Fabrication and characterization of electrospun laminin-functionalized silk fibroin/poly(ethylene oxide) nanofibrous scaffolds for peripheral nerve regeneration

Electrical stimulation enhances sciatic nerve regeneration using a silk-based conductive scaffold beyond traditional nerve guide conduits

Despite recent advancements in peripheral nerve regeneration, the creation of nerve conduits with chemical and physical cues to enhance glial cell function and support axonal growth remains challenging. This study aimed to assess the impact of electrical stimulation (ES) using a conductive nerve conduit on sciatic nerve regeneration in a rat model with transection injury. The study involved the fabrication of conductive nerve conduits using silk fibroin and Au nanoparticles (AuNPs). Collagen hydrogel loaded with green fluorescent protein (GFP)-positive adipose-derived mesenchymal stem cells (ADSCs) served as the filling for the conduit. Both conductive and non-conductive conduits were applied with and without ES in rat models. Locomotor recovery was assessed using walking track analysis. Histological evaluations were performed using H&E, luxol fast blue staining and immunohistochemistry. Moreover, TEM analysis was conducted to distinguish various ultrastructural aspects of sciatic tissue. In the ES + conductive conduit group, higher S100 (p < 0.0001) and neurofilament (p < 0.001) expression was seen after 6 weeks. Ultrastructural evaluations showed that conductive scaffolds with ES minimized Wallerian degeneration. Furthermore, the conductive conduit with ES group demonstrated significantly increased myelin sheet thickness and decreased G. ratio compared to the autograft. Immunofluorescent images confirmed the presence of GFP-positive ADSCs by the 6th week. Locomotor recovery assessments revealed improved function in the conductive conduit with ES group compared to the control group and groups without ES. These results show that a Silk/AuNPs conduit filled with ADSC-seeded collagen hydrogel can function as a nerve conduit, aiding in the restoration of substantial gaps in the sciatic nerve with ES. Histological and locomotor evaluations indicated that ES had a greater impact on functional recovery compared to using a conductive conduit alone, although the use of conductive conduits did enhance the effects of ES.

Silk fibroin-based scaffolds for tissue engineering

Silk fibroin is an important natural fibrous protein with excellent prospects for tissue engineering applications. With profound studies in recent years, its potential in tissue repair has been developed. A growing body of literature has investigated various fabricating methods of silk fibroin and their application in tissue repair. The purpose of this paper is to trace the latest developments of SF-based scaffolds for tissue engineering. In this review, we first presented the primary and secondary structures of silk fibroin. The processing methods of SF scaffolds were then summarized. Lastly, we examined the contribution of new studies applying SF as scaffolds in tissue regeneration applications. Overall, this review showed the latest progress in the fabrication and utilization of silk fibroin-based scaffolds.

Silk fibroin-derived electrospun materials for biomedical applications: A review

Electrospinning is a versatile technique for fabricating polymeric fibers with diameters ranging from micro- to nanoscale, exhibiting multiple morphologies and arrangements. By combining silk fibroin (SF) with synthetic and/or natural polymers, electrospun materials with outstanding biological, chemical, electrical, physical, mechanical, and optical properties can be achieved, fulfilling the evolving biomedical demands. This review highlights the remarkable versatility of SF-derived electrospun materials, specifically focusing on their application in tissue regeneration (including cartilage, cornea, nerves, blood vessels, bones, and skin), disease treatment (such as cancer and diabetes), and the development of controlled drug delivery systems. Additionally, we explore the potential future trends in utilizing these nanofibrous materials for creating intelligent biomaterials, incorporating biosensors and wearable sensors for monitoring human health, and also discuss the bottlenecks for its widespread use. This comprehensive overview illuminates the significant impact and exciting prospects of SF-derived electrospun materials in advancing biomedical research and applications.

