Peripheral Nerve Tissue Engineering Research Articles

3D printed poly(lactic acid)/poly(ε-caprolactone)/graphene nanocomposite scaffolds for peripheral nerve tissue engineering

This research aimed to fabricate and evaluate Poly(lactic acid)/poly(ε-caprolactone)/graphene (PLA/PCL/G) nanocomposite scaffolds for peripheral nerve tissue engineering. To achieve this goal, scaffolds were fabricated using the fused deposition modeling (FDM) 3D printing method with the following compositions: 50 wt% PLA-50 wt% PCL (PLA-PCL), 98.5 wt% PLA-1.5 wt% G (PLA-G), 98.5 wt% PCL-1.5 wt% G (PCL-G), and 50 wt% PLA-48.5 wt% PCL-1.5 wt% G (PLA-PCL-G). The microstructure and chemical composition of the scaffolds were characterized using SEM, XRD, and FTIR. SEM images revealed that the PLA-PCL-G scaffold exhibited a more regular and uniform morphology compared to the others, with the PLA-PCL scaffold displaying the least regularity. The porosity percentage and pore size of the scaffolds ranged from 50 % to 86 % and 300 to 500 µm, respectively. Mechanical properties were assessed via compression testing, indicating that the elastic modulus of the PLA-PCL-G scaffold was approximately 22.36 MPa, suitable for peripheral nerve tissue applications. Electrical conductivity testing showed that PLA-PCL-G had a conductivity of about 8.2E-5 S/cm, similar to PLA-G. Biodegradability was evaluated by immersing samples in phosphate-buffered saline (PBS), revealing that PLA-PCL-G exhibited a weight loss of approximately 1.3 % and a degradation rate of 0.14 mm/day over four weeks, closely matching peripheral nerve tissue regeneration rates. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay results confirmed that PLA-PCL-G scaffolds were non-cytotoxic to PC12 cells. Overall, these findings suggest that the 50 wt% PLA-48.5 wt% PCL-1.5 wt% G scaffold holds promise for peripheral nerve tissue engineering applications.

An injectable and adaptable hydrogen sulfide delivery system for modulating neuroregenerative microenvironment.

Peripheral nerve regeneration is a complex physiological process. Single-function nerve scaffolds often struggle to quickly adapt to the imbalanced regenerative microenvironment, leading to slow nerve regeneration and limited functional recovery. In this study, we demonstrate a "pleiotropic gas transmitter" strategy based on endogenous reactive oxygen species (ROS), which trigger the on-demand H2S release at the defect area for transected peripheral nerve injury (PNI) repair through concurrent neuroregeneration and neuroprotection processing. This H2S delivery system consists of an H2S donor (peroxyTCM) encapsulated in a ROS-responsive polymer (mPEG-PMet) and loaded into a temperature-sensitive poly (amino acid) hydrogel (mPEG-PA-PP). This multi-effect combination strategy greatly promotes the regeneration of PNI, attributed to the physiological effects of H2S. These effects include the inhibition of inflammation and oxidative stress, protection of nerve cells, promotion of angiogenesis, and the restoration of normal mitochondrial function. The adaptive release of pleiotropic messengers to modulate the tissue regeneration microenvironment offers promising peripheral nerve repair and tissue engineering opportunities.

Effect of Electrical Stimulation on PC12 Cells Cultured in Different Hydrogels: Basis for the Development of Biomaterials in Peripheral Nerve Tissue Engineering.

Extensive damage to peripheral nerves is a health problem with few therapeutic alternatives. In this context, the development of tissue engineering seeks to obtain materials that can help recreate environments conducive to cellular development and functional repair of peripheral nerves. Different hydrogels have been studied and presented as alternatives for future treatments to emulate the morphological characteristics of nerves. Along with this, other research proposes the need to incorporate electrical stimuli into treatments as agents that promote cell growth and differentiation; however, no precedent correlates the simultaneous effects of the types of hydrogel and electrical stimuli. This research evaluates the neural differentiation of PC12 cells, relating the effect of collagen, alginate, GelMA, and PEGDA hydrogels with electrical stimulation modulated in four different ways. Our results show significant correlations for different cultivation conditions. Electrical stimuli significantly increase neural differentiation for specific experimental conditions dependent on electrical frequency, not voltage. These backgrounds allow new material treatment schemes to be formulated through electrical stimulation in peripheral nerve tissue engineering.

