Graphene-based Hydrogel Research Articles

Graphene-Based Hydrogels for Controlled Drug Delivery: Opportunities and Challenges

Abstract: Graphene is a remarkable substance that has revolutionized numerous disciplines, including electronics, materials science, condensed physics, quantum physics, energy systems, and many more. Its physical and chemical properties have been the subject of a great deal of research since its 2004 discovery. Because of its unique properties, it has swiftly become a contender worth investigating for biomedical uses by nano-bio researchers. Studies on graphene and related materials have attracted a great deal of interest from the biomedical community in the last decade, with a focus on their potential applications in cancer treatment, smart drug delivery, and gene therapy. Graphene oxide (GO) has many desirable properties, including a high adsorption capacity, a big surface area, biocompatibility, and colloidal stability. To get around the problems with traditional treatment methods, researchers have been working on new drug delivery systems that include biocompatible polymers as nanocomposite carriers, a three- -dimensional (3D) hydrogel network, and controlled medication release. In this review, we compiled the latest findings from graphene's biomedical uses, took a look at the latest innovations in graphene-based hydrogels for medication delivery, and offered some exciting predictions for the future of this material's function in this field.

Novel Photothermal Graphene-Based Hydrogels in Biomedical Applications.

In the last decade, photothermal therapy (PTT) has attracted tremendous attention because it is non-invasive, shows high efficiency and antibacterial activity, and minimizes drug side effects. Previous studies demonstrated that PTT can effectively inhibit the growth of bacteria and promotes cell proliferation, accelerating wound healing and tissue regeneration. Among different NIR-responsive biomaterials, graphene-based hydrogels with photothermal properties are considered as the best candidates for biomedical applications, due to their excellent properties. This review summarizes the current advances in the development of innovative graphene-based hydrogels for PTT-based biomedical applications. Also, the information about photothermal properties and the potential applications of graphene-based hydrogels in biomedical therapies are provided. These findings provide a great potential for supporting their applications in photothermal biomedicine.

Adhesive, self-healing polydopamine/reduced graphene oxide composite hydrogel for self-powered application

ABSTRACT Graphene-based hydrogels have a broad application prospect in various fields due to their excellent adsorption, electrical conductivity, water retention, flexibility, etc. In this work, polydopamine/reduced graphene oxide (PDA/rGO) composite hydrogel was prepared using water bath heating. The prepared PDA/rGO hydrogel has high swelling ratio, good adhesiveness, and self-healing ability. Furthermore, the generation of electric current was observed when pressure was applied to the PDA/rGO hydrogel filled with NaCl solution, indicating the self-powered property of the hydrogel. The PDA/rGO hydrogel is self-powered because the negative groups on the hydrogel matrix attract cations from the NaCl solution, leaving mobile negative ions in the solution. The pressure-induced flow of liquid in the hydrogel' s nanochannels drives the migration of mobile ions through the channels, generating a net ionic flow. These properties of PDA/rGO hydrogel suggest that the material would be promising for power sources of wearable devices by harvesting ambient mechanical energy.

Graphene-based hydrogel silver nano-composites for antibacterial and antitumor applications: In vitro evaluation

Graphene-based hydrogel silver nano-composites for antibacterial and antitumor applications: In vitro evaluation

ROS Scavenging Graphene-Based Hydrogel Enhances Type H Vessel Formation and Vascularized Bone Regeneration via ZEB1/Notch1 Mediation.

The regeneration strategy for bone defects is greatly limited by the bone microenvironment, and excessive reactive oxygen species (ROS) seriously hinder the formation of new bone. Reduced graphene oxide (rGO) is expected to meet the requirements because of its ability to scavenge free radicals through electron transfer. Antioxidant hydrogels based on gelatine methacrylate (GM), acrylyl-β-cyclodextrin (Ac-CD), and rGO functionalized with β-cyclodextrin (β-CD) are developed for skull defect regeneration, but the mechanism of how rGO-based hydrogels enhance bone repair remains unclear. In this work, it is confirmed that the GM/Ac-CD/rGO hydrogel has good antioxidant capacity, and promotes osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and angiogenesis of human umbilical vein endothelial cells (HUVECs). The rGO-based hydrogel affects ZEB1/Notch1 to promote tube formation. Furthermore, two-photon laser scanning microscopy is used to observe the ROS in a skull defect. The rGO-based hydrogel promotes type H vessel formation in a skull defect. In conclusion, the hydrogel neutralizes ROS in the vicinity of a skull defect and stimulates ZEB1/Notch1 to promote the coupling of osteogenesis and angiogenesis, which may be a possible approach for bone regeneration.

Graphene-based hydrogel with embedded gold nanoparticles as a recyclable catalyst for the degradation of 4-nitrophenol

Hydrogels have been utilized as a sort of scaffold in catalytic field since they can offer good accommodation for noble metal nanoparticles (NPs) to the preparation of recyclable catalysts. In this work, the poly(4-vinylpyridine) (P4VP) grafted graphene oxide (GO) was firstly synthesized through surface-initiated atom transfer radical polymerization (SI−ATRP). Then, a tough and self-healable composite hydrogel was fabricated by integration of the P4VP-grafted GO into poly(acrylic acid) (PAA) matrix through hierarchically hydrogen-bonding interactions and simultaneous in-situ growth of gold nanoparticles (AuNPs) in the hydrogel scaffold. The as-prepared AuNPs@GO-g-P4VP/PAA composite hydrogel possesses improved mechanical strength and integrity, and exhibits higher catalytic activity in the reductive degradation of 4-nitrophenol into 4-aminophenol than other reported AuNPs-loaded hydrogel catalysts. In addition, the self-healing composite hydrogel catalyst shows ease of separation as well as good reusability without obvious loss of catalytic activity. This work provides an attractive method for the synthesis of robust functional nanoparticle-embedded composite hydrogel for application in various fields.

