Exceptional Mechanical Properties of Phase-Separation-Free Mo3Se3--Chain-Reinforced Hydrogel Prepared by Polymer Wrapping Process.

As Mo3Se3- chain nanowires have dimensions comparable to those of natural hydrogel chains (molecular-level diameters of ∼0.6 nm and lengths of several micrometers) and excellent mechanical strength and flexibility, they have large potential to reinforce hydrogels and improve their mechanical properties. When a Mo3Se3--chain-nanowire-gelatin composite hydrogel is prepared simply by mixing Mo3Se3- nanowires with gelatin, phase separation of the Mo3Se3- nanowires from the gelatin matrix occurs in the micronetwork, providing only small improvements in their mechanical properties. In contrast, when the surface of the Mo3Se3- nanowire is wrapped with the gelatin polymer, the chemical compatibility of the Mo3Se3- nanowire with the gelatin matrix is significantly improved, which enables the fabrication of a phase-separation-free Mo3Se3--reinforced gelatin hydrogel. The composite gelatin hydrogel exhibits significantly improved mechanical properties, including a tensile strength of 27.6 kPa, fracture toughness of 26.9 kJ/m3, and elastic modulus of 54.8 kPa, which are 367%, 868%, and 378% higher than those of the pure gelatin hydrogel, respectively. Furthermore, the amount of Mo3Se3- nanowires added in the composite hydrogel is as low as 0.01 wt %. The improvements in the mechanical properties are significantly larger than those for other reported composite hydrogels reinforced with one-dimensional materials.

Enhanced Mechanical Strength and Sustained Drug Release in Carrier-Free Silver-Coordinated Anthraquinone Natural Antibacterial Anti-Inflammatory Hydrogel for Infectious Wound Healing.

The persistent challenge of healing infectious wounds and the rise of bacterial resistance represent significant hurdles in contemporary medicine. In this study, based on the natural small molecule drug Rhein self-assembly to form hydrogels and coordinate assembly with silver ions (Ag+), a sustained-release carrier-free hydrogel with compact structure is constructed to promote the repair of bacterial-infected wounds. As a broad-spectrum antimicrobial agent, Ag+ can avoid the problem of bacterial resistance caused by the abuse of traditional antibiotics. In addition, due to the slow-release properties of Rhein hydrogel, continuous effective concentration of Ag+ at the wound site can be ensured. The assembly of Ag+ and Rhein makes the hydrogel system with enhanced mechanical stability. More importantly, it is found that Rhein effectively promotes skin tissue regeneration and wound healing by reprogramming M1 macrophages into M2 macrophages. Further mechanism studies show that Rhein realizes its powerful anti-inflammatory activity through NRF2/HO-1 activation and NF-κB inhibition. Thus, the hydrogel system combines the excellent antibacterial properties of Ag+ with the excellent anti-inflammatory and tissue regeneration ability of Rhein, providing a new strategy for wound management with dual roles.

Enhanced healing of burn wounds by multifunctional alginate-chitosan hydrogel enclosing silymarin and zinc oxide nanoparticles.

Multifunctional wound dressings have been applied for burn injuries to avoid complications and promote tissue regeneration. In the present study, we fabricated a natural alginate-chitosan hydrogel comprising silymarin and green-synthesized zinc oxide nanoparticles (ZnO NPs). Then, the physicochemical attributes of ZnO NPs and loaded hydrogels were analyzed. Afterward, wound healing efficacy was evaluated in a rat model of full-thickness dermal burn wounds. The findings indicated that ZnO NPs were synthesized via reduction with phytochemicals from Elettaria cardamomum seeds extract. The microscopic images exhibited fairly spherical ZnO NPs (35-45 nm), and elemental analysis verified the relevant composition. The hydrogel, containing silymarin and biosynthesized ZnO NPs, displayed a uniform appearance, smooth surfaces, and a porous structure. Moreover, infrared spectroscopy identified functional groups, confirming the successful loading without adverse interactions. The obtained hydrogel exhibited great water absorption, high porosity, sustainable degradation for several days, and enhanced antioxidant capability of the combined loaded component. In vivo studies revealed faster and superior wound healing, achieving nearly complete closure by day 21. Histopathology confirmed improved cell growth, tissue regeneration, collagen deposition, and neovascularization. It is believed that this multifunctional hydrogel-based wound dressing can be applied for effective burn wound treatment.

