Schwann Cell Adhesion Research Articles

Nanographene-Au fine-tuning to intensify plasmonic-resonance of polymeric hybrid bionanosystem for synergistic phototherapy and nerve photobiomodulation

Here, we report the multi-photo-bioactivity of the plasmonic-nano graphitic coordinated polycaprolactone-based aligned nanofibrous scaffolds-based bionanosystem for photothermal breast and colon cancer therapies and peripheral nerve photobiomodulation. The size-optimized colloidal reduced graphene oxide (nRGO, 180 nm) nanosheets, for enhanced photothermal impact, were surface-functionalized with gold nanospheres (AuNPs) to prepare the nRGO@AuNP monodispersed nano-composite and then doped 2.0 mg of nRGO@AuNP in biocompatible and biodegradable polymer polycaprolactone (PCL) to fabricate the nRGO@AuNP-PCL (2.0 mg) plasmonic aligned nanofibrous scaffolds. More than 90% of cancer cells, breast cancer (MCF-7) as well as colon cancer (CT-26), ablated after 5 min of low NIR (808 nm) laser power (0.72 W/cm2) illumination with nRGO@AuNP-PCL (2.0 mg) aligned nanofibrous scaffolds. Besides, the nRGO@AuNP-PCL (2.0 mg) provided an extraordinary microenvironment for adhesion, nerve growth, proliferation, and differentiation of PC12 and S42 cells which mimics the natural extracellular matrix. The 2.5-fold increase in neurite length was observed with NIR illumination after 3 days whereas 1.7-fold was found without NIR illumination after 7 days in comparison to PCL (pure). The current findings will be useful to provide a new crucial approach for preparing biocompatible multifunctional composite plasmonic nanofibers as a highly efficient distinct platform for photothermal therapies and promising bioimplants to overcome the loss of sensation after cancer surgery through nerve photobiomodulation.

Electrospun Composite PLLA-PPSB Nanofiber Nerve Conduits for Peripheral Nerve Defects Repair and Regeneration.

Peripheral nerve injury (PNI) is a common clinical problem and regenerating peripheral nerve defects remain a significant challenge. Poly(polyol sebacate) (PPS) polymers are developed as promising materials for biomedical applications due to their biodegradability, biocompatibility, elastomeric properties, and ease of production. However, the application of PPS-based biomaterials in nerve tissue engineering, especially in PNI repair, is limited. In this study, PPS-based composite nanofibers poly(l-lactic acid)-poly(polycaprolactone triol-co-sebacic acid-co-N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid sodium salt) (PLLA-PPSB) are aimed to construct through electrospinning and assess their in vitro biocompatibility with Schwann cells (SCs) and in vivo repair capabilities for peripheral nerve defects. For the first time, the biocompatibility and bioactivity of PPS-based nanomaterial are examined at the molecular, cellular, and animal levels for PNI repair. Electrospun PLLA-PPSB nanofibers display favorable physicochemical properties and biocompatibility, providing an effective interface for the proliferation, glial expression, and adhesion of SCs in vitro. In vivo experiments using a 10-mm rat sciatic nerve defect model show that PLLA-PPSB nanofiber nerve conduits enhance myelin formation, axonal regeneration, angiogenesis, and functional recovery. Transcriptome analysis and biological validation indicate that PLLA-PPSB nanofibers may promote SC proliferation by activating the PI3K/Akt signaling pathway. This suggests the promising potential of PLLA-PPSB nanomaterial for PNI repair.

