Comprehensive Review on the Use of Graphene-Based Substrates for Regenerative Medicine and Biomedical Devices

MXenes as emerging materials to repair electroactive tissues and organs

Nanomaterials with electroactive properties have taken a big leap for tissue repair and regeneration due to their unique physiochemical properties and biocompatibility. MXenes, an emerging class of electroactive materials have generated considerable interest for their biomedical applications from bench to bedside. Recently, the application of these two-dimensional wonder materials have been extensively investigated in the areas of biosensors, bioimaging and repair of electroactive organs, owing to their outstanding electromechanical properties, photothermal capabilities, hydrophilicity, and flexibility. The currently available data reports that there is significant potential to employ MXene nanomaterials for repair, regeneration and functioning of electroactive tissues and organs such as brain, spinal cord, heart, bone, skeletal muscle and skin. The current review is the first report that compiles the most recent advances in the application of MXenes in bioelectronics and the development of biomimetic scaffolds for repair, regeneration and functioning of electroactive tissues and organs including heart, nervous system, skin, bone and skeletal muscle. The content in this article focuses on unique features of MXenes, synthesis process, with emphasis on MXene-based electroactive tissue engineering constructs, biosensors and wearable biointerfaces. Additionally, a section on the future of MXenes is presented with a focus on the clinical applications of MXenes.

Facile universal strategy of presenting multifunctional short peptides for customizing desired surfaces

Interfacial properties determine biomaterial performances, such as cell adhesion, signal exchange, and biomineralization, which affect the tissue repair cycle and efficiency of clinical applications. Peptides, as short protein sequences that have defined functionalities, are highly stable and easy to synthesize and have enormous potential to reshape interfacial properties. However, the lack of a universal strategy for presenting peptides on various substrates substantially hinders the application of peptides. In this study, we report a facile and universal strategy for customizing desired interfacial functionalities by a well-known layer-by-layer (LbL) technique through the assembly polyphenols with positively charged short peptide-coupling functional sequences. Polyphenol-peptide interactions were elucidated in detail by assembling polyphenols and peptides possessing different characteristics (charged, uncharged, hydrophobic, and sequence length) in combination with molecular dynamics simulations, and isothermal titration calorimetry further revealed the favorable enthalpy change due to electrostatic interactions is the main driving force for assembling peptides with polyphenols. LbL coatings assembled from polyphenols and positively charged peptides exhibited good substrate generalization, stability, cell proliferation, and antioxidant properties, when prepared as hollow capsules by sacrificing the template, exhibited significant pH and ultrasound stimulation responses, which could be suitable candidates for drug carriers. Most importantly, the LbL assembly strategy of positively charged peptides could be utilized to present various functional molecules (such as arginyl-glycyl-aspartic acid (RGD), a cell adhesion motif; CM15, an antibacterial peptide; and PEG, an antifouling surface) on various substrates for customizing desired surfaces. This study not only provides new insights into the understanding and regulation of interactions between proteins/peptides and polyphenols but also paves the way toward the interfacial functionalization of biomaterials.

Nanocarbon-Polymer Composites for Next-Generation Breast Implant Materials

Most breast implants currently used in both reconstructive and cosmetic surgery have a silicone outer shell, which, despite much progress, remains susceptible to mechanical failure, infection, and foreign body response. This study shows that the durability and biocompatibility of breast implant-grade silicone can be enhanced by incorporating carbon nanomaterials of sp2 and sp3 hybridization into the polymer matrix and onto its surface. Plasma treatment of the implant surface can be used to modify platelet adhesion and activation to prevent thrombosis, postoperative infection, and inflammation disorders. The addition of 0.8% graphene flakes resulted in an increase in mechanical strength by 64% and rupture strength by around 77% when compared to pure silicone, whereas when nanodiamond (ND) was used as the additive, the mechanical strength was increased by 19.4% and rupture strength by 37.5%. Composites with a partially embedded surface layer of either graphene or ND showed superior antimicrobial activity and biocompatibility compared to pure silicone. All composite materials were able to sustain the attachment and growth of human dermal fibroblast, with the preferred growth noted on ND-coated surfaces when compared to graphene-coated surfaces. Exposure of these materials to hydrogen plasma for 5, 10, and 20 s led to substantially reduced platelet attachment on the surfaces. Hydrogen-treated pure silicone showed a decrease in platelet attachment for samples treated for 5-20 s, whereas silicone composite showed an almost threefold decrease in platelet attachment for the same plasma treatment times. The absence of platelet activation on the surface of composite materials suggests a significant improvement in hemocompatibility of the material.

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Synergistic effects of graphene microgrooves and electrical stimulation on M2 macrophage polarization

Macrophages play a crucial role in host response and wound healing, with M2 polarization contributing to the reduction of foreign-body reactions induced by the implantation of biomaterials and promoting tissue regeneration. Electrical stimulation (ES) and micropatterned substrates have a significant impact on the macrophage polarization. However, there is currently a lack of well-established cell culture platforms for studying the synergistic effects of these two factors. In this study, we prepared a graphene free-standing substrate with 20 μm microgrooves using capillary forces induced by water evaporation. Subsequently, we established an ES cell culture platform for macrophage cultivation by integrating a self-designed multi-well chamber cell culture device. We observed that graphene microgrooves, in combination with ES, significantly reduce cell spreading area and circularity. Results from immunofluorescence, ELISA, and flow cytometry demonstrate that the synergistic effect of graphene microgrooves and ES effectively promotes macrophage M2 phenotypic polarization. Finally, RNA sequencing results reveal that the synergistic effects of ES and graphene microgrooves inhibit the macrophage actin polymerization and the downstream PI3K signaling pathway, thereby influencing the phenotypic transition. Our results demonstrate the potential of graphene-based microgrooves and ES to synergistically modulate macrophage polarization, offering promising applications in regenerative medicine.