Bacterial Nanocellulose Hydrogel: A Promising Alternative Material for the Fabrication of Engineered Vascular Grafts.

Blood vessels are crucial in the human body, providing essential nutrients to all tissues while facilitating waste removal. As the incidence of cardiovascular disease rises, the demand for efficient treatments increases concurrently. Currently, the predominant interventions for cardiovascular disease are autografts and allografts. Although effective, they present limitations including high costs and inconsistent success rates. Recently, synthetic vascular grafts, made from artificial materials, have emerged as promising alternatives to traditional methods. Among these materials, bacterial cellulose hydrogel exhibits significant potential for tissue engineering applications, particularly in developing nanoscale platforms that regulate cell behavior and promote tissue regeneration, attributed to its notable physicochemical and biocompatible properties. This study reviews recent progress in fabricating engineered vascular grafts using bacterial nanocellulose, demonstrating the efficacy of bacterial cellulose hydrogel as a biomaterial for synthetic vascular grafts, specifically for stimulating angiogenesis and neovascularization.

Locust bean gum provides excellent mechanical and release attributes to soy protein-based natural hydrogels.

The current study concentrated on designing soy protein (SP)-based natural hydrogels in the presence of locust bean gum (LBG). For this, the gums were recovered from the kernel of the relevant plant and incorporated into SP gel models. Three more hydrogels were fabricated using commercial carbohydrates (gum Arabic (GA), maltodextrin (MD), and pectin (PC)) to decipher exactly the ability of LBG in these models. The chemical and morphological structures of the samples were elaborated by FTIR and SEM analyses. The coexistence of protein and carbohydrates led to an enhancement in functional (water holding capacity (WHC), swelling ratio, protein leachability, volumetric gel index (VGI)) and mechanical (textural and rheological behavior) features of natural gels compared to SP alone (control) but the quality of hydrogels was impressed by the carbohydrate type. Hydrogels designed with LBG came to the fore in terms of these attributes. Additionally, these gel models created awareness for phenolic delivery.

Enzymatically crosslinked magnetic starch-grafted poly(tannic acid) hydrogel for "smart" cancer treatment: An in vitro chemo/hyperthermia therapy study.

A novel strategy was designed and developed based of horseradish peroxidase (HRP)-mediated crosslinking of tyramine-functionalized starch (Tyr-St), tannic acid (TA) and phenolated-magnetic nanoparticles (Fe3O4-PhOH NPs), and simultaneous loading of doxorubicin hydrochloride (Dox) to afford a pH-responsive magnetic hydrogel-based drug delivery system (DDS) for synergistic in vitro chemo/hyperthermia therapy of human breast cancer (MCF-7) cells. The developed St-g-PTA/Fe3O4 magnetic hydrogel showed porous micro-structure with saturation magnetization (δs) value of 19.2 emu g-1 for Fe3O4 NPs content of ∼7.4 wt%. The pore sizes of the St-g-PTA/Fe3O4 hydrogel was calculated to be 2400 ± 200 nm-2. In vitro drug release experiments exhibited the developed DDS has pH-dependent drug release behavior, while at physiological pH (7.4) released only 30 % of the loaded drug after 100 h. Human serum albumin (HSA) adsorption capacities of the synthesized St/Fe3O4 and St-g-PTA/Fe3O4 magnetic hydrogels were obtained as 86 ± 2.2 and 77 ± 1.9 µgmg-1, respectively. The well-known MTT-assay approved the cytocompatibility of the developed St-g-PTA/Fe3O4 hydrogel, while the Dox-loaded system exhibited higher anti-cancer activity than those of the free Dox as verified by MTT-assay, and optical as well as florescent microscopies imaging. The synergistic chemo/hyperthermia therapy effect was also verified for the developed St-g-PTA/Fe3O4-Dox via hot water approach.

