Biodegradable CSMA/PECA/Graphene Porous Hybrid Scaffold for Cartilage Tissue Engineering

Advanced nanofibers integrating vitamin D3 and cerium oxide nanoparticles for enhanced diabetic wound healing: Co-electrospun silk fibroin-collagen and chitosan-PVA systems

This study investigates the co-electrospinning of polyvinyl alcohol-chitosan (PVA-CS) with cerium oxide nanoparticles (CeNPs) and silk fibroin-collagen (SF-Col) with vitamin D3 for diabetic wound healing applications. The SEM results showed smooth, bead-free nanofiber structures. The diameters of the SF-Col and PVA-CS nanofibers ranged from 168 ± 51 nm to 1956 ± 450 nm and 211.4 ± 37.2 nm, respectively. By surface modification using fetal bovine serum (FBS), CeNPs dispersion was enhanced. The average diameter of the uniformly distributed fibers on the SF-Co-D/PVA-CS-CeNPs nanofibers was 621.4 ± 50.6 nm. The addition of CeNPs and vitamin D3 improved cytocompatibility at lower doses. The FTIR test confirmed polymer interactions. Contact angle measurements indicated increased hydrophilicity. SEM analysis demonstrated excellent adhesion and growth of L929 fibroblast cells and significant HUVEC migration on SF-Col-D/PVA-CS-CeNP mats, emphasizing their potential to support cell proliferation and tissue regeneration. Blood compatibility assays exhibited hemolysis percentages below 2 %, classifying the nanofibers as non-hemolytic. Antibacterial tests revealed significant reductions in Staphylococcus aureus and Pseudomonas aeruginosa survival, addressing infection concerns in chronic wounds. Furthermore, in vivo studies have demonstrated that the utilization of SF-Co-D/PVA-CS-CeNPs nanofibrous membrane as a dressing for full-thickness skin wounds in rats has resulted in accelerated tissue regeneration.

A multicrosslinked network composite hydrogel scaffold based on DLP photocuring printing for nasal cartilage repair

Natural hydrogels are widely employed in tissue engineering and have excellent biodegradability and biocompatibility. Unfortunately, the utilization of such hydrogels in the field of three-dimensional (3D) printing nasal cartilage is constrained by their subpar mechanical characteristics. In this study, we provide a multicrosslinked network hybrid ink made of photocurable gelatin, hyaluronic acid, and acrylamide (AM). The ink may be processed into intricate 3D hydrogel structures with good biocompatibility and high stiffness properties using 3D printing technology based on digital light processing (DLP), including intricate shapes resembling noses. By varying the AM content, the mechanical behavior and biocompatibility of the hydrogels can be adjusted. In comparison to the gelatin methacryloyl (GelMA)/hyaluronic acid methacryloyl (HAMA) hydrogel, adding AM considerably enhances the hydrogel's mechanical properties while also enhancing printing quality. Meanwhile, the biocompatibility of the multicrosslinked network hydrogels and the development of cartilage were assessed using neonatal Sprague-Dawley (SD) rat chondrocytes (CChons). Cells sown on the hydrogels considerably multiplied after 7 days of culture and kept up the expression of particular proteins. Together, our findings point to GelMA/HAMA/polyacrylamide (PAM) hydrogel as a potential material for nasal cartilage restoration. The photocuring multicrosslinked network ink composed of appropriate proportions of GelMA/HAMA/PAM is very suitable for DLP 3D printing and will play an important role in the construction of nasal cartilage, ear cartilage, articular cartilage, and other tissues and organs in the future. Notably, previous studies have not explored the application of 3D-printed GelMA/HAMA/PAM hydrogels for nasal cartilage regeneration.

Designing polysaccharide materials for tissue repair and regeneration

Tissue repair and regeneration are critical processes for maintaining the integrity and function of various organs and tissues. Recently, polysaccharide materials and protein materials have garnered interest for use in tissue repair strategies. However, polysaccharides are more stable and unaffected by temperature and pH changes compared to proteins, and some polysaccharides can provide stronger mechanical support, which is particularly important for constructing tissue-engineered scaffolds and wound dressings. This Review provides an in-depth overview of the origins of polysaccharides, the advantages of polysaccharide materials, and processing and design strategies. In addition, the potential of polysaccharide materials for the restoration of tissues such as skin, heart, and nerves is highlighted. Finally, we discuss in depth the challenges that polysaccharide materials still face in tissue repair, such as the stability of the material, regulating mechanical characteristics and deterioration rates under different conditions. To achieve more effective tissue repair and regeneration, future research must focus on further improving the characteristics and functionalities of polysaccharide materials.

A review of advanced hydrogels for cartilage tissue engineering

With the increase in weight and age of the population, the consumption of tobacco, inappropriate foods, and the reduction of sports activities in recent years, bone and joint diseases such as osteoarthritis (OA) have become more common in the world. From the past until now, various treatment strategies (e.g., microfracture treatment, Autologous Chondrocyte Implantation (ACI), and Mosaicplasty) have been investigated and studied for the prevention and treatment of this disease. However, these methods face problems such as being invasive, not fully repairing the tissue, and damaging the surrounding tissues. Tissue engineering, including cartilage tissue engineering, is one of the minimally invasive, innovative, and effective methods for the treatment and regeneration of damaged cartilage, which has attracted the attention of scientists in the fields of medicine and biomaterials engineering in the past several years. Hydrogels of different types with diverse properties have become desirable candidates for engineering and treating cartilage tissue. They can cover most of the shortcomings of other treatment methods and cause the least secondary damage to the patient. Besides using hydrogels as an ideal strategy, new drug delivery and treatment methods, such as targeted drug delivery and treatment through mechanical signaling, have been studied as interesting strategies. In this study, we review and discuss various types of hydrogels, biomaterials used for hydrogel manufacturing, cartilage-targeting drug delivery, and mechanosignaling as modern strategies for cartilage treatment.

Bioengineered cartilaginous grafts for repairing segmental mandibular defects

Reconstructing critical-sized craniofacial bone defects is a global healthcare challenge. Current methods, like autologous bone transplantation, face limitations. Bone tissue engineering offers an alternative to autologous bone, with traditional approaches focusing on stimulating osteogenesis via the intramembranous ossification (IMO) pathway. However, IMO falls short in addressing larger defects, particularly in clinical scenarios where there is insufficient vascularisation. This review explores redirecting bone regeneration through endochondral ossification (ECO), a process observed in long bone healing stimulated by hypoxic conditions. Despite its promise, gaps exist in applying ECO to bone tissue engineering experiments, requiring the elucidation of key aspects such as cell sources, biomaterials and priming protocols. This review discusses various scaffold biomaterials and cellular sources for chondrogenesis and hypertrophic chondrocyte priming, mirroring the ECO pathway. The review highlights challenges in current endochondral priming and proposes alternative approaches. Emphasis is on segmental mandibular defect repair, offering insights for future research and clinical application. This concise review aims to advance bone tissue engineering by addressing critical gaps in ECO strategies.