3D printing of chitooligosaccharide-polyethylene glycol diacrylate hydrogel inks for bone tissue regeneration

To date, lack of functional hydrogel inks has limited 3D printing applications in tissue engineering. This study developed a series of photocurable hydrogel inks based on chitooligosaccharide (COS)-polyethylene glycol diacrylate (PEGDA) for extrusion-based 3D printing of bone tissue scaffolds. The scaffolds were prepared by aza-Michael addition of COS and PEGDA followed by photopolymerisation of unreacted PEGDA. The hydrogel inks showed sufficient shear thinning properties required for extrusion 3D printing. The printed scaffolds exhibited excellent shape fidelity and fine microstructure with a resolution of 250 μm. By increasing the COS content, the swelling ratio of the scaffolds decreased, while the compressive strength increased. 3D printed COS-PEGDA scaffolds showed high viability of human bone mesenchymal stem cells in vitro. In addition, scaffolds containing 2 wt% COS showed significantly higher alkaline phosphatase activity, calcium deposition, and bioactivity in simulated body fluid compared to the control (PEGDA). Altogether, 3D printed COS-PEGDA scaffolds represent promising candidates for bone tissue regeneration.

Mimicking the Natural Basement Membrane for Advanced Tissue Engineering

Advancements in the field of tissue engineering have led to the elucidation of physical and chemical characteristics of physiological basement membranes (BM) as specialized forms of the extracellular matrix. Efforts to recapitulate the intricate structure and biological composition of the BM have encountered various advancements due to its impact on cell fate, function, and regulation. More attention has been paid to synthesizing biocompatible and biofunctional fibrillar scaffolds that closely mimic the natural BM. Specific modifications in biomimetic BM have paved the way for the development of in vitro models like alveolar-capillary barrier, airway models, skin, blood-brain barrier, kidney barrier, and metastatic models, which can be used for personalized drug screening, understanding physiological and pathological pathways, and tissue implants. In this Review, we focus on the structure, composition, and functions of in vivo BM and the ongoing efforts to mimic it synthetically. Light has been shed on the advantages and limitations of various forms of biomimetic BM scaffolds including porous polymeric membranes, hydrogels, and electrospun membranes This Review further elaborates and justifies the significance of BM mimics in tissue engineering, in particular in the development of in vitro organ model systems.

Influence of reducing agents on in situ synthesis of gold nanoparticles and scaffold conductivity with emphasis on neural differentiation

BACKGROUND

Recorded advancements in nerve tissue regeneration have still not provided satisfactory results, and complete physiological recovery is not assured. The engineering of nanofibrous scaffolds provides a suitable platform for stem cell transplantation by controlling cell proliferation and differentiation to replace lost cells. In this study, a conductive scaffold was fabricated by in situ synthesis of gold nanoparticles (Au-NPs) on electrospun polycaprolactone/chitosan nanofibrous scaffolds and its effect on neural differentiation of mesenchymal stem cells was investigated.

METHOD

The conductive scaffold was prepared using polycaprolactone/chitosan solution containing soluble Au ions by electrospinning approach. In situ synthesis of Au-NPs was conducted using two reducing agents, Tetrakis(hydroxymethyl)phosphonium chloride (THPC) as an organophosphorus compound and formaldehyde, and also different reduction times. Morphology and distribution of the Au-NPs on the nanofibrous scaffolds were assessed using field emission scanning electron microscopy (FE-SEM) and energy dispersed X-ray spectroscopy (EDX). The hydrophilicity and biocompatibility of the scaffolds were determined by water contact angle and MTT assays respectively. The characterization of the scaffolds was proceeded by testing the porosity, tensile strength and electrical conductivity. Also, the scaffold's ability to support neural differentiation of mesenchymal stem cells was evaluated by immune-staining/blotting of Beta tubulin III.

RESULTS & CONCLUSION

FE-SEM and EDX results demonstrated the uniform distribution of Au-NPs on electrospun nanofibers made of a combination of polycaprolactone and chitosan (PCL/CS). We found that electrical conductivity of the scaffolds fabricated using THPC for 4 days and formaldehyde for 7 days was in the range of electrical conductivity of the scaffolds suitable for nerve regeneration. Contact angle measurements showed the effect of Au-NPs on the hydrophilic properties of the scaffolds, where the scaffold showed the porosity of 50% in the presence of Au-NPs. Au-NPs decoration on the scaffold decreased the mechanical properties with the ultimate strength of 14 (MPa). In vitro assessment demonstrated the potential of the fabricated conductive scaffold to enhance the attachment and proliferation of fibroblast cells, and differentiation potential of mesenchymal stem cells toward neuron-like cells. This designed scaffold holds promise as a future carrier and delivery platform in nerve tissue engineering.

