Graphene-based materials: an innovative approach for neural regeneration and spinal cord injury repair

Spinal cord injury (SCI), the most serious disease affecting the central nervous system (CNS), is one of contemporary medicine's most difficult challenges, causing patients to suffer physically, emotionally, and socially. However, due to recent advances in medical science and biomaterials, graphene-based materials (GBMs) have tremendous potential in SCI therapy due to their wonderful and valuable properties, such as physicochemical properties, extraordinary electrical conductivity, distinct morphology, and high mechanical strength. This review discusses SCI pathology and GBM characteristics, as well as recent in vitro and in vivo findings on graphenic scaffolds, electrodes, and injectable achievements for SCI improvement using neuroprotective and neuroregenerative techniques to improve neural structural and functional repair. Additionally, it suggests possible ideas and desirable products for graphene-based technological advances, intending to reach therapeutic importance for SCI.

Upgrading skin barrier Protection: Addition of active ingredients to a Gelatin/Tannic Acid-Based hydrogel patch for treating skin lesions related to Personal protective Equipment

Prolonged use of Personal Protective Equipment, like surgical masks, can cause skin issues such as acne ("maskne") and rosacea flare-ups due to pressure and moisture. While dressings can protect the skin, they often reduce mask effectiveness and lack pharmaceuticals to treat common skin lesions. This study introduces an innovative dual-function gelatin/tannic acid-based hydrogel patch incorporating metronidazole (1% w/w) or salicylic acid (2% w/w) to offer both skin protection and treatment. The hydrogels were characterized for gelation temperature, burst strength, extensibility, adhesivity, and tribological properties to assess the effects of the active ingredients on their mechanical performance. In vitro release studies using Franz diffusion cells under occlusive conditions evaluated the drug release profile from the patches. Results showed that gelatin/tannic acid and gelatin/tannic acid-metronidazole hydrogels had similar gelation temperatures (41.65 ± 1.95 °C), while the salicylic acid formulation exhibited a lower gelation temperature (33.24 ± 0.40 °C). Adhesivity improved with the addition of active ingredients, increasing by about 0.5 N, and burst strength significantly increased with metronidazole (about 6 N). Both formulations demonstrated enhanced extensibility and were suitable for all skin types in tribological studies. The in vitro release studies showed an initial burst release followed by controlled release, unaffected by mask placement. These findings suggest that dual-function hydrogel patches could provide effective skin protection and improve skin health during prolonged mask use, offering a promising solution for conditions like "maskne" and rosacea.

Hofmeister effect-based soaking strategy for gelatin hydrogels with adjustable gelation temperature, mechanical properties, and ionic conductivity

As a natural polymer with good biocompatibility, gelatin hydrogel has been widely used in the field of biomedical science for a long time. However, the lack of suitable gelation temperature and mechanical properties often limit the clinical applicability in diverse and complex environments. Here, we proposed a strategy based on the Hofmeister effect that gelatin hydrogels were soaked in the appropriate concentration of sodium sulfate solution, and the change in molecular chain interactions mainly guided by kosmotropic ions resulted in a comprehensive adjustment of multiple properties. A series of gelatin hydrogels treated with different concentrations of the salt solution gave rise to microstructural changes, which brought a decrease in the number and size of pores, a wide range of gelation temperature from 32 °C to 46 °C, a stress enhancement of about 40 times stronger to 0.8345 MPa, a strain increase of about 7 times higher to 238.05 %, and a certain degree of electrical conductivity to be utilized for versatile applications. In this regard, for example, we prepared microneedles and obtained a remarkable compression (punctuation) strength of 0.661 N/needle, which was 55 times greater than those of untreated ones. Overall, by integrating various characterizations and suggesting the corresponding mechanism behind the phenomenon, this method provides a simpler and more convenient performance control procedure. This allowed us to easily modulate the properties of the hydrogel as per the intended purpose, revealing its vast potential applications such as smart sensors, electronic skin, and drug delivery.

"Salting out" in Hofmeister Effect Enhancing Mechanical and Electrochemical Performance of Amide-based Hydrogel Electrolytes for Flexible Zinc-Ion Battery

With the development of flexible and wearable electronic devices, it is a new challenge for polymer hydrogel electrolytes to combine high mechanical flexibility and electrochemical performance into one membrane. In general, the high content of water in hydrogel electrolyte membranes always leads to poor mechanical strength, and limits their applications in flexible energy storage devices. In this work, based on the "salting out" phenomenon in Hofmeister effect, a kind of gelatin-based hydrogel electrolyte membrane is fabricated with high mechanical strength and ionic conductivity by soaking pre-gelated gelatin hydrogel in 2 m ZnSO₄ aqueous. Among various gelatin-based electrolyte membranes, the gelatin-ZnSO₄ electrolyte membrane delivers the "salting out" property of Hofmeister effect, which improves both the mechanical strength and electrochemical performance of gelatin-based electrolyte membranes. The breaking strength reaches 1.5 MPa. When applied to supercapacitors and zinc-ion batteries, it can sustain over 7500 and 9300 cycles for repeated charging and discharging processes. This study provides a very simple and universal method to prepare polymer hydrogel electrolytes with high strength, toughness, and stability, and its applications in flexible energy storage devices provide a new idea for the construction of secure and stable flexible and wearable electronic devices.