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

An injectable, self-healing, electroconductive hydrogel loaded with neural stem cells and donepezil for enhancing local therapy effect of spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a serious injury with high mortality and disability rates, and there is no effective treatment at present. It has been reported that some treatments, such as drug intervention and stem cell transplantation have positive effects in promoting neurological recovery. Although those treatments are effective for nerve regeneration, many drawbacks, such as low stem cell survival rates and side effects caused by systemic medication, have limited their development. In recent years, injectable hydrogel materials have been widely used in tissue engineering due to their good biocompatibility, biodegradability, controllable properties, and low invasiveness. The treatment strategy of injectable hydrogels combined with stem cells or drugs has made some progress in SCI repair, showing the potential to overcome the drawbacks of traditional drugs and stem cell therapy.

METHODS

In this study, a novel injectable electroactive hydrogel (NGP) based on sodium hyaluronate oxide (SAO) and polyaniline-grafted gelatine (NH₂-Gel-PANI) was developed as a material in which to load neural stem cells (NSCs) and donepezil (DPL) to facilitate nerve regeneration after SCI. To evaluate the potential of the prepared NGP hydrogel in SCI repair applications, the surface morphology, self-repairing properties, electrical conductivity and cytocompatibility of the resulting hydrogel were analysed. Meanwhile, we evaluated the neural repair ability of NGP hydrogels loaded with DPL and NSCs using a rat model of spinal cord injury.

RESULTS

The NGP hydrogel has a suitable pore size, good biocompatibility, excellent conductivity, and injectable and self-repairing properties, and its degradation rate matches the repair cycle of spinal cord injury. In addition, DPL could be released continuously and slowly from the NGP hydrogel; thus, the NGP hydrogel could serve as an excellent carrier for drugs and cells. The results of in vitro cell experiments showed that the NGP hydrogel had good cytocompatibility and could significantly promote the neuronal differentiation and axon growth of NSCs, and loading the hydrogel with DPL could significantly enhance this effect. More importantly, the NGP hydrogel loaded with DPL showed a significant inhibitory effect on astrocytic differentiation of NSCs in vitro. Animal experiments showed that the combination of NGP hydrogel, DPL, and NSCs had the best therapeutic effect on the recovery of motor function and nerve conduction function in rats. NGP hydrogel loaded with NSCs and DPL not only significantly increased the myelin sheath area, number of new neurons and axon area but also minimized the area of the cystic cavity and glial scar and promoted neural circuit reconstruction.

CONCLUSIONS

The DPL- and NSC-laden electroactive hydrogel developed in this study is an ideal biomaterial for the treatment of traumatic spinal cord injury.

Research Progress of Design Drugs and Composite Biomaterials in Bone Tissue Engineering

Bone, like most organs, has the ability to heal naturally and can be repaired slowly when it is slightly injured. However, in the case of bone defects caused by diseases or large shocks, surgical intervention and treatment of bone substitutes are needed, and drugs are actively matched to promote osteogenesis or prevent infection. Oral administration or injection for systemic therapy is a common way of administration in clinic, although it is not suitable for the long treatment cycle of bone tissue, and the drugs cannot exert the greatest effect or even produce toxic and side effects. In order to solve this problem, the structure or carrier simulating natural bone tissue is constructed to control the loading or release of the preparation with osteogenic potential, thus accelerating the repair of bone defect. Bioactive materials provide potential advantages for bone tissue regeneration, such as physical support, cell coverage and growth factors. In this review, we discuss the application of bone scaffolds with different structural characteristics made of polymers, ceramics and other composite materials in bone regeneration engineering and drug release, and look forward to its prospect.

Progress of research on graphene and its derivatives in bone and cartilage repair

In recent years, graphene and its derivatives have gained wide attention in the biomedical field due to their good physicochemical properties, biocompatibility, and bioactivity. Its good antibacterial, osteoinductive and drug-carrying properties make it a promising application in the field of orthopedic biomaterials. This paper introduces the research progress of graphene and its derivatives in bone tissue engineering and cartilage tissue engineering and presents an outlook on the future development of graphene-based materials in orthopedics.

Bioinspired Construction of Annulus Fibrosus Implants with a Negative Poisson's Ratio for Intervertebral Disc Repair and Restraining Disc Herniation

Inspired by the negative Poisson's ratio (NPR) effects of the annulus fibrosus (AF) in intervertebral discs (IVDs), we designed a re-entrant honeycomb model and then 3D printed it into a poly(ε-caprolactone) (PCL) scaffold with NPR effects, which was followed by in situ polymerization of polypyrrole (PPy), thus constructing a PPy-coated NPR-structured PCL scaffold (-vPCL-PPy) to be used as the AF implant for the treatment of lumbar herniated discs. Mechanical testing and finite element (FE) simulation indicated that the NPR composite implant could sustain axial spine loading and resist nucleus pulposus (NP) swelling while displaying uniform stress diffusion under NP swelling and contraction. More interestingly, the NPR-structured composite scaffold could also apply a reacting force to restrain NP herniation owing to the NPR effect. In addition, the in vitro biological assessment and in vivo implantation demonstrated that the NPR composite scaffold exhibited good biocompatibility and exerted the ability to restore the physiological function of the disc segments.

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

Graphene Family Nanomaterials for Stem Cell Neurogenic Differentiation and Peripheral Nerve Regeneration

Stem cells play a critical role in peripheral nerve regeneration. Nerve scaffolds fabricated by specific materials can help induce the neurogenic differentiation of stem cells. Therefore, it is a potential strategy to enhance therapeutic efficiency. Graphene family nanomaterials are widely applied in repairing peripheral nerves. However, the mechanism underlying the pro-regeneration effects remains elusive. In this review, we first discuss the properties of graphene family nanomaterials, including monolayer and multilayer graphene, few-layer graphene, graphene oxide, reduced graphene oxide, and graphene quantum dots. We also introduce their applications in regulating stem cell differentiation. Then, we review the potential mechanisms of the neurogenic differentiation of stem cells facilitated by the materials. Finally, we discuss the existing challenges in this field to advance the development of nerve biomaterials.

