Accelerated Outgrowth of Neurites on Graphene Oxide-Based Hybrid Electrospun Fibro-Porous Polymeric Substrates

Influence of Graphene-Based Nanocomposites in Neurogenesis and Neuritogenesis: A Brief Summary

Graphene is a prospective candidate for various biomedical applications, including drug transporters, bioimaging agents, and scaffolds for tissue engineering, thanks to its superior electrical conductivity and biocompatibility. The clinical issue of nerve regeneration and rehabilitation still has a major influence on people's lives. Nanomaterials based on graphene have been exploited extensively to promote nerve cell differentiation and proliferation. Their high electrical conductivity and mechanical robustness make them appropriate for nerve tissue engineering. Combining graphene with other substances, such as biopolymers, may transmit biochemical signals that support brain cell division, proliferation, and regeneration. The utilization of nanocomposites based on graphene in neurogenesis and neuritogenesis is the primary emphasis of this review. Here are some examples of the many synthetic strategies used. For neuritogenesis and neurogenesis, it has also been explored to combine electrical stimulation with graphene-based materials.

Magnetic-Responsive Carbon Nanotubes Composite Scaffolds for Chondrogenic Tissue Engineering

The demand for engineered scaffolds capable of delivering multiple cues to cells continues to grow as the interplay between cell fate with microenvironmental and external cues is revealed. Emphasis has been given to develop stimuli-responsive scaffolds. These scaffolds are designed to sense an external stimulus triggering a specific response (e.g., change in the microenvironment, release therapeutics, etc.) and then initiate/modulate a desired biofunction. Here, magnetic-responsive carboxylated multi-walled carbon nanotubes (cMWCNTs) are integrated into 3D collagen/polylactic acid (PLA) scaffold via a reproducible filtration-based method. The integrity and biomechanical performance of the collagen/PLA scaffolds are preserved after cMWCNT integration. In vitro safety assessment of cMWCNT/collagen/PLA scaffolds shows neither cytotoxicity effects nor macrophage pro-inflammatory response, supporting further in vitro studies. The cMWCNT/collagen/PLA scaffolds enhance chondrocytes metabolic activity while maintaining high cell viability and extracellular matrix (i.e., type II collagen and aggrecan) production. Comprehensive in vitro study applying static and pulsed magnetic field on seeded scaffolds shows no specific cell response in dependence with the applied field. This result is independent of the presence or absence of cMWCNT into the collagen/PLA scaffolds. Taken together, these findings provide additional evidence of the benefits to exploit the CNTs outstanding properties in the design of stimuli-responsive scaffolds.

Aligned core-shell fibrous nerve wrap containing Bletilla striata polysaccharide improves functional outcomes of peripheral nerve repair

Peripheral nerve injuries are commonly encountered in extremity traumas. Their motor and sensory recovery following microsurgical repair is limited by slow regeneration speed (<1 mm/d) and subsequent muscle atrophy, which are consequently correlated with the activity of local Schwann cells and efficacy of axon outgrowth. To promote post-surgical nerve regeneration, we synthesized a nerve wrap consisting of an aligned polycaprolactone (PCL) fiber shell with a Bletilla striata polysaccharide (BSP) core (APB). Cell experiments demonstrated that the APB nerve wrap markedly promoted neurite outgrowth and Schwann cell migration and proliferation. Animal experiments applying a rat sciatic nerve repair model indicated that the APB nerve wrap restored conduction efficacy of the repaired nerve and the compound action potential as well as contraction force of the related leg muscles. Histology of the downstream nerves disclosed significantly higher fascicle diameter and myelin thickness with the APB nerve wrap compared to those without BSP. Thus, the BSP-loaded nerve wrap is potentially beneficial for the functional recovery after peripheral nerve repair and offers sustained targeted release of a natural polysaccharide with good bioactivity.