Enhanced neural differentiation of human-induced pluripotent stem cells on aligned laminin-functionalized polyethersulfone nanofibers; a comparison between aligned and random fibers on neurogenesis

Despite the numerous attempts in nerve tissue engineering, no ideal strategy has been translated into effective therapy for neuronal regeneration yet. Here, we designed a novel nerve regeneration scaffold combining aligned laminin-immobilized polyethersulfone (PES) nanofibers and human-induced pluripotent stem cells (hiPSCs) for transplantation strategies. Aligned and random PES nanofibers were fabricated by electrospinning method with a diameter of 95-500 nm and were then modified with covalent laminin bounding subsequent to O₂ plasma treatment. PES-functionalized fibers found to induce a remarkable higher rate of neuronal genes expression as compared to nontreated group. In addition, hiPSCs cultured on aligned pure fibers exhibited the extension of neurites along with fibers direction and an exponentially elevated expression of neuron specific enolase (early neuroectoderm marker), Tuj-1 (axonal marker), and microtubule-associated protein 2 (dendritic marker) in comparison with random pure fibers. The concomitant of increased hydrophilicity and biocompatibility along with exploiting topographical cues and directional guidance make aligned PES-plasma-laminin a versatile scaffold for adhesion, proliferation, spreading, and differentiation of hiPSCs into nerve cells.

Research progress, models and simulation of electrospinning technology: a review

In recent years, nanomaterials have aroused extensive research interest in the world's material science community. Electrospinning has the advantages of wide range of available raw materials, simple process, small fiber diameter and high porosity. Electrospinning as a nanomaterial preparation technology with obvious advantages has been studied, such as its influencing parameters, physical models and computer simulation. In this review, the influencing parameters, simulation and models of electrospinning technology are summarized. In addition, the progresses in applications of the technology in biomedicine, energy and catalysis are reported. This technology has many applications in many fields, such as electrospun polymers in various aspects of biomedical engineering. The latest achievements in recent years are summarized, and the existing problems and development trends are analyzed and discussed.

Bionic microenvironment-inspired synergistic effect of anisotropic micro-nanocomposite topology and biology cues on peripheral nerve regeneration

Anisotropic topographies and biological cues can simulate the regenerative microenvironment of nerve from physical and biological aspects, which show promising application in nerve regeneration. However, their synergetic influence on injured peripheral nerve is rarely reported. In the present study, we constructed a bionic microenvironment-inspired scaffold integrated with both anisotropic micro-nanocomposite topographies and IKVAV peptide. The results showed that both the topographies and peptide displayed good stability. The scaffolds could effectively induce the orientation growth of Schwann cells and up-regulate the genes and proteins relevant to myelination. Last, three signal pathways including the Wnt/β-catenin pathway, the extracellular signal-regulated kinase/mitogen-activated protein pathway, and the transforming growth factor-β pathway were put forward, revealing the main path of synergistic effects of anisotropic micro-nanocomposite topographies and biological cues on neuroregeneration. The present study may supply an important strategy for developing functional of artificial nerve implants.

Utilizing Radio Frequency Plasma Treatment to Modify Polymeric Materials for Biomedical Applications

Studies that utilize radio frequency plasma modification as a strategy to tune the surface properties of polymeric constructs with the goal of enhancing their use as biomedical devices have grown considerably in number over the past decade. In this Review, we present the importance of plasma surface treatment to biomedical applications, including tissue engineering and wound healing. First, we introduce several key polymeric materials of interest for use as biomaterials, including those that are naturally derived and synthetic. We, then, provide an overview of possible outcomes of plasma modification, such as surface activation, etching, and deposition of a thin film, all of which can be used to alter the surface properties of a given polymer. Following this discussion, we review the methods used to characterize plasma-treated polymer surface properties, as well as the techniques used to evaluate their interactions with biological species of interest such as mammalian cells, bacteria, and blood components. To close, we provide a perspective on future outlooks of this exciting and rapidly evolving field.