Electroactive injectable hydrogel based on oxidized sodium alginate and carboxymethyl chitosan for wound healing.

Electroactive hydrogel is of great significance in restoring wound currents, promoting cell proliferation, and accelerating the wound healing process. However, the poor dispersity and underlying toxicity of electronic conductive fillers and high concentration of ionic conductors in traditional electroactive hydrogel limited its application in medical care. Herein, an electroactive oxidized sodium alginate/carboxymethyl chitosan/silver nanoparticles (OSA/CMCS/AgNPs) hydrogel was constructed with no additional conductive fillers or synthesized conductive polymers being added, in which the dynamic imine bonds were rapidly formed between aldehyde groups in OSA and amino groups in CMCS, and AgNPs were further in situ formed by UV irradiation. The electroactive hydrogel exhibited the injectable property, strong self-healing ability, excellent biocompatibility, and high antibacterial activities. Moreover, the electroactive hydrogel can significantly promote the proliferation of L929 cells under electrical stimulation. Furthermore, the electroactive hydrogel was proved to significantly accelerate the wound healing process in the full-thickness skin defect model, exhibiting anti-inflammation, promoting the fibroblasts proliferation, angiogenesis, and collagen deposition under electrical stimulation. In summary, the current work explored a novel strategy to construct the polysaccharides-based electroactive hydrogel with good biocompatibility and multi-functions, which is promising to be used in deep wound treatment.

Designing Nanoliposome-in-Natural Hydrogel Hybrid System for Controllable Release of Essential Oil in Gastrointestinal Tract: A Novel Vehicle.

In this study, thyme essential oil (essential oil to total lipid: 14.23, 20, 25, and 33.33%)-burdened nanoliposomes with/without maltodextrin solution were infused with natural hydrogels fabricated using equal volumes (1:1, v/v) of pea protein (30%) and gum Arabic (1.5%) solutions. The production process of the solutions infused with gels was verified using FTIR spectroscopy. In comparison to the nanoliposome solution (NL1) containing soybean lecithin and essential oil, the addition of maltodextrin (molar ratio of lecithin to maltodextrin: 0.80, 0.40, and 0.20 for NL2, NL3, and NL4, respectively) to these solutions led to a remarkable shift in particle size (487.10-664.40 nm), negative zeta potential (23.50-38.30 mV), and encapsulation efficiency (56.25-67.62%) values. Distortions in the three-dimensional structure of the hydrogel (H2) constructed in the presence of free (uncoated) essential oil were obvious in the photographs when compared to the control (H1) consisting of a pea protein-gum Arabic matrix. Additionally, the incorporation of NL1 caused visible deformations in the gel (HNL1). Porous surfaces were dominant in H1 and the hydrogels (HNL2, HNL3, and HNL4) containing NL2, NL3, and NL4 in the SEM images. The most convenient values for functional behaviors were found in H1 and HNL4, followed by HNL3, HNL2, HNL1, and H2. This hierarchical order was also valid for mechanical properties. The prominent hydrogels in terms of essential oil delivery throughout the simulated gastrointestinal tract were HNL2, HNL3, and HNL4. To sum up, findings showed the necessity of mediators such as maltodextrin in the establishment of such systems.

All-Natural Immunomodulatory Bioadhesive Hydrogel Promotes Angiogenesis and Diabetic Wound Healing by Regulating Macrophage Heterogeneity.