Synthesis and characterization of hydroxyapatite self-assembled nanocomposites on graphene oxide sheets from seashell waste: A green process for regenerative medicine

Bone transplantation is the second most common transplantation surgery in the world. Therefore, there is an urgent need for artificial bone transplantation to repair bone defects. In bone tissue engineering, hydroxyapatite (HA) plays a major role in bone graft applications. This study deals with a facile method for synthesizing HA hexagonal nanorods from seashells by a solid-state hydrothermal transition process. The synthesized HA nanorods (∼2.29 nm) were reinforced with carbon nanotube and chitosan on graphene oxide sheets with polymeric support by in-situ synthetic approach. Among the synthesized nanocomposites viz., hydroxyapatite-graphene oxide (HA-GO), hydroxyapatite-graphene oxide-chitosan (HA-GO-CS), hydroxyapatite-graphene oxide-chitosan-carbon nanotube-polylactic acid (HA-GO-CS-CNT-PLA). Among them, the HA-GO-CS-CNT-PLA composite exhibits micro and macro porosity (∼200 to 600 μm), higher mechanical strength, (Hardness ∼90.5 ± 1.33 MPa; Tensile strength 25.62 MPa), and maximum cell viability in MG63 osteoblast-like cells (80%). The self-assembled hybrid-nanocomposite of HA-GO-CS-CNT-PLA is a promising material for bone filler application and could efficiently utilize seashell waste through the green process.

The effect of graphene and graphene oxide induced reactive oxygen species on polycaprolactone scaffolds for bone cancer applications

Bone cancer remains a critical healthcare problem. Among current clinical treatments, tumour resection is the most common strategy. It is usually effective but may present several limitations such as multiple operations, long hospital time, and the potential recurrence caused by the incomplete removal of cancer cells. To address these limitations, three-dimensional (3D) scaffolds fabricated through additive manufacturing have been researched for both bone cancer treatment and post-treatment rehabilitation. Polycaprolactone (PCL)-based scaffolds play an important role in bone regeneration, serving as a physical substrate to fill the defect site, recruiting cells, and promoting cell proliferation and differentiation, ultimately leading to the regeneration of the bone tissue without multiple surgical applications. Multiple advanced materials have been incorporated during the fabrication process to improve certain functions and/or modulate biological performances. Graphene-based nanomaterials, particularly graphene (G) and graphene oxide (GO), have been investigated both in vitro and in vivo, significantly improving the scaffold's physical, chemical, and biological properties, which strongly depend on the material type and concentration. A unique targeted inhibition effect on cancer cells was also discovered. However, limited research has been conducted on utilising graphene-based nanomaterials for both bone regeneration and bone cancer treatment, and there is no systematic study into the material- and dose-dependent effects, as well as the working mechanism on 3D scaffolds to realise these functions. This paper addresses these limitations by designing and fabricating PCL-based scaffolds containing different concentrations of G and GO and assessing their biological behaviour correlating it to the reactive oxygen species (ROS) release level. Results suggest that the ROS release from the scaffolds is a dominant mechanism that affects the biological behaviour of the scaffolds. ROS release also contributes to the inhibition effect on bone cancer due to healthy cells and cancer cells responding differently to ROS, and the osteogenesis results also present a certain correlation with ROS. These observations revealed a new route for realising bone cancer treatment and subsequent new bone regeneration, using a single dual-functional 3D scaffold.

Effect of anode material and dispersal limitation on the performance and biofilm community in microbial electrolysis cells

In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54-80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10-16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61-98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0-20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64-89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.

2D Materials for Combination Therapy to Address Challenges in the Treatment of Cancer

2D materials exhibit a variety of characteristics that make them appealing platforms for cancer treatment such as high drug loading capacity and photothermal and photodynamic properties. A key advantage of 2D material platforms for oncological applications is the ability to harness multiple modalities including drug delivery, photothermal therapy, photodynamic therapy, chemodynamic therapy, gene delivery, and immunotherapy approaches for improved efficacy. In this review, a comparison of the unique properties of different classes of 2D materials that enable their usage as platforms for multimodal therapy is provided. Further, the benefits and drawbacks of different platforms are also highlighted. Finally, current challenges and emerging opportunities for future development of 2D materials to further enable combination therapy and translation from the bench to clinical oncology applications are discussed.

Production of Reduced Graphene Oxide by Using Three Different Microorganisms and Investigation of Their Cell Interactions

Despite the huge and efficient functionalities of reduced graphene oxide (RGO) for bioengineering applications, the use of harsh chemicals and unfavorable techniques in their production remains a major challenge. Microbial production of reduced graphene oxide (RGO) using specific bacterial strains has gained interest as a sustainable and efficient method. The reduction of GO to RGO by selected bacterial strains was achieved through their enzymatic activities and resulted in the removal of oxygen functional groups from GO, leading to the formation of RGO with enhanced structural integrity. The use of microorganisms offers a sustainable approach, utilizing renewable carbon sources and mild reaction conditions. This study investigates the production of RGO using three different bacterial strains: Lactococcus lactis (L. Lactis), Lactobacillus plantarum (L. plantarum), and Escherichia coli (E. coli) and evaluates its toxicity for safe utilization. The aim is to assess the quality of the produced RGO and evaluate its toxicity for potential applications. Thus, this study focused on the microbial production of reduced graphene oxides well as the investigation of their cellular interactions. Graphite-derived graphene oxide was used as a starting material and microbially reduced GO products were characterized using the FTIR, Raman, XRD, TGA, and XPS methods to determine their physical and chemical properties. FTIR shows that the epoxy and some of the alkoxy and carboxyl functional groups were reduced by E. coli and L. lactis, whereas the alkoxy groups were mostly reduced by L. plantarum. The ID/IG ratio from Raman spectra was found as 2.41 for GO. A substantial decrease in the ratio as well as defects was observed as 1.26, 1.35, and 1.46 for ERGO, LLRGO, and LPRGO after microbial reduction. The XRD analysis also showed a significant reduction in the interlayer spacing of the GO from 0.89 to 0.34 nm for all the reduced graphene oxides. TGA results showed that reduction of GO with L. lactis provided more reduction than other bacteria and formed a structure closer to graphene. Similarly, analysis with XPS showed that L lactis provides the most effective reduction with a C/O ratio of 3.70. In the XPS results obtained with all bacteria, it was observed that the C/O ratio increased because of the microbial reduction. Toxicity evaluations were performed to assess the biocompatibility and safety of the produced RGO. Cell viability assays were conducted using DLD-1 and CHO cell lines to determine the potential cytotoxic effects of RGO produced by each bacterial strain. Additionally, apoptotic, and necrotic responses were examined to understand the cellular mechanisms affected by RGO exposure. The results indicated that all the RGOs have concentration-dependent cytotoxicity. A significant amount of cell viability of DLD-1 cells was observed for L. lactis reduced graphene oxide. However, the highest cell viability of CHO cells was observed for L. plantarum reduced graphene oxide. All reduced graphene oxides have low apoptotic and necrotic responses in both cell lines. These findings highlight the importance of considering the specific bacterial strain used in RGO production as it can influence the toxicity and cellular response of the resulting RGO. The toxicity and cellular response to the final RGO can be affected by the particular bacterial strain that is employed to produce it. This information will help to ensure that RGO is used safely in a variety of applications, including tissue engineering, drug delivery systems, and biosensors, where comprehension of its toxicity profile is essential.