Prospects of Polymeric Nanofibers Loaded with Essential Oils for Biomedical and Food-Packaging Applications

Essential oils prevent superbug formation, which is mainly caused by the continuous use of synthetic drugs. This is a significant threat to health, the environment, and food safety. Plant extracts in the form of essential oils are good enough to destroy pests and fight bacterial infections in animals and humans. In this review article, different essential oils containing polymeric nanofibers fabricated by electrospinning are reviewed. These nanofibers containing essential oils have shown applications in biomedical applications and as food-packaging materials. This approach of delivering essential oils in nanoformulations has attracted considerable attention in the scientific community due to its low price, a considerable ratio of surface area to volume, versatility, and high yield. It is observed that the resulting nanofibers possess antimicrobial, anti-inflammatory, and antioxidant properties. Therefore, they can reduce the use of toxic synthetic drugs that are utilized in the cosmetics, medicine, and food industries. These nanofibers increase barrier properties against light, oxygen, and heat, thereby protecting and preserving the food from oxidative damage. Moreover, the nanofibers discussed are introduced with naturally derived chemical compounds in a controlled manner, which simultaneously prevents their degradation. The nanofibers loaded with different essential oils demonstrate an ability to increase the shelf-life of various food products while using them as active packaging materials.

Fabrication and evaluation of porous and conductive nanofibrous scaffolds for nerve tissue engineering

Peripheral nerve repair is still one of the major clinical challenges which has received a great deal of attention. Nerve tissue engineering is a novel treatment approach that provides a permissive environment for neural cells to overcome the constraints of repair. Conductivity and interconnected porosity are two required characteristics for a scaffold to be effective in nerve regeneration. In this study, we aimed to fabricate a conductive scaffold with controlled porosity using polycaprolactone (PCL) and chitosan (Chit), FDA approved materials for the use in implantable medical devices. A novel method of using tetrakis (hydroxymethyl) phosphonium chloride (THPC) and formaldehyde was applied for in situ synthesis of gold nanoparticles (AuNPs) on the scaffolds. In order to achieve desirable porosity, different percentage of polyethylene oxide (PEO) was used as sacrificial fiber. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) results demonstrated the complete removing of PEO from the scaffolds after washing and construction of interconnected porosities, respectively. Elemental and electrical analysis revealed the successful synthesis of AuNPs with uniform distribution and small average diameter on the PCL/Chit scaffold. Contact angle measurements showed the effect of porosity on hydrophilic properties of the scaffolds, where the porosity of 75-80% remarkably improved surface hydrophilicity. Finally, the effect of conductive nanofibrous scaffold on Schwann cells morphology and vaibility was investigated using FE-SEM and MTT assay, respectively. The results showed that these conductive scaffolds had no cytotoxic effect and support the spindle-shaped morphology of cells with elongated process which are typical of Schwann cell cultures.

Fabrication and in vitro evaluation of 3D composite scaffold based on collagen/hyaluronic acid sponge and electrospun polycaprolactone nanofibers for peripheral nerve regeneration

Replacement of peripheral nerve autografts with tissue engineered nerve grafts will potentially resolve the lack of nerve tissue especially in patients with severe concomitant soft tissue injuries. This study attempted to fabricate a tissue engineered nerve graft composed of electrospun PCL conduit filled with collagen-hyaluronic acid (COL-HA) sponge with different COL-HA weight ratios including 100:0, 98:2, 95:5 and 90:10. The effect of HA addition on the sponge porosity, mechanical properties, water absorption and degradation rate was assessed. A good cohesion between the electrospun PCL nanofibers and COL-HA sponges were seen in all sponges with different HA contents. Mechanical properties of PCL nanofibrous layer were similar to the rat sciatic nerve; the ultimate tensile strength was 2.23 ± 0.35 MPa at the elongation of 35%. Additionally, Schwann cell proliferation and morphology on three dimensional (3D) composite scaffold were evaluated by using MTT and SEM assays, respectively. Rising the HA content resulted in higher water absorption as well as greater pore size and porosity, while a decrease in Schwann cell proliferation compared to pure collagen sponge, although reduction in cell proliferation was not statistically significant. The lower Schwann cell proliferation on the COL-HA was attributed to the greater degradation rate and pore size of the COL-HA sponges. Also, dorsal root ganglion assay showed that the engineered 3D construct significantly increases axon growth. Taken together, these results suggest that the fabricated 3D composite scaffold provide a permissive environment for Schwann cells proliferation and maturation and can encourage axon growth.