Graphdiyne oxide elicits a minor foreign-body response and generates quantum dots due to fast degradation

Graphdiyne (GDY) is a novel two-dimensional (2D) carbon allotrope that has attracted much attention in materials, physics, chemistry, and microelectronics for its excellent properties. Much effort has been devoted to exploring the biomedical applications of GDY in 2D carbon nanomaterials, especially for smart drugs and gene delivery. However, few studies have focused on the biocompatibility and potential environmental hazards of GDY and its derivatives. In this study, graphdiyne oxide (GDYO) and graphene oxide (GO) were obtained using different oxidation methods. Their cytotoxicity and hemolysis in vitro and biocompatibility in subcutaneous and peritoneal locations in vivo were compared. GDYO had very low biotoxicity in vitro and was moderately biocompatible in the muscle and abdominal cavity in vivo. Highly oxidized products and graphdiyne quantum dots (GDQDs) were observed in peritoneal cells. GDYO had better biocompatibility and its sheet size was easily diminished through oxidative degradation. Therefore, GDYO is a good candidate for use in 2D carbon nanomaterials in biomedicine.

A Review on Synthesis Methods of Phyllosilicate- and Graphene-Filled Composite Hydrogels

This review discusses, in brief, the various synthetic methods of two widely-used nanofillers; phyllosilicate and graphene. Both are 2D fillers introduced into hydrogel matrices to achieve mechanical robustness and water uptake behavior. Both the fillers are inserted by physical and chemical gelation methods where most of the chemical gelation, i.e., covalent approaches, results in better physical properties compared to their physical gels. Physical gels occur due to supramolecular assembly, van der Waals interactions, electrostatic interactions, hydrophobic associations, and H-bonding. For chemical gelation, in situ radical triggered gelation mostly occurs.

Graphene oxide modulates inter-particle interactions in 3D printable soft nanocomposite hydrogels restoring magnetic hyperthermia responses

Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications.

Injectable nanocomposite hydrogels as an emerging platform for biomedical applications: A review

Hydrogels have attracted much attention for biomedical and pharmaceutical applications due to the similarity of their biomimetic structure to the extracellular matrix of natural living tissues, tunable soft porous microarchitecture, superb biomechanical properties, proper biocompatibility, etc. Injectable hydrogels are an exciting type of hydrogels that can be easily injected into the target sites using needles or catheters in a minimally invasive manner. The more comfortable use, less pain, faster recovery period, lower costs, and fewer side effects make injectable hydrogels more attractive to both patients and clinicians in comparison to non-injectable hydrogels. However, it is difficult to achieve an ideal injectable hydrogel using just a single material (i.e., polymer). This challenge can be overcome by incorporating nanofillers into the polymeric matrix to engineer injectable nanocomposite hydrogels with combined or synergistic properties gained from the constituents. This work aims to critically review injectable nanocomposite hydrogels, their preparation methods, properties, functionalities, and versatile biomedical and pharmaceutical applications such as tissue engineering, drug delivery, and cancer labeling and therapy. The most common natural and synthetic polymers as matrices together with the most popular nanomaterials as reinforcements, including nanoceramics, carbon-based nanostructures, metallic nanomaterials, and various nanosized polymeric materials, are highlighted in this review.

A thermo-sensitive chitosan/pectin hydrogel for long-term tumor spheroid culture

Hydrogels represent a key element in the development of in vitro tumor models, by mimicking the typical 3D tumor architecture in a physicochemical manner and allowing the study of tumor mechanisms. Here we developed a thermo-sensitive, natural polymer-based hydrogel, where chitosan and pectin were mixed and, after a weak base-induced chitosan gelation, a stable semi-Interpenetrating Polymer Network formed. This resulted thermo-responsive at 37 °C, injectable at room temperature, stable up to 6 weeks in vitro, permeable to small/medium-sized molecules (3 to 70 kDa) and suitable for cell-encapsulation. Tunable mechanical and permeability properties were obtained by varying the polymer content. Optimized formulations successfully supported the formation and growth of human colorectal cancer spheroids up to 44 days of culture. The spheroid dimension and density were influenced by the semi-IPN stiffness and permeability. These encouraging results would allow the implementation of faithful tumor models for the study and development of personalized oncological treatments.