The Porous Structure of Peripheral Nerve Guidance Conduits: Features, Fabrication, and Implications for Peripheral Nerve Regeneration.

Porous structure is an important three-dimensional morphological feature of the peripheral nerve guidance conduit (NGC), which permits the infiltration of cells, nutrients, and molecular signals and the discharge of metabolic waste. Porous structures with precisely customized pore sizes, porosities, and connectivities are being used to construct fully permeable, semi-permeable, and asymmetric peripheral NGCs for the replacement of traditional nerve autografts in the treatment of long-segment peripheral nerve injury. In this review, the features of porous structures and the classification of NGCs based on these characteristics are discussed. Common methods for constructing 3D porous NGCs in current research are described, as well as the pore characteristics and the parameters used to tune the pores. The effects of the porous structure on the physical properties of NGCs, including biodegradation, mechanical performance, and permeability, were analyzed. Pore structure affects the biological behavior of Schwann cells, macrophages, fibroblasts, and vascular endothelial cells during peripheral nerve regeneration. The construction of ideal porous structures is a significant advancement in the regeneration of peripheral nerve tissue engineering materials. The purpose of this review is to generalize, summarize, and analyze methods for the preparation of porous NGCs and their biological functions in promoting peripheral nerve regeneration to guide the development of medical nerve repair materials.

Effect of chitosan structure and deposition time on structural and mechanical properties of chitosan-hydroxyapatite tubular-shaped electrodeposits for biomedical applications

Chitosan-hydroxyapatite tubular-shaped hydrogel structures have been successfully obtained by electrophoretic deposition. The deposits show great potential in the regeneration of tubular organs and tissues, in particular peripheral nerve tissue engineering. The mechanism for their formation has been investigated by studying the deposition yield from solutions differing in chitosan structure. The resulting deposit mass is higher for 95% deacetylated chitosan than one for 75% deacetylated chitosan in all analyzed time intervals. The longer the deposition time, the higher the deposit mass is observed up to 40 min. The performed elemental analysis sets the foundation for the understanding of the electrodeposition mechanism from chitosan-hydroxyapatite solution in lactic acid. It is suggested that protonation of chitosan ions and their attraction to H2PO4− groups on hydroxyapatite particles in the acidic environment is a prerequisite to electrophoretic deposition. Upon application of an electric field, pH increases in the vicinity of the cathode, and the positively charged chitosan chain is neutralized. The chitosan-hydroxyapatite precipitation is accompanied by calcium carbonate deposition. Consequently, an insoluble chitosan-hydroxyapatite-calcium carbonate deposit is formed on the cathode surface. It is anticipated that the presented mechanism will provide insight into modeling deposit properties desired on an industrial scale.

Instructive electroactive electrospun silk fibroin-based biomaterials for peripheral nerve tissue engineering.

Aligned sub-micron fibres are an outstanding surface for orienting and promoting neurite outgrowth; therefore, attractive features to include in peripheral nerve tissue scaffolds. A new generation of peripheral nerve tissue scaffolds is under development incorporating electroactive materials and electrical regimes as instructive cues in order to facilitate fully functional regeneration. Herein, electroactive fibres composed of silk fibroin (SF) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) were developed as a novel peripheral nerve tissue scaffold. Mats of SF with sub-micron fibre diameters of 190±50nm were fabricated by double layer electrospinning with thicknesses of ∼100μm (∼70-80μm random fibres and ∼20-30μm aligned fibres). Electrospun SF mats were modified with interpenetrating polymer networks (IPN) of PEDOT:PSS in various ratios of PSS/EDOT (α) and the polymerisation was assessed by hard X-ray photoelectron spectroscopy (HAXPES). The mechanical properties of electrospun SF and IPNs mats were characterised in the wet state tensile and the electrical properties were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The cytotoxicity and biocompatibility of the optimal IPNs (α=2.3 and 3.3) mats were ascertained via the growth and neurite extension of mouse neuroblastoma x rat glioma hybrid cells (NG108-15) for 7days. The longest neurite outgrowth of 300μm was observed in the parallel direction of fibre alignment on laminin-coated electrospun SF and IPN (α=2.3) mats which is the material with the lowest electron transfer resistance (Ret, ca. 330Ω). These electrically conductive composites with aligned sub-micron fibres exhibit promise for axon guidance and also have the potential to be combined with electrical stimulation treatment as a further step for the effective regeneration of nerves.