Influence of cold-stimulated adipocyte supernatant on the expression of adhesion-related molecules in Schwann cell line

Bell's palsy is the most common form of facial nerve palsy. This study aimed to explore the pathogenesis of Bell's palsy by investigating the effect of cold-stimulated adipocyte supernatant on adhesion molecule expression in Schwann cell line. Schwann cells were cultured in regular or adipocyte-conditioned medium and analyzed using RNA sequencing. The mRNA expression of Schwann cell adhesion molecules melanoma cell adhesion molecule (MCAM), protocadherin 9 (PCDH9), and intercellular cell adhesion molecule 1 (ICAM1) was determined using real-time reverse-transcription polymerase chain reaction. Differentially expressed genes were identified, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were conducted. Compared with Schwann cells in 37 °C, the expression of MCAM, PCDH9, and ICAM1 was downregulated in Schwann cells treated with cold-stimulated adipocyte supernatant compared with Schwann cells in 37 °C. Adipocytes subjected to cold exposure may weaken the adhesion capacity of Schwann cells and disrupt the local homeostasis of Schwann cell–axon interactions by affecting the expression of MCAM, PCDH9, and ICAM1, ultimately leading to the development of demyelinating lesions.

Aminosilane Functionalized Aligned Fiber PCL Scaffolds for Peripheral Nerve Repair.

Silane modification is a simple and cost-effective tool to modify existing biomaterials for tissue engineering applications. Aminosilane layer deposition has previously been shown to control NG108-15 neuronal cell and primary Schwann cell adhesion and differentiation by controlling deposition of ─NH2 groups at the submicron scale across the entirety of a surface by varying silane chain length. This is the first study toreport depositing 11-aminoundecyltriethoxysilane (CL11) onto aligned Polycaprolactone (PCL) scaffolds for peripheral nerve regeneration. Fibers are manufactured via electrospinning and characterized using water contact angle measurements, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Confirmed modified fibers are investigated using in vitro cell culture of NG108-15 neuronal cells and primary Schwann cells to determine cell viability, cell differentiation, and phenotype. CL11-modified fibers significantly support NG108-15 neuronal cell and Schwann cell viability. NG108-15 neuronal cell differentiation maintains Schwann cell phenotype compared to unmodified PCL fiber scaffolds. 3D ex vivo culture of Dorsal root ganglion explants (DRGs) confirms further Schwann cell migration and longer neurite outgrowth from DRG explants cultured on CL11 fiber scaffolds compared to unmodified scaffolds. Thus, a reproducible and cost-effective tool is reported to modify biomaterials with functional amine groups that can significantly improve nerve guidance devices and enhance nerve regeneration.

3D printed elastic hydrogel conduits with 7,8-dihydroxyflavone release for peripheral nerve repair.

Nerve guide conduit is a promising treatment for long gap peripheral nerve injuries, yet its efficacy is limited. Drug-releasable scaffolds may provide reliable platforms to build a regenerative microenvironment for nerve recovery. In this study, an elastic hydrogel conduit encapsulating with prodrug nanoassemblies is fabricated by a continuous 3D printing technique for promoting nerve regeneration. The bioactive hydrogel is comprised of gelatin methacryloyl (GelMA) and silk fibroin glycidyl methacrylate (SF-MA), exhibiting positive effects on adhesion, proliferation, and migration of Schwann cells. Meanwhile, 7,8-dihydroxyflavone (7,8-DHF) prodrug nanoassemblies with high drug-loading capacities are developed through self-assembly of the lipophilic prodrug and loaded into the GelMA/SF-MA hydrogel. The drug loading conduit could sustainedly release 7,8-DHF to facilitate neurite elongation. A 12​mm nerve defect model is established for therapeutic efficiency evaluation by implanting the conduit through surgical suturing with rat sciatic nerve. The electrophysiological, morphological, and histological assessments indicate that this conduit can promote axon regeneration, remyelination, and function recovery by providing a favorable microenvironment. These findings implicate that the GelMA/SF-MA conduit with 7,8-DHF release has potentials in the treatment of long-gap peripheral nerve injury.