Osteoinductive and antimicrobial mechanisms of graphene-based materials for enhancing bone tissue engineering

Graphene-based materials (GMs) have great application prospects in bone tissue engineering due to their osteoinductive ability and antimicrobial activity. GMs induce osteogenic differentiation through several mechanisms and pathways in bone tissue engineering. First of all, the surface and high hardness of the porous folds of graphene or graphene oxide (GO) can generate mechanical stimulation to initiate a cascade of reactions that promote osteogenic differentiation without any chemical inducers. In addition, change of the extracellular matrix (ECM), regulation of macrophage polarization, the oncostatin M (OSM) signaling pathway, the MAPK signaling pathway, the BMP signaling pathway, the Wnt/β-catenin signaling pathway, and other pathways are involved in GMs' regulation of osteogenesis. In bone tissue engineering, GMs prevent the formation of microbial biofilms mainly through preventing microbial adhesion and killing them. The former is mainly achieved by reducing surface free energy (SFE) and increasing hydrophobicity. The latter mainly includes oxidative stress and photothermal/photodynamic effects. Graphene and its derivatives (GDs) are mainly combined with bioactive ceramic materials, metal materials and macromolecular polymers to play an antimicrobial effect in bone tissue engineering. Concentration, number of layers, and type of GDs often affect the antimicrobial activity of GMs. In this paper, we reviewed relevant osteoinductive and antimicrobial mechanisms of GMs and their applications in bone tissue engineering.

In situ formation of nanocomposite double-network hydrogels with shear-thinning and self-healing properties

Nanocomposite double-network hydrogels (ncDN hydrogels) are recently introduced to address the limitations of traditional DN hydrogels, such as the lack of diversity in the network structure and the restricted functionalities. However, two challenges remain, including the time-consuming preparation and the lack of shear-thinning and self-healing properties. Here, our approach to developing versatile ncDN hydrogels is through the use of multiple interfacial crosslinking chemistries (i.e., noncovalent interactions of electrostatic interaction and hydrogen bonds as well as dynamic covalent interactions of imine bonds and boronate ester bonds) and surface functionalized nanomaterials (i.e. phenylboronic acid modified reduced graphene oxide (PBA-rGO)). PBA-rGO was used as a multivalent gelator to further crosslink the two polymer chains (i.e. triethylene glycol-grafted chitosan (TEG-CS) and polydextran aldehyde (PDA)) in DN hydrogels, forming the TEG-CS/PDA/PBA-rGO ncDN hydrogels in seconds. The microstructures (i.e. pore size) and properties (i.e. rheological, mechanical, and swelling properties) of the ncDN hydrogels can be simply modulated by changing the amount of PBA-rGO. The dynamic bonds in the polymeric network provided the shear-thinning and self-healing properties to the ncDN hydrogels, allowing the hydrogels to be injected and molded into varied shapes as well as self-repair the damaged structure. Besides, the designed TEG-CS/PDA/PBA-rGO ncDN hydrogels were cytocompatible and also exhibited antibacterial activity. Taken together, we hereby provide a nanomaterial approach to fabricate a new class of ncDN hydrogels with tailorable networks and favorite properties for specific applications.

Graphene Integrated Hydrogels Based Biomaterials in Photothermal Biomedicine

Recently, photothermal therapy (PTT) has emerged as one of the most promising biomedical strategies for different areas in the biomedical field owing to its superior advantages, such as being noninvasive, target-specific and having fewer side effects. Graphene-based hydrogels (GGels), which have excellent mechanical and optical properties, high light-to-heat conversion efficiency and good biocompatibility, have been intensively exploited as potential photothermal conversion materials. This comprehensive review summarizes the current development of graphene-integrated hydrogel composites and their application in photothermal biomedicine. The latest advances in the synthesis strategies, unique properties and potential applications of photothermal-responsive GGel nanocomposites in biomedical fields are introduced in detail. This review aims to provide a better understanding of the current progress in GGel material fabrication, photothermal properties and potential PTT-based biomedical applications, thereby aiding in more research efforts to facilitate the further advancement of photothermal biomedicine.

