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.

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.

Simvastatin-loaded graphene oxide embedded in polycaprolactone-polyurethane nanofibers for bone tissue engineering applications

Here, the role of simvastatin-loaded graphene oxide embedded in polyurethane-polycaprolactone nanofibers for bone tissue engineering has been investigated. The scaffolds were physicochemically and mechanically characterized, and obtained polymeric composites were used as MG-63 cell culture scaffolds. The addition of graphene oxide-simvastatin to nanofibers generates a homogeneous and uniform microstructure as well as a reduction in fiber diameter. Results of water-scaffolds interaction indicated higher hydrophilicity and absorption capacity as a function of graphene oxide addition. Scaffolds’ mechanical properties and physical stability improved after the addition of graphene oxide. Inducing bioactivity after the addition of simvastatin-loaded graphene oxide terminated its capability for hard tissue engineering application, evidenced by microscopy images and phase characterization. Nanofibrous scaffolds could act as a sustained drug carrier. Using the optimal concentration of graphene oxide-simvastatin is necessary to avoid toxic effects on tissue. Results show that the scaffolds are biocompatible to the MG-63 cell and support alkaline phosphatase activity, illustrating their potential use in bone tissue engineering. Briefly, graphene-simvastatin-incorporated in polymeric nanofibers was developed to increase bioactive components’ synergistic effect to induce more bioactivity and improve physical and mechanical properties as well as in vitro interactions for better results in bone repair.

Fabrication and characterization of mechanically competent 3D printed polycaprolactone-reduced graphene oxide scaffolds

The ability to produce constructs with a high control over the bulk geometry and internal architecture has situated 3D printing as an attractive fabrication technique for scaffolds. Various designs and inks are actively investigated to prepare scaffolds for different tissues. In this work, we prepared 3D printed composite scaffolds comprising polycaprolactone (PCL) and various amounts of reduced graphene oxide (rGO) at 0.5, 1, and 3 wt.%. We employed a two-step fabrication process to ensure an even mixture and distribution of the rGO sheets within the PCL matrix. The inks were prepared by creating composite PCL-rGO films through solvent evaporation casting that were subsequently fed into the 3D printer for extrusion. The resultant scaffolds were seamlessly integrated, and 3D printed with high fidelity and consistency across all groups. This, together with the homogeneous dispersion of the rGO sheets within the polymer matrix, significantly improved the compressive strength and stiffness by 185% and 150%, respectively, at 0.5 wt.% rGO inclusion. The in vitro response of the scaffolds was assessed using human adipose-derived stem cells. All scaffolds were cytocompatible and supported cell growth and viability. These mechanically reinforced and biologically compatible 3D printed PCL-rGO scaffolds are a promising platform for regenerative engineering applications.

Electrospinning of polyurethane/graphene oxide for skin wound dressing and its in vitro characterization

Electrospinning polyurethane has been utilized as skin wound dressing for protecting skin wounds from infection and thus facilitating their healings, but also limited by its imperfect biocompatibility, mechanical and antibacterial properties. This paper presents our study on the addition of graphene oxide to electrospinning polyurethane for improved properties, as well as its in vitro characterization. Polyurethane/graphene oxide wound dressing was electrospun with varying amount of graphene oxide (from 0.0% to 2.0%); and in vitro tests was carried out to characterize the wound dressing properties and performance from the structural, mechanical, and biological perspectives. Scanning electron microscopy and Fourier-transform infrared spectroscopy were used to confirm the interaction between graphene oxide particles and polyurethane fibers, while the scanning electron microscopy images further illustrated that the wound dressing was of a porous structure with fibre diameters depending on the amount of graphene oxide added; specifically, 20 to 180 nm were for composite polyurethane/graphene oxide fibers and 600 to 900 nm for pure polyurethane. Our results also revealed that the hydrophilicity and swelling properties of the wound dressing could be regulated by the amount of graphene oxide added to the polyurethane/graphene oxide composites. Mechanical, antibacterial, and cytotoxicity properties of the composite polyurethane/graphene oxide wound dressing were examined with the results illustrating that the addition of graphene oxide could improve the properties of the electrospun wound dressing. Combined together, our study illustrates that electrospinning polyurethane/graphene oxide composite is promising as skin wound dressing.

Graphene oxide incorporated polycaprolactone/chitosan/collagen electrospun scaffold: Enhanced osteogenic properties for bone tissue engineering

This in vitro study aimed to evaluate the physicochemical and biological activity of the polycaprolactone/chitosan/collagen scaffolds incorporated with 0, 0.5, 3, and 6 wt% of graphene oxide (GO). Using standard tests and MG‐63 cells, the characteristics of scaffolds were evaluated, and the behavior of osteoblasts were simulated, respectively. A non‐significant decrease in nanofibers diameter was noted in scaffolds with a higher ratio of GO. The hydrophilicity and bioactivity of the scaffold surface, as well as cell attachment and proliferation, increased in correspondence to an increase in GO. The higher ratio of GO also improved the osteogenesis activity. GO increased the degradation rate, but it was negligible and seemed not enough to endanger stability. Modifying the scaffolds with GO did not make a significant change to the antibacterial effect.