Graphene Hollow Micropatterns via Capillarity-Driven Assembly for Drug Storage and Neural Cell Alignment

Electrical conductivity, cell-guided surface topology, and drug storage capacity of biomaterials are attractive properties for the repair and regeneration of anisotropic tissues with electrical sensitivity, such as nerves. However, designing and fabricating implantable biomaterials with all these functions remain challenging. Herein, we developed a freestanding graphene substrate with micropatterned surfaces by a simple templating method. Importantly, the raised surface micropatterns had an internal hollow structure. The morphology results showed that the template microgroove width and the graphene nanosheet size were important indicators of the formation of the hollow structures. Through real-time monitoring and theoretical analysis of the formation process, it was found that the main formation mechanism was the delamination and interlayer movement of the graphene nanosheets triggered by the evaporation-induced capillary force. Finally, we achieved the controlled release of loaded microparticles and promoted the orientation of rat dorsal root ganglion neurons by applying an electric field to the hollow micropatterns. This capillarity-induced self-assembly strategy paves the way for the development of high-performance graphene micropatterned films with a hollow structure that have potential for clinical application in the repair of nerve injury.

Biological Evaluation of Graphene Quantum Dots and Nitrogen-Doped Graphene Quantum Dots as Neurotrophic Agents

Over time, developments in nano-biomedical research have led to the creation of a number of systems to cure serious illnesses. Tandem use of nano-theragnostics such as diagnostic and therapeutic approaches tailored to the individual disease treatment is crucial for further development in the field of biomedical advancements. Graphene has garnered attention in the recent times as a potential nanomaterial for tissue engineering and regenerative medicines owing to its biocompatibility among the several other unique properties it possesses. The zero-dimensional graphene quantum dots (GQDs) and their nitrogen-doped variant, nitrogen-doped GQDs (N-GQDs), have good biocompatibility, and optical and physicochemical properties. GQDs have been extensively researched owing to several factors such as their size, surface charge, and interactions with other molecules found in biological media. This work briefly elucidates the potential of electroactive GQDs as well as N-GQDs as neurotrophic agents. In vitro investigations employing the N2A cell line were used to evaluate the effectiveness of GQDs and N-GQDs as neurotrophic agents, wherein basic investigations such as SRB assay and neurite outgrowth assay were performed. The results inferred from immunohistochemistry followed by confocal imaging studies as well as quantitative real-time PCR (qPCR) studies corroborated those obtained from neurite outgrowth assay. We have also conducted a preliminary investigation of the pattern of gene expression for neurotrophic and gliotrophic growth factors using ex vivo neuronal and mixed glial cultures taken from the brains of postnatal day 2 mice pups. Overall, the studies indicated that GQDs and N-GQDs hold prospect as a framework for further development of neuroactive compounds for relevant central nervous system (CNS) purposes.

Porous BCP ceramics with nanoscale whisker structure accelerate bone regeneration by regulating inflammatory response

Inflammation-induced by biomaterials is a critical event to determine the success and efficiency of tissue repair. Macrophages are a major population that participates the biomaterial induced inflammation. The response of macrophages depends on the characteristics of biomaterials, thus causing a cascade reaction in subsequent biological processes. In this study, porous biphase calcium phosphate (BCP) ceramics with the different surface structures were constructed to compare the effect of surface structure on bone generation potential, and further reveal the inflammation-involved mechanism. Our results demonstrated that macrophages on three ceramics showed distinct morphologies and spreading areas. The nanoscale whisker structure did induce more bone generation in the mice thigh muscle. The in vitro result revealed that nanoscale whisker structure could drive macrophage polarization towards M1-like phenotype, indicated by a higher expression of pro-inflammatory specific markers (iNOS and CCR7), and mass secretion of TNF-α. Further research indicated that additional TNF-α could promote the osteogenic differentiation of mesenchymal stem cells (MSCs). However, excess addition of TNF-α showed an opposite effect on the osteogenic differentiation of MSCs by initiating the NF-κB signaling pathway, which suppresses the osteogenesis process.

Functionally gradient three-dimensional graphene foam-based polymeric scaffolds for multilayered tissue regeneration

Physiological bioengineering of multilayered tissues requires an optimized geometric organization with comparable biomechanics. Currently, polymer-reinforced three-dimensional (3D) graphene foams (GFs) are gaining interest in tissue engineering due to their unique morphology, biocompatibility, and similarity to extracellular matrixes. However, the homogeneous reinforcement of single polymers throughout a GF matrix does not provide tissue-level organization. Therefore, a triple-layered structure is developed in a GF matrix to closely mimic native tissue structures of the periodontium of the teeth. The scaffold aims to overcome the issue of layer separation, which generally occurs in multilayered structures due to the poor integration of various layers. The 3D GF matrix was reinforced with a polycaprolactone (PCL), polyvinyl alcohol (PVA), and PCL-hydroxyapatite (HA) mixture, added sequentially, via spin coating, vacuum, and hot air drying. Later, PVA was dissolved to create a middle layer, mimicking the periodontal fibers, while the layers present on either side resembled cementum and alveolar bone, respectively. Scanning electron microscopy and micro-computed tomography revealed the structure of the scaffold with internal differential porosities. The nanoindentation and tensile testing demonstrated the closeness of mechanical properties to that of native tissues. The biocompatibility was assessed by the MTT assay with MG63 cells (human osteosarcoma cells) exhibiting high adhesion and proliferation rate inside the 3D architecture. Summing up, this scaffold has the potential for enhancing the regeneration of various multilayered tissues.