In Situ Formation of 3D Conductive and Cell-Laden Graphene Hydrogel for Electrically Regulating Cellular Behavior

Electroconductive and injectable hydrogels are attracting increasing attention owing to the needs of electrically induced regulation of cell behavior, tissue engineering of electroactive tissues, and achieving minimum invasiveness during tissue repair. In this study, a novel in situ formed 3D conductive and cell-laden hydrogel is developed, which can be broadly used in bioprinting, tissue engineering, neuroengineering etc. An instantaneous, uniform spatial distribution and encapsulation of cells can be achieved as a result of hydrogen bonding induced hydrogel formation. Particularly, the cell-laden hydrogel can be easily obtained by simply mixing and shaking the polydopamine (PDA) functionalized rGO (rGO-PDA) with polyvinyl alcohol (PVA) solution containing cells. Graphene oxide is reduced and functionalized by dopamine to restore the electrical conductivity, while simultaneously enhancing both hydrophilicity and biocompatibility of reduced graphene oxide. In vitro culture of PC12 cells within the cell-laden hydrogel demonstrates its biocompatibility, noncytotoxicity as well as the ability to support long-term cell growth and proliferation. Enhanced neuronal differentiation is also observed, both with and without electrical stimulation. Overall, this 3D conductive, cell-laden hydrogel holds great promise as potential platform for tissue engineering of electroactive tissues.

Thermally Induced Switch of Coupling Reaction Using the Morphological Change of a Thermoresponsive Polymer on a Reactive Heteroarmed Nanoparticle

Control of the cross-linking reaction is imperative when developing a sophisticated in situ forming hydrogel in the body. In this study, a heteroarmed thermoresponsive (TR) nanoparticle was designed to investigate the mechanism of controlling reactivity of the functional groups introduced into the nanoparticles. The coupling reaction was suppressed/proceeded by utilizing temperature-induced morphological changes of the TR polymer. The heteroarmed TR nanoparticle was prepared by the coassembly of amphiphilic block copolymers possessing both a TR segment and hydrophilic segment with reactive functional groups of succinimide. The longer TR chain on the nanoparticle covered the succinimide group and suppressed the reaction with the primary amine on the external nanoparticle. In contrast, the coupling reaction was promoted at a high temperature to create the chemical cross-linking structure between the nanoparticles because of the exposure of the succinimide group on the surface of the particle as a consequence of the morphological change of the TR polymer. In addition, the thermally controlled chemical reaction modulated initiation of the gelation using a highly concentrated nanoparticle solution. The heteroarmed TR nanoparticle offers great practical advantages for clinical uses, such as embolization agents, through precise control of the reaction.

Nanomechanics of graphene oxide-bacteriophage based self-assembled porous composites

Graphene oxide, integrated with the filamentous bacteriophage M13, forms a 3D large-scale multifunctional porous structure by self-assembly, with considerable potential for applications. We performed Raman spectroscopy under pressure on this porous composite to understand its fundamental mechanics. The results show that at low applied pressure, the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$sp^2$$\end{document}sp2 bonds of graphene oxide stiffen very little with increasing pressure, suggesting a complicated behaviour of water intercalated between the graphene layers. The key message of this paper is that water in a confined space can have a significant impact on the nanostructure that hosts it. We introduced carbon nanotubes during the self-assembly of graphene oxide and M13, and a similar porous macro-structure was observed. However, in the presence of carbon nanotubes, pressure is transmitted to the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$sp^2$$\end{document}sp2 bonds of graphene oxide straightforwardly as in graphite. The electrical conductivity of the composite containing carbon nanotubes is improved by about 30 times at a bias voltage of 10 V. This observation suggests that the porous structure has potential in applications where good electrical conductivity is desired, such as sensors and batteries.

Bacterial Cellulose-Graphene Based Nanocomposites

Bacterial cellulose (BC) and graphene are materials that have attracted the attention of researchers due to their outstanding properties. BC is a nanostructured 3D network of pure and highly crystalline cellulose nanofibres that can act as a host matrix for the incorporation of other nano-sized materials. Graphene features high mechanical properties, thermal and electric conductivity and specific surface area. In this paper we review the most recent studies regarding the development of novel BC-graphene nanocomposites that take advantage of the exceptional properties of BC and graphene. The most important applications of these novel BC-graphene nanocomposites include the development of novel electric conductive materials and energy storage devices, the preparation of aerogels and membranes with very high specific area as sorbent materials for the removal of oil and metal ions from water and a variety of biomedical applications, such as tissue engineering and drug delivery. The main properties of these BC-graphene nanocomposites associated with these applications, such as electric conductivity, biocompatibility and specific surface area, are systematically presented together with the processing routes used to fabricate such nanocomposites.

Three-dimensional printing of black phosphorous/polypyrrole electrode for energy storage using thermoresponsive ink

Three-dimensional (3D) printing techniques bring the possibility of making electronic devices in any desired shape and dimensions. Here, we report on a printable black phosphorous nanosheet/polypyrrole composite ink for constructing a high-performance supercapacitor (SC) electrode. The printed BPNS/PPy electrode shows a good energy storage performance with a specific capacitance of up to 417 F g^-1 and an excellent cycling stability.