Neuronal cell response on aligned fibroporous electrospun mat generated from silver ion complexed ethylene vinyl alcohol copolymer

Generating electrospun mats with aligned fibers and obtaining neurite extension in the aligned fiber direction could provide hope for fabricating nerve guidance conduits or wraps through an easy method. The growing interest in generating electrospun mats with aligned fibers for tissue engineering is looking for simple methods to generate the same. Here, in this study, ethylene vinyl alcohol copolymer (EVAL) chains were complexed with silver ions (Ag⁺ ) to generate aligned fibers during the electrospinning process. The fibers thus produced were subjected to physico-chemical characterization and biological studies to ensure their properties and to examine whether suitable for neuronal cell attachment and neurite extension that may be useful in making nerve guidance conduits or wraps. The presence of silver ions and its complex formation with -OH of EVAL has been confirmed with EDX and XPS analysis respectively. The alignment of fibers was visualized from SEM analysis and confirmed using directionality analysis using Fiji-ImageJ software. Mechanical properties done with dumbbells punched out in longitudinal and transverse directions also substantiated the alignment of fibers. The results obtained from direct contact, MTT, and live/dead assay showed the cells are viable on the material. From the actin staining and immunostaining assays, it was evident that the PC12 cells could attach and extend their neurites in an aligned manner on the fibers. The maximum neurite extension was up to 200 μm in length. These properties of electrospun EVAL-Ag mat with aligned fibers indicated that it could be developed as a biocompatible nerve guidance conduit or wrap.

Graphene Incorporated Electrospun Nanofiber for Electrochemical Sensing and Biomedical Applications: A Critical Review

The extraordinary material graphene arrived in the fields of engineering and science to instigate a material revolution in 2004. Graphene has promptly risen as the super star due to its outstanding properties. Graphene is an allotrope of carbon and is made up of sp²-bonded carbon atoms placed in a two-dimensional honeycomb lattice. Graphite consists of stacked layers of graphene. Due to the distinctive structural features as well as excellent physico-chemical and electrical conductivity, graphene allows remarkable improvement in the performance of electrospun nanofibers (NFs), which results in the enhancement of promising applications in NF-based sensor and biomedical technologies. Electrospinning is an easy, economical, and versatile technology depending on electrostatic repulsion between the surface charges to generate fibers from the extensive list of polymeric and ceramic materials with diameters down to a few nanometers. NFs have emerged as important and attractive platform with outstanding properties for biosensing and biomedical applications, because of their excellent functional features, that include high porosity, high surface area to volume ratio, high catalytic and charge transfer, much better electrical conductivity, controllable nanofiber mat configuration, biocompatibility, and bioresorbability. The inclusion of graphene nanomaterials (GNMs) into NFs is highly desirable. Pre-processing techniques and post-processing techniques to incorporate GNMs into electrospun polymer NFs are precisely discussed. The accomplishment and the utilization of NFs containing GNMs in the electrochemical biosensing pathway for the detection of a broad range biological analytes are discussed. Graphene oxide (GO) has great importance and potential in the biomedical field and can imitate the composition of the extracellular matrix. The oxygen-rich GO is hydrophilic in nature and easily disperses in water, and assists in cell growth, drug delivery, and antimicrobial properties of electrospun nanofiber matrices. NFs containing GO for tissue engineering, drug and gene delivery, wound healing applications, and medical equipment are discussed. NFs containing GO have importance in biomedical applications, which include engineered cardiac patches, instrument coatings, and triboelectric nanogenerators (TENGs) for motion sensing applications. This review deals with graphene-based nanomaterials (GNMs) such as GO incorporated electrospun polymeric NFs for biosensing and biomedical applications, that can bridge the gap between the laboratory facility and industry.

Is Graphene Shortening the Path toward Spinal Cord Regeneration?

Along with the development of the next generation of biomedical platforms, the inclusion of graphene-based materials (GBMs) into therapeutics for spinal cord injury (SCI) has potential to nourish topmost neuroprotective and neuroregenerative strategies for enhancing neural structural and physiological recovery. In the context of SCI, contemplated as one of the most convoluted challenges of modern medicine, this review first provides an overview of its characteristics and pathophysiological features. Then, the most relevant ongoing clinical trials targeting SCI, including pharmaceutical, robotics/neuromodulation, and scaffolding approaches, are introduced and discussed in sequence with the most important insights brought by GBMs into each particular topic. The current role of these nanomaterials on restoring the spinal cord microenvironment after injury is critically contextualized, while proposing future concepts and desirable outputs for graphene-based technologies aiming to reach clinical significance for SCI.

UV-Crosslinked Electrospun Zein/PEO Fibroporous Membranes for Wound Dressing

Electrospun zein membranes are suitable for various biomedical applications. A UV-crosslinked electrospun membrane of a zein/PEO blend for wound healing application was explored in this work. The improvement in mechanical properties of the membrane after UV crosslinking was attributed to the change in protein conformation from an α-helix to a β-sheet. The circular dichroism (CD) spectra and FTIR spectra confirmed this conformational change. XRD analysis was shown to prove the amorphous nature of polymer blends with specific broad peaks at 2θ = 9° and 20°. The water vapor transmission rate (WVTR) of the membrane was found to be in the range of 1500-2000 g m^-2 day^-1, which was well suited with that of commercially available wound dressing material. Enough number of available functional groups like thiol, amino, and hydroxyl groups supplement a blood clotting index (BCI) to the matrix, causing 99% BCI within 4 min. A 91% cell viability result in the MTT assay with human dermal fibroblast cells confirmed the noncytotoxicity of the membrane. Tripeptides produced after the thermolysin-based hydrolysis of zein caused inhibition of TGF β1 expression and thus increased fibroblast and collagen production. The membrane stimulated 54% more collagen production compared to control cells at day 2 and caused 84% wound closure in human dermal fibroblast cells, which were desirable index markers of a potential wound care material.

Collagen/chitosan-functionalized graphene oxide hydrogel provide a 3D matrix for neural stem/precursor cells survival, adhesion, infiltration and migration

To have therapeutic promise of neural stem/precursor cells (NS/PCs) an appropriate scaffold is mostly essential. This study was conducted to fabricate collagen (Col)/chitosan-functionalized graphene oxide (CSGO) nanocomposite hydrogel and evaluated it as scaffold for NS/PCs. Graphene oxide was first functionalized with chitosan and the obtained CSGO was then added to Col solution and the solution underwent hydrogel formation. GO sheets were exfoliated after CS functionalization and the CSGO was homogenously dispersed in Col hydrogel. CSGO addition resulted in hydrogels with higher porosity and smaller Col fibers. Furthermore, CSGO increased the gelation time and water absorption capacity while the degradation was decreased. Cell studies demonstrated higher viability of NS/PCs on Col/CSGO hydrogel comparing with Col and poly-l-lysine as control (Cnt). NS/PCs were also penetrated into the Col/CSGO hydrogel and showed more cell spreading, neurite outgrowth and inter-cell connections in comparison with Col hydrogel. In addition, the cells traveled longer distance on Col/CSGO hydrogels than on Col and Cnt, indicating excellent migration capacity of NS/PCs on Col/CSGO hydrogel. Our results indicate the potential Col/CSGO hydrogels as an appropriate scaffold for NS/PCs.

Biomedical Applications of Electrospun Graphene Oxide

Graphene oxide (GO) has broad potential in the biomedical sector. The oxygen-abundant nature of GO means the material is hydrophilic and readily dispersible in water. GO has also been known to improve cell proliferation, drug loading, and antimicrobial properties of composites. Electrospun composites likewise have great potential for biomedical applications because they are generally biocompatible and bioresorbable, possess low immune rejection risk, and can mimic the structure of the extracellular matrix. In the current review, GO-containing electrospun composites for tissue engineering applications are described in detail. In addition, electrospun GO-containing materials for their use in drug and gene delivery, wound healing, and biomaterials/medical devices have been examined. Good biocompatibility and anionic-exchange properties of GO make it an ideal candidate for drug and gene delivery systems. Drug/gene delivery applications for electrospun GO composites are described with a number of examples. Various systems using electrospun GO-containing therapeutics have been compared for their potential uses in cancer therapy. Micro- to nanosized electrospun fibers for wound healing applications and antimicrobial applications are explained in detail. Applications of various GO-containing electrospun composite materials for medical device applications are listed. It is concluded that the electrospun GO materials will find a broad range of biomedical applications such as cardiac patches, medical device coatings, sensors, and triboelectric nanogenerators for motion sensing and biosensing.