Graphdiyne-loaded polycaprolactone nanofiber scaffold for peripheral nerve regeneration

Graphdiyne (GDY) is a kind of nanomaterial from the graphene carbon family with excellent physical and chemical properties. Despite some applications in medical engineering, GDY has not been used as an electroactive scaffold for tissue regeneration because of its unclear in vitro and in vivo biosafety profiles. Here, a conductive GDY nanomaterial-loaded polycaprolactone (PCL) scaffold was prepared by electrospinning technique. For the first time, the biocompatibility of GDY-based scaffold was assessed at the cellular and animal levels in a peripheral nerve injury (PNI) model. The findings indicated that the conductive three-dimensional (3D) GDY/PCL nerve guide conduits (NGCs) could significantly improve the proliferation, adhesion and glial expression of Schwann cells (SCs). The conduits were implanted into a rat 10-mm sciatic nerve defect model for 3 months in vivo. The toxicity of scaffolds to the organs was negligible, while the GDY/PCL NGCs significantly promoted myelination and axonal growth by upregulating the expression levels of SC marker (S100 β protein), Myelin basic protein (MBP), and axon regeneration marker (β3-tubulin protein (Tuj1) and neurofilament protein 200 (NF200)). In addition, upregulation of vascular factor expression in GDY/PCL NGC group suggested the potential role in angiogenesis to improve nerve repair by GDY nanomaterials. Our findings provide new perspectives on biocompatibility and effectiveness of GDY nanomaterial scaffold in peripheral nerve regeneration for preclinical application.

Matrilin-2 within a three-dimensional lysine-modified chitosan porous scaffold enhances Schwann cell migration and axonal outgrowth for peripheral nerve regeneration.

Background: Matrilin-2 is a key extracellular matrix protein involved in peripheral nerve regeneration. We sought to develop a biomimetic scaffold to enhance peripheral nerve regeneration by incorporating matrilin-2 within a chitosan-derived porous scaffold. We hypothesized that the use of such a novel biomaterial delivers microenvironmental cues to facilitate Schwann cell (SC) migration and enhance axonal outgrowth during peripheral nerve regeneration. Materials and Methods: The effect of matrilin-2 on SC migration was evaluated with agarose drop migration assay on matrilin-2 coated dishes. SC adhesion was determined with SCs cultured atop tissue culture dishes coated with matrilin-2. Various formulations of chitosan vs matrilin-2 in scaffold constructs were examined with scanning electron microscopy. The effect of the matrilin-2/chitosan scaffold on SC migration in the collagen conduits was determined by capillary migration assays. Neuronal adhesion and axonal outgrowth were evaluated with three-dimensional (3D) organotypic assay of dorsal root ganglions (DRG). DRG axonal outgrowth within the scaffolds was determined by immunofluorescence staining of neurofilaments. Results: Matrilin-2 induced SC migration and enhanced its adhesion. A formulation of 2% chitosan with matrilin-2 demonstrated an optimal 3D porous architecture for SC interaction. Matrilin-2/chitosan scaffold enabled SCs to migrate against gravity within conduits. Chemical modification of chitosan with lysine (K-chitosan) further improved DRG adhesion and axonal outgrowth than the matrilin-2/chitosan scaffold without lysine modification. Conclusion: We developed a matrilin-2/K-chitosan scaffold to mimic extracellular matrix cues and provide a porous matrix to enhance peripheral nerve regeneration. Taking advantage of matrilin-2's capability to stimulate SC migration and adhesion, we formulated a porous matrilin-2/chitosan scaffold to support axongal outgrowth. Chemical modification of chitosan with lysine further improved matrilin-2 bioactivity in the 3D scaffold. The 3D porous matrilin-2/K-chitosan scaffolds have high potential for enhancing nerve repair by stimulating SC migration, neuronal adhesion, and axonal outgrowth.

Effects of ECM proteins (laminin, fibronectin, and type IV collagen) on the biological behavior of Schwann cells and their roles in the process of remyelination after peripheral nerve injury.