Composite Microgels Created by Complexation between Polyvinyl Alcohol and Graphene Oxide in Compressed Double-Emulsion Drops

Microgels, microparticles made of hydrogels, show fast diffusion kinetics and high reconfigurability while maintaining the advantages of hydrogels, being useful for various applications. Here, presented is a new microfluidic strategy for producing polymer-graphene oxide (GO) composite microgels without chemical cues or a temperature swing for gelation. As a main component of microgels, polymers that are able to form hydrogen bonds, such as polyvinyl alcohol (PVA), are used. In the mixture of PVA and GO, GO is tethered by PVA through hydrogen bonding. When the mixture is rapidly concentrated in the core of double-emulsion drops by osmotic-pressure-driven water pumping, PVA-tethered GO sheets form a nematic phase with a planar alignment. In addition, the GO sheets are linked by additional hydrogen bonds, leading to a sol-gel transition. Therefore, the PVA-GO composite remains undissolved when it is directly exposed to water by oil-shell rupture. These composite microgels can be also produced using poly(ethylene oxide) or poly(acrylic acid), instead of PVA. In addition, the microgels can be functionalized by incorporating other polymers in the presence of the hydrogel-forming polymers. It is shown that the multicomponent microgels made from a mixture of polyacrylamide, PVA, and GO show an excellent adsorption capacity for impurities.

Assembly and application advancement of organic-functionalized graphene-based materials: A review

Owing to the remarkable physicochemical properties such as hydrophobicity, conductivity, elasticity, and light weight, graphene-based materials have emerged as one of the most appealing carbon allotropes in materials science and chemical engineering. Unfortunately, pristine graphene materials lack functional groups for further modification, severely hindering their practical applications. To render graphene materials with special characters for different applications, graphene oxide or reduced graphene oxide has been functionalized with different organic agents and assembled together, via covalent binding and various noncovalent forces such as π-π interaction, electrostatic interaction, and hydrogen bonding. In this review, we briefly discuss the state-of-the-art synthetic strategies and properties of organic-functionalized graphene-based materials, and then, present the prospective applications of organic-functionalized graphene-based materials in sample preparation.

Metallic Fingerprints of Carbon: Label-Free Tracking and Imaging of Graphene in Plants

Detection and quantification of carbon nanomaterials are extremely challenging, especially under the background interference of carbon. Here, we propose a new label-free method to quantify, track, and in situ image graphene and graphene oxide (GO) in plants based on their inherent metallic impurities as fingerprints. We show the ubiquity and high stability of inherent metallic fingerprints of graphene and GO obtained from different exposure routes under the natural environments, which enables the materials to be easily quantified and in situ imaged by high-sensitivity (laser ablation) inductively coupled plasma mass spectrometry. The method was applied to investigate the uptake and spatial distribution of graphene and GO in soybean plants. The plants were cultivated in graphene or GO solutions for 7 days, and the indicative elements (Ni or Mn) in different parts of plants were monitored and imaged. We found that graphene and GO showed different distribution patterns in plants (the highest uptake percentages in root up to 14.4% for graphene and 47.8% for GO), and high concentration of material exposure might cause excessive accumulation of materials in roots which blocked their further transport to the other parts of plants. The present method is more straightforward, accessible, and economical than normally used isotopic or metal-labeling methods. It also avoids the uncertainties or alterations of properties caused by the labeling process and thus has great promise in analysis and risk assessment of carbon nanomaterials.

Graphene Oxide Enhances Chitosan-Based 3D Scaffold Properties for Bone Tissue Engineering

The main goal of bone tissue engineering (BTE) is to refine and repair major bone defects based on bioactive biomaterials with distinct properties that can induce and support bone tissue formation. Graphene and its derivatives, such as graphene oxide (GO), display optimal properties for BTE, being able to support cell growth and proliferation, cell attachment, and cytoskeleton development as well as the activation of osteogenesis and bone development pathways. Conversely, the presence of GO within a polymer matrix produces favorable changes to scaffold morphologies that facilitate cell attachment and migration i.e., more ordered morphologies, greater surface area, and higher total porosity. Therefore, there is a need to explore the potential of GO for tissue engineering applications and regenerative medicine. Here, we aim to promote one novel scaffold based on a natural compound of chitosan, improved with 3 wt.% GO, for BTE approaches, considering its good biocompatibility, remarkable 3D characteristics, and ability to support stem cell differentiation processes towards the bone lineage.