Macrophages are highly heterogeneous and exhibit a diversity of functions and phenotypes. They can be divided into pro-inflammatory macrophages (M1) and anti-inflammatory macrophages (M2). Diabetic wounds are characterized by a prolonged inflammatory phase and difficulty in healing due to the accumulation of pro-inflammatory (M1) macrophages in the wound. Therefore, hydrogel dressings with macrophage heterogeneity regulation function hold great promise in promoting diabetic wound healing in clinical applications. However, the precise conversion of pro-inflammatory M1 to anti-inflammatory M2 macrophages by simple and biosafe approaches is still a great challenge. Here, an all-natural hydrogel with the ability to regulate macrophage heterogeneity is developed to promote angiogenesis and diabetic wound healing. The protocatechuic aldehyde hybridized collagen-based all-natural hydrogel exhibits good bioadhesive and antibacterial properties as well as reactive oxygen species scavenging ability. More importantly, the hydrogel is able to convert M1 macrophages into M2 macrophages without the need for any additional ingredients or external intervention. This simple and safe immunomodulatory approach shows great application potential for shortening the inflammatory phase of diabetic wound repair and accelerating wound healing.

Drying Technique Providing Maximum Benefits on Hydrogelling Ability of Avocado Seed Protein: Spray Drying.

The current study focused on creating natural hydrogels consisting of mixtures of avocado seed proteins dried with different techniques and locust bean gum. Proteins were extracted from avocado seed by alkali and isoelectric precipitation methods. Avocado seed proteins were dried by five different drying methods, namely ambient drying, oven drying, vacuum drying, freeze drying, and spray drying. FT-IR spectra were used to analyze the chemical structure of proteins dried using various techniques. Additionally, hydrogel models were constructed in the presence of avocado seed proteins and locust bean gum to clarify the effect of drying techniques on their hydrogelling ability. The impact of drying techniques on the functional behavior of hydrogels was notable. The maximum water holding capacity values were detected in the hydrogel system containing spray-dried proteins (93.79%), followed by freeze-dried (86.83%), vacuum-dried (76.17%), oven-dried (72.29%), and ambient-dried (64.8%) counterparts. The swelling ratio was 34.10, 33.51, 23.05, 18.93, and 14.39% for gels in the presence of freeze-dried, spray-dried, vacuum-dried, oven-dried, and ambient-dried proteins, respectively. Additionally, the desirable values for the amount of protein leaking from the systems prepared using spray-dried (7.99%) and freeze-dried (12.14%) proteins were obtained compared to others (ambient-dried: 24.03%; oven-dried: 17.69%; vacuum-dried: 19.10%). Superior results in terms of textural properties were achieved in hydrogel models containing spray-dried and freeze-dried proteins. In general, hydrogel models exhibited elastic behavior rather than viscous properties; however, the magnitudes of elasticity varied. Furthermore, the success of gels containing hydrogel models containing spray-dried protein and locust bean gum in the bioactive compound delivery system was obvious compared with protein ones alone.

In Situ Implantation of Chitosan Oligosaccharide-Doped Lipoic Acid Hydrogel Breaks the "Vicious Cycle" of Inflammation and Residual Tumor Cell for Postoperative Skin Cancer Therapy.

Surgical excision is the main treatment for skin cancer, but the tumor recurrence caused by the "vicious cycle" between residual tumor cells and postoperative inflammation remains a challenge. Herein, a new material, which can break the "vicious cycle", was developed by incorporating chitosan oligosaccharides into lipoic acid hydrogel (COS@LA-hydrogel). When implanted at the resection site, the COS@LA-hydrogel would have a sustained release of LA and COS, which could not only kill residual tumor cells by synergistically reducing AKT phosphorylation but also decrease inflammation by inhibiting the expression of tumor necrosis factor-α (TNF-α) and inhibiting bacterial infection, respectively. As a proof of concept, in the postoperative melanoma resection model, the COS@LA-hydrogel reduced the expression of pro-inflammatory factors TNF-α and interleukin-6 (IL-6) by up to 78 and 80%, respectively, and they showed almost no tumors and the median survival of the mice was 2.5 times longer than that of the control group. The hydrogel with the function of "vicious cycle" breaking holds clinical potential.

Regenerative Potential of A Bovine ECM-Derived Hydrogel for Biomedical Applications.

Recent advancements in regenerative medicine have enhanced the development of biomaterials as multi-functional dressings, capable of accelerating wound healing and addressing the challenge of chronic wounds. Hydrogels obtained from decellularized tissues have a complex composition, comparable to the native extracellular environment, showing highly interesting characteristics for wound healing applications. In this study, a bovine pericardium decellularized extracellular matrix (dECM) hydrogel was characterized in terms of macromolecules content, and its immunomodulatory, angiogenic and wound healing potential has been evaluated. The polarization profile of human monocytes-derived macrophages seeded on dECM hydrogel was assessed by RT-qPCR. Angiogenic markers expression has been evaluated by Western blot and antibody array on cell lysates derived from endothelial cells cultured on dECM hydrogel, and a murine in vivo model of hindlimb ischemia was used to evaluate the angiogenic potential. Fibroblast migration was assessed by a transwell migration assay, and an in vivo murine wound healing model treated with dECM hydrogels was also used. The results showed a complex composition, of which the major component is collagen type I. The dECM hydrogel is biocompatible, able to drive M2 phenotype polarization, stimulate the expression of angiogenic markers in vitro, and prevent loss of functionality in hindlimb ischemia model. Furthermore, it drives fibroblast migration and shows ability to facilitate wound closure in vivo, demonstrating its great potential for regenerative applications.

Material Properties and Cell Compatibility of Photo-Crosslinked Sericin Urethane Methacryloyl Hydrogel.

There is a need to develop novel cytocompatible hydrogels for cell encapsulation and delivery in regenerative medicine. The objective of this work was to synthesize isocyanato ethyl methacryloyl-functionalized sericin and determine its material properties as a natural hydrogel for the encapsulation and delivery of human mesenchymal stem cells (MSCs) in regenerative medicine. Sericin extracted from silk cocoons was reacted with 2-isocyanatoethyl methacrylate (IEM) or methacrylic anhydride (MA) to produce sericin urethane methacryloyl (SerAte-UM) or sericin methacryloyl (SerAte-M, control) biopolymers, respectively. The hydrogels produced by photo-crosslinking of the biopolymers in an aqueous solution were characterized with respect to gelation kinetics, microstructure, compressive modulus, water content, degradation, permeability, and viability of encapsulated cells. The secondary structure of citric acid-extracted sericin was not affected by functionalization with IEM or MA. SerAte-UM hydrogel was slightly more hydrophilic than SerAte-M. The gelation time of SerAte-UM hydrogel decreased with an increasing degree of modification. The photo-polymerized SerAte-UM hydrogel had a highly porous, fibrous, honeycomb microstructure with an average pore size in the 40−50 µm range. The compressive modulus, swelling ratio, and permeability of SerAte-UM hydrogel depended on the degree of modification of sericin, and the mass loss after 21 days of incubation in aqueous solution was <25%. Both SerAte-UM and SerAte-M hydrogels supported viability and growth in encapsulated MSCs. The SerAte-UM hydrogel, with its higher hydrophilicity compared to SerAte-M, is promising as a matrix for encapsulation and delivery of stem cells in tissue engineering.

Chemical and Bioactive Characterization of Spanish and Belgian Apple Pomace for Its Potential Use as a Novel Dermocosmetic Formulation.

Currently, there is a general trend towards reutilizing industrial by-products that would otherwise be discarded or considered as waste, aiming to explore them as alternative sources of valuable compounds. The apple pomace remaining from cider and apple juice industries represents a high-potential source of bioactive compounds with putative application in food or pharmaceutical-related products. Accordingly, the work reported herein was conducted to characterize the phenolic compounds in apple pomace from Belgium and Spain, as well as to evaluate its chemical composition and particular types of bioactivity. As a proof of concept, a new hydrogel was prepared, incorporated with the bioactive compounds and pectin extracted from apple pomace, aiming to obtain the most organic formulation possible. Independently of the extracting agent, it became evident that using lyophilization as the drying step is a better choice than thermal processes as it yielded a richer phenolic profile (fifteen individual compounds), with 5-O-caffeoylquinic acid as the major compound (66 to 114 mg/100 g dw) in Belgian samples. In general, the hydroethanolic extracts showed the strongest antioxidant and antimicrobial (particularly against Propionibacterium acnes: MIC = 2.5 mg/mL) activities. This result, together with the lipid nature of human skin, led it to be chosen as the extract type to be incorporated in the hydrogel. In general, apple pomace stood out as a valuable source of bioactive compounds, especially polyphenols and pectin, with good potential to be incorporated in dermal formulations.

Photocrosslinked natural hydrogel composed of hyaluronic acid and gelatin enhances cartilage regeneration of decellularized trachea matrix.

Repair of long segmental trachea defects is always a great challenge in the clinic. The key to solving this problem is to develop an ideal trachea substitute with biological function. Using of a decellularized trachea matrix based on laser micropore technique (LDTM) demonstrated the possibility of preparing ideal trachea substitutes with tubular shape and satisfactory cartilage regeneration for tissue-engineered trachea regeneration. However, as a result of the very low cell adhesion of LDTM, an overly high concentration of seeding cell is required, which greatly restricts its clinical translation. To address this issue, the current study proposed a novel strategy using a photocrosslinked natural hydrogel (PNH) carrier to enhance cell retention efficiency and improve tracheal cartilage regeneration. Our results demonstrated that PNH underwent a rapid liquid-solid phase conversion under ultraviolet light. Moreover, the photo-generated aldehyde groups in PNH could rapidly react with inherent amino groups on LDTM surfaces to form imine bonds, which efficiently immobilized the cell-PNH composite to the surfaces of LDTM and/or maintained the composite in the LDTM micropores. Therefore, PNH significantly enhanced cell-seeding efficiency and achieved both stable cell retention and homogenous cell distribution throughout the LDTM. Moreover, PNH exhibited excellent biocompatibility and low cytotoxicity, and provided a natural three-dimensional biomimetic microenvironment to efficiently promote chondrocyte survival and proliferation, extracellular matrix production, and cartilage regeneration. Most importantly, at a relatively low cell-seeding concentration, homogeneous tubular cartilage was successfully regenerated with an accurate tracheal shape, sufficient mechanical strength, good elasticity, typical lacuna structure, and cartilage-specific extracellular matrix deposition. Our findings establish a versatile and efficient cell-seeding strategy for regeneration of various tissue and provide a satisfactory trachea substitute for repair and functional reconstruction of long segmental tracheal defects.

Advancements and Frontiers in the High Performance of Natural Hydrogels for Cartilage Tissue Engineering.

Cartilage injury originating from trauma or osteoarthritis is a common joint disease that can bring about an increasing social and economic burden in modern society. On account of its avascular, neural, and lymphatic characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Natural hydrogels, occurring abundantly with characteristics such as high water absorption, biodegradation, adjustable porosity, and biocompatibility like that of the natural extracellular matrix (ECM), have been developed into one of the most suitable scaffold biomaterials for the regeneration of cartilage in material science and tissue engineering. Notably, natural hydrogels derived from sources such as animal or human cadaver tissues possess the bionic mechanical behaviors of physiological cartilage that are required for usage as articular cartilage substitutes, by which the enhanced chondrogenic phenotype ability may be achieved by facilely embedding living cells, controlling degradation profiles, and releasing stimulatory growth factors. Hence, we summarize an overview of strategies and developments of the various kinds and functions of natural hydrogels for cartilage tissue engineering in this review. The main concepts and recent essential research found that great challenges like vascularity, clinically relevant size, and mechanical performances were still difficult to overcome because the current limitations of technologies need to be severely addressed in practical settings, particularly in unpredictable preclinical trials and during future forays into cartilage regeneration using natural hydrogel scaffolds with high mechanical properties. Therefore, the grand aim of this current review is to underpin the importance of preparation, modification, and application for the high performance of natural hydrogels for cartilage tissue engineering, which has been achieved by presenting a promising avenue in various fields and postulating real-world respective potentials.

Advances of Naturally Derived and Synthetic Hydrogels for Intervertebral Disk Regeneration.

Intervertebral disk (IVD) degeneration is associated with most cases of cervical and lumbar spine pathologies, amongst which chronic low back pain has become the primary cause for loss of quality-adjusted life years. Biomaterials science and tissue engineering have made significant progress in the replacement, repair and regeneration of IVD tissue, wherein hydrogel has been recognized as an ideal biomaterial to promote IVD regeneration in recent years. Aspects such as ease of use, mechanical properties, regenerative capacity, and their applicability as carriers for regenerative and anti-degenerative factors determine their suitability for IVD regeneration. This current review provides an overview of naturally derived and synthetic hydrogels that are related to their clinical applications for IVD regeneration. Although each type has its own unique advantages, it rarely becomes a standard product in truly clinical practice, and a more rational design is proposed for future use of biomaterials for IVD regeneration. This review aims to provide a starting point and inspiration for future research work on development of novel biomaterials and biotechnology.

Natural hydrogels for cartilage regeneration: Modification, preparation and application.

Hydrogels, consisting of hydrophilic polymers, can be used as films, scaffolds, nanoparticles and drug carriers. They are one of the hot research topics in material science and tissue engineering and are widely used in the field of biomedical and biological sciences. Researchers are seeking for a type of material that is similar to human tissues and can partially replace human tissues or organs. The hydrogel has brought possibility to solve this problem. It has good biocompatibility and biodegradability. After entering the body, it does not cause immune and toxic reactions. The degradation time can be controlled, and the degradation products are nontoxic and nonimmunogenic; the final metabolites can be excreted outside the body. Owing to the lack of blood vessels and poor migration ability of chondrocytes, the self-healing ability of damaged cartilage is limited. Tissue engineering has brought a new direction for the regeneration of cartilage. Drug carriers and scaffolds made of hydrogels are widely used in cartilage tissue engineering. The present review introduces the natural hydrogels, which are often used for cartilage tissue engineering with respect to synthesis, modification and application methods. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: This review introduces the natural hydrogels that are often used in cartilage tissue engineering with respect to synthesis, modification and application methods. Furthermore, the essential concepts and recent discoveries were demonstrated to illustrate the achievable goals and the current limitations. In addition, we propose the putative challenges and directions for the use of natural hydrogels in cartilage regeneration.

Natural polymeric hydrogel evaluation for skeletal muscle tissue engineering.

Although skeletal muscle has a remarkable ability to repair/regenerate after most types of injuries, there is limited regeneration after volumetric muscle loss (VML). A number of scaffold materials have been used in the development of grafts to treat VML, however, there is still a need to better understand the most appropriate material with regards to its ability to maintain mechanical integrity while also supporting myogenesis. Five commonly used natural polymeric materials (Collagen I, Agarose, Alginate, Fibrin, and Collagen Chitosan) used in skeletal muscle tissue engineering grafts were evaluated for their mechanical properties and myogenic capacity. Rheological properties, water absorption rates, degradation stability, tensile characteristics, and the ability to support in vitro myogenesis were compared in all five materials. Collagen, Collagen Chitosan, and Fibrin demonstrated high elasticity and 100% stretch without failure, Agarose was the most brittle (20% max stretch), and Alginate demonstrated poor handleabilty. While Collagen was supportive of myogenesis, overall, Fibrin demonstrated the highest myogenic potential as indicated by the earliest and highest increases in myogenin and myosin heavy chain mRNA in satellite cells along with the most extensive myotube development as evaluated with immunohistochemistry. The findings herein support the notion that under the conditions used in this study, Fibrin is the most suitable scaffold for the development of scaffolds for skeletal muscle tissue engineering. Future studies are required to determine whether the differences in mechanical properties and myogenic potential observed in vitro in the current study translate to better skeletal muscle development in a VML injury model. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 672-679, 2018.