Introduction: It is important to note that complete myelination and formation of myelinated fibers are essential for functional nerve regeneration after peripheral nerve injury (PNI). However, suboptimal myelin regeneration is common and can hinder ideal nerve regeneration. Therefore, it is important to closely monitor and support myelin regeneration in patients with PNI to achieve optimal outcomes. Methods: This study analyzed the effects of three extracellular matrix (ECM) proteins on Schwann cells (SCs) in the nerve regeneration environment, including their adhesion, proliferation, and migration. The study also explored the use of composite sodium alginate hydrogel neural scaffolds with ECM components and investigated the effects of ECM proteins on remyelination following peripheral nerve injury. Results: The results showed that laminin (LN), fibronectin (FN), and collagen Ⅳ (type IV Col) promoted the early adhesion of SCs in 2-dimensional culture but the ratios of early cell adhesion were quite different and the maintenance of cells' morphology by different ECM proteins were significantly different. In transwell experiment, the ability of LN and FN to induce the migration of SCs was obviously higher than that of type IV Col. An vitro co-culture model of SCs and dorsal root ganglia (DRG) neurons showed that LN promoted the transition of SCs to a myelinated state and the maturation of the myelin sheath, and increased the thickness of neurofilaments. Animal experiments showed that LN had superior effects in promoting myelin sheath formation, axon repair, and reaching an ideal G-ratio after injury compared to FN and Col IV. The situation of gastrocnemius atrophy was significantly better in the LN group. Notably, the thickness of the regenerated myelin sheaths in the type IV Col group was the thickest. Conclusion: In this experiment, we analyzed and compared the effects of LN, FN, and type IV Col on the biological behavior of SCs and their effects on remyelination after PNI and further clarified their unique roles in the process of remyelination. Further research is necessary to explore the underlying mechanisms.

Aligned Polyhydroxyalkanoate Blend Electrospun Fibers as Intraluminal Guidance Scaffolds for Peripheral Nerve Repair.

The use of nerve guidance conduits (NGCs) to treat peripheral nerve injuries is a favorable approach to the current "gold standard" of autografting. However, as simple hollow tubes, they lack specific topographical and mechanical guidance cues present in nerve grafts and therefore are not suitable for treating large gap injuries (30-50 mm). The incorporation of intraluminal guidance scaffolds, such as aligned fibers, has been shown to increase neuronal cell neurite outgrowth and Schwann cell migration distances. A novel blend of PHAs, P(3HO)/P(3HB) (50:50), was investigated for its potential as an intraluminal aligned fiber guidance scaffold. Aligned fibers of 5 and 8 μm diameter were manufactured by electrospinning and characterized using SEM. Fibers were investigated for their effect on neuronal cell differentiation, Schwann cell phenotype, and cell viability in vitro. Overall, P(3HO)/P(3HB) (50:50) fibers supported higher neuronal and Schwann cell adhesion compared to PCL fibers. The 5 μm PHA blend fibers also supported significantly higher DRG neurite outgrowth and Schwann cell migration distance using a 3D ex vivo nerve injury model.

The influence of tag sequence on recombinant humanized collagen (rhCol) and the evaluation of rhCol on Schwann cell behaviors.

Recombinant humanized collagen (rhCol) was an extracellular matrix (ECM)-inspired biomimetic biomaterial prepared by biosynthesis technology, which was considered non-allergenic and could possibly activate tissue regeneration. The influence of tag sequence on both structures and performances of rhCol type III (rhCol III) was investigated, and the effect of rhCol III on cell behaviors was evaluated and discussed using Schwann cells (SCs) as in vitro model that was critical in the repair process after peripheral nerve injury. The results demonstrated that the introduction of tag sequence would influence both advanced structures and properties of rhCol III, while rhCol III regulated SCs adhesion, spreading, migration and proliferation. Also, both nerve growth factor and brain-derived neurotrophic factor increased when exposed to rhCol III. As the downstream proteins of integrin-mediated cell adhesions, phosphorylation of focal adhesion kinase and expression of vinculin was up-regulated along with the promotion of SCs adhesion and migration. The current findings contributed to a better knowledge of the interactions between rhCol III and SCs, and further offered a theoretical and experimental foundation for the development of rhCol III-based medical devices and clinical management of peripheral nerve injury.