One-Step Preparation of a Highly Stretchable, Conductive, and Transparent Poly(vinyl alcohol)-Phytic Acid Hydrogel for Casual Writing Circuits

Conductive hydrogels have shown great potential applications in a wide variety of fields, including artificial intelligence devices and biomedical engineering. However, it still remains a great challenge to develop a facile and cost-effective approach to achieve a conductive hydrogel with favorable qualities. Herein, we have changed the traditional ingredient of poly(vinyl alcohol) (PVA) hydrogel by the addition of phytic acid (PA), which could yield a conductive hydrogel through one freeze-thaw cycle. The PVA-PA hydrogel holds several virtues including a large stretchability (about 1100% strain), excellent conductivity (1.34 kΩ cm), and high optical transparence (about 95%). By assembling the PVA-PA hydrogel into a wearable strain sensor, the gel-based sensor has shown good performance for the real-time monitoring of human daily activities and health conditions. Moreover, one formula of the PVA-PA sol ink could rapidly convert to the gel state just by being injected on a flexible substrate under an ice-bath, which would satisfy the demand of casual writing circuits. This one-step preparation method of the PVA-PA hydrogel may open an innovative avenue for the fabrication of easy-molding and functional hydrogels with only two components under mild ambient conditions.

Multifunctional graphene oxide-bacteriophage based porous three-dimensional micro-nanocomposites

Graphene, since its successful exfoliation and characterisation has been continuously drawing extensive research interests due to its potential for a broad range of applications ranging from energy, microelectronics, through polymer fillers and sensors to environmental and biomedical devices. Exploitation of its unique chemical and physical properties for the manufacturing of functional materials, requires careful structural control and scaling-up into three-dimensional morphologies. Here, a facile method is established to create and control the bottom-up self-assembly of graphene oxide nano-sheets via unprecedented integration with a highly versatile bio-ingredient, the filamentous bacteriophage M13, into hierarchical, three-dimensional, porous sponges of GraPhage13. This study explores the interplay of the GraPhage13 structure formation and studies the mechanisms that give rise to the controllable self-assembly. The straightforward fabrication of robust hierarchical micro-nano-architectures further lays a platform for applications in energy storage and conversion, catalysis and sensing.

Graphene Composites for Lead Ions Removal from Aqueous Solutions

The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed.

Nanocomposite Hydrogels: Advances in Nanofillers Used for Nanomedicine

The ongoing progress in the development of hydrogel technology has led to the emergence of materials with unique features and applications in medicine. The innovations behind the invention of nanocomposite hydrogels include new approaches towards synthesizing and modifying the hydrogels using diverse nanofillers synergistically with conventional polymeric hydrogel matrices. The present review focuses on the unique features of various important nanofillers used to develop nanocomposite hydrogels and the ongoing development of newly hydrogel systems designed using these nanofillers. This article gives an insight in the advancement of nanocomposite hydrogels for nanomedicine.

Translational Regenerative Therapies for Chronic Spinal Cord Injury

Spinal cord injury is a chronic and debilitating neurological condition that is currently being managed symptomatically with no real therapeutic strategies available. Even though there is no consensus on the best time to start interventions, the chronic phase is definitely the most stable target in order to determine whether a therapy can effectively restore neurological function. The advancements of nanoscience and stem cell technology, combined with the powerful, novel neuroimaging modalities that have arisen can now accelerate the path of promising novel therapeutic strategies from bench to bedside. Several types of stem cells have reached up to clinical trials phase II, including adult neural stem cells, human spinal cord stem cells, olfactory ensheathing cells, autologous Schwann cells, umbilical cord blood-derived mononuclear cells, adult mesenchymal cells, and autologous bone-marrow-derived stem cells. There also have been combinations of different molecular therapies; these have been either alone or combined with supportive scaffolds with nanostructures to facilitate favorable cell⁻material interactions. The results already show promise but it will take some coordinated actions in order to develop a proper step-by-step approach to solve impactful problems with neural repair.

An injectable and physical levan-based hydrogel as a dermal filler for soft tissue augmentation

A novel levan-based injectable hydrogel was developed as a dermal filler having better in vivo stability and efficacy compared to HA-based hydrogel.

Antimicrobial colloidal hydrogels assembled by graphene oxide and thermo-sensitive nanogels for cell encapsulation

Hydrogels are promising 3D materials that have demonstrated increasing applications in the encapsulation and delivery of drugs and cells. Herein we report an injectable colloidal hydrogel that directly assembled by graphene oxide (GO) and thermo-sensitive nanogels (tNG). The pH dependent hydrogen bonding interactions between the carboxyl and oxethyl groups induce the reversible assembly of GO and nanogels. The hydrogel is mouldable and can be shaped into different macroscopic objects, and the mechanical strengths are tunable with pH and temperature adjustment. The hybrid hydrogel by its own possesses high antibacterial activity, and demonstrates responsive drug release behaviour and high viability of 3D encapsulated cells. We expect this hybrid colloidal hydrogel can serve as an interesting scaffold for active cargo delivery and cell culture.