The Effect of Vitamin C-Loaded Electrospun Polycaprolactone/Poly (Glycerol Sebacate) Fibers for Peripheral Nerve Tissue Engineering

Vitamin C (VC) is an essential supplement that plays a vital role in cellular processes and functions and has been applied for therapeutic purposes for many years. The beneficial effects of VC on peripheral nerve regeneration have been gained lots of attention. In this study, electrospun polycaprolactone (PCL)/polyglycerol sebacate (PGS) fibers incorporated with different concentrations of VC (5, 10, and 15 wt.%) were developed for peripheral nerve tissue engineering. The morphology of the fibers was investigated using scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), tensile analysis (Young’s modulus, ultimate tensile strength (UTS), and elongation at break), release profile of VC from the PCL/PGS fibers, in vitro degradation, water uptake behavior, and contact angle measurements were also studied. MTT assay and SEM were utilized to evaluate the attachment and viability of pheochromocytoma cells (PC12) on the scaffolds. The results showed that all scaffolds had a uniform diameter and mean diameter deceased from 1.24 to 0.88 µm followed by increasing VC. Young’s modulus and UTS enhanced with increasing in VC percentage. MTT assay demonstrated that PCL/PGS containing 5 wt.% VC had a greater viability rate among other scaffolds. Our outcome indicated possible applicability of VC containing scaffolds for nerve tissue engineering.

Properties of Electrospun Aligned Poly(lactic acid)/Collagen Fibers with Nanoporous Surface for Peripheral Nerve Tissue Engineering

AbstractIt is important for the functional recovery of defective nerves to construct a suitable microenvironment for nerve regeneration by optimizing the topological structure and biological functions of nerve grafts. Electrospun fibers are employed to mimic the extracellular matrix (ECM) and the effect of the porous features on fiber surface draws much attention. Yet, little is known about the effect of the nanotopology of the fiber surface in conjunction with collagen I (COL) on neural cells. Herein, poly(lactic acid) (PLA)/COL hybrid fibrous membranes with a nanoporous structure on a fiber surface are fabricated. The performance of the obtained fibrous membranes is investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), water contact angle (WCA), and tensile test measurements. The cytotoxicity and biocompatibility of PLA/COL hybrid fibrous membranes and their effects on neural cells are systematically investigated. The physicochemical test results show that the PLA/COL hybrid fibrous membranes have appropriate mechanical properties and improved hydrophilicity. The MTT assay and hemolysis assay suggest the nontoxicity and good hemocompatibility of PLA/COL membranes. The nanoporous structure on the fiber surface and the introduction of COL synergistically promote proliferation and elongation of Schwann cells (SCs) and the extension of dorsal root ganglion (DRG) neurites.

Alginate-Based Hydrogels and Tubes, as Biological Macromolecule-Based Platforms for Peripheral Nerve Tissue Engineering: A Review.

Unlike the central nervous system, the peripheral nervous system (PNS) has an inherent capacity to regenerate following injury. However, in the case of large nerve defects where end-to-end cooptation of two nerve stumps is not tension-free, autologous nerve grafting is often utilized to bridge the nerve gaps. To address the challenges associated with autologous nerve grafting, neural guidance channels (NGCs) have been successfully translated into clinic. Furthermore, hydrogel-based drug delivery systems have been extensively studied for the repair of PNS injuries. There are numerous biomaterial options for the production of NGCs and hydrogels. Among different candidates, alginate has shown promising results in PNS tissue engineering. Alginate is a naturally occurring polysaccharide which is biocompatible, non-toxic, non-immunogenic, and possesses modifiable properties. In the current review, applications, challenges, and future perspectives of alginate-based NGCs and hydrogels in the repair of PNS injuries will be discussed.