Engineering a wirelessly self-powered and electroconductive scaffold to promote peripheral nerve regeneration

Electroactive biomaterials have been shown useful for the repair of injured peripheral nerve. While for conventional conductive conduits, outer electrical stimulation device is unavoidably employed to exert electrical signals, and their rigid microstructures are usually incompatible with neural cells. Herein, a soft carbon nanotubes@gelatin methacryloyl/poly(L-lactic acid) (CNTs@GelMA/PLLA) nerve tissue-engineering scaffold was fabricated, which provided an endogenous piezoelectric stimulation and conductive microenvironment. Based on amounts of in-vitro experiment data, such composite scaffold significantly improved adhesion and elongation of Schwann cells, and meanwhile promoted axonal outgrowth and neurites number of dorsal root ganglions. More interestingly, the scaffold was applied to a 10-mm sciatic nerve defect in rats and harvested at 12 weeks post-implantation. Immunohistochemical staining results indicated that our proposed graft significantly facilitated peripheral nerve regeneration by promoting myelination and axon outgrowth, meanwhile an enhanced motor functional recovery caused by the scaffold was also revealed due to the obviously-improved sciatic functional index and muscle weights. Overall, the soft, self-powered, and electroconductive CNTs@GelMA/PLLA scaffold is a promising candidate for the treatment of peripheral nerve injuries.

Surface Modification of Titanium by Micro-Arc Oxidation in Promoting Schwann Cell Proliferation and Secretion of Neurotrophic Factors

Titanium and its alloys have been widely used in the field of oral implants over the past few decades. However, the effect of micro-arc oxidation modified titanium surface on Schwann cells has not been studied, which is of great significance for nerve regeneration around implants and improvement of osseoperception. In this study, the characterization of the titanium surface modified by micro-arc oxidation (MAO) was detected by scanning electron microscope (SEM), XPS and a contact angle measurement system. Schwann cells (SCs) were cultured on titanium surfaces of micro-arc oxidation (MAO) and pure titanium (Ti). At different time points, the morphology and adhesion of SCs on the titanium surfaces were observed by SEM. Cell proliferation activity was detected by the CCK-8 method. The expression levels of mRNA and proteins of nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF) were detected by RT-PCR, immunofluorescence and western blot. The results of this in vitro study revealed that micro-arc-oxidation-modified titanium surfaces promoted Schwann cell proliferation and secretion of neurotrophic factors compared with pure titanium. CCK-8 results showed that the number of Schwann cells on MAO surfaces was significantly higher than that of the Ti group on day 7. The mRNA expressions of Ngf and Gdnf were up-regulated in both groups from day 1 to day 7. On day 3 and day 7, the gene expression of Ngf in the MAO group was significantly higher than that of the Ti group. On day 7, the MAO group appeared significantly up-regulated in gene expression level of Gdnf. The results of western blot were consistent. Micro-arc oxidation modification provides an accurate and effective method for promoting nerve regeneration of titanium microtopography coatings, which have potential significance for promoting patients’ osseoperception ability in clinical practice.