Considerations for Safe Innovation: The Case of Graphene

The terms "Safe innovation" and "Safe(r)-by-design" are currently popular in the field of nanotechnology. These terms are used to describe approaches that advocate the consideration of safety aspects already at an early stage of the innovation process of (nano)materials and nanoenabled products. Here, we investigate the possibilities of considering safety aspects during various stages of the innovation process of graphene, outlining what information is already available for assessing potential hazard, exposure, and risks. In addition, we recommend further steps to be taken by various stakeholders to promote the safe production and safe use of graphene.

Biosafety and Antibacterial Ability of Graphene and Graphene Oxide In Vitro and In Vivo

In recent years, graphene (G) and graphene oxide (GO) nanoparticles have begun to be applied in surgical implant surface modification. However, biosafety and antibacterial ability of G and GO are still unclear. In this study, the biosafety of G and GO in vitro was evaluated by co-culture with bone marrow mesenchymal stem cells (BMSCs) and biosafety in vivo was observed by implanting materials into mice muscle tissue. Biosafety results showed that 10 μg/ml was the safety critical concentration for G and GO. When the concentration was more than 10 μg/ml, the cytotoxicity of G and GO showed a dose-dependent manner.Antibacterial results showed that G presented the antibacterial ability with the concentration equal to and more than 100 μg/ml; GO presented the antibacterial ability with the concentration equal to and more than 50 μg/ml. The antibacterial effect of G and GO were in a dose-dependent manner in vitro.The GO or G concentration between 50 and 100 μg/ml may be the better range to keep the balance of cytotoxicity and antibacterial ability. Our study reveals that G and GO have potential to be used in clinic with good biosafety and antibacterial properties in a certain concentration range.

Toxicity of graphene-family nanoparticles: a general review of the origins and mechanisms

Due to their unique physicochemical properties, graphene-family nanomaterials (GFNs) are widely used in many fields, especially in biomedical applications. Currently, many studies have investigated the biocompatibility and toxicity of GFNs in vivo and in intro. Generally, GFNs may exert different degrees of toxicity in animals or cell models by following with different administration routes and penetrating through physiological barriers, subsequently being distributed in tissues or located in cells, eventually being excreted out of the bodies. This review collects studies on the toxic effects of GFNs in several organs and cell models. We also point out that various factors determine the toxicity of GFNs including the lateral size, surface structure, functionalization, charge, impurities, aggregations, and corona effect ect. In addition, several typical mechanisms underlying GFN toxicity have been revealed, for instance, physical destruction, oxidative stress, DNA damage, inflammatory response, apoptosis, autophagy, and necrosis. In these mechanisms, (toll-like receptors-) TLR-, transforming growth factor β- (TGF-β-) and tumor necrosis factor-alpha (TNF-α) dependent-pathways are involved in the signalling pathway network, and oxidative stress plays a crucial role in these pathways. In this review, we summarize the available information on regulating factors and the mechanisms of GFNs toxicity, and propose some challenges and suggestions for further investigations of GFNs, with the aim of completing the toxicology mechanisms, and providing suggestions to improve the biological safety of GFNs and facilitate their wide application.

Antimicrobial graphene family materials: Progress, advances, hopes and fears

Graphene-based materials have become very popular bionanotechnological instruments in the last few years. Since 2010, the graphene family materials have been recognized as worthy of attention due to its antimicrobial properties. Functionalization of graphene (or rather graphene oxide) surface creates the possibilities to obtain efficient antimicrobial agents. In this review, progress and advances in this field in the last few years are described and discussed. Special attention is devoted to materials based on graphene oxide in which specifically selected components significantly modify biological activity of this carbon structure. Short introduction concerns the physicochemical properties of the graphene family materials. In the section on antimicrobial properties, proposed mechanisms of activity against microorganisms are given showing enhanced action of nanocomposites also under light irradiation (photoinduced activity). Another important feature, i.e. toxicity against eukaryotic cells, is presented with up-to-date data. Taking into account all the information on the properties of the described materials and usefulness of the graphene family as antimicrobial agents, hopes and fears concerning their application are discussed. Finally, some examples of promising usage in medicine and other fields, e.g. in phytobiology and water remediation, are shown.