Polydopamine-coated polycaprolactone/carbon nanotube fibrous scaffolds loaded with brain-derived neurotrophic factor for peripheral nerve regeneration

Carbon nanotubes (CNTs) have attracted increasing attention in the field of peripheral nerve tissue engineering due to their unique structural and physical characteristics. In this study, a novel type of aligned conductive scaffolds composed of polycaprolactone (PCL) and CNTs were fabricated via electrospinning. Utilizing mussel-inspired polydopamine (PDA) surface modification, brain-derived neurotrophic factor (BDNF) was loaded onto PCL/CNT fibrous scaffolds to obtain PCL/CNT-PDA-BDNF fibrous scaffolds capable of the sustained release of BDNF over 28 d. Schwann cells were cultured on these scaffolds, and the effect of the scaffolds on peripheral nerve regeneration in vitro was assessed by studying cell proliferation, morphology and the expressions of myelination-related genes S100, P0 and myelin basic protein. Furthermore, the effect of these scaffolds on peripheral nerve regeneration in vivo was investigated using a 10 mm rat sciatic nerve defect model. Both the in vitro and in vivo results indicate that PCL/CNT-PDA-BDNF fibrous scaffolds effectively promote sciatic nerve regeneration and functional recovery. Therefore, PCL/CNT-PDA-BDNF fibrous scaffolds have great potential for peripheral nerve restoration.

A Shock to the (Nervous) System: Bioelectricity Within Peripheral Nerve Tissue Engineering.

The peripheral nervous system has the remarkable ability to regenerate in response to injury. However, this is only successful over shorter nerve gaps and often provides poor outcomes for patients. Currently, the gold standard of treatment is the surgical intervention of an autograft, whereby patient tissue is harvested and transplanted to bridge the nerve gap. Despite being the gold standard, more than half of patients have dissatisfactory functional recovery after an autograft. Peripheral nerve tissue engineering aims to create biomaterials that can therapeutically surpass the autograft. Current tissue-engineered constructs are designed to deliver a combination of therapeutic benefits to the regenerating nerve, such as supportive cells, alignment, extracellular matrix, soluble factors, immunosuppressants, and other therapies. An emerging therapeutic opportunity in nerve tissue engineering is the use of electrical stimulation (ES) to modify and enhance cell function. ES has been shown to positively affect four key cell types, such as neurons, endothelial cells, macrophages, and Schwann cells, involved in peripheral nerve repair. Changes elicited include faster neurite extension, cellular alignment, and changes in cell phenotype associated with improved regeneration and functional recovery. This review considers the relevant modes of administration and cellular responses that could underpin incorporation of ES into nerve tissue engineering strategies. Impact Statement Tissue engineering is becoming increasingly complex, with multiple therapeutic modalities often included within the final tissue-engineered construct. Electrical stimulation (ES) is emerging as a viable therapeutic intervention to be included within peripheral nerve tissue engineering strategies; however, to date, there have been no review articles that collate the information regarding the effects of ES on key cell within peripheral nerve injury. This review article aims to inform the field on the different therapeutic effects that may be achieved by using ES and how they may become incorporated into existing strategies.

Design of ECM Functionalized Polycaprolactone Aligned Nanofibers for Peripheral Nerve Tissue Engineering

PurposePeripheral nerve injury (PNI) and its regeneration continue to remain a significant medical burden worldwide. The current treatment strategies used to treat PNI are often associated with multiple complications and yet do not achieve complete motor and sensory functions. Recently, synthetic biodegradable nerve conduits have become one the most commonly used conduits to repair small gaps in nerve injury. But they have not shown better results than nerve grafts possibly because of the lack of biological microenvironment required for axonal growth. Schwann cells play a very crucial role in peripheral nerve regeneration where activated SCs produce multiple neurotrophic factors that help in remyelination and immune modulation during nerve repair. Studies have shown that nanofibrous scaffolds have better bioactivity and more closely mimic the native structure of the extracellular matrix. Therefore, the present study was focused on designing a nanofibrous scaffold that would cover the roles of both structural support for the cells that can provide a microenvironment with biological cues for nerve growth and regeneration.MethodsDecellularized Schwann cell ECM were spin-coated on polycaprolactone random and aligned nanofibrous scaffolds and their compatibility was evaluated using Schwann cells.ResultsSchwann cells displayed growth in the direction of the aligned PCL nanofibers and ACM treated exhibited appropriate bipolar morphology indicating that these modified fibers could provide directional cues making them highly suitable for neuronal cell growth.ConclusionOur results indicate that the fabricated aligned SC-ACM treated PCL scaffolds would be a potential biomaterial to treat peripheral nerve injuries and promote regeneration.Graphical

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.

Graphdiyne-Related Materials in Biomedical Applications and Their Potential in Peripheral Nerve Tissue Engineering.

