changes become more complicated when different materials are combined together to fabricate a composite or heterogeneous scaffold. This review undertakes a systematic analysis of the basic characteristics of biodegradable polymers and describe recent advances in making composite biodegradable scaffolds for in situ tissue engineering and regenerative medicine. The interaction between implanted biodegradable biomaterials and the in vivo environment are also discussed, including the properties and functional changes of the degradable scaffold, the local effect of degradation on the contiguous tissue and their evaluation using both in vitro and in vivo models.

Synthesis, Characterization, and Histological Evaluation of Chitosan-Ruta Graveolens Essential Oil Films

The development of new biocompatible materials for application in the replacement of deteriorated tissues (due to accidents and diseases) has gained a lot of attention due to the high demand around the world. Tissue engineering offers multiple options from biocompatible materials with easy resorption. Chitosan (CS) is a biopolymer derived from chitin, the second most abundant polysaccharide in nature, which has been highly used for cell regeneration applications. In this work, CS films and Ruta graveolens essential oil (RGEO) were incorporated to obtain porous and resorbable materials, which did not generate allergic reactions. An oil-free formulation (F1: CS) and three different formulations containing R. graveolens essential oil were prepared (F2: CS-RGEO 0.5%; F3: CS+RGEO 1.0%; and F4: CS+RGEO 1.5%) to evaluate the effect of the RGEO incorporation in the mechanical and thermal stability of the films. Infrared spectroscopy (FTIR) analyses demonstrated the presence of RGEO. In contrast, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis showed that the crystalline structure and percentage of CS were slightly affected by the RGEO incorporation. Interesting saturation phenomena were observed for mechanical and water permeability tests when RGEO was incorporated at higher than 0.5% (v/v). The results of subdermal implantation after 30 days in Wistar rats showed that increasing the amount of RGEO resulted in greater resorption of the material, but also more significant inflammation of the tissue surrounding the materials. On the other hand, the thermal analysis showed that the RGEO incorporation almost did not affect thermal degradation. However, mechanical properties demonstrated an understandable loss of tensile strength and Young’s modulus for F3 and F4. However, given the volatility of the RGEO, it was possible to generate a slightly porous structure, as can be seen in the microstructure analysis of the surface and the cross-section of the films. The cytotoxicity analysis of the CS+RGEO compositions by the hemolysis technique agreed with in vivo results of the low toxicity observed. All these results demonstrate that films including crude essential oil have great application potential in the biomedical field.

Fabrication of Nanofibrous/Xerogel Layer-by-Layer Biocomposite Scaffolds for Skin Tissue Regeneration: In Vitro Study

Skin burn wounds are a crucial issue that could reduce life quality. Although numerous effective skin products have invaded the biomedical market, most of them still demonstrate some limitations regarding their porosity, swelling and degradation behaviors, antibacterial properties, and cytotoxicity. Thus, the aim of this study is to fabricate novel trilayered asymmetric porous scaffolds that can mimic the natural skin layers. In particular, the fabricated scaffold constitutes an upper electrospun chitosan-poly(vinyl alcohol) layer and a lower xerogel layer, which is made of effective skin extracellular matrix components. Both layers are fixed together using fibrin glue as a middle layer. The results of this study revealed promising scaffold swelling capability suitable for absorbing wound exudates, followed by a constant degradable weight over time, which is appropriate for a burn wound environment. Scanning electron microscopy images revealed an average pore diameter in the range of 138.39-170.18 nm for the cross-linked electrospun mats and an average pore size of 2.29-30.62 μm for the fabricated xerogel layers. This further provided an optimum environment for fibroblast migration and proliferation. The electrospun nanofibrous layer was examined for its antibacterial properties and showed expressive complete bacterial inhibition against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains (log reduction = 3 and 2.70, respectively). Next, mouse embryonic fibroblast cytotoxicity and migration rate were investigated against the developed asymmetrical composite to assess its biocompatibility. Tissue culture experiments demonstrated significant cell proliferation and migration in the presence of the constructed scaffold (P < 0.0001). A complete wound closure was observed in vitro in the presence of the three scaffold asymmetrical layers against the mouse embryonic fibroblast. The results of this study proved superior biological characteristics of the innovative asymmetrical composite that could further replace the burned or damaged skin layers with promising potential for clinical applications.

Tissue Engineering: Understanding the Role of Biomaterials and Biophysical Forces on Cell Functionality Through Computational and Structural Biotechnology Analytical Methods

Within the past 25 years, tissue engineering (TE) has grown enormously as a science and as an industry. Although classically concerned with the recapitulation of tissue and organ formation in our body for regenerative medicine, the evolution of TE research is intertwined with progress in other fields through the examination of cell function and behaviour in isolated biomimetic microenvironments. As such, TE applications now extend beyond the field of tissue regeneration research, operating as a platform for modifiable, physiologically-representative in vitro models with the potential to improve the translation of novel therapeutics into the clinic through a more informed understanding of the relevant molecular biology, structural biology, anatomy, and physiology. By virtue of their biomimicry, TE constructs incorporate features of extracellular macrostructure, molecular adhesive moieties, and biomechanical properties, converging with computational and structural biotechnology advances. Accordingly, this mini-review serves to contextualise TE for the computational and structural biotechnology reader and provides an outlook on how the disciplines overlap with respect to relevant advanced analytical applications.

Soy Protein-Based Composite Hydrogels: Physico-Chemical Characterization and In Vitro Cytocompatibility

Novel composite hydrogels based on the combination of alginate (Alg), soy protein isolate (SPI) and bioactive glass (BG) nanoparticles were developed for soft tissue engineering. Human umbilical vein endothelial cells (HUVEC) and normal human dermal fibroblasts were cultivated on hydrogels for 7, 14 and 21 days. Cell morphology was visualized using fluorescent staining at Days 7 and 14 for fibroblast cells and Days 14 and 21 for HUVEC. Metabolic activity of cells was analyzed using a colorimetric assay (water soluble tetrazolium (WST) assay). Compared to pure Alg, Alg/SPI and Alg/SPI/BG provided superior surfaces for both types of cells, supporting their attachment, growth, spreading and metabolic activity. Fibroblasts showed better colonization and growth on Alg/SPI/BG hydrogels compared to Alg/SPI hydrogels. The results indicate that such novel composite hydrogels might find applications in soft tissue regeneration.