Toxicology of graphene-based nanomaterials

Graphene based nanomaterials possess remarkable physiochemical properties suitable for diverse applications in electronics, telecommunications, energy and healthcare. The human and environmental exposure to graphene-based nanomaterials is increasing due to advancements in the synthesis, characterization and large-scale production of graphene and the subsequent development of graphene based biomedical and consumer products. A large number of in vitro and in vivo toxicological studies have evaluated the interactions of graphene-based nanomaterials with various living systems such as microbes, mammalian cells, and animal models. A significant number of studies have examined the short- and long-term in vivo toxicity and biodistribution of graphene synthesized by variety of methods and starting materials. A key focus of these examinations is to properly associate the biological responses with chemical and morphological properties of graphene. Several studies also report the environmental and genotoxicity response of pristine and functionalized graphene. This review summarizes these in vitro and in vivo studies and critically examines the methodologies used to perform these evaluations. Our overarching goal is to provide a comprehensive overview of the complex interplay of biological responses of graphene as a function of their physiochemical properties.

Reversible Assembly of Graphitic Carbon Nitride 3D Network for Highly Selective Dyes Absorption and Regeneration

Responsive assembly of 2D materials is of great interest for a range of applications. In this work, interfacial functionalized carbon nitride (CN) nanofibers were synthesized by hydrolyzing bulk CN in sodium hydroxide solution. The reversible assemble and disassemble behavior of the as-prepared CN nanofibers was investigated by using CO2 as a trigger to form a hydrogel network at first. Compared to the most widespread absorbent materials such as active carbon, graphene and previously reported supramolecular gel, the proposed CN hydrogel not only exhibited a competitive absorbing capacity (maximum absorbing capacity of methylene blue up to 402 mg/g) but also overcame the typical deficiencies such as poor selectivity and high energy-consuming regeneration. This work would provide a strategy to construct a 3D CN network and open an avenue for developing smart assembly for potential applications ranging from environment to selective extraction.

A Universal Soaking Strategy to Convert Composite Hydrogels into Extremely Tough and Rapidly Recoverable Double-Network Hydrogels

Soak n' Boost: A universal strategy to manufacture hybrid double-network hydrogels with eminent mechanical properties is developed by postformation of the chitosan microcrystalline and chain-entanglement physical networks via simple treatment of the chitosan composite hydrogels using alkaline and saline solutions. The strategy may open an avenue to fabricate multifarious double-network hydrogels for promising applications in antifouling materials, drug delivery, and tissue engineering.

Novel Hydrogel Material as a Potential Embolic Agent in Embolization Treatments

We report a novel graphene-oxide (GO) enhanced polymer hydrogel (GPH) as a promising embolic agent capable of treating cerebrovascular diseases and malignant tumors, using the trans-catheter arterial embolization (TAE) technique. Simply composed of GO and generation five poly(amidoamine) dendrimers (PAMAM-5), our rheology experiments reveal that GPH exhibits satisfactory mechanical strength, which resist the high pressures of blood flow. Subcutaneous experiments on Sprague-Dawley (SD) rats demonstrate the qualified biocompatibility of GPH. Finally, our in vivo experiments on New Zealand rabbits, which mix GPH with the X-ray absorbing contrast agent, Iohexol, reveal complete embolization of the artery. We also note that GPH shortens embolization time and exhibits low toxicity in follow-up experiments. Altogether, our study demonstrates that GPH has many advantages over the currently used embolic agents and has potential applications in clinical practice.

An In Situ Gelling Drug Delivery System for Improved Recovery after Spinal Cord Injury

Therapeutic strategies for the spinal cord injury (SCI) are limited by the current available drug delivery techniques. Here, an in situ gelling drug delivery system (DDS), composed of a Poloxamer-407, a 188 mixture-based thermoresponsive hydrogel matrix and, an incorporated therapeutic compound (monosialoganglioside, GM1), is developed for SCI therapy. A low-thoracic hemisection in rats is used as SCI model to evaluate therapeutic efficiency. The GM1-incorporating Poloxamer-407 and 188 polymer solution is converted to a hydrogel (GM1-hydrogel) upon instillation to the injured spinal cord, due to the increased temperature. At body temperature, the thermoresponsive hydrogel prolongs the release of GM1 for about 1 month, due to the superposition of dissolution and swelling (anomalous transport) of the hydrogel matrix. The sustained release of the GM1-hydrogel enables the prolonged residence time of GM1 at the injured spinal cord, decreases the frequency of administration and, consequently, may improve patient compliance. After SCI, the administration of GM1-hydrogel to the lesion site inhibits the apoptotic cell death and glial scar formation, enhances the neuron regeneration, provides neuroprotection to the injured spinal cord, and improves the locomotor recovery. Overall, this study opens future perspectives for the treatment of SCI with a prolonged drug release DDS.