Application of Bone Marrow-Derived Macrophages Combined with Bone Mesenchymal Stem Cells in Dual-Channel Three-Dimensional Bioprinting Scaffolds for Early Immune Regulation and Osteogenic Induction in Rat Calvarial Defects

The host immune response to biomaterials is critical for determining scaffold fate and bone regeneration outcomes. Three-dimensional (3D) bioprinted scaffolds encapsulated with living cells can improve the inflammatory microenvironment and further accelerate bone repair. Here, we screened and adopted 8% methacrylamidated gelatin (GelMA)/1% methacrylamidated hyaluronic acid (HAMA) as the encapsulation system for rat bone marrow-derived macrophages (BMMs) and 3% Alginate/0.5 mg/mL graphene oxide (GO) as the encapsulation system for rat bone mesenchymal stem cells (BMSCs), thus forming a dual-channel bioprinting scaffold. The 8% GelMA/1% HAMA/3% Alginate/0.5 mg/mL GO (8/1/3/0.5) group could form a scaffold with a stable structure, good mechanical properties, and satisfied biocompatibility. When exploring the crosstalk between BMMs and BMSCs in vitro, we found that BMSCs could promote the polarization of BMMs to M2 type at the early stage, reduce the pro-inflammatory gene expression, and increase anti-inflammatory gene expression; conversely, BMMs can promote the osteogenic differentiation of BMSCs. In addition, in the model of rat calvarial defects, the dual-channel scaffold encapsulated with BMMs and BMSCs was more effective than the single-cell scaffold and the acellular scaffold. The paracrine of BMMs and BMSCs in the biodegradable dual-channel scaffold effectively promoted the M2-type polarization of macrophages in the microenvironment of early bone defects, avoided excessive inflammatory responses, and further promoted bone repair. In conclusion, our findings suggested that using 3D bioprinting to simultaneously encapsulate two primary cells of BMMs and BMSCs in a dual-channel system may be an effective way to promote bone repair from the perspective of early immune regulation and late induction of osteogenesis.

Multi-biofunctional graphene oxide-enhanced poly-L-lactic acid composite nanofiber scaffolds for ovarian function recovery of transplanted-tissue

In this study, we successfully constructed the new graphene oxide/poly-L-lactic acid (GO/PLLA) nanofiber scaffolds with a hydrophilic surface and porous network structure that were highly favorable for cell infiltration. When employed these new nanofiber scaffolds for a wide range of tissue engineering applications, it was expected to promote graft tissue survival and angiogenesis. The new GO/PLLA nanofiber scaffold with an appropriate concentration of 1.0 wt% was applied for the restoration of ovarian function and reserve in mice with primary ovarian insufficiency (POI). After co-transplanting the normal ovarian cortex loaded on these new nanomaterials into the in situ ovarian tissue of POI mice, the fusion of transplanted ovarian cortex with damaged ovarian tissue was improved, as well as the ovarian function and the follicle numbers. Moreover, angiogenesis was observed clearly and proved to exist in the transplanted tissue and nanomaterials, with the most conspicuous effect after co-transplantation with 1.0 wt% GO/PLLA nanofiber scaffold. In addition, nitric oxide (NO) production by phosphorylated endothelial nitric oxide synthase (p-eNOS) in vivo was proven to be involved in the effect of GO and PLLA on the improved survival rate of the transplanted ovarian cortex. This study provides a new method for the fertility preservation of ovarian tissue cryopreservation and transplantation, as well as a new strategy for the transplantation of other organs.

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.

Graphene-MoS2 polyfunctional hybrid hydrogels for the healing of transected Achilles tendon

Healing of injured tendon is a major clinical challenge in orthopaedic medicine, due to the poor regenerative potential of this tissue. Two-dimensional nanomaterials, as versatile scaffolds, have shown a great potential to support, trigger and accelerate the tendon regeneration. However, weak mechanical properties, poor functionality and low biocompatibility of these scaffolds as well as post-surgery infections are main drawbacks that limit their development in the higher clinical phases. In this work, a series of hydrogels consisting polyglycerol functionalized reduced graphene oxide (PG), polyglycerol-functionalized molybdenum disulfide (PMoS₂) and PG/PMoS₂ hybrid within the gelatin matrix are formulated in new scaffolds and their ability for the healing of injured Achilles tendon, due to their high mechanical properties, low toxicity, cell proliferation enhancement, and antibacterial activities is investigated. While scaffolds containing PG and PMoS₂ showed a moderate tendon regeneration and anti-inflammatory effect, respectively, their hybridization into PG/PMoS₂ demonstrated a synergistic healing efficiency. Along the same line, an accelerated return of tendon function with low peritendinous adhesion and low cross-sectional area in animal group treated with scaffold containing PG/PMoS₂ was observed. Taking advantage of the high biocompatibility, high strength, straightforward construction and fast tendon regeneration, PG/PMoS₂ can be used as a new scaffold for the future tissue engineering.

Engineering Tissues of the Central Nervous System: Interfacing Conductive Biomaterials with Neural Stem/Progenitor Cells

Conductive biomaterials provide an important control for engineering neural tissues, where electrical stimulation can potentially direct neural stem/progenitor cell (NS/PC) maturation into functional neuronal networks. It is anticipated that stem cell-based therapies to repair damaged central nervous system (CNS) tissues and ex vivo, "tissue chip" models of the CNS and its pathologies will each benefit from the development of biocompatible, biodegradable, and conductive biomaterials. Here, technological advances in conductive biomaterials are reviewed over the past two decades that may facilitate the development of engineered tissues with integrated physiological and electrical functionalities. First, one briefly introduces NS/PCs of the CNS. Then, the significance of incorporating microenvironmental cues, to which NS/PCs are naturally programmed to respond, into biomaterial scaffolds is discussed with a focus on electrical cues. Next, practical design considerations for conductive biomaterials are discussed followed by a review of studies evaluating how conductive biomaterials can be engineered to control NS/PC behavior by mimicking specific functionalities in the CNS microenvironment. Finally, steps researchers can take to move NS/PC-interfacing, conductive materials closer to clinical translation are discussed.

Graphene Oxide-Protein-Based Scaffolds for Tissue Engineering: Recent Advances and Applications

The field of tissue engineering is constantly evolving as it aims to develop bioengineered and functional tissues and organs for repair or replacement. Due to their large surface area and ability to interact with proteins and peptides, graphene oxides offer valuable physiochemical and biological features for biomedical applications and have been successfully employed for optimizing scaffold architectures for a wide range of organs, from the skin to cardiac tissue. This review critically focuses on opportunities to employ protein-graphene oxide structures either as nanocomposites or as biocomplexes and highlights the effects of carbonaceous nanostructures on protein conformation and structural stability for applications in tissue engineering and regenerative medicine. Herein, recent applications and the biological activity of nanocomposite bioconjugates are analyzed with respect to cell viability and proliferation, along with the ability of these constructs to sustain the formation of new and functional tissue. Novel strategies and approaches based on stem cell therapy, as well as the involvement of the extracellular matrix in the design of smart nanoplatforms, are discussed.