Tissue Engineering in Musculoskeletal Tissue: A Review of the Literature

Tissue engineering refers to the attempt to create functional human tissue from cells in a laboratory. This is a field that uses living cells, biocompatible materials, suitable biochemical and physical factors, and their combinations to create tissue-like structures. To date, no tissue engineered skeletal muscle implants have been developed for clinical use, but they may represent a valid alternative for the treatment of volumetric muscle loss in the near future. Herein, we reviewed the literature and showed different techniques to produce synthetic tissues with the same architectural, structural and functional properties as native tissues.

A Bio-inspired Multifunctionalized Silk Fibroin

A bio-inspired multifunctionalized silk fibroin (BMS) was synthesized in order to mimic the interaction of nidogen with the type IV collagen and laminin of basement membranes. The designed BMS consists of a motif of laminin α-chain-derived, called IK peptide, and type IV collagen covalently bound to the silk fibroin (SF) by using EDC/NHS coupling and a Cu-free click chemistry reaction, respectively. Silk fibroin was chosen as the main component of the BMS because it is versatile and biocompatible, induces an in vivo favorable bioresponse, and moreover can be functionalized with different methods. The chemical structure of BMS was analyzed by using X-ray photoelectron spectroscopy, attenuated total reflection-Fourier transform infrared, cross-polarization magic angle spinning nuclear magnetic resonance techniques, and colorimetric assay. The SF and BMS solutions were cross-linked by sonication to form hydrogels or casted to make films in order to evaluate and compare the early adhesion and viability of MRC5 cells. BMS hydrogels were also characterized by rheological and thermal analyses.

Laminin-Modified Dental Pulp Extracellular Matrix for Dental Pulp Regeneration

Native dental pulp extracellular matrix (DPEM) has proven to be an effective biomaterial for dental pulp regeneration. However, as a significant extracellular matrix glycoprotein, partial laminins were lost during the decellularization process, which were essential for odontoblast differentiation. Thereby, this study investigated the feasibility of LN supplementation to improve the surface of DPEM for odontoblast layer regeneration. The influences of laminin on cell adhesion and odontogenic differentiation were evaluated in vitro. Then, we fabricated laminin-modified DPEM based on the physical coating strategy and observed the location and persistency of laminin coating by immunofluorescent staining. Finally, laminin-modified DPEM combined with treated dentin matrix (TDM) was transplanted in orthotopic jaw bone of beagles (n = 3) to assess the effect of LNs on dental pulp tissue regeneration. The in vitro results showed that laminins could improve the adhesion of dental pulp stem cells (DPSCs) and promoted DPSCs toward odontogenic differentiation. Continuous odontoblastic layer-like structure was observed in laminin-modified DPEM group, expressing the markers for odontoblastogenesis, dentine matrix protein-1 (DMP-1) and dentin sialophosphoprotein (DSPP). Overall, these studies demonstrate that the supplementation of laminins to DPEM contributes to the odontogenic differentiation of cells and to the formation of odontoblast layer in dental pulp regeneration.