Polyarylene ether nitrile and boron nitride composites: coating with sulfonated polyarylene ether nitrile

Boron nitride (BN) coated with sulfonated poly-arylene ether nitrile (SPEN) (BN@SPEN) was used as additive to enhance the thermal conductivity of polyarylene ether nitrile. BN@SPEN was prepared by coating BN micro-platelets with SPEN through ultrasonic technology combined with the post-treatment bonding process. The prepared BN@SPEN was characterized by FTIR, TGA, SEM and TEM, which confirmed the successful coating of BN micro-platelets. The obtained BN@SPEN was introduced into the PEN matrix to prepare composite films by a solution casting method. The compatibility between BN and PEN matrix was studied by using SEM observation and rheology measurement. Furthermore, thermal conductivity of BN@SPEN/PEN films were carefully characterized. Thermal conductivity of BN@SPEN/PEN films was increased to 0.69 W/(m⋅K) at 20 wt% content of BN@SPEN, having 138% increment comparing with pure PEN.

A facile method to synthesize mussel-inspired polydopamine nanospheres as an active template for in situ formation of biomimetic hydroxyapatite

In this study, Mussel-inspired polydopamine (PDA) nanospheres were synthesized via spontaneous oxidative polymerization of dopamine hydrochloride (dopa-HCl) in a deionized water-alcohol mixed solvent at room temperature and atmospheric air, under alkaline condition. Field-emission scanning electron microscopy (FE-SEM) demonstrated production of sphere-like shape with a smooth surface and tunable size, while monodispersity increased by utilizing isopropanol instead of ethanol owing to lower R_a values based on Hansen solubility parameter (HSP) theory. Dropwise addition of monomer played an undeniable role in the fabrication of uniform and smaller spheres. The difference of the charge repulsion of constructs in the range of pH led to different dispersive behavior in a variety of solvents, exhibiting versatile applications. The presence of active functional groups on the surface of PDA spheres made them an appropriate option for PDA-assisted biomimetic mineralization of hydroxyapatite (HA), which is the result of the interaction between abundant catecholamine moieties in PDA and Ca⁺² ions in simulated body fluid. Bio-adhesive nature of PDA in water and the presence of amino and hydroxyl functional groups support desirable L929 mouse fibroblast cell spreading. The viability of >90% fibroblast cells proved the biocompatibility of polymerized structure. All the achievements indicated that PDA nanospheres provide a biocompatible and bioactive template for green synthesizing hydroxyapatite and the innovative basis for further tissue engineering applications.

Oxygen-plasma treatment-induced surface engineering of biomimetic polyurethane nanofibrous scaffolds for gelatin-heparin immobilization

Polyurethane (PU) has been extensively used in vascular tissue engineering due to its outstanding mechanical performance and blood compatibility behavior. Here, biomimetic PU-based scaffolds were prepared using an electrospinning technique and gelatin-heparin was introduced as a surface modifier after oxygen plasma treatment to improve cell attachment and release an anticoagulation agent. Morphology, Fourier transform infrared (FTIR) spectroscopy, compression strength, swelling and biodegradation ratio, drug release level and cellular interactions were evaluated. According to the scanning electron microscopy (SEM) micrographs, gelatin-heparin immobilized PU nanofibers exhibited a smooth surface and a bead free structure that nanofibers distributed in the range of 300–1000 nm. The mechanical strength of constructs, swelling and biodegradation ratio, and drug release level illustrated higher values for oxygen plasma-treated samples compared with bilayered scaffolds. Cellular adhesion and biocompatibility ameliorated after plasma treatment. All the mentioned findings indicated the initial physicomechanical and biological potential of biomimetic PU-based fibers in the improvements of vascular scaffolds.

Microwave-induced rapid formation of biomimetic hydroxyapatite coating on gelatin-siloxane hybrid microspheres in 10X-SBF solution

Bioactive materials can attract calcium and phosphate ions in simulated body fluid (SBF) solution to mimic the composition of extracellular matrix (ECM). Rapid biodegradation rate of natural polymers in contact with water-based solutions and time-consuming process of mineralization in SBF led to using concentrated simulated media. Herein, gelatin-siloxane microspheres were fabricated via single emulsion method. Then hybrid spheres were immersed in the modified 10X-SBF solution, and microwave energy (600 W) was expanded for the rapid formation of hydroxyapatite (HA) on the spheres. Results indicated homogeneous coating of microspheres and high similarity of synthesized HA to the bone composition. Increasing intensity of HA-related peaks in Fourier transform infrared spectrum, X-ray diffraction and surface roughness after utilizing microwave-assisted method confirmed high efficiency of this technique in biomimetic mineralization of structures. Cell culture studies with human osteosarcoma cell lines (MG-63) demonstrated that mineralized HA in 10X-SBF solution under microwave treatment could be able to mimic bone ECM for tissue regeneration applications in the shortest time and highest similarity to the natural tissue.

Electrospun nanofiber reinforced composites: a review

High performance electrospun nanofibers could be used to fabricate nanofiber reinforced composites.