Highly Stable Buffer-Based Zinc Oxide/Reduced Graphene Oxide Nanosurface Chemistry for Rapid Immunosensing of SARS-CoV-2 Antigens

The widespread and long-lasting effect of the COVID-19 pandemic has called attention to the significance of technological advances in the rapid diagnosis of SARS-CoV-2 virus. This study reports the use of a highly stable buffer-based zinc oxide/reduced graphene oxide (bbZnO/rGO) nanocomposite coated on carbon screen-printed electrodes for electrochemical immuno-biosensing of SARS-CoV-2 nuelocapsid (N-) protein antigens in spiked and clinical samples. The incorporation of a salt-based (ionic) matrix for uniform dispersion of the nanomixture eliminates multistep nanomaterial synthesis on the surface of the electrode and enables a stable single-step sensor nanocoating. The immuno-biosensor provides a limit of detection of 21 fg/mL over a linear range of 1-10 000 pg/mL and exhibits a sensitivity of 32.07 ohms·mL/pg·mm² for detection of N-protein in spiked samples. The N-protein biosensor is successful in discriminating positive and negative clinical samples within 15 min, demonstrating its proof of concept used as a COVID-19 rapid antigen test.

Nanostructured Carbons: towards Soft-Bioelectronics, Biosensing and Theraputic Applications

Recently, nanostructured carbon-based soft bioelectronics and biosensors have received tremendous attention due to their outstanding physical and chemical properties. The ultrahigh specific surface area, high flexibility, lightweight, high electrical conductivity, and biocompatibility of 1D and 2D nanocarbons, such as carbon nanotubes (CNT) and graphene, are advantageous for bioelectronics applications. These materials improve human life by delivering therapeutic advancements in gene, tumor, chemo, photothermal, immune, radio, and precision therapies. They are also utilized in biosensing platforms, including optical and electrochemical biosensors to detect cholesterol, glucose, pathogenic bacteria (e. g., coronavirus), and avian leucosis virus. This review summarizes the most recent advancements in bioelectronics and biosensors by exploiting the outstanding characteristics of nanocarbon materials. The synthesis and biocompatibility of nanocarbon materials are briefly discussed. In the following sections, applications of graphene and CNTs for different therapies and biosensing are elaborated. Finally, the key challenges and future perspectives of nanocarbon materials for biomedical applications are highlighted.

Converging 2D Nanomaterials and 3D Bioprinting Technology: State-of-the-Art, Challenges, and Potential Outlook in Biomedical Applications

The development of next-generation of bioinks aims to fabricate anatomical size 3D scaffold with high printability and biocompatibility. Along with the progress in 3D bioprinting, 2D nanomaterials (2D NMs) prove to be emerging frontiers in the development of advanced materials owing to their extraordinary properties. Harnessing the properties of 2D NMs in 3D bioprinting technologies can revolutionize the development of bioinks by endowing new functionalities to the current bioinks. First the main contributions of 2D NMS in 3D bioprinting technologies are categorized here into six main classes: 1) reinforcement effect, 2) delivery of bioactive molecules, 3) improved electrical conductivity, 4) enhanced tissue formation, 5) photothermal effect, 6) and stronger antibacterial properties. Next, the recent advances in the use of each certain 2D NMs (1) graphene, 2) nanosilicate, 3) black phosphorus, 4) MXene, 5) transition metal dichalcogenides, 6) hexagonal boron nitride, and 7) metal-organic frameworks) in 3D bioprinting technology are critically summarized and evaluated thoroughly. Third, the role of physicochemical properties of 2D NMSs on their cytotoxicity is uncovered, with several representative examples of each studied 2D NMs. Finally, current challenges, opportunities, and outlook for the development of nanocomposite bioinks are discussed thoroughly.

Nanogold-Carried Graphene Oxide: Anti-Inflammation and Increased Differentiation Capacity of Mesenchymal Stem Cells

Graphene-based nanocomposites such as graphene oxide (GO) and nanoparticle-decorated graphene with demonstrated excellent physicochemical properties have worthwhile applications in biomedicine and bioengineering such as tissue engineering. In this study, we fabricated gold nanoparticle-decorated GO (GO-Au) nanocomposites and characterized their physicochemical properties using UV-Vis absorption spectra, FTIR spectra, contact angle analyses, and free radical scavenging potential. Moreover, we investigated the potent applications of GO-Au nanocomposites on directing mesenchymal stem cells (MSCs) for tissue regeneration. We compared the efficacy of as-prepared GO-derived nanocomposites including GO, GO-Au, and GO-Au (×2) on the biocompatibility of MSCs, immune cell identification, anti-inflammatory effects, differentiation capacity, as well as animal immune compatibility. Our results showed that Au-deposited GO nanocomposites, especially GO-Au (×2), significantly exhibited increased cell viability of MSCs, had good anti-oxidative ability, sponged the immune response toward monocyte-macrophage transition, as well as inhibited the activity of platelets. Moreover, we also validated the superior efficacy of Au-deposited GO nanocomposites on the enhancement of cell motility and various MSCs-derived cell types of differentiation including neuron cells, adipocytes, osteocytes, and endothelial cells. Additionally, the lower induction of fibrotic formation, reduced M1 macrophage polarization, and higher induction of M2 macrophage, as well as promotion of the endothelialization, were also found in the Au-deposited GO nanocomposites implanted animal model. These results suggest that the Au-deposited GO nanocomposites have excellent immune compatibility and anti-inflammatory effects in vivo and in vitro. Altogether, our findings indicate that Au-decorated GO nanocomposites, especially GO-Au (×2), can be a potent nanocarrier for tissue engineering and an effective clinical strategy for anti-inflammation.

Recent Advances in the Application of Two-Dimensional Nanomaterials for Neural Tissue Engineering and Regeneration

The complexity of the nervous system structure and function, and its slow regeneration rate, makes it more difficult to treat compared to other tissues in the human body when an injury occurs. Moreover, the current therapeutic approaches including the use of autografts, allografts, and pharmacological agents have several drawbacks and can not fully restore nervous system injuries. Recently, nanotechnology and tissue engineering approaches have attracted many researchers to guide tissue regeneration in an effective manner. Owing to their remarkable physicochemical and biological properties, two-dimensional (2D) nanomaterials have been extensively studied in the tissue engineering and regenerative medicine field. The great conductivity of these materials makes them a promising candidate for the development of novel scaffolds for neural tissue engineering application. Moreover, the high loading capacity of 2D nanomaterials also has attracted many researchers to utilize them as a drug/gene delivery method to treat various devastating nervous system disorders. This review will first introduce the fundamental physicochemical properties of 2D nanomaterials used in biomedicine and the supporting biological properties of 2D nanomaterials for inducing neuroregeneration, including their biocompatibility on neural cells, the ability to promote the neural differentiation of stem cells, and their immunomodulatory properties which are beneficial for alleviating chronic inflammation at the site of the nervous system injury. It also discusses various types of 2D nanomaterials-based scaffolds for neural tissue engineering applications. Then, the latest progress on the use of 2D nanomaterials for nervous system disorder treatment is summarized. Finally, a discussion of the challenges and prospects of 2D nanomaterials-based applications in neural tissue engineering is provided.

Functionalization of Graphene Oxide with Porphyrins: Synthetic Routes and Biological Applications

Among the available carbon nanomaterials, graphene oxide (GO) has been widely studied because of the possibility of anchoring different chemical species for a large number of applications, including those requiring water-compatible systems. This Review summarizes the state-of-the-art of synthetic routes used to functionalize GO, such as those involving multiple covalent and non-covalent bonds to organic molecules, functionalization with nanoparticles and doping. As a recent development in this field, special focus is given to the formation of nanocomposites comprising GO and porphyrins, and their characterization through spectroscopic techniques (such as UV-Vis, fluorescence, Raman spectroscopy), among others. The potential of such hybrid systems in targeted biological applications is also discussed, namely for cancer therapies relying on photodynamic and photothermal therapies and for the inhibition of telomerase enzyme. Lastly, some promising alternative materials to GO are presented to overcome current challenges of GO-based research and to inspire future research directions in this field.

Graphene Oxide Functionalized Double-Layered Patch with Anti-Adhesion Ability for Abdominal Wall Defects

Background

Effective repair of full-thickness abdominal wall defects requires a patch with sufficient mechanical strength and anti-adhesion characteristics to avoid the formation of hernias and intra-abdominal complications such as intestinal obstruction and fistula. However, patches made from polymers or bio-derived materials may not meet these requirements and lack the bionic characteristics of the abdominal wall.

Materials and Methods

In this study, we report a consecutive electrospun method for preparing a double-layer structured nanofiber membrane (GO-PCL/CS-PCL) using polycaprolactone (PCL), graphene oxide (GO) and chitosan (CS). To expand the bio-functions (angiogenesis/reducing reactive oxygen species) of the patch (GO-PCL/NAC-CS-PCL), N-acetylcysteine (NAC) was loaded for the repair of full-thickness abdominal wall defects (2×1.5cm) in rat model.

Results

The double-layered patch (GO-PCL/NAC-CS-PCL) showed excellent mechanical strength and biocompatibility. After 2 months, rats treated with the patch exhibited the desired repair effect with no hernia formation, less adhesion (adhesion score: 1.50±0.50, P<0.001) and more collagen deposition (percentage of collagen deposition: 34.94%±3.31%, P<0.001).

Conclusion

The double-layered nanomembranes presented in this study have good anti-hernia and anti-adhesion effects, as well as improve the microenvironment in vivo. It, therefore, holds good prospects for the repair of abdominal wall defects and provides a promising key as a postoperative anti-adhesion agent.

Investigations of Graphene and Nitrogen-Doped Graphene Enhanced Polycaprolactone 3D Scaffolds for Bone Tissue Engineering

Scaffolds play a key role in tissue engineering applications. In the case of bone tissue engineering, scaffolds are expected to provide both sufficient mechanical properties to withstand the physiological loads, and appropriate bioactivity to stimulate cell growth. In order to further enhance cell-cell signaling and cell-material interaction, electro-active scaffolds have been developed based on the use of electrically conductive biomaterials or blending electrically conductive fillers to non-conductive biomaterials. Graphene has been widely used as functioning filler for the fabrication of electro-active bone tissue engineering scaffolds, due to its high electrical conductivity and potential to enhance both mechanical and biological properties. Nitrogen-doped graphene, a unique form of graphene-derived nanomaterials, presents significantly higher electrical conductivity than pristine graphene, and better surface hydrophilicity while maintaining a similar mechanical property. This paper investigates the synthesis and use of high-performance nitrogen-doped graphene as a functional filler of poly(ɛ-caprolactone) (PCL) scaffolds enabling to develop the next generation of electro-active scaffolds. Compared to PCL scaffolds and PCL/graphene scaffolds, these novel scaffolds present improved in vitro biological performance.

Molecular Control of Interfacial Fibronectin Structure on Graphene Oxide Steers Cell Fate

The use of graphene-based materials (GBMs) for tissue-engineering applications has been growing exponentially because of the seemingly endless multifunctional and tunable physicochemical properties of graphene that can be exploited to influence cellular behavior. Despite many demonstrations wherein cell physiology has been modulated on different GBMs, a clear mechanism connecting the different physicochemical properties of GBMs to cell fate has remained elusive. In this work, we demonstrate how different GBMs can be used to bias cell fate in a multiscale study-starting from serum protein (fibronectin) adsorption and its molecular scale morphology, structure, and bioactivity and ending with stem cell response. Using heat to chemically reduce graphene oxide without changing physical properties, we show that graphene chemistry controls surface-adsorbed molecular conformation and morphology, epitope presentation, and stem cell attachment. Moreover, this subtle change in the protein structure was found to drive increased bone differentiation of stem cells, suggesting that the physicochemical properties of graphene biases cell fate by directly influencing the adsorbed protein structure and subsequent biochemical activity.

A Review on Recent Advancements of Graphene and Graphene-Related Materials in Biological Applications

Graphene is the most outstanding material among the new nanostructured carbonaceous species discovered and produced. Graphene’s astonishing properties (i.e., electronic conductivity, mechanical robustness, large surface area) have led to a deep change in the material science field. In this review, after a brief overview of the main characteristics of graphene and related materials, we present an extensive overview of the most recent achievements in biological uses of graphene and related materials.

Graphene: An Antibacterial Agent or a Promoter of Bacterial Proliferation?

Graphene materials (GMs) are being investigated for multiple microbiological applications because of their unique physicochemical characteristics including high electrical conductivity, large specific surface area, and robust mechanical strength. In the last decade, studies on the interaction of GMs with bacterial cells appear conflicting. On one side, GMs have been developed to promote the proliferation of electroactive bacteria on the surface of electrodes in bioelectrochemical systems or to accelerate interspecies electron transfer during anaerobic digestion. On the other side, GMs with antibacterial properties have been synthesized to prevent biofilm formation on membranes for water treatment, on medical equipment, and on tissue engineering scaffolds. In this review, we discuss the mechanisms and factors determining the positive or negative impact of GMs on bacteria. Furthermore, we examine the bacterial growth-promoting and antibacterial applications of GMs and debate their practicability.

Development of fluorescein isothiocyanate conjugated gellan gum for application of bioimaging for biomedical application

Herein, gellan gum (GG), a nature-derived polysaccharide, was applied to combine fluorescein isothiocyanate (FITC) to fabricate a bio-imaging material. The synthesis process of the FITC grafted GG (GG-F) and manufacturing method of GG-F scaffolds are presented. Chemical, physicochemical, and mechanical properties were characterized. In vitro study and in vivo study by implanting the GG-F scaffolds under the subcutaneous area of the nude mice were carried out to verify biocompatibility and safety of the material. The emission of the FITC was confirmed with high-resolution confocal laser scanning microscope (SR CLMS) and fluorescence in vivo imaging (FOBI). The results exhibited well-synthesized GG-F and the manufactured GG-F scaffolds showed similar property of GG scaffolds which confirms that the chemical modification does not affect the property of GG scaffolds. The in vitro and in vivo study exhibited biocompatibility of the GG-F material. Overall, the properly blended GG-F in GG did not influence the characteristics of the pristine GG except for the chemical property. Therefore, the GG-F can be applied for the future analysis in verifying the mechanism of GG characters and can be a promising candidate for bio-imaging.

Ultrathin Transition Metal Chalcogenide Nanosheets Synthesized via Topotactic Transformation for Effective Cancer Theranostics

Ultrathin transition metal chalcogenide (TMC) nanosheets with ultrahigh photothermal conversion efficiency (η) and excellent stability are strongly desired in the application of photothermal therapy (PTT). However, the current synthetic methods of ultrathin TMC nanosheets have issues in obtaining uniform morphology, good dispersion, and satisfactory PTT behavior. Herein, ultrathin nanosheets of CoFe-selenide (CFS) with a finely controlled structure were prepared via a topological structural transformation process from an ultrathin CoFe-layered double hydroxide (LDH) precursor, followed by surface modification with poly(ethylene glycol) (PEG). The as-prepared CFS-PEG nanosheets inherit the ultrathin morphology of CoFe-LDH and exhibit an outstanding photothermal performance with a η of 74.5%, which is the first rank level of reported two-dimensional (2D) TMC nanosheet materials. The CFS-PEG nanosheets possess a satisfactory photoacoustic (PA) imaging capability with an ultralow detection limit (5 ppm) and simultaneously superior T₂ magnetic resonance imaging (MRI) performance with a large transverse MR relaxivity value (r₂) of 347.7 mM^-1 s^-1. Moreover, in vitro and in vivo assays verify superior anticancer activity with a dramatic photoinduced cancer cell apoptosis and tumor ablation. Therefore, a successful paradigm is provided for rational design and preparation of ultrathin TMC nanosheets in this work, holding enormous potential in cancer theranostics.

Novel Poly(ɛ-caprolactone)/Graphene Scaffolds for Bone Cancer Treatment and Bone Regeneration

Scaffold-based bone tissue engineering is the most relevant approach for critical-sized bone defects. It is based on the use of three-dimensional substrates to provide the appropriate biomechanical environment for bone regeneration. Despite some successful results previously reported, scaffolds were never designed for disease treatment applications. This article proposes a novel dual-functional scaffold for cancer applications, comprising both treatment and regeneration functions. These functions are achieved by combining a biocompatible and biodegradable polymer and graphene. Results indicate that high concentrations of graphene enhance the mechanical properties of the scaffolds, also increasing the inhibition on cancer cell viability and proliferation.

Strong Reinforcement Effects in 2D Cellulose Nanofibril-Graphene Oxide (CNF-GO) Nanocomposites due to GO-Induced CNF Ordering

Nanocomposites from native cellulose with low 2D nanoplatelet content are of interest as sustainable materials combining functional and structural performance. Cellulose nanofibril-graphene oxide (CNF-GO) nanocomposite films are prepared by a physical mixing-drying method, with focus on low GO content, the use of very large GO platelets (2-45μm) and nanostructural characterization using synchrotron x-ray source for WAXS and SAXS. These nanocomposites can be used as transparent coatings, strong films or membranes, as gas barriers or in laminated form. CNF nanofibrils with random in-plane orientation, form a continuous non-porous matrix with GO platelets oriented in-plane. GO reinforcement mechanisms in CNF are investigated, and relationships between nanostructure and suspension rheology, mechanical properties, optical transmittance and oxygen barrier properties are investigated as a function of GO content. A much higher modulus reinforcement efficency is observed than in previous polymer-GO studies. The absolute values for modulus and ultimate strength are as high as 17 GPa and 250 MPa at a GO content as small as 0.07 vol%. The remarkable reinforcement efficiency is due to improved organization of the CNF matrix; and this GO-induced mechanism is of general interest for nanostructural tailoring of CNF-2D nanoplatelet composites.