An Update on Graphene Oxide: Applications and Toxicity

Graphene oxide (GO) has attracted much attention in the past few years because of its interesting and promising electrical, thermal, mechanical, and structural properties. These properties can be altered, as GO can be readily functionalized. Brodie synthesized the GO in 1859 by reacting graphite with KClO3 in the presence of fuming HNO3; the reaction took 3-4 days to complete at 333 K. Since then, various schemes have been developed to reduce the reaction time, increase the yield, and minimize the release of toxic byproducts (NO2 and N2O4). The modified Hummers method has been widely accepted to produce GO in bulk. Due to its versatile characteristics, GO has a wide range of applications in different fields like tissue engineering, photocatalysis, catalysis, and biomedical applications. Its porous structure is considered appropriate for tissue and organ regeneration. Various branches of tissue engineering are being extensively explored, such as bone, neural, dentistry, cartilage, and skin tissue engineering. The band gap of GO can be easily tuned, and therefore it has a wide range of photocatalytic applications as well: the degradation of organic contaminants, hydrogen generation, and CO2 reduction, etc. GO could be a potential nanocarrier in drug delivery systems, gene delivery, biological sensing, and antibacterial nanocomposites due to its large surface area and high density, as it is highly functionalized with oxygen-containing functional groups. GO or its composites are found to be toxic to various biological species and as also discussed in this review. It has been observed that superoxide dismutase (SOD) and reactive oxygen species (ROS) levels gradually increase over a period after GO is introduced in the biological systems. Hence, GO at specific concentrations is toxic for various species like earthworms, Chironomus riparius, Zebrafish, etc.

Climate refugia on the Great Barrier Reef fail when global warming exceeds 3°C

Increases in the magnitude, frequency, and duration of warm seawater temperatures are causing mass coral mortality events across the globe. Although, even during the most extensive bleaching events, some reefs escape exposure to severe stress, constituting potential refugia. Here, we identify present-day climate refugia on the Great Barrier Reef (GBR) and project their persistence into the future. To do this, we apply semi-dynamic downscaling to an ensemble of climate projections released for the IPCC's recent sixth Assessment Report. We find that GBR locations experiencing the least thermal stress over the past 20 years have done so because of their oceanographic circumstance, which implies that longer-term persistence of climate refugia is feasible. Specifically, tidal and wind mixing of warm water away from the sea surface appears to provide relief from warming. However, on average this relative advantage only persists until global warming exceeds ~3°C.

A cell-free difunctional demineralized bone matrix scaffold enhances the recruitment and osteogenesis of mesenchymal stem cells by promoting inflammation resolution

The dialogue between host macrophages (Mφs) and endogenous mesenchymal stem cells (MSCs) promotes M2 Mφs polarization to resolve early-stage inflammation, thereby effectively guiding in situ bone regeneration. Once inflammation is unresolved/incontrollable, it will induce the impediment of MSCs homing at bone defect site, implying the seasonable resolution of inflammation in balancing bone homeostasis. Repeatedly, evidence elucidated that specialized pro-resolving mediators (SPMs) could conduce to proper resolve inflammation and promote the repairing of bone defect. A difunctional demineralized bone matrix (DBM) scaffold co-modified by maresin 1 (MaR1) and aptamer 19S (Apt19S) was fabricated to facilitate the osteogenesis of MSCs. To confirm the osteogenesis and immunomodulatory role of the difunctional DBM scaffold, the proliferation, recruitment, and osteogenic differentiation of MSCs and the Mφs M2 subtype polarization were evaluated in vitro. Then, the DBM scaffolds were implanted into mice model with critical size calvarial defect to evaluate bone repair efficiency. Finally, the specific resolution mechanism in Mφs cultured on the difunctional DBM scaffold was further in-depth investigated. This difunctional DBM scaffold exhibited an enhanced function on the recruitment, proliferation, migration, osteogenesis of MSCs and the resolution of inflammation, finally improved bone-scaffold integration. At the same time, MaR1 modified on the difunctional DBM scaffold increased the biosynthesis of 12-lipoxygenase (12-LOX) and 12S-hydroxy-eicosatetraenoic acid (12S-HETE), and also directly stimulated lipid droplets (LDs) biogenesis in Mφs, which suggested that MaR1 regulated Mφ lipid metabolism at bone repair site. Findings based on this synergy strategy demonstrated that Mφ lipid metabolism was essential in bone homeostasis, which might provide a theoretical direction for the treatment-associated application of MaR1 in inflammatory bone disease.

Natural polymer-based scaffolds for soft tissue repair

Soft tissues such as skin, muscle, and tendon are easily damaged due to injury from physical activity and pathological lesions. For soft tissue repair and regeneration, biomaterials are often used to build scaffolds with appropriate structures and tailored functionalities that can support cell growth and new tissue formation. Among all types of scaffolds, natural polymer-based scaffolds attract much attention due to their excellent biocompatibility and tunable mechanical properties. In this comprehensive mini-review, we summarize recent progress on natural polymer-based scaffolds for soft tissue repair, focusing on clinical translations and materials design. Furthermore, the limitations and challenges, such as unsatisfied mechanical properties and unfavorable biological responses, are discussed to advance the development of novel scaffolds for soft tissue repair and regeneration toward clinical translation.

Recent advances and challenges in graphene-based nanocomposite scaffolds for tissue engineering application

Graphene-based nanocomposites have recently attracted increasing attention in tissue engineering because of their extraordinary features. These biocompatible substances, in the presence of an apt microenvironment, can stimulate and sustain the growth and differentiation of stem cells into different lineages. This review discusses the characteristics of graphene and its derivatives, such as their excellent electrical signal transduction, carrier mobility, outstanding mechanical strength with improving surface characteristics, self-lubrication, antiwear properties, enormous specific surface area, and ease of functional group modification. Moreover, safety issues in the application of graphene and its derivatives in terms of biocompatibility, toxicity, and interaction with immune cells are discussed. We also describe the applicability of graphene-based nanocomposites in tissue healing and organ regeneration, particularly in the bone, cartilage, teeth, neurons, heart, skeletal muscle, and skin. The impacts of special textural and structural characteristics of graphene-based nanomaterials on the regeneration of various tissues are highlighted. Finally, the present review gives some hints on future research for the transformation of these exciting materials in clinical studies.

Hydrogels for Treatment of Different Degrees of Osteoarthritis

Osteoarthritis (OA) is a common disease that severely restricts human activities and degrades the quality of life. Every year, millions of people worldwide are diagnosed with osteoarthritis, placing a heavy burden on society. Hydrogels, a polymeric material with good biocompatibility and biodegradability, are a novel approach for the treatment of osteoarthritis. In recent years, this approach has been widely studied with the development of materials science and tissue engineering technology. We reviewed the research progress of hydrogels in the treatment of osteoarthritis in the past 3 years. We summarized the required hydrogel properties and current applications according to the development and treatment of osteoarthritis. Furthermore, we listed the challenges of hydrogels for different types of osteoarthritis and presented prospects for future development.