Multifaceted polymeric nerve guidance conduits with distinctive double-layered architecture and plasma-induced inner chemistry gradient for the repair of critical-sized defects

Despite tissue engineering advances, current nerve guidance conduits (NGCs) are still failing in repairing critical-sized defects. This study aims, therefore, at tackling large nerve gaps (2 cm) by designing NGCs possessing refined physicochemical properties enhancing the activity of Schwann cells (SCs) that support nerve regeneration over long distances. As such, a combinatorial strategy adopting novel plasma-induced surface chemistry and architectural heterogeneity was considered. A mechanically suitable copolymer (Polyactive®) was electrospun to produce nanofibrous NGCs mimicking the extracellular matrix. An innovative seamless double-layered architecture consisting of an inner wall comprised of bundles of aligned fibers with intercalated random fibers and an outer wall fully composed of random fibers was conceived to synergistically provide cell guidance cues and sufficient nutrient inflow. NGCs were subjected to argon plasma treatments using a dielectric barrier discharge (DBD) and a plasma jet (PJ). Surface chemical changes were examined by advanced X-ray photoelectron spectroscopy (XPS) micro-mappings. The DBD homogeneously increased the surface oxygen content from 17 % to 28 % on the inner wall. The PJ created a gradient chemistry throughout the inner wall with an oxygen content gradually increasing from 21 % to 30 %. In vitro studies revealed enhanced primary SC adhesion, elongation and proliferation on plasma-treated NGCs. A cell gradient was observed on the PJ-treated NGCs thus underlining the favorable oxygen gradient in promoting cell chemotaxis. A gradual change from circular to highly elongated SC morphologies mimicking the bands of Büngner was visualized along the gradient. Overall, plasma-treated NGCs are promising candidates paving the way towards critical nerve gap repair.

Construction of a mineralized collagen nerve conduit for peripheral nerve injury repair.

A new nerve guidance conduits (NGCs) named MC@Col containing Type I collagen (Col) and mineralized collagen (MC) was developed, enhancing mechanical and degradation behavior. The physicochemical properties, the mechanical properties and in vitro degradation behavior were all evaluated. The adhesion and proliferation of Schwann cells (SCs) were observed. In the in vivo experiment, MC@Col NGC and other conduits including Col, chitosan (CST) and polycaprolactone (PCL) conduit were implanted to repair a 10-mm-long Sprague-Dawley rat's sciatic nerve defect. Histological analyses, morphological analyses, electrophysiological analyses and further gait analyses were all evaluated after implantation in 12 weeks. The strength and degradation performance of the MC@Col NGC were improved by the addition of MC in comparison with pure Col NGC. In vitro cytocompatibility evaluation revealed that the SCs had good viability, attachment and proliferation in the MC@Col. In in vivo results, the regenerative outcomes of MC@Col NGC were close to those by an autologous nerve graft in some respects, but superior to those by Col, CST and PCL conduits. The MC@Col NGC exhibited good mechanical performance as well as biocompatibility to bridge nerve gap and guide nerve regeneration, thus showing great promising potential as a new type of conduit in clinical applications.

Preparation and mechanical optimization of a two‐layer silk/magnesium wires braided porous artificial nerve guidance conduit

Peripheral nerve injures have long been a tricky problem in surgery and a feasible treatment is the transplantation of nerve guidance conduits (NGCs). This study presents a two-layer composite NGC with fair mechanical properties and good biocompatibility. The inner layer was made of degummed silk yarns/magnesium wires using braiding technology, and the outer layer was made from mixed solution of silk fibroin/chitosan (SF/CS) using freeze-drying treatment. Orthogonal experimental design was applied to rationally design the braided structural layer and obtain the optimal combination of technical process parameters. Meanwhile, the SF/CS porous outer layer was optimized from three concentrations of SF/CS solution. In vitro and in vivo study suggested that the textile-forming scaffold exhibited good biocompatibility and no toxicity. During 4 weeks' degradation, the skeleton of conduits retained its shape, and magnesium ions released from degraded magnesium wires contributed to sustainable release and uniform dispersion, proliferation and adhesion of Schwann cells, indicating potential approach in the development of NGCs.