3D Reduced Graphene Oxide Scaffolds with a Combinatorial Fibrous-Porous Architecture for Neural Tissue Engineering

Graphene oxide (GO) assists a diverse set of promising routes to build bioactive neural microenvironments by easily interacting with other biomaterials to enhance their bulk features or, alternatively, self-assembling toward the construction of biocompatible systems with specific three-dimensional (3D) geometries. Herein, we first modulate both size and available oxygen groups in GO nanosheets to adjust the physicochemical and biological properties of polycaprolactone-gelatin electrospun nanofibrous systems. The results show that the incorporation of customized GO nanosheets modulates the properties of the nanofibers and, subsequently, markedly influences the viability of neural progenitor cell cultures. Interestingly, the partially reduced GO (rGO) nanosheets with larger dimensions trigger the best cell response, while the rGO nanosheets with smaller size provoke an accentuated decrease in the cytocompatibility of the resulting electrospun meshes. Then, the most auspicious nanofibers are synergistically accommodated onto the surface of 3D-rGO heterogeneous porous networks, giving rise to fibrous-porous combinatorial architectures suitable for enhancing adhesion and differentiation of neural cells. By varying the chemical composition of the nanofibers, it is possible to adapt their performance as physical crosslinkers for the rGO sheets, leading to the modulation of both pore size and structural/mechanical integrity of the scaffold. Importantly, the biocompatibility of the resultant fibrous-porous systems is not compromised after 14 days of cell culture, including standard differentiation patterns of neural progenitor cells. Overall, in light of these in vitro results, the reported scaffolding approach presents not only an indisputable capacity to support highly viable and interconnected neural circuits but also the potential to unlock novel strategies for neural tissue engineering applications.

Recent advances in graphene monolayers growth and their biological applications: A review

Development of two-dimensional high-quality graphene monolayers has recently received great concern owing to their enormous applications in diverging fields including electronics, photonics, composite materials, paints and coatings, energy harvesting and storage, sensors and metrology, and biotechnology. As a result, various groups have successfully developed graphene layers on different substrates by using the chemical vapor deposition method and explored their physical properties. In this direction, we have focused on the state-of-the-art developments in the growth of graphene layers, and their functional applications in biotechnology. The review starts with the introduction, which contains outlines about the graphene and their basic characteristics. A brief history and inherent applications of graphene layers followed by recent developments in growth and properties are described. Then, the application of graphene layers in biodevices is reviewed. Finally, the review is summarized with perspectives and future challenges along with the scope for future technological applications.

Poly(Ethylene Glycol) Functionalized Graphene Oxide in Tissue Engineering: A Review on Recent Advances

Owing to the unique physical, chemical, mechanical and electrical properties, graphene and its derivatives have been extensively researched for diverse biomedical applications including in tissue engineering since the past decade. Tunable chemical functionalities of graphene oxide (GO), a graphene derivative, allow easy surface functionalization. Functionalization of GO with poly(ethylene glycol) (PEG) (PEG-GO) has received significant attention as it offers superior solubility, stability, and biocompatibility. Besides being an attractive candidate for drug delivery, PEG-GO can aid in the attachment, proliferation, and differentiation of stem cells, thereby augmenting tissue engineering. PEG-GO has shown excellent antibacterial efficacy, which could be an added advantage to minimize implant-associated infections. This review describes the synthesis techniques, properties, and biological potential of PEG-GO towards mammalian and bacterial cells. Studies wherein these nanomaterials have been explored for engineering various tissues are reviewed along with future opportunities in this field.

Graphene impregnated electrospun nanofiber sensing materials: a comprehensive overview on bridging laboratory set-up to industry

Owing to the unique structural characteristics as well as outstanding physio-chemical and electrical properties, graphene enables significant enhancement with the performance of electrospun nanofibers, leading to the generation of promising applications in electrospun-mediated sensor technologies. Electrospinning is a simple, cost-effective, and versatile technique relying on electrostatic repulsion between the surface charges to continuously synthesize various scalable assemblies from a wide array of raw materials with diameters down to few nanometers. Recently, electrospun nanocomposites have emerged as promising substrates with a great potential for constructing nanoscale biosensors due to their exceptional functional characteristics such as complex pore structures, high surface area, high catalytic and electron transfer, controllable surface conformation and modification, superior electric conductivity and unique mat structure. This review comprehends graphene-based nanomaterials (GNMs) (graphene, graphene oxide (GO), reduced GO and graphene quantum dots) impregnated electrospun polymer composites for the electro-device developments, which bridges the laboratory set-up to the industry. Different techniques in the base polymers (pre-processing methods) and surface modification methods (post-processing methods) to impregnate GNMs within electrospun polymer nanofibers are critically discussed. The performance and the usage as the electrochemical biosensors for the detection of wide range analytes are further elaborated. This overview catches a great interest and inspires various new opportunities across a wide range of disciplines and designs of miniaturized point-of-care devices.

In Vivo Disintegration and Bioresorption of a Nacre-Inspired Graphene-Silk Film Caused by the Foreign-Body Reaction

Graphene-based substrates are emerging as a promising functional platform for biomedical applications. Although dispersible graphene sheets have been demonstrated to be biodegradable, their assembled macroscopic architectures are biopersistent because of strong π-π interactions. In this study, we developed a nacre-inspired graphene-silk nanocomposite film by vacuum filtration with a subsequent green chemical reduction procedure. The "brick-and-mortar" architecture not only ensures the mechanical and electrical properties of the film but also endows it with disintegrable and bioresorbable properties following rat subcutaneous implantation. Furthermore, covalent cross-linking leads to the formation of graphene with decreased interlayer spacing, which effectively prolongs the residence time in vivo. We found that enzymatic treatment created microcracks on the film surface and that the foreign-body reaction was involved in the deformation, delamination, disintegration, and phagocytosis processes of the nanocomposite films. This bioinspired strategy paves the way for the development of high-performance graphene-based macroscopic biomaterials with tunable bioresorbability.

Delivery of Salvianolic Acid B for Efficient Osteogenesis and Angiogenesis from Silk Fibroin Combined with Graphene Oxide

The efficiency of drugs often hinges on drug carriers. To effectively transport therapeutic plant molecules, drug delivery carriers should be able to carry large doses of therapeutic drugs, enable their sustained release, and maintain their biological activity. Here, graphene oxide (GO) is demonstrated to be a valid carrier for delivering therapeutic plant molecules. Salvianolic acid B (SB), which contains a large number of hydroxyl groups, bound to the carboxyl groups of GO by self-assembly. Silk fibroin (SF) substrates were combined with functionalized GO through the freeze-drying method. SF/GO scaffolds could be loaded with large doses of SB, maintain the biological activity of SB while continuously releasing SB, and significantly promote the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs). SF/GO/SB also dramatically enhanced endothelial cell (EA-hy9.26) migration and tubulogenesis in vitro. Eight weeks after implantation of SF/GO/SB scaffolds in a rat cranial defect model, the defect area showed more new bone and angiogenesis than that following SF and SF/GO scaffold implantation. Therefore, GO is an effective sustained-release carrier for therapeutic plant molecules, such as SB, which can repair bone defects by promoting osteogenic differentiation and angiogenesis.