Effect of polycaprolactone scaffolds containing different weights of graphene on healing in large osteochondral defect model

Now it is possible to combine the different biomaterial properties of graphene and 3 D printing scaffolds produced by tissue engineering for cartilage repair. In the study graphene-containing (1, 3, 5, 10 wt%), porous and oriented poly-ε-caprolactone-based scaffolds were prepared by robocasting method to use in the regeneration of large osteochondral defects. The scaffolds were implanted into the full-thickness osteochondral defect in a rabbit model to evaluate the regeneration of the defect in vivo. For this purpose, twenty female New Zealand white rabbits were used and they were euthanized at 4 and 8 weeks of implantation. The reparative osteochondral tissues were harvested from rabbit distal femurs and then processed for gross appearance assessment, radiographic imaging, histopathological, histochemical and immunohistochemical examinations. Results revealed that graphene-containing graft materials caused significant amelioration at the defect areas. Graphene-containing graft materials improved the fibrous, chondroid and osseous tissue regeneration compared to the control group. The expressions of bone morphogenetic protein-2 (BMP-2), collagen-1 (col-1), vascular endothelial growth factor (VEGF) and alkaline phosphatase (ALP) expressions were more prominent in graphene-containing PCL implanted groups (p < .001). Picrosirrius red method was used for to evaluate connective and muscle tissues. Results also revealed that the ameliorative effect of graphene increased by the elevation in concentration. The most prominent healing was observed in 10 wt% graphene-containing PCL based composite scaffold implanted group. This study results showed that graphene-containing PCL scaffolds enhanced the healing significantly in large osteochondral defect areas compared to the control groups.

Advanced 3D-Printing Bioinks for Articular Cartilage Repair

Chondral lesions caused by stressors, such as injury or inflammation, lead to osteoarthritis (OA). OA is a degenerative joint disease that has become a challenge worldwide. As the articular cartilage is incapable of self-regeneration due to the absence of vessels and nerves, novel cartilage repair techniques are urgently needed. Three-dimensional (3D) bioprinting, which allows the precise control of internal architecture and geometry of printed scaffolds, has stepped up to be a promising strategy in cartilage restoration. With regards to 3D bioprinting, bioinks with proper chemical and mechanical properties play one of the most critical roles in designing successful cartilage tissue constructs. In particular, hydrogels as 3D hydrophilic cross-linked polymer networks are highly recommended as bioinks because of their fine biocompatibility, easy fabrication, and tunable mechanical strength. Herein, we highlight the widely used polymers for hydrogel preparation and further provide a non-exhaustive overview of various functional modified additives (such as cells, drugs, bioactive factors and ceramic) to exploit the unique properties suitable for bioprinted cartilage. Finally, a prospective on future development for 3D-bioprinting in cartilage repair is elucidated in this review.

Two-Dimensional Nanomaterials beyond Graphene for Biomedical Applications

Two-dimensional (2D) nanomaterials (e.g., graphene) have shown to have a high potential in future biomedical applications due to their unique physicochemical properties such as unusual electrical conductivity, high biocompatibility, large surface area, and extraordinary thermal and mechanical properties. Although the potential of graphene as the most common 2D nanomaterials in biomedical applications has been extensively investigated, the practical use of other nanoengineered 2D materials beyond graphene such as transition metal dichalcogenides (TMDs), topological insulators (TIs), phosphorene, antimonene, bismuthene, metal-organic frameworks (MOFs) and MXenes for biomedical applications have not been appreciated so far. This review highlights not only the unique opportunities of 2D nanomaterials beyond graphene in various biomedical research areas such as bioelectronics, imaging, drug delivery, tissue engineering, and regenerative medicine but also addresses the risk factors and challenges ahead from the medical perspective and clinical translation of nanoengineered 2D materials. In conclusion, the perspectives and future roadmap of nanoengineered 2D materials beyond graphene are outlined for biomedical applications.

Tricomposite gelatin-carboxymethylcellulose-alginate bioink for direct and indirect 3D printing of human knee meniscal scaffold

The development of technologies that could ease the production of customizable patient-specific tissue engineering constructs having required biomechanical properties and restoring function in damaged tissue is the need of the hour. In this study, we report the optimization of composite, bioactive and biocompatible tripolymeric hydrogel bioink, suitable for both direct and indirect printing of customizable scaffolds for cartilage tissue engineering applications. A customized hierarchical meniscal scaffold was designed using solid works software and developed using a negative mould made of polylactic acid (PLA) filament and by a direct 3D printing process. A composite tripolymeric bioink made of gelatin, carboxymethyl cellulose (CMC) and alginate was optimized and characterized for its printability, structural, bio-mechanical and bio-functional properties. The optimized composite hydrogel bioink was extruded into the negative mould with and without live cells, cross-linked and the replica of meniscus structure was retrieved aseptically. The cellular proliferation, apatite formation, and extracellular matrix secretion from negative printed meniscal scaffold were determined using MTT, live/dead and collagen estimation assays. A significant increase in collagen secretion, cellular proliferation and changes in biomechanical properties was observed in the 3D scaffolds with MG63-osteosarcoma cells indicating its suitability for cartilage tissue engineering.

A rabbit femoral trochlear defect model for chondral and osteochondral regeneration

Articular cartilage degeneration represents one of the main features of osteoarthritis. Recently, novel approaches based on biomaterials have been successfully applied to osteochondral regeneration. Our study was carried out on rabbits to assess a model of articular cartilage damage to test biomaterials for osteochondral regeneration. We created osteochondral defects on the surface of the trochlear groove area of the femurs in 15 white male New Zealand rabbits of the size of 3 mm × 3 mm (diameter × depth). Rabbits were then monitored and samples were collected 2 weeks, 4 weeks, and 6 weeks after the operation. The reconstruction of defects was assessed macroscopically according to the International Cartilage Repair Society (ICRS) scale and radiography (X-ray). For microscopic evaluation, haematoxylin-eosin staining and safranin O staining were used. The defects were repaired by regenerative tissue, and the recovery results gradually increased after 2 weeks, 4 weeks, and 6 weeks, showing both microscopically and macroscopically. However, the regenerative tissue was mainly fibrous connective tissue, not cartilage or bone. This is a model of articular cartilage damage that is suitable for early screening of preclinical studies related to osteochondral regeneration using biomaterials.