Nanoarchitectonics of the supercapacitor performance of LaNiO3 perovskite on the graphitic-C3N4 doped reduced graphene oxide hydrogel

Designing highly efficient, low-cost hybrid nanostructures with having favorable morphology and excellent conductivity is very promising for electrodes used in electrochemical storage devices. This study shows the synthesis of a new three-dimensional (3D) hybrid structure consisting of lanthanum nickel oxide (LaNiO3) perovskite, graphite carbon nitride (g-C3N4), and reduced graphene oxide hydrogel (RGOH) structures for the new hybrid supercapacitor (SC) application. The 3D hybrid structure, which is a new SC application, draws attention according to the specific capacitance (Cs) result for graphene-based hydrogel structure. For this purpose, while g-C3N4 is selected to plays an important role to increase the electrochemical activity of SC, the LaNiO3 perovskite structure is used to increase the discharge capacity of SC as well as to provide high discharge current and long cycle life. As a result of electrochemical studies, the superior capacitive performance of LaFeO3/g-C3N4@RGOH showed Cs and unique performance of 750.56 F g−1 at a current density of 1 A g–1. The 3D structure is used as anode material for fabricating symmetric two-electrode supercapacitor systems. Moreover, the LaFeO3/g-C3N4@RGOH materials display magnificent cyclic stability of 82% for 5000 cycles at a current density of 10 A g − 1, which claims the new material progress in the energy field.

Accessing effects of aliphatic dicarboxylic acid towards the physical and chemical changes in low temperature hydrothermally reduced graphene hydrogel

To date, studies pertaining the usage of aliphatic dicarboxylic acids (DCAs) in the preparation of graphene-based hydrogels are limited and mainly has been applied either as a reducing agent or cross-linkers. The modification of the hydrogels' properties can be achieved via the introduction of small amount of additive into the starting material, graphene oxide (GO). The facile synthetic protocol enables the impartation of desired properties to the graphene-based hydrogel as intended for their specific applications. In this study, the in-situ preparation of reduced graphene hydrogel (rGH) was carried out in the presence of a series of aliphatic DCAs namely oxalic acid (OA), malonic acid (MA), succinic acid (SA), glutaric acid (GA) and adipic acid (AA) in the GO reaction mixture via green hydrothermal method and freeze-drying. The as-prepared hydrogels were systematically characterized to probe the changes in their chemical and physical changes. Higher specific surface (SSA) of the hydrogel is obtained for shorter chain length DCAs. The FTIR and XPS results also indicated that shorter chain DCAs exhibited better reducing capability in the removal of oxygen functional groups. The C/O ratio obtained showed decrement with the increase in the chain length of the DCA. On the other hand, good dispersity was found for longer chain DCAs in polar solvent. Overall, this study should provide a comprehensive understanding on hydrothermally reduced graphene hydrogels prepared in the presence of dicarboxylic acids.

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.

Hydrothermally Reduced Graphene Hydrogel Intercalated with Divalent Ions for Dye Adsorption Studies

Fundamental studies involving divalent ion intercalated graphene-based hydrogel are still lacking in terms of their adsorption behavior towards dye pollutants. In this study, we prepared a self-assembled Mg2+ and Ca2+ intercalated reduced graphene hydrogel (rGH) using hydrothermal treatment to evaluate the intercalation impact on the adsorption capability towards cationic dyes, methylene blue and rhodamine B. The morphological, structural, thermal, and textural properties of the divalent ion intercalated reduced graphene hydrogels were studied using Fourier transform infrared spectrometer, thermogravimetric analysis, Raman spectroscopy, scanning electron microscope-energy dispersive spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area analysis, and X-ray diffraction. The increased adsorption capacity of the divalent ion intercalated reduced graphene-based hydrogels towards the dye molecules resulted from the increase in the specific surface area and pore volume due to the Mg2+ and Ca2+ bridging that formed spaces between the graphene sheets framework. Adsorption kinetics and the equilibrium adsorption isotherm were fitted by a pseudo-second-order alongside intraparticle diffusion kinetic models and Langmuir isotherm respectively. In addition, the divalent ion intercalated reduced graphene hydrogel showed good generation after three cycles of simultaneous adsorption.

A graphene-based hydrogel monolith with tailored surface chemistry for PFAS passive sampling.

Aquatic contamination by per- and polyfluorinated alkyl substances (PFAS) has attracted global attention due to their environmental and health concerns. Current health advisories and surface water regulatory limits require PFAS detection in the parts per trillion (ppt) range. One way to achieve those low detection limits is to use a reliable passive sampling-based monitoring tool for PFAS, as exists for numerous nonpolar persistent organic pollutants. Here we introduce a new graphene-based hydrogel monolith and describe its synthesis, chemical functionalization, property characterