Photo-crosslinked hydrogels for tissue engineering of corneal epithelium.

The vast majority of patients with corneal blindness cannot recover their vision due to the serious shortage of donor cornea. However, the technology to construct a feasible corneal substitute is a promising treatment method for corneal blindness. In this paper, methacrylated gelatin (GelMA)-methacrylated hyaluronic acid (HAMA) double network (GHDN) hydrogels were prepared by modifying gelatin and hyaluronic acid with methacrylate anhydride (MA). GHDN hydrogel was compared with GelMA single network and HAMA single network hydrogels through characterization experiments of mechanical properties, optical properties, hydrophilicity and in-situ degradation in vitro. At the same time, the biocompatibility of hydrogel was tested by inoculating rabbit corneal epithelial cells (CEpCs) epidermal cells on hydrogels using CCK-8 test, live/dead staining, immunofluorescence staining and qRT-PCR. It was found that the GHDN hydrogel has optical transparency in the visible region, and its mechanical properties are better than those of GelMA and HAMA hydrogels, and its hydrophilicity is similar to that of normal human corneas. The results of in vitro hydrogel culture of CEpCs showed that the proliferation of CEpCs on GHDN hydrogel was two times higher than that of HAMA hydrogel, and the expression of specific marker Cytokeratin 3 (CK3) and Cytokeratin 12 (CK12) could be better maintained on GHDN hydrogel. All the experimental results proved that GHDN hydrogel has good physical properties and biocompatibility and is a potential candidate for corneal tissue engineering scaffolds.

Photobiomodulation combined with adipose-derived stem cells encapsulated in methacrylated gelatin hydrogels enhances in vivo bone regeneration.

Reconstruction of bone defects is still a significant challenge. The aim of this study was to evaluate the effect of application of photobiomodulation (PBM) to enhance in vivo bone regeneration and osteogenic differentiation potential of adipose-derived stem cells (ADSCs) encapsulated in methacrylated gelatin (GEL-MA) hydrogels. Thirty-six Sprague-Dawley rats were randomly separated into 3 experimental groups (n = 12 each). The groups were control/blank defect (I), GEL-MA hydrogel (II), and ADSC-loaded GEL-MA (GEL-MA+ADSC) hydrogel (III). Biparietal critical sized bone defects (6 mm in size) are created in each animal. Half of the animals from each group (n = 6 each) were randomly selected for PBM application using polychromatic light in the near infrared region, 600-1200 nm. PBM was administered from 10 cm distance cranially in 48 h interval. The calvaria were harvested at the 20th week, and macroscopic, microtomographic, and histologic evaluation were performed for further analysis. Microtomographic evaluation demonstrated the highest result for mineralized matrix formation (MMF) in group III. PBM receiving samples of group III showed mean MMF of 79.93±3.41%, whereas the non-PBM receiving samples revealed mean MMF of 60.62±6.34 % (p=0.002). In terms of histologic evaluation of bone defect repair, the higher scores were obtained in the groups II and III when compared to the control group (2.0 for both PBM receiving and non-receiving specimens; p<0.001). ADSC-loaded microwave-induced GEL-MA hydrogels and periodic application of photobiomodulation with polychromatic light appear to have beneficial effect on bone regeneration and can stimulate ADSCs for osteogenic differentiation.

Injectable GelMA Cryogel Microspheres for Modularized Cell Delivery and Potential Vascularized Bone Regeneration.

Cell therapeutics hold tremendous regenerative potential and the therapeutic effect depends on the effective delivery of cells. However, current cell delivery carriers with unsuitable cytocompatibility and topological structure demonstrate poor cell viability during injection. Therefore, porous shape-memory cryogel microspheres (CMS) are prepared from methacrylated gelatin (GelMA) by combining an emulsion technique with gradient-cooling cryogelation. Pore sizes of the CMS are adjusted via the gradient-cooling procedure, with the optimized pore size (15.5 ± 6.0 µm) being achieved on the 30-min gradient-cooled variant (CMS-30). Unlike hydrogel microspheres (HMS), CMS promotes human bone marrow stromal cell (hBMSC) and human umbilical vein endothelial cell (HUVEC) adhesion, proliferated with high levels of stemness for 7 d, and protects cells during the injection process using a 26G syringe needle. Moreover, CMS-30 enhances the osteogenic differentiation of hBMSCs in osteoinductive media. CMS can serve as building blocks for delivering multiple cell types. Here, hBMSC-loaded and HUVEC-loaded CMS-30, mixed at a 1:1 ratio, are injected subcutaneously into nude mice for 2 months. Results show the development of vascularized bone-like tissue with high levels of OCN and CD31. These findings indicate that GelMA CMS of a certain pore size can effectively deliver multiple cells to achieve functional tissue regeneration.

Controlling mechanical properties of cell-laden hydrogels by covalent incorporation of graphene oxide.

Graphene-based materials are useful reinforcing agents to modify the mechanical properties of hydrogels. Here, an approach is presented to covalently incorporate graphene oxide (GO) into hydrogels via radical copolymerization to enhance the dispersion and conjugation of GO sheets within the hydrogels. GO is chemically modified to present surface-grafted methacrylate groups (MeGO). In comparison to GO, higher concentrations of MeGO can be stably dispersed in a pre-gel solution containing methacrylated gelatin (GelMA) without aggregation or significant increase in viscosity. In addition, the resulting MeGO-GelMA hydrogels demonstrate a significant increase in fracture strength with increasing MeGO concentration. Interestingly, the rigidity of the hydrogels is not significantly affected by the covalently incorporated GO. Therefore, this approach can be used to enhance the structural integrity and resistance to fracture of the hydrogels without inadvertently affecting their rigidity, which is known to affect the behavior of encapsulated cells. The biocompatibility of MeGO-GelMA hydrogels is confirmed by measuring the viability and proliferation of the encapsulated fibroblasts. Overall, this study highlights the advantage of covalently incorporating GO into a hydrogel system, and improves the quality of cell-laden hydrogels.

Double-layered microneedle patch loaded with bioinspired nano-vaccine for melanoma treatment and wound healing.

Malignant melanoma is a challenging problem worldwide, because the remaining tumor cells and extensive skin defects following surgical resection are difficult to treat. Biomaterial-mediated immunotherapy has emerged as a superior strategy for anti-tumor applications in recent years. Herein, a unique double-layer MNP was developed to address the problem of malignant melanoma. Hydroxyapatite (HAP) and short-chain peptides from tumor cells were self-assembled to prepare the bioinspired nano-vaccine, and then they were loaded onto the microneedle tips of methacrylated gelatin (GelMA)-based MNP. The products (dubbed HVMN) demonstrated relatively good biocompatibility and immune activity, inhibiting the proliferation and inducing apoptosis of malignant melanoma in a B16 cell-bearing model of C57BL/6 mice, and promoting skin tissue regeneration in a full thickness skin defect model of SD rats in 15 days. The putative molecular pathways were examined preliminarily. In conclusion, this research will develop a competitive microneedle patch with dual anti-tumor and pro-regenerative properties for the postoperative treatment of malignant melanoma.

GelMA-based hydrogel biomaterial scaffold: A versatile platform for regenerative endodontics.

Endodontic therapy, while generally successful, is primarily limited to mature teeth, hence the pressing need to explore regenerative approaches. Gelatin methacryloyl (GelMA) hydrogels have emerged as pivotal biomaterials, promising a bright future for dental pulp regeneration. Despite advancements in tissue engineering and biomaterials, achieving true pulp tissue regeneration remains a formidable task. GelMA stands out for its injectability, rapid gelation, and excellent biocompatibility, serving as the cornerstone of scaffold materials. In the pursuit of dental pulp regeneration, GelMA holds significant potential, facilitating the delivery of stem cells, growth factors, and other vital substances crucial for tissue repair. Presently, in the field of dental pulp regeneration, researchers have been diligently utilizing GelMA hydrogels as engineering scaffolds to transport various effective substances to promote pulp regeneration. However, existing research is relatively scattered and lacks comprehensive reviews and summaries. Therefore, the primary objective of this article is to elucidate the application of GelMA hydrogels as regenerative scaffolds in this field, thereby providing clear direction for future researchers. Additionally, this article provides a comprehensive discussion on the synthesis, characterization, and application of GelMA hydrogels in root canal therapy regeneration. Furthermore, it offers new application strategies and profound insights into future challenges, such as optimizing GelMA formulations to mimic the complex microenvironment of pulp tissue and enhancing its integration with host tissues.

Development of cell-laden photopolymerized constructs with bioactive amorphous calcium magnesium phosphate for bone tissue regeneration via 3D bioprinting.

The synthesis of ideal bioceramics to guide the fate of cells and subsequent bone regeneration within the chemical, biological, and physical microenvironment is a challenging long-term task. This study developed amorphous calcium magnesium phosphate (ACMP) bioceramics via a simple co-precipitation method. The role of Mg2+ in the formation of ACMP is investigated using physicochemical and biological characterization at different Ca/Mg molar ratio of the initial reaction solution. Additionally, ACMP bioceramics show superior cytocompatibility and improved osteogenic differentiation of co-cultured MC3T3-E1 cells. Regulation of the microenvironment with Mg2+ can promote early-stage bone regeneration. For this, bioprinting technology is employed to prepare ACMP-modified 3D porous structures. Our hypothesis is that the incorporation of ACMP into methacrylated gelatin (GelMA) bioink can trigger the osteogenic differentiation of encapsulated preosteoblast and stimulate bone regeneration. The cell-laden ACMP composite structures display stable printability and superior cell viability and cell proliferation. Also, constructs loading the appropriate amount of ACMP bioceramic showed significant osteogenic differentiation activity compared to the pure GelMA. We demonstrate that the dissolved Mg2+ cation microenvironment in ACMP-modified composite constructs plays an effective biochemical role, and can regulate cell fate. Our results predict that GelMA/ACMP bioink has significant potential in patient-specific bone tissue regeneration.

3D printing of MOF-reinforced methacrylated gelatin scaffolds for bone regeneration.

Scaffolds based on gelatin (Gel) play a crucial role in bone tissue engineering. However, the low mechanical properties, rapid biodegradation rate, insufficient osteogenic activity and lacking anti-infective properties limit their applications in bone regeneration. Herein, the incorporation of ibuprofen (IBU)-loaded zeolitic imidazolate framework-8 (ZIF-8) in a methacrylated gelatin (GelMA) matrix was proposed as a simple and effective strategy to develop the IBU-ZIF-8@GelMA scaffolds for enhanced bone regeneration capacity. Results indicated that the IBU-loaded ZIF-8 nanoparticles with tiny particle sizes were uniformly distributed in the GelMA matrix of the IBU-ZIF-8@GelMA scaffolds, and the IBU-loaded ZIF-8 growing in the scaffolds enabled the controlled and sustained releasing of Zn2+ and IBU in pH = 5.5 over a long period for efficient bone repair and long-term anti-inflammatory activity. Furthermore, the doping of the IBU-loaded ZIF-8 nanoparticles efficiently enhanced the compression performance of the GelMA scaffolds. In vitro studies indicated that the prepared scaffolds presented no cytotoxicity to MC3T3-E1 cells and the released Zn2+ during the degradation of the scaffolds promoted MC3T3-E1 cell osteogenic differentiation. Thus, the drug-loaded ZIF-8 modified 3D printed GelMA scaffolds demonstrated great potential in treating bone defects.

Microfluidic Controllable Preparation of Iodine-131-Labeled Microspheres for Radioembolization Therapy of Liver Tumors.

Transcatheter arterial radioembolization (TARE) is of great significance for the treatment of advanced hepatocellular carcinoma (HCC). However, the existing radioembolic microspheres still have problems such as non-degradability, non-uniform size, and inability to directly monitor in vivo, which hinders the development of TARE. In this paper, a novel radioembolic agent, 131 I-labeled methacrylated gelatin microspheres (131 I-GMs), is prepared for the treatment of HCC. Water-in-oil (W/O) emulsion templates are prepared by a simple one-step microfluidic method to obtain methacrylated gelatin microspheres (GMs) after UV irradiation. A series of GMs with uniform and controllable size is obtained by adjusting the flow rate of each fluid. Both air-dried and freeze-dried GMs can quickly restore their original shape and size, and still have good monodispersity, elasticity, and biocompatibility. The radiolabeling experiments show that 131 I can efficiently bind to GMs by chloramine-T method, and the obtained 131 I-GMs have good radioactive stability in vitro. The results of in vivo TARE treatment in rats show that 131 I-GMs can be well retained in the hepatic artery and have a good inhibitory effect on the progression of liver cancer, showing the potential for the treatment of HCC.

Effects of Gamma Irradiation and Supercritical Carbon Dioxide Sterilization on Methacrylated Gelatin/Hyaluronan Hydrogels.

Biopolymer hydrogels have become an important group of biomaterials in experimental and clinical use. However, unlike metallic or mineral materials, they are quite sensitive to sterilization. The aim of this study was to compare the effects of gamma irradiation and supercritical carbon dioxide (scCO2) treatment on the physicochemical properties of different hyaluronan (HA)- and/or gelatin (GEL)-based hydrogels and the cellular response of human bone marrow-derived mesenchymal stem cells (hBMSC). Hydrogels were photo-polymerized from methacrylated HA, methacrylated GEL, or a mixture of GEL/HA. The composition and sterilization methods altered the dissolution behavior of the biopolymeric hydrogels. There were no significant differences in methacrylated GEL release but increased methacrylated HA degradation of gamma-irradiated samples. Pore size/form remained unchanged, while gamma irradiation decreased the elastic modulus from about 29 kPa to 19 kPa compared to aseptic samples. HBMSC proliferated and increased alkaline phosphatase activity (ALP) particularly in aseptic and gamma-irradiated methacrylated GEL/HA hydrogels alike, while scCO2 treatment had a negative effect on both proliferation and osteogenic differentiation. Thus, gamma-irradiated methacrylated GEL/HA hydrogels are a promising base for multi-component bone substitute materials.

Advantages of photo-curable collagen-based cell-laden bioinks compared to methacrylated gelatin (GelMA) in digital light processing (DLP) and extrusion bioprinting.

The development of cell-laden bioinks that possess high biocompatibility and printability is crucial in the field of bioprinting for the creation of cell-embedded tissue engineering scaffolds. As widely known, methacrylated gelatin (GelMA) is one of the most commonly used photo-crosslinkable bioink for cell-laden bioprinting with different printing methods, but GelMA is the derivative of gelatin, so it loses the unique triple-helix molecular structure of collagen and may not be able to successfully activate the cellular pathways or facilitate cell-matrix interaction as effectively as collagen. Recently, methacrylated collagen (CMA) was developed to be an alternative photocrosslinkable bioink with a good bioactivity, but its low printability and biocompatibility limited that application in tissue engineering. In this study, the synthetic process for CMA was improved by synthesizing under 4 °C and using acidic aqueous solution as solvent. Our CMA bioinks were demonstrated a similar printability as GelMA in extrusion bioprinting, while a better formability in digital light processing (DLP). To further analyze the bioactive properties, CMA bioinks were encapsulated with Schwann cells (SCs) and bone mesenchymal stem cells (BMSCs) for printing. SCs-laden CMA bioinks had a significantly higher proliferation rate and expression of neural stem cell-associated genes than GelMA in DLP bioprinting. While, BMSCs-laden CMA bioinks demonstrated >95% cellular viability, better cell spreading and higher expression of osteogenesis-related genes than that of GelMA. Overall, we speculate that the CMA-based bioink developed in this study could be potential bioinks for 3D cell-laden bioprinting in the future.

Injectable methacrylated gelatin/thiolated pectin hydrogels carrying melatonin/tideglusib-loaded core/shell PMMA/silk fibroin electrospun fibers for vital pulp regeneration.

Use of injectable hydrogels attract attention in the regeneration of dental pulp due to their ability to fill non-uniform voids such as pulp cavities. Here, gelatin methacrylate/thiolated pectin hydrogels (GelMA/PecTH) carrying electrospun core/shell fibers of melatonin (Mel)-polymethylmethacrylate (PMMA)/Tideglusib (Td)-silk fibroin (SF) were designed as an injectable hydrogel for vital pulp regeneration, through prolonged release of Td and Mel to induce proliferation and odontoblastic differentiation of dental pulp stem cells (DPSC). H NMR and FTIR confirmed methacrylation of Gel and thiolation of Pec. Addition of PMMA/SF increased degradation and water retention capacities of GelMA/PecTH. Rheological analyses and syringe tests proved the injectability of the hydrogel systems. Release studies indicated that Td and Mel were released from the fibers inside the hydrogels sequentially due to their specific locations. This release pattern from the hydrogels resulted in DPSC proliferation and odontogenic differentiation in vitro. Gene expression studies showed that the upregulation of DMP1, DSPP, and Axin-2 genes was promoted by GelMA/PecTH carrying PMMA/SF loaded with Mel (50 µg/mL) and Td (200 nM), respectively. Our results suggest that this hydrogel system holds promise for use in the regeneration of pulp tissue.

In vitrolong term differentiation and functionality of three-dimensional bioprinted primary human hepatocytes: application forin vivoengraftment.

In recent decades, 3Din vitrocultures of primary human hepatocytes (PHHs) have been increasingly developed to establish models capable of faithfully mimicking main liver functions. The use of 3D bioprinting, capable of recreating structures composed of cells embedded in matrix with controlled microarchitectures, is an emergent key feature for tissue engineering. In this work, we used an extrusion-based system to print PHH in a methacrylated gelatin (GelMa) matrix. PHH bioprinted in GelMa rapidly organized into polarized hollow spheroids and were viable for at least 28 d of culture. These PHH were highly differentiated with maintenance of liver differentiation genes over time, as demonstrated by transcriptomic analysis and functional approaches. The cells were polarized with localization of apico/canalicular regions, and displayed activities of phase I and II biotransformation enzymes that could be regulated by inducers. Furthermore, the implantation of the bioprinted structures in mice demonstrated their capability to vascularize, and their ability to maintain human hepatic specific functions for at least 28 d was illustrated by albumin secretion and debrisoquine metabolism. This model could hold great promise for human liver tissue generation and its use in future biotechnological developments.

Stem Cells-Loaded 3D-Printed Scaffolds for the Reconstruction of Alveolar Cleft.

The advances in the field of tissue engineering and regenerative medicine have opened new vistas for the repair of alveolar clefts. However, the currently available biomaterials used for the repair of alveolar clefts have poor mechanical properties and biocompatibility, which hinders the treatment outcomes. Here, we aimed to develop 3D printed biomimetic scaffolds that fuses ß-tricalcium phosphate (ß-TCP) and bone marrow mesenchymal stem cells (BMSCs) for improving the repair of alveolar clefts. The methacrylate gelatin (GelMA) was mixed with ß-TCP for the preparation of GelMA/ß-TCP hybrid scaffolds via 3D printing platform and chemically cross-linking with UV light. The physicochemical properties of the hydrogel scaffolds were characterized. Moreover, the survival state, proliferation ability, morphological characteristics, and osteogenic induction of BMSCs were examined. The prepared hybrid scaffolds showed good biocompatibility and mechanical properties. BMSCs attached well to the scaffolds and proliferated, survived, differentiated, and stimulated osteogenesis for the reconstruction of alveolar clefts. We expect that use of the prepared hybrid hydrogel scaffold can improve the outcomes of alveolar cleft repair in clinic and expand the application of hybrid hydrogel in tissue engineering repair.

Incorporating nanocrystalline cellulose into a multifunctional hydrogel for heart valve tissue engineering applications.

Functional tissue engineered heart valves (TEHV) have been an elusive goal for nearly 30 years. Among the persistent challenges are the requirements for engineered valve leaflets that possess nonlinear elastic tissue biomechanical properties, support quiescent fibroblast phenotype, and resist osteogenic differentiation. Nanocellulose is an attractive tunable biological material that has not been employed to this application. In this study, we fabricated a series of photocrosslinkable composite hydrogels mNCC-MeGel (mNG) by conjugating TEMPO-modified nanocrystalline cellulose (mNCC) onto the backbone of methacrylated gelatin (MeGel). Their structures were characterized by FTIR, 1 HNMR and uniaxial compression testing. Human adipose-derived mesenchymal stem cells (HADMSC) were encapsulated within the material and evaluated for valve interstitial cell phenotypes over 14 days culture in both normal and osteogenic media. Compared to the MeGel control group, the HADMSC encapsulated within mNG showed decreased alpha smooth muscle actin (αSMA) expression and increased vimentin and aggrecan expression, suggesting the material supports a quiescent fibroblastic phenotype. Under osteogenic media conditions, HADMSC within mNG hydrogels showed lower expression of osteogenic genes, including Runx2 and osteocalcin, indicating resistance toward calcification. As a proof of principle, the mNG hydrogel, combined with a viscosity enhancing agent, was used to 3D bioprint a tall, self-standing tubular structure that sustained cell viability. Together, these results identify mNG as an attractive biomaterial for TEHV applications.

Modeling early changes associated with cartilage trauma using human-cell-laden hydrogel cartilage models.

BACKGROUND: Traumatic impacts to the articular joint surface are known to lead to cartilage degeneration, as in post-traumatic osteoarthritis (PTOA). Limited progress in the development of disease-modifying OA drugs (DMOADs) may be due to insufficient mechanistic understanding of human disease onset/progression and insufficient in vitro models for disease and therapeutic modeling. In this study, biomimetic hydrogels laden with adult human mesenchymal stromal cells (MSC) are used to examine the effects of traumatic impacts as a model of PTOA. We hypothesize that MSC-based, engineered cartilage models will respond to traumatic impacts in a manner congruent with early PTOA pathogenesis observed in animal models. METHODS: Engineered cartilage constructs were fabricated by encapsulating adult human bone marrow-derived mesenchymal stem cells in a photocross-linkable, biomimetic hydrogel of 15% methacrylated gelatin and promoting chondrogenic differentiation for 28 days in a defined medium and TGF-ß3. Constructs were subjected to traumatic impacts with different strains or 10 ng/ml IL-1ß, as a common comparative method of modeling OA. Cell viability and metabolism, elastic modulus, gene expression, matrix protein production and activation of catabolic enzymes were assessed. RESULTS: Cell viability staining showed that traumatic impacts of 30% strain caused an appropriate level of cell death in engineered cartilage constructs. Gene expression and histo/immunohistochemical analyses revealed an acute decrease in anabolic activities, such as COL2 and ACAN expression, and a rapid increase in catabolic enzyme expression, e.g., MMP13, and inflammatory modulators, e.g., COX2. Safranin O staining and GAG assays together revealed a transient decrease in matrix production 24 h after trauma that recovered within 7 days. The decrease in elastic modulus of engineered cartilage constructs was coincident with GAG loss and mediated by the encapsulated cells. The acute and transient changes observed after traumatic impacts contrasted with progressive changes observed using continual IL-1ß treatment. CONCLUSIONS: Traumatic impacts delivered to engineered cartilage constructs induced PTOA-like changes in the encapsulated cells. While IL-1b may be appropriate in modeling OA pathogenesis, the results of this study indicate it may not be appropriate in understanding the etiology of PTOA. The development of a more physiological in vitro PTOA model may contribute to the more rapid development of DMOADs.

Human gelatin-based composite hydrogels for osteochondral tissue engineering and their adaptation into bioinks for extrusion, inkjet, and digital light processing bioprinting.

The investigation of novel hydrogel systems allows for the study of relationships between biomaterials, cells, and other factors within osteochondral tissue engineering. Three-dimensional (3D) printing is a popular research method that can allow for further interrogation of these questions via the fabrication of 3D hydrogel environments that mimic tissue-specific, complex architectures. However, the adaptation of promising hydrogel biomaterial systems into 3D-printable bioinks remains a challenge. Here, we delineated an approach to that process. First, we characterized a novel methacryloylated gelatin composite hydrogel system and assessed how calcium phosphate and glycosaminoglycan additives upregulated bone- and cartilage-like matrix deposition and certain genetic markers of differentiation within human mesenchymal stem cells (hMSCs), such as RUNX2 and SOX9. Then, new assays were developed and utilized to study the effects of xanthan gum and nanofibrillated cellulose, which allowed for cohesive fiber deposition, reliable droplet formation, and non-fracturing digital light processing (DLP)-printed constructs within extrusion, inkjet, and DLP techniques, respectively. Finally, these bioinks were used to 3D print constructs containing viable encapsulated hMSCs over a 7 d period, where DLP printed constructs facilitated the highest observed increase in cell number over 7 d (∼2.4×). The results presented here describe the promotion of osteochondral phenotypes via these novel composite hydrogel formulations, establish their ability to bioprint viable, cell-encapsulating constructs using three different 3D printing methods on multiple bioprinters, and document how a library of modular bioink additives affected those physicochemical properties important to printability.

State-of-the-art review of advanced electrospun nanofiber yarn-based textiles for biomedical applications.

The pandemic of the coronavirus disease 2019 (COVID-19) has made biotextiles, including face masks and protective clothing, quite familiar in our daily lives. Biotextiles are one broad category of textile products that are beyond our imagination. Currently, biotextiles have been routinely utilized in various biomedical fields, like daily protection, wound healing, tissue regeneration, drug delivery, and sensing, to improve the health and medical conditions of individuals. However, these biotextiles are commonly manufactured with fibers with diameters on the micrometer scale (> 10 µm). Recently, nanofibrous materials have aroused extensive attention in the fields of fiber science and textile engineering because the fibers with nanoscale diameters exhibited obviously superior performances, such as size and surface/interface effects as well as optical, electrical, mechanical, and biological properties, compared to microfibers. A combination of innovative electrospinning techniques and traditional textile-forming strategies opens a new window for the generation of nanofibrous biotextiles to renew and update traditional microfibrous biotextiles. In the last two decades, the conventional electrospinning device has been widely modified to generate nanofiber yarns (NYs) with the fiber diameters less than 1000 nm. The electrospun NYs can be further employed as the primary processing unit for manufacturing a new generation of nano-textiles using various textile-forming strategies. In this review, starting from the basic information of conventional electrospinning techniques, we summarize the innovative electrospinning strategies for NY fabrication and critically discuss their advantages and limitations. This review further covers the progress in the construction of electrospun NY-based nanotextiles and their recent applications in biomedical fields, mainly including surgical sutures, various scaffolds and implants for tissue engineering, smart wearable bioelectronics, and their current and potential applications in the COVID-19 pandemic. At the end, this review highlights and identifies the future needs and opportunities of electrospun NYs and NY-based nanotextiles for clinical use.

3D culture of HepaRG cells in GelMa and its application to bioprinting of a multicellular hepatic model.

Bioprinting is an emergent technology that has already demonstrated the capacity to create complex and/or vascularized multicellular structures with defined and organized architectures, in a reproducible and high throughput way. Here, we present the implementation of a complex liver model by the development of a three-dimensional extrusion bioprinting process, including parameters for matrix polymerization of methacrylated gelatin, using two hepatic cell lines, Huh7 and HepaRG. The printed structures exhibited long-term viability (28 days), proliferative ability, a relevant hepatocyte phenotype and functions equivalent to or better than those of their 2D counterparts using standard DMSO treatment. This work served as a basis for the bioprinting of complex multicellular models associating the hepatic parenchymal cells, HepaRG, with stellate cells (LX-2) and endothelial cells (HUVECs), able of colonizing the surface of the structure and thus recreating a pseudo endothelial barrier. When bioprinted in 3D monocultures, LX-2 expression was modulated by TGFß-1 toward the induction of myofibroblastic genes such as ACTA2 and COL1A1. In 3D multicellular bioprinted structures comprising HepaRG, LX-2 and endothelial cells, we evidenced fibrillar collagen deposition, which is never observed in monocultures of either HepaRG or LX-2 alone. These observations indicate that a precise control of cellular communication is required to recapitulate key steps of fibrogenesis. Bioprinted 3D co-cultures therefore open up new perspectives in studying the molecular and cellular basis of fibrosis development and provide better access to potential inducers and inhibitors of collagen expression and deposition.

Electrospun Methacrylated Gelatin/Poly(L-Lactic Acid) Nanofibrous Hydrogel Scaffolds for Potential Wound Dressing Application.

Electrospun nanofiber mats have attracted intense attention as advanced wound dressing materials. The objective of this study was to fabricate methacrylated gelatin (MeGel)/poly(L-lactic acid) (PLLA) hybrid nanofiber mats with an extracellular matrix (ECM) mimicking nanofibrous structure and hydrogel-like properties for potential use as wound dressing materials. MeGel was first synthesized via the methacryloyl substitution of gelatin (Gel), a series of MeGel and PLLA blends with various mass ratios were electrospun into nanofiber mats, and a UV crosslinking process was subsequently utilized to stabilize the MeGel components in the nanofibers. All the as-crosslinked nanofiber mats exhibited smooth and bead-free fiber morphologies. The MeGel-containing and crosslinked nanofiber mats presented significantly improved hydrophilic properties (water contact angle = 0°; 100% wettability) compared to the pure PLLA nanofiber mats (~127°). The swelling ratio of crosslinked nanofiber mats notably increased with the increase of MeGel (143.6 ± 7.4% for PLLA mats vs. 875.0 ± 17.1% for crosslinked 1:1 MeGel/PLLA mats vs. 1135.2 ± 16.0% for crosslinked MeGel mats). The UV crosslinking process was demonstrated to significantly improve the structural stability and mechanical properties of MeGel/PLLA nanofiber mats. The Young's modulus and ultimate strength of the crosslinked nanofiber mats were demonstrated to obviously decrease when more MeGel was introduced in both dry and wet conditions. The biological tests showed that all the crosslinked nanofiber mats presented great biocompatibility, but the crosslinked nanofiber mats with more MeGel were able to notably promote the attachment, growth, and proliferation of human dermal fibroblasts. Overall, this study demonstrates that our MeGel/PLLA blend nanofiber mats are attractive candidates for wound dressing material research and application.