Development and Characterization of Acellular Caprine Choncal Cartilage Matrix for Tissue Engineering Applications

Because of poor regenerative capabilities of cartilage, reconstruction of similar rigidity and flexibility is difficult, challenging, and restricted. The aim of the present investigation was to develop cost-effective acellular xenogeneic biomaterial as cartilage substitution. Two novel biometrics have been developed using different chemical processes (Na-deoxycholate + SDS and GndHCl + NaOH) to decellularize caprine (goat) ear cartilage and further extensively characterized before preclinical investigation. Complete cell removal was ascertained by hematoxylin and eosin staining followed by DNA estimation. No adverse effect on extracellular matrix (ECM) was found by quantifying collagen and sulfated glycosaminoglycans (sGAG) content as well as collagen, sGAG and elastin staining. Results showed no drastic changes in ECM structure apart from desired sGAG loss. Scanning electron microscopy images confirmed cellular loss and unaltered orientation. Nano-indentation study on cartilage matrices indicated interesting output showing better results among decellularized groups. Increased elastic modulus and hardness indicated better stiffness and more active energy dissipation mechanism due to decellularization. Fluid uptake and retention property remained unchanged after decellularization as analyzed by swelling behavior study. Additionally, acellular materials were confirmed to be nonreactive and nonhemolytic as assessed by in vitro hemocompatibility study. In vivo study (up to 3 months) on rabbits showed no symptoms of graft rejection/ tissue necrosis, established through postoperative histology and biochemical analyses of tissue explants. With regard to size, shape, biomechanics, source of origin and nonimmunogenic properties, these developed materials can play versatile role in biomedical/ clinical applications and pave a new insight as alternatives in cartilage reconstruction.

Preparation, properties and application of graphene-based materials in tissue engineering scaffolds

Tissue engineering has great application prospect as an effective treatment for tissue and organ injury, functional reduction or loss. Bioactive tissues are reconstructed and damaged organs are repaired by the three elements including cells, scaffold materials and growth factors. Graphene-based composites can be used as reinforcing auxiliary materials for tissue scaffold preparation because of their large specific surface area, and good mechanical support. Tissue engineering scaffolds with graphene-based composites have been widely studied. Part of research have focused on the application of graphene-based composites in single tissue engineering; The basic principles of graphene materials used in tissue engineering are summarized in some researches. Some studies emphasized the key problems and solutions urgently needed to be solved in the development of tissue engineering, and discussed their application prospect. Some related studies mainly focused on the conductivity of graphene, and discussed the application of electroactive scaffolds in tissue engineering. In this review, the composite materials for preparing tissue engineering scaffolds are briefly described, which emphasizes the preparation methods, biological properties and practical applications of graphene-based composite scaffolds. The synthetic techniques with stressing solvent casting, electrospinning and 3D printing are introduced in detail. The mechanical, cell-oriented and biocompatible properties of graphene-based composite scaffolds in tissue engineering are analyzed and summarized. Their applications in bone tissue engineering, nerve tissue engineering, cardiovascular tissue engineering and other tissue engineering are summarized systematically. In addition, this work also looks forward to the difficulties and challenges in the future research, providing some references for the follow-up research of graphene-based composites in tissue engineering scaffolds.

Bio-inspired graphene-based nano-systems for biomedical applications

The increasing demands of environmentally sustainable, affordable, and scalable materials have inspired researchers to explore greener nanosystems of unique properties which can enhance the performance of existing systems. Such nanosystems, extracted from nature, are state-of-art high-performance nanostructures due to intrinsic hierarchical micro/nanoscale architecture and generous interfacial interactions in natural resources. Among several, bio-inspired nanosystems graphene nanosystems have emerged as an essential nano-platform wherein a highly electroactive, scalable, functional, flexible, and adaptable to a living being is a key factor. Preliminary investigation project bio-inspired graphene nanosystems as a multi-functional nano-platform suitable for electronic devices, energy storage, sensors, and medical sciences application. However, a broad understanding of bio-inspired graphene nanosystems and their projection towards applied application is not well-explored yet. Considering this as a motivation, this mini-review highlights the following; the emergence of bio-inspired graphene nanosystems, over time development to make them more efficient, state-of-art technology, and potential applications, mainly biomedical including biosensors, drug delivery, imaging, and biomedical systems. The outcomes of this review will certainly serve as a guideline to motivate scholars to design and develop novel bio-inspired graphene nanosystems to develop greener, affordable, and scalable next-generation biomedical systems.

Redox Polymers for Tissue Engineering

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

2D Nanomaterials for Tissue Engineering and Regenerative Nanomedicines: Recent Advances and Future Challenges

Regenerative medicine has become one of the hottest research topics in medical science that provides a promising way for repairing tissue defects in the human body. Due to their excellent physicochemical properties, the application of 2D nanomaterials in regenerative medicine has gradually developed and has been attracting a wide range of research interests in recent years. In particular, graphene and its derivatives, black phosphorus, and transition metal dichalcogenides are applied in all the aspects of tissue engineering to replace or restore tissues. This review focuses on the latest advances in the application of 2D-nanomaterial-based hydrogels, nanosheets, or scaffolds that are engineered to repair skin, bone, and cartilage tissues. Reviews on other applications, including cardiac muscle regeneration, skeletal muscle repair, nerve regeneration, brain disease treatment, and spinal cord healing are also provided. The challenges and prospects of applications of 2D nanomaterials in regenerative medicine are discussed.

Graphene Oxide-Doped Gellan Gum-PEGDA Bilayered Hydrogel Mimicking the Mechanical and Lubrication Properties of Articular Cartilage

Articular cartilage (AC) is a specialized connective tissue able to provide a low-friction gliding surface supporting shock-absorption, reducing stresses, and guaranteeing wear-resistance thanks to its structure and mechanical and lubrication properties. Being an avascular tissue, AC has a limited ability to heal defects. Nowadays, conventional strategies show several limitations, which results in ineffective restoration of chondral defects. Several tissue engineering approaches have been proposed to restore the AC's native properties without reproducing its mechanical and lubrication properties yet. This work reports the fabrication of a bilayered structure made of gellan gum (GG) and poly (ethylene glycol) diacrylate (PEGDA), able to mimic the mechanical and lubrication features of both AC superficial and deep zones. Through appropriate combinations of GG and PEGDA, cartilage Young's modulus is effectively mimicked for both zones. Graphene oxide is used as a dopant agent for the superficial hydrogel layer, demonstrating a lower friction than the nondoped counterpart. The bilayered hydrogel's antiwear properties are confirmed by using a knee simulator, following ISO 14243. Finally, in vitro tests with human chondrocytes confirm the absence of cytotoxicity effects. The results shown in this paper open the way to a multilayered synthetic injectable or surgically implantable filler for restoring AC defects.

Research Progress on Stem Cell Therapies for Articular Cartilage Regeneration

Injury of articular cartilage can cause osteoarthritis and seriously affect the physical and mental health of patients. Unfortunately, current surgical treatment techniques that are commonly used in the clinic cannot regenerate articular cartilage. Regenerative medicine involving stem cells has entered a new stage and is considered the most promising way to regenerate articular cartilage. In terms of theories on the mechanism, it was thought that stem cell-mediated articular cartilage regeneration was achieved through the directional differentiation of stem cells into chondrocytes. However, recent evidence has shown that the stem cell secretome plays an important role in biological processes such as the immune response, inflammation regulation, and drug delivery. At the same time, the stem cell secretome can effectively mediate the process of tissue regeneration. This new theory has attributed the therapeutic effect of stem cells to their paracrine effects. The application of stem cells is not limited to exogenous stem cell transplantation. Endogenous stem cell homing and in situ regeneration strategies have received extensive attention. The application of stem cell derivatives, such as conditioned media, extracellular vesicles, and extracellular matrix, is an extension of stem cell paracrine theory. On the other hand, stem cell pretreatment strategies have also shown promising therapeutic effects. This article will systematically review the latest developments in these areas, summarize challenges in articular cartilage regeneration strategies involving stem cells, and describe prospects for future development.

Graphene-Based Scaffolds for Regenerative Medicine

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with next-generation scaffolds consisting of smart nanocomposites and/or hydrogels with nanofillers, where balanced combinations of specific matrices and nanomaterials can mediate and finely tune such stimuli and cues. In this review, we focus on graphene-based nanomaterials as, in addition to modulating nanotopography, elastic modulus and viscoelastic features of the scaffold, they can also regulate its conductivity. This feature is crucial to the determination and differentiation of some cell lineages and is of special interest to neural regenerative medicine. Hereafter we depict relevant properties of such nanofillers, illustrate how problems related to their eventual cytotoxicity are solved via enhanced synthesis, purification and derivatization protocols, and finally provide examples of successful applications in regenerative medicine on a number of tissues.

Tissue-Adhesive Chondroitin Sulfate Hydrogel for Cartilage Reconstruction

Chondroitin sulfate (CS), the main component of cartilage extracellular matrix, has attracted attention as a biomaterial for cartilage tissue engineering. However, current CS hydrogel systems still have limitations for application in successful cartilage tissue engineering owing to their unsuitable degradation kinetics, insufficient mechanical similarity, and lack of integration with the native cartilage tissue. In this study, using mussel adhesive-inspired catechol chemistry, we developed a functional CS hydrogel that exhibits tunable physical and mechanical properties as well as excellent tissue adhesion for efficient integration with native tissues. Various properties of the developed catechol-functionalized CS (CS-CA) hydrogel, including swelling, degradation, mechanical properties, and adhesiveness, could be tailored by varying the conjugation ratio of the catechol group to the CS backbone and the concentration of the CS-CA conjugates. CS-CA hydrogels exhibited significantly increased modulus (∼10 kPa) and superior adhesive properties (∼3 N) over conventional CS hydrogels (∼hundreds Pa and ∼0.05 N). In addition, CS-CA hydrogels incorporating decellularized cartilage tissue dice promoted the chondrogenic differentiation of human adipose-derived mesenchymal stem cells by providing a cartilage-like microenvironment. Finally, the transplantation of autologous cartilage dice using tissue-adhesive CS-CA hydrogels enhanced cartilage integration with host tissue and neo-cartilage formation owing to favorable physical, mechanical, and biological properties for cartilage formation. In conclusion, our study demonstrated the potential utility of the CS-CA hydrogel system in cartilage tissue reconstruction.

Hyaluronic acid and chondroitin sulfate (meth)acrylate-based hydrogels for tissue engineering: Synthesis, characteristics and pre-clinical evaluation

Hydrogels based on photocrosslinkable Hyaluronic Acid Methacrylate (HAMA) and Chondroitin Sulfate Methacrylate (CSMA) are presently under investigation for tissue engineering applications. HAMA and CSMA gels offer tunable characteristics such as tailorable mechanical properties, swelling characteristics, and enzymatic degradability. This review gives an overview of the scientific literature published regarding the pre-clinical development of covalently crosslinked hydrogels that (partially) are based on HAMA and/or CSMA. Throughout the review, recommendations for the next steps in clinical translation of hydrogels based on HAMA or CSMA are made and potential pitfalls are defined. Specifically, a myriad of different synthetic routes to obtain polymerizable hyaluronic acid and chondroitin sulfate derivatives are described. The effects of important parameters such as degree of (meth)acrylation and molecular weight of the synthesized polymers on the formed hydrogels are discussed and useful analytical techniques for their characterization are summarized. Furthermore, the characteristics of the formed hydrogels including their enzymatic degradability are discussed. Finally, a summary of several recent applications of these hydrogels in applied fields such as cartilage and cardiac regeneration and advanced tissue modelling is presented.

Carbon Nanomaterials for Electro-Active Structures: A Review

The use of electrically conductive materials to impart electrical properties to substrates for cell attachment proliferation and differentiation represents an important strategy in the field of tissue engineering. This paper discusses the concept of electro-active structures and their roles in tissue engineering, accelerating cell proliferation and differentiation, consequently leading to tissue regeneration. The most relevant carbon-based materials used to produce electro-active structures are presented, and their main advantages and limitations are discussed in detail. Particular emphasis is put on the electrically conductive property, material synthesis and their applications on tissue engineering. Different technologies, allowing the fabrication of two-dimensional and three-dimensional structures in a controlled way, are also presented. Finally, challenges for future research are highlighted. This review shows that electrical stimulation plays an important role in modulating the growth of different types of cells. As highlighted, carbon nanomaterials, especially graphene and carbon nanotubes, have great potential for fabricating electro-active structures due to their exceptional electrical and surface properties, opening new routes for more efficient tissue engineering approaches.

Review of Synthetic and Hybrid Scaffolds in Cartilage Tissue Engineering

Cartilage tissue is under extensive investigation in tissue engineering and regenerative medicine studies because of its limited regenerative potential. Currently, many scaffolds are undergoing scientific and clinical research. A key for appropriate scaffolding is the assurance of a temporary cellular environment that allows the cells to function as in native tissue. These scaffolds should meet the relevant requirements, including appropriate architecture and physicochemical and biological properties. This is necessary for proper cell growth, which is associated with the adequate regeneration of cartilage. This paper presents a review of the development of scaffolds from synthetic polymers and hybrid materials employed for the engineering of cartilage tissue and regenerative medicine. Initially, general information on articular cartilage and an overview of the clinical strategies for the treatment of cartilage defects are presented. Then, the requirements for scaffolds in regenerative medicine, materials intended for membranes, and methods for obtaining them are briefly described. We also describe the hybrid materials that combine the advantages of both synthetic and natural polymers, which provide better properties for the scaffold. The last part of the article is focused on scaffolds in cartilage tissue engineering that have been confirmed by undergoing preclinical and clinical tests.

Novel Biocompatible Amino Acids-Functionalized Three-dimensional Graphene Foams: As the Attractive and Promising Cisplatin Carriers for Sustained Release Goals

Application of amino acids-immobilized porous materials for drug delivery studies has been attracted a lot of attention in the recent years. In this study, amino acids-grafted graphene foams were prepared by anchoring of Alanine (Ala), Cysteine (Cys) and Glycine (Gly) amino acids on the surface of graphene oxide (GO) nanostructures and used as the novel biocompatible carriers to control releasing of the cisplatin as the cytotoxic anticancer drug. The characterization of prepared compounds was done by the FT-IR, Raman, TGA, N₂ adsorption-desorption isotherms, SEM, and TEM techniques. Adsorption and in vitro release behavior of amino acids-functionalized foams were studied using ICP standard method. The results show that the drug loading amount and the drug releasing rate are significantly enhanced upon functionalization process. The Ala-Foam sample with the larger surface area and pore volume showed a higher loading content (4.53%) than other samples. In addition, the MTT test on the two MCF-7 and HepG2 human cancer cell lines exhibited an acceptable biocompatibility and sustainable drug releasing from the carriers up to 48 h, leading to the dosage frequency decrease and the patient compliance improvement.

Graphene Oxide Reinforcement Enhances the Piezoelectric and Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxy valerate)-Based Nanofibrous Scaffolds for Improved Proliferation of Chondrocytes and ECM Production

The discovery of piezoelectricity in natural cartilage has inspired the development of piezoelectric biomaterials for its repair and regeneration using tissue engineering approaches. In the present work, piezoelectric scaffolds composed of poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PB) and graphene oxide (GO) have been successfully fabricated by the electrospinning technology. The fabricated scaffolds were examined for their morphological, physical, chemical, piezoelectric, and biological characterizations. The fiber diameter was found to be in the range of 600-800 nm appropriate for chondrogenic growth. Reinforcement of 1.5% GO enhanced the tensile strength of PB to 2.08 ± 0.33 MPa compared to PB alone (0.59 ± 0.12). Reinforcement of GO significantly enhances the piezoelectric coefficient (d₃₃), and for 0.5, 1, and 1.5% GO in PB, it was found to be 0.12 ± 0.015, 0.57 ± 0.19, and 0.94 ± 0.03 pC/N, respectively, and corresponding voltages of 11.84 ± 1.4, 54.69 ± 18.29, and 100.2 ± 3.2 mV, respectively, were generated. The biological activity of the smart piezo scaffolds was also evaluated on freshly isolated goat chondrocytes. The GO-reinforced scaffold showed higher cell proliferation and cell adhesion as confirmed by alamarBlue assay and field emission scanning electron microscopy imaging. The GO-reinforced scaffold has demonstrated significantly higher extracellular matrix production compared to PB as confirmed by histochemistry and real-time polymerase chain reaction. Hence, the GO-based piezoelectric PB electrospun scaffold can be a better alternative for cell-free and growth factor-free approach for cartilage tissue engineering.

Numerical Simulations as Means for Tailoring Electrically Conductive Hydrogels Towards Cartilage Tissue Engineering by Electrical Stimulation

Cartilage regeneration is a clinical challenge. In recent years, hydrogels have emerged as implantable scaffolds in cartilage tissue engineering. Similarly, electrical stimulation has been employed to improve matrix synthesis of cartilage cells, and thus to foster engineering and regeneration of cartilage tissue. The combination of hydrogels and electrical stimulation may pave the way for new clinical treatment of cartilage lesions. To find the optimal electric properties of hydrogels, theoretical considerations and corresponding numerical simulations are needed to identify well-suited initial parameters for experimental studies. We present the theoretical analysis of a hydrogel in a frequently used electrical stimulation device for cartilage regeneration and tissue engineering. By means of equivalent circuits, finite element analysis, and uncertainty quantification, we elucidate the influence of the geometric and dielectric properties of cell-seeded hydrogels on the capacitive-coupling electrical field stimulation. Moreover, we discuss the possibility of cellular organisation inside the hydrogel due to forces generated by the external electric field. The introduced methodology is easily reusable by other researchers and allows to directly develop novel electrical stimulation study designs. Thus, this study paves the way for the design of future experimental studies using electrically conductive hydrogels and electrical stimulation for tissue engineering.

Advanced hydrogels for the repair of cartilage defects and regeneration

Cartilage defects are one of the most common symptoms of osteoarthritis (OA), a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society. Hydrogels, which are a class of biomaterials that are elastic, and display smooth surfaces while exhibiting high water content, are promising candidates for cartilage regeneration. In recent years, various kinds of hydrogels have been developed and applied for the repair of cartilage defects in vitro or in vivo, some of which are hopeful to enter clinical trials. In this review, recent research findings and developments of hydrogels for cartilage defects repair are summarized. We discuss the principle of cartilage regeneration, and outline the requirements that have to be fulfilled for the deployment of hydrogels for medical applications. We also highlight the development of advanced hydrogels with tailored properties for different kinds of cartilage defects to meet the requirements of cartilage tissue engineering and precision medicine.

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The biotechnology of developing hydrogels for cartilage defects repair is promising.

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The principle for cartilage regeneration using hydrogels and requirements for clinical transformation are summarized.

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Advanced hydrogels with tailored properties for different kinds of cartilage defects are discussed.