Electrospun regenerated Antheraea pernyi silk fibroin scaffolds with improved pore size, mechanical properties and cytocompatibility using mesh collectors

Generally, electrospun silk fibroin scaffolds collected by traditional plates present limited pore size and mechanical properties, which may restrict their biomedical applications. Herein, regenerated Antheraea pernyi silk fibroin (RASF) with excellent inherent cell adhesion property was chosen as a raw material and the conductive metal meshes were used as collectors to prepare modified RASF scaffolds by electrospinning from its aqueous solution. A traditional intact plate was used as a control. The morphology and mechanical properties of the obtained scaffolds were investigated. Schwann cells were further used to assess the cytocompatibility and cell migration ability of the typical scaffolds. Interestingly, compared with the traditional intact plate, the mesh collector with an appropriate gap size (circa 7 mm) could significantly improve the pore size, porosity and mechanical properties of the RASF scaffolds simultaneously. In addition, the scaffold collected under this condition (RASF-7mmG) showed higher cell viability, deeper cell permeation and faster cell migration of Schwann cells. Combined with the excellent inherent properties of ASF and the obviously enhanced scaffold cytocompatibility and mechanical properties, the RASF-7mmG scaffold is expected to be a candidate with great potential for biomedical applications.

Electrospun Fiber Scaffolds for Engineering Glial Cell Behavior to Promote Neural Regeneration

Electrospinning is a fabrication technique used to produce nano- or micro- diameter fibers to generate biocompatible, biodegradable scaffolds for tissue engineering applications. Electrospun fiber scaffolds are advantageous for neural regeneration because they mimic the structure of the nervous system extracellular matrix and provide contact guidance for regenerating axons. Glia are non-neuronal regulatory cells that maintain homeostasis in the healthy nervous system and regulate regeneration in the injured nervous system. Electrospun fiber scaffolds offer a wide range of characteristics, such as fiber alignment, diameter, surface nanotopography, and surface chemistry that can be engineered to achieve a desired glial cell response to injury. Further, electrospun fibers can be loaded with drugs, nucleic acids, or proteins to provide the local, sustained release of such therapeutics to alter glial cell phenotype to better support regeneration. This review provides the first comprehensive overview of how electrospun fiber alignment, diameter, surface nanotopography, surface functionalization, and therapeutic delivery affect Schwann cells in the peripheral nervous system and astrocytes, oligodendrocytes, and microglia in the central nervous system both in vitro and in vivo. The information presented can be used to design and optimize electrospun fiber scaffolds to target glial cell response to mitigate nervous system injury and improve regeneration.

Regeneration of the peripheral nerve via multifunctional electrospun scaffolds

Over the last two decades, electrospun scaffolds have proved to be advantageous in the field of nerve tissue regeneration by connecting the cavity among the proximal and distal nerve stumps growth cones and leading to functional recovery after injury. Multifunctional nanofibrous structure of these scaffolds provides enormous potential by combining the advantages of nano-scale topography, and biological science. In these structures, selecting the appropriate materials, designing an optimized structure, modifying the surface to enhance biological functions and neurotrophic factors loading, and native cell-like stem cells should be considered as the essential factors. In this systematic review paper, the fabrication methods for the preparation of aligned nanofibrous scaffolds in yarn or conduit architecture are reviewed. Subsequently, the utilized polymeric materials, including natural, synthetic and blend are presented. Finally, their surface modification techniques, as well as, the recent advances and outcomes of the scaffolds, both in vitro and in vivo, are reviewed and discussed.

Fabrication and Plasma Modification of Nanofibrous Tissue Engineering Scaffolds

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

Keratinous materials: Structures and functions in biomedical applications

Keratins are a family of fibrous proteins anticipated to possess wide-ranging biomedical applications due to their abundance, physicochemical properties and intrinsic biological activity. This review mainly focuses on the biomaterials derived from three major sources of keratins; namely human hair, wool and feather, that have effective applications in tissue engineering, wound healing and drug delivery. This article offers five viewpoints regarding keratin i) an introduction to keratin protein extraction and keratin-based scaffold fabrication methods ii) applications in nerve and bone tissue engineering iii) a review on the keratin dressings applied to different types of wounds to facilitate wound healing and thereby repair the skin iv) the utilization of keratinous materials as a carrier system for therapeutics with a controlled manner v) a discussion regarding the main challenges for using keratin in biomedical applications as well as its future prospects.