QS50. Elucidating the Reasons Behind the Success of Spider Silk In Nerve Regeneration

Purpose: The successful reconstruction of peripheral nerve injuries remains a major clinical challenge. Nerve guidance conduits are a promising alternative to autologous nerve transplantation and conduits filled with fibrous materials have shown great potential in bridging nerve gaps. The application of spider silk as a filament material for nerve guidance conduits has led to results comparable to nerve autograft. However, the use of spider silk has been phenomenological so far and the reasons for its success are still not identified. The aim of this study is to elucidate the material properties of spider silk leading to its unique medical performance. This knowledge enables a targeted production of synthetic alternatives such as recombinant silk. Methods: In this work, various silk types from golden orb weavers and tarantulas were investigated. In vitro experiments were conducted, and Schwann cells were seeded on the spider silks and monitored by live cell imaging. The extent of proliferation was analyzed by immunofluorescent staining and confocal microscopy. In addition, the silk fibers were inspected with an electron microscope for differences in their morphology and with Raman spectroscopy as well as wide angle X-ray scattering to determine their secondary protein structure and crystallinity. Results: It was found that the adhesion of Schwann cells on spider silk is independent of the size and morphology of fibers. However, the secondary protein structure and specifically the high content of β-sheets in the direction of silk’s axis gives the fiber its ability to act as a guiding element for Schwann cells. In addition, the results show that the crystallinity of the silk does not affect the proliferation of Schwann cells, while the directed movement of cells is affected by this material property. Conclusion: This direct comparison demonstrated the crucial role of the secondary protein structures and crystallinity of spider silk for the guidance properties of fibers during nerve regeneration. These results should be considered during the targeted production of synthetic fibrous materials for nerve regeneration.

Preparation and characterization of multi-network hydrogels based on sodium alginate/krill protein/polyacrylamide—Strength, shape memory, conductivity and biocompatibility

Sodium alginate/krill protein/polyacrylamide (SA/AKP/PAM) hydrogel with “covalent bond―ion complex―hydrogen bond” multi-network structure was prepared by covalent cross-linking and complexion ion crosslinking using SA, AKP, and acrylamide (AM) as raw materials. The effects of ion species (Fe3+, Ba2+, Sr2+, Ca2+, and Zn2+) on the structure, morphology, and properties of multi-network hydrogels were studied in detail. The results showed that the mechanical strength of ionic cross-linked hydrogels increased significantly. The compressive strength of Fe3+ cross-linked hydrogels was 5.56 MPa, 16.13 times that of non-ionic crosslinked hydrogels. The results of ionic conductivity measurements showed that hydrogels had significant ionic conductivity and were sensitive to external forces. Interestingly, the hydrogel can be used as a capacitive pen in mobile phone writing, painting and dialing numbers. Moreover, ionic cross-linked hydrogels had a unique three-dimensional porous structure with gradient distribution, excellent shape memory effect, and good biocompatibility. Fe3+, Ba2+, Sr2+, and Ca2+ cross-linked hydrogels were nontoxic and conducive to the adhesion and growth of Schwann cells. These excellent properties of ionic cross-linked SA/AKP/PAM hydrogels have broad applications prospects in flexible electronic devices, sensors, soft electronic skins, and tissue engineering.