Advances of nanomaterial applications in oral and maxillofacial tissue regeneration and disease treatment

Using bioactive nanomaterials in clinical treatment has been widely aroused. Nanomaterials provide substantial improvements in the prevention and treatment of oral and maxillofacial diseases. This review aims to discuss new progresses in nanomaterials applied to oral and maxillofacial tissue regeneration and disease treatment, focusing on the use of nanomaterials in improving the quality of oral and maxillofacial healthcare, and discuss the perspectives of research in this arena. Details are provided on the tissue regeneration, wound healing, angiogenesis, remineralization, antitumor, and antibacterial regulation properties of nanomaterials including polymers, micelles, dendrimers, liposomes, nanocapsules, nanoparticles and nanostructured scaffolds, etc. Clinical applications of nanomaterials as nanocomposites, dental implants, mouthwashes, biomimetic dental materials, and factors that may interact with nanomaterials behaviors and bioactivities in oral cavity are addressed as well. In the last section, the clinical safety concerns of their usage as dental materials are updated, and the key knowledge gaps for future research with some recommendation are discussed. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Three Dimensional Quercetin-Functionalized Patterned Scaffold: Development, Characterization, and In Vitro Assessment for Neural Tissue Engineering

Regeneration of injured neuronal areas is a big challenge owing to the complex structure and function of the nervous system along with the limited regeneration capacity of neural cells. Recent reports show that patterned and functionalized scaffolds could control neural cell directional growth. In this study, aligned nanofibers (ANFs) were fabricated using a versatile and cost-effective approach, electrospinning, and further processed to make a patterned hybrid scaffold (HANF). The patterned scaffold had circular rings of ANFs reinforced in a biocompatible gellan-gelatin hydrogel matrix to provide adequate mechanical strength and contact guidance for adhesion and growth of neural cells in vitro. Quercetin was loaded into the nanofibrous scaffold to provide a functional agent that supported regeneration of neural cells. The reinforced ANFs enhanced the mechanical strength of the scaffold and provided a cylindrical nerve conduit structure to support neuronal cell growth. The influence of scaffold topology on cell behavior was assessed in in vitro cell culture conditions that revealed that the functionalized patterned scaffolds favored directed neurite cell growth/extension with favored cell culture morphology and showed no cytotoxicity toward neural cells. The results ultimately indicated that the fabricated scaffold has potential for guiding nerve tissue growth and can be used as nerve regeneration scaffolds.

Tissue Engineering: An Alternative to Repair Cartilage

Herein we review the state-of-the-art in tissue engineering for repair of articular cartilage. First, we describe the molecular, cellular, and histologic structure and function of endogenous cartilage, focusing on chondrocytes, collagens, extracellular matrix, and proteoglycans. We then explore in vitro cell culture on scaffolds, discussing the difficulties involved in maintaining or obtaining a chondrocytic phenotype. Next, we discuss the diverse compounds and designs used for these scaffolds, including natural and synthetic biomaterials and porous, fibrous, and multilayer architectures. We then report on the mechanical properties of different cell-loaded scaffolds, and the success of these scaffolds following in vivo implantation in small animals, in terms of generating tissue that structurally and functionally resembles native tissue. Last, we highlight future trends in this field. We conclude that despite major technical advances made over the past 15 years, and continually improving results in cartilage repair experiments in animals, the development of clinically useful implants for regeneration of articular cartilage remains a challenge

Synthesis, characterization, and biological activity of selenium nanoparticles conjugated with polysaccharides

Nanoparticles with unique properties have potential applications in food, medicine, pharmacology, and agriculture industries. Accordingly, many significant researches have been conducted to develop novel nanoparticles using chemical and biological techniques. This review focuses on the synthesis of selenium nanoparticles (SeNPs) using polysaccharides as templates. Various instrumental techniques being used to confirm the formation of polysaccharide-SeNPs conjugates and characterize the properties of nanoparticles are also introduced. Finally, the biological activities of the synthesized SeNPs and the influence of structural factors of polysaccharides on the property of synthetic nanocomposites are highlighted. In general, the polysaccharides functionalized SeNPs can be easily obtained using sodium selenite as precursor and ascorbic acid as reductant. The final products having different particle size, morphology, and selenium content exhibit abundant physiological activities. Structural factors of polysacchairdes involving molecular weights, substitution of functional groups, and chain conformation play determinant roles on the properties of nanocomposites, resulting in different biological performances. The review on the achievements and current status of polysaccharides conjugated SeNPs provides insights into this exciting research topic for further studies in the future.

Tanshinone IIA Delivery Silk Fibroin Scaffolds Significantly Enhance Articular Cartilage Defect Repairing via Promoting Cartilage Regeneration

Cartilage tissue engineering is a promising approach for repairing articular cartilage defects and requires proper scaffolds and necessary growth factors. Herein, tanshinone IIA (TAN) delivery silk fibroin scaffolds were prepared for efficient cartilage defect repair by bioactivities of TAN. By incubating with the TAN delivery silk fibroin scaffold, the transcription of the chondrocytic activity-related genes was enhanced in chondrocytes, and it also can inhibit cell apoptosis and reduce the oxidative stress by regulating the transcription of related genes, indicating that these scaffolds may promote cartilage regeneration. TAN10 delivery silk fibroin scaffolds, in which the concentration of TAN is 10 μg/mL, significantly promotes chondrocytes to generate the cartilage-specific extracellular matrix and tissue both in vitro and in vivo, compared with silk fibroin scaffolds. By treating rabbit articular cartilage defects with TAN10 delivery silk fibroin scaffolds, cartilage defects were filled with hyaline-cartilage-like tissue that integrated with the surrounding cartilage perfectly and displayed strong mechanical properties and higher extracellular matrix content. Hence, TAN facilitates cartilage regeneration, and TAN delivery silk fibroin scaffolds can be potentially applied in the clinics treating cartilage defects in the future.

Animal Models of Osteochondral Defect for Testing Biomaterials

The treatment of osteochondral defects (OCD) remains a great challenge in orthopaedics. Tissue engineering holds a good promise for regeneration of OCD. In the light of tissue engineering, it is critical to establish an appropriate animal model to evaluate the degradability, biocompatibility, and interaction of implanted biomaterials with host bone/cartilage tissues for OCD repair in vivo. Currently, model animals that are commonly deployed to create osteochondral lesions range from rats, rabbits, dogs, pigs, goats, and sheep horses to nonhuman primates. It is essential to understand the advantages and disadvantages of each animal model in terms of the accuracy and effectiveness of the experiment. Therefore, this review aims to introduce the common animal models of OCD for testing biomaterials and to discuss their applications in translational research. In addition, we have reviewed surgical protocols for establishing OCD models and biomaterials that promote osteochondral regeneration. For small animals, the non-load-bearing region such as the groove of femoral condyle is commonly chosen for testing degradation, biocompatibility, and interaction of implanted biomaterials with host tissues. For large animals, closer to clinical application, the load-bearing region (medial femoral condyle) is chosen for testing the durability and healing outcome of biomaterials. This review provides an important reference for selecting a suitable animal model for the development of new strategies for osteochondral regeneration.