Graphdiyne (GDY) is a new member of the family of carbon-based nanomaterials with hybridized carbon atoms of sp and sp2, including α, β, γ, and (6,6,12)-GDY, which differ in their percentage of acetylene bonds. The unique structure of GDY provides many attractive features, such as uniformly distributed pores, highly π-conjugated structure, high thermal stability, low toxicity, biodegradability, large specific surface area, tunable electrical conductivity, and remarkable thermal conductivity. Therefore, GDY is widely used in energy storage, catalysis, and energy fields, in addition to biomedical fields, such as biosensing, cancer therapy, drug delivery, radiation protection, and tissue engineering. In this review, we first discuss the synthesis of GDY with different shapes, including nanotubes, nanowires, nanowalls, and nanosheets. Second, we present the research progress in the biomedical field in recent years, along with the biodegradability and biocompatibility of GDY based on the existing literature. Subsequently, we present recent research results on the use of nanomaterials in peripheral nerve regeneration (PNR). Based on the wide application of nanomaterials in PNR and the remarkable properties of GDY, we predict the prospects and current challenges of GDY-based materials for PNR.

Novel electrospun conduit based on polyurethane/collagen enhanced by nanobioglass for peripheral nerve tissue engineering

Peripheral nerve injury can significantly affect the daily life of individuals with impaired nerve function and permanent nerve deformity. One of the most common treatments is autograft transplantation. Tissue engineering is one of the efficient methods to regenerate injured nerves using scaffolds, cells, and growth factors. Conduits, which are produced by a variety of techniques, could be used as an alternative treatment for patients with damaged nerves. The electrospinning technique is one of the most important and widely used methods for generating nanofiber conduits from biocompatible polymers. In this study, using the electrospinning method, three different conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and a new conduit based on polyurethane + collagen + nanobioglass (PU/C/NBG), were prepared. The characteristics of these three types of conduits were evaluated by SEM, XRD, and various experiments, including porosity, degradation, contact angle, DMTA, FTIR, MTT, and DAPI staining. The results of MTT and DAPI assays revealed the safety of conduits and proper cell attachment. Overall, the results obtained from various experiments showed that the novel PU/C/NBG conduit has better mechanical properties in terms of porosity, hydrophilicity, and biocompatibility in comparison with PU and PU/C conduits and could be a suitable candidate for peripheral nerve regeneration and axonal growth due to its repair potential.

Natural Biomaterials as Instructive Engineered Microenvironments That Direct Cellular Function in Peripheral Nerve Tissue Engineering.

Nerve tissue function and regeneration depend on precise and well-synchronised spatial and temporal control of biological, physical, and chemotactic cues, which are provided by cellular components and the surrounding extracellular matrix. Therefore, natural biomaterials currently used in peripheral nerve tissue engineering are selected on the basis that they can act as instructive extracellular microenvironments. Despite emerging knowledge regarding cell-matrix interactions, the exact mechanisms through which these biomaterials alter the behaviour of the host and implanted cells, including neurons, Schwann cells and immune cells, remain largely unclear. Here, we review some of the physical processes by which natural biomaterials mimic the function of the extracellular matrix and regulate cellular behaviour. We also highlight some representative cases of controllable cell microenvironments developed by combining cell biology and tissue engineering principles.

Fabrication and characterization of chitosan-based composite scaffolds for neural tissue engineering

With the development of peripheral nerve tissue engineering, study of biodegradable materials have extensive applied prospect. Chitosan (Cs) is a promising candidate for neural tissue engineering due to its similar chemical structure to glycosaminoglycan. However, due to its lack of elasticity and flexibility, Cs often needs to be used in combination with other materials. In this study, three composite scaffolds were prepared by freeze-drying method: Cs/hyaluronic acid (HA)/gelatin (Gel), Cs/collagen (Col), and Cs/polyethylene glycol (PEG). Mechanical properties, swelling behavior, porosity, and conductivity of these materials have been characterized. Compared with pure Cs, the addition of other materials reduced the average pore size, while improved the mechanical properties of the composite scaffold. Furthermore, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), live/dead staining, cell morphology, and immunofluorescence staining were performed to evaluate the cytotoxicity, biocompatibility, and differentiation of rat pheochromocytoma (PC12) cells on Cs/HA/Gel, Cs/Col, and Cs/PEG composite scaffolds. Our results indicated that all these Cs-based composite scaffolds had good biocompatibility without cytotoxicity, while Cs/PEG scaffolds possessed higher cell survival rate and could promote the adhesion, proliferation, and differentiation of PC12 cells. The Cs-based composite scaffolds developed in this study can serve as promising substitutes for neural tissue regeneration.

Reduced Graphene Oxide Fibers for Guidance Growth of Trigeminal Sensory Neurons.

Neurite alignment and elongation play special roles in the treatment of neuron disease, design of tissue engineering implants, and bioelectrodes applications. For instance, the trigeminal neurons (TGNs) free nerve endings are a key component of the pulp-dentin complex. The reinnervation of the pulp canal space requires the recruitment of apically positioned free nerve endings through axonal guidance. Many studies have been carried to develop patterned two-dimensional substrates or three-dimensional scaffolds with aligned topographical structures to guide axonal growth. However, most of the strategies are either complicated/inconvenient in process or time-/cost-sacrifice. One-step dimensionally confined hydrothermal (DCH) technique has been considered an effective and facile approach to fabricate reduced graphene oxide fibers (rGOFs), and the rGOFs have shown significant potential in regulating neural stem cells differentiation toward neurons. Here, inspired by the relationship between the lateral size of GO nanosheets and the electrical conductivity of GO films made from GO sheets as a building block, we fabricated surface conductivity and topography-controlled rGOFs based on the DCH method. Well "self-patterned" directional channel structure of rGOF showed outstanding ability to improve the neurofilament alignment and migration, with the cell deviation angle less than 10° for over 90% of the cells, while a porous surface structure tended to form neuron nets. All of the rGOF possessed excellent cytocompatibility with TGNs. Our results underlined the high degree of alignment of topographical cues in guidance of neurite over high electrical conductivity. The as-prepared rGOFs could be used in many areas including biosensing, electrochemistry, energy, and peripheral or central nerve tissue engineering.

Natural and synthetic polymeric scaffolds used in peripheral nerve tissue engineering: Advantages and disadvantages

The nervous system is a compound network of nerves, cells and is a vital part of the body. The injuries to this system can occur either via traumatic hurt happening after the accident, disease, tumorous outgrowth, or surgical side results. The regeneration of the nervous system is complex and takes big challenges to researchers. Nerve tissue engineering (NTE) is the most promising approach to repair nerve tissue in human health care. One of the most common solutions widely used for repairing functions in damaged neural tissues utilizes polymeric materials either natural or synthetic in origin. Polymers are able to develop into help structures, such as scaffold, electrospun matrices, and nerve conduit for promoting the regeneration of the damaged neural tissues that many investigations have shown. As usual, synthetic polymers suggest better structural stability and mechanical properties while natural polymers are highly useful for their high biocompatibility and natural biodegradation properties. However, low mechanical characteristics, processing difficulties and, thermal sensitivity that commonly need the use of solvents, limit the efficacy of natural polymers, stimulating researchers to blend them with synthetic or electroconductive polymers. Mostly, the blending of natural and synthetic allows for expanding polymeric conduits that help to mimic the substrate environment of healthy neural tissues. This review represents the most advanced and various recent findings in terms of the forms of natural and Synthetic polymers used in peripheral NTE, advantages, and disadvantages.

Electroactive nanomaterials in the peripheral nerve regeneration.

Severe peripheral nerve injuries are threatening the life quality of human beings. Current clinical treatments contain some limitations and therefore extensive research and efforts are geared towards tissue engineering approaches and development. The biophysical and biochemical characteristics of nanomaterials are highly focused on as critical elements in the design and fabrication of regenerative scaffolds. Recent studies indicate that the electrical properties and nanostructure of biomaterials can significantly affect the progress of nerve repair. More importantly, these studies also demonstrate the fact that electroactive nanomaterials have substantial implications for regulating the viability and fate of primary supporting cells in nerve regeneration. In this review, we summarize the current knowledge of electroconductive and piezoelectric nanomaterials. We exemplify typical cellular responses through cell-material interfaces, and the nanomaterial-induced microenvironment rebalance in terms of several key factors, immune responses, angiogenesis and oxidative stress. This work highlights the mechanism and application of electroactive nanomaterials to the development of regenerative scaffolds for peripheral nerve tissue engineering.