Establishment of FK506‐Enriched PLGA Nanomaterial Neural Conduit Produced by Electrospinning for the Repair of Long‐Distance Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a serious complication of trauma. Autologous nerve transplantation is the gold standard for the treatment of long‐distance peripheral nerve defects, but is often limited by insufficient donor sites, postoperative pain, and paresthesia at the donor site. Peripheral nerve tissue engineering has led to the development of neural conduits to replace autologous nerve grafts. This study aimed to evaluate a new type of electrospun nanomaterial neural conduit, enriched with tacrolimus (FK506), which is an FDA‐approved immunosuppressant, for the repair of long‐distance peripheral nerve injuries. Poly (lactic‐co‐glycolic acid) (PLGA) nanofibrous films, with FK506, were prepared by electrostatic spinning and rolled into hollow cylindrical nerve vessels with an inner diameter of 1 mm and length of 15 mm. Material characterization, mechanical testing, degradation, drug release, cytotoxicity, cell proliferation, and migration assays were performed in vitro. Long‐distance sciatic nerve injuries in rats were repaired in vivo using electrospun nerve conduit bridging, and nerve regeneration and muscle and motor function recovery were evaluated by gait analysis, electrophysiology, and neuromuscular histology. Compared to PLGA, the PLGA/FK506 nanomaterial neural conduit showed little change in morphology, mechanical properties, and chemical structure. In vitro, PLGA/FK506 showed lower cytotoxicity and better biocompatibility and effectively promoted the proliferation, adhesion, and migration of Schwann cells. In vivo, PLGA/FK506 had a better effect on sciatic nerve index, compound muscle action potential intensity and delay time, and nerve regeneration quality 12 weeks post‐transplantation, effectively promoting long‐distance defect sciatic nerve regeneration and functional recovery in rats. FK506‐enriched PLGA nanomaterial neural conduits offer an effective method for repairing long‐distance peripheral nerve injury and have potential clinical applications.

In Situ Fabrication of Nerve Growth Factor Encapsulated Chitosan Nanoparticles in Oxidized Bacterial Nanocellulose for Rat Sciatic Nerve Regeneration.

Autograft is currently the gold standard in the clinical treatment of peripheral nerve injury (PNI), which, however, is limited by the availability of a donor nerve and secondary injuries. Nerve guidance conduits (NGC) provide a suitable microenvironment to promote the regeneration of injured nerves, which could be the substitutes for autografts. In this study, nerve growth factor (NGF) encapsulated chitosan nanoparticles (CSNPs) were first constructed in situ in an oxidized bacterial cellulose (OBC) conduit using the ion gel method after the introduction of a CS/NGF solution under pressure to enable a sustainable release of NGF. A novel NGF@CSNPs/OBC nanocomposite with antibacterial activity, biodegradability, and porous microstructure was successfully developed. In vitro experiments showed that the nanocomposite promoted the adhesion and proliferation of Schwann cells. When the nanocomposite was applied as NGC to repair the sciatic nerve defect of rats, a successful repair of the 10 mm nerve defect was observed after 4 weeks. At week 9, the diameter, morphology, histology, and functional recovery of the regenerated nerve was comparable to the autografts, indicating that the NGC effectively promoted the regeneration and function recovery of the nerve. In summary, the NGF@CSNPs/OBC as a novel NGC provides great potential in the treatment of PNI.

Characteristics of electrospun membranes in different spidroin/PCL ratios

Spider silk is a protein fiber with the highest strength and elasticity known in nature, even higher than that of silkworm silk. It was a biological and technical reserve material with great potential. However, the low yield of natural spider silk limits the application of spider silk, and the development of genetic engineering provides opportunities for the mass production of spider silk. We constructed a mini-recombinant spidroin NRC based on spider silk gene from Araneus ventricosus and successfully expressed it through Prokaryotic expression that provide a high production for application using electrospinning, which is a mature technique to produce micro-nano scale fibers as thin as natural spider silks. By blending the purified and lyophilized NRC with polycaprolactone (PCL) in different mass ratio for electrospinning, different electrospun membranes were obtained, and then characterized in terms of morphology, chemical structure, mechanical and Schwann cell proliferation. Compared the difference between polycaprolactone (PCL) and NRC, the fiber diameter decreased from 1.0779 μm to 0.5785 μm, water contact angel decreased from 104.1 ± 2° to 56.9 ± 5°, and elongation decreased from 240.97 ± 89% to 37.76 ± 13%, while tensile strength increased from 1.74 ± 1.2 MPa to 3.18 ± 0.9 MPa and Young’s Module increased from 3.05 ± 1.6 MPa to 16.54 ± 6.7 MPa. In this study, we obtained a thinner fiber, hydrophilicity and high strengthen electrospinning spidroin contained membrane, which can also promote Schwann cell proliferation and adhesion.