Construction of Dual-Biofunctionalized Chitosan/Collagen Scaffolds for Simultaneous Neovascularization and Nerve Regeneration

Biofunctionalization of artificial nerve implants by incorporation of specific bioactive factors has greatly enhanced the success of grafting procedures for peripheral nerve regeneration. However, most studies on novel biofunctionalized implants have emphasized the promotion of neuronal and axonal repair over vascularization, a process critical for long-term functional restoration. We constructed a dual-biofunctionalized chitosan/collagen composite scaffold with Ile-Lys-Val-Ala-Val (IKVAV) and vascular endothelial growth factor (VEGF) by combining solution blending, in situ lyophilization, and surface biomodification. Immobilization of VEGF and IKVAV on the scaffolds was confirmed both qualitatively by staining and quantitatively by ELISA. Various single- and dual-biofunctionalized scaffolds were compared for the promotion of endothelial cell (EC) and Schwann cell (SC) proliferation as well as the induction of angiogenic and neuroregeneration-associated genes by these cells in culture. The efficacy of these scaffolds for vascularization was evaluated by implantation in chicken embryos, while functional repair capacity in vivo was assessed in rats subjected to a 10 mm sciatic nerve injury. Dual-biofunctionalized scaffolds supported robust EC and SC proliferation and upregulated the expression levels of multiple genes and proteins related to neuroregeneration and vascularization. Dual-biofunctionalized scaffolds demonstrated superior vascularization induction in embryos and greater promotion of vascularization, myelination, and functional recovery in rats. These findings support the clinical potential of VEGF/IKVAV dual-biofunctionalized chitosan/collagen composite scaffolds for facilitating peripheral nerve regeneration, making it an attractive candidate for repairing critical nerve defect. The study may provide a critical experimental and theoretical basis for the development and design of new artificial nerve implants with excellent biological performance.

Biofunctionalized silk fibroin nanofibers for directional and long neurite outgrowth

Engineered scaffolds simultaneously exhibiting multiple cues are highly desirable for neural tissue regeneration. Silk fibroin is a promising natural protein material for nerve repair. However, the lack of specific bioactive cues significantly hinders its application. In this study, the electrospun silk fibroin nanofibers with both biochemical and topographical cues were prepared. The alignment of electrospun nanofibers was optimized by controlling the surface linear velocity of a rotating drum. The silk fibroin nanofibers were further functionalized with laminin through covalent binding, confirmed by immunostaining observation. Cell proliferation and neurite outgrowth assays confirmed that the functionalized aligned nanofibers significantly enhanced directional axonal extensions, providing physical and bioactive cues for neurite outgrowth. Furthermore, the tubular scaffolds with longitudinally aligned microchannels were designed by rolling the functionalized silk fibroin nanofibers. The neurite extension across the lumen of the conduit along the direction of the aligned fibers is apparent. These results highlight the ability of laminin-immobilized silk fibroin nanofibers to enhance neurite outgrowth and to control directional neurite extension, providing a useful approach to construct a regenerative microenvironment for nerve repair materials.

In vitro and in vivo assessment of glucose cross-linked gelatin/zein nanofibrous scaffolds for cranial bone defects regeneration

The purpose of this study was to evaluate the glucose cross-linked gelatin/zein scaffolds for bone regeneration in vitro and in vivo. The nanofibrous scaffolds exhibited fast mineralization in the concentrated simulated body fluid with the deposited octacalcium phosphate and dicalcium phosphate dehydrate. The nanofibrous scaffolds exhibited no cytotoxic effect on MC3T3e1 cells in a CCK-8 test. Additionally, scanning electron microscope and confocal laser scanning microscopy images revealed that all the scaffolds were biocompatible and showed excellent support for MC3T3e1 cells. In the osteogenesis characterizations, Alizarin Red staining experiments indicated the improved calcium deposits on the cross-linked scaffolds, while the alkaline phosphatase activity showed no difference. Furthermore, the in vivo cranial bone regeneration results suggested that the cross-linked gelatin/zein scaffolds presented a strong positive effect on the cranial bone regeneration with the increased new bone volume and connective tissue formation, but the incorporation of zein in the gelatin scaffolds did not favor the bone regeneration. Moreover, the cross-linked gelatin scaffold retarded the bone resorption as indicated by the higher levels of IFN-γ and lower levels of IL-6, which restricted the differentiation of osteoclasts.

Tailoring the Interface of Biomaterials to Design Effective Scaffolds

Tissue engineering (TE) is a multidisciplinary science, which including principles from material science, biology and medicine aims to develop biological substitutes to restore damaged tissues and organs. A major challenge in TE is the choice of suitable biomaterial to fabricate a scaffold that mimics native extracellular matrix guiding resident stem cells to regenerate the functional tissue. Ideally, the biomaterial should be tailored in order that the final scaffold would be (i) biodegradable to be gradually replaced by regenerating new tissue, (ii) mechanically similar to the tissue to regenerate, (iii) porous to allow cell growth as nutrient, oxygen and waste transport and (iv) bioactive to promote cell adhesion and differentiation. With this perspective, this review discusses the options and challenges facing biomaterial selection when a scaffold has to be designed. We highlight the possibilities in the final mold the materials should assume and the most effective techniques for its fabrication depending on the target tissue, including the alternatives to ameliorate its bioactivity. Furthermore, particular attention has been given to the influence that all these aspects have on resident cells considering the frontiers of materiobiology. In addition, a focus on chitosan as a versatile biomaterial for TE scaffold fabrication has been done, highlighting its latest advances in the literature on bone, skin, cartilage and cornea TE.

Fabrication and characterization of gold nanoparticle-doped electrospun PCL/chitosan nanofibrous scaffolds for nerve tissue engineering

In the field of nerve tissue engineering, nanofibrous scaffolds could be a promising candidate when they are incorporated with electrical cues. Unique physico-chemical properties of gold nanoparticles (AuNPs) make them an appropriate component for increasing the conductivity of scaffolds to enhance the electrical signal transfer between neural cells. The aim of this study was fabrication of AuNPs-doped nanofibrous scaffolds for peripheral nerve tissue engineering. Polycaprolactone (PCL)/chitosan mixtures with different concentrations of chitosan (0.5, 1 and 1.5) were electrospun to obtain nanofibrous scaffolds. AuNPs were synthesized by the reduction of HAuCl₄ using chitosan as a reducing/stabilizing agent. A uniform distribution of AuNPs with spherical shape was achieved throughout the PCL/chitosan matrix. The UV-Vis spectrum revealed that the amount of gold ions absorbed by nanofibrous scaffolds is in direct relationship with their chitosan content. Evaluation of electrical property showed that inclusion of AuNPs significantly enhanced the conductivity of scaffolds. Finally, after 5 days of culture, biological response of Schwann cells on the AuNPs-doped scaffolds was superior to that on as-prepared scaffolds in terms of improved cell attachment and higher proliferation. It can be concluded that the prepared AuNPs-doped scaffolds can be used to promote peripheral nerve regeneration.

High-Throughput Preparation of Silk Fibroin Nanofibers by Modified Bubble-Electrospinning

As a kind of natural macromolecular protein molecule extracted from silk, silk fibroin (SF) has been widely used as biological materials in recent years due to its good physical and chemical properties. In this paper, a modified bubble-electrospinning (MBE) using a cone-shaped gas nozzle combined with a copper solution reservoir was applied to obtain high-throughput fabrication of SF nanofibers. In the MBE process, sodium dodecyl benzene sulfonates (SDBS) were used as the surfactant to improve the spinnability of SF solution. The rheological properties and conductivity of the electrospun SF solutions were investigated. And the effects of gas flow volume, SF solution concentration and additive amounts of SDBS on the morphology, property and production of SF nanofibers were studied. The results showed the decrease of gas flow volume could decrease the nanofiber diameter, enhance the diameter distribution, and increase the production of nanofibers. And the maximum yield could reach 3.10 g/h at the SF concentration of 10 wt % and the SDBS concentration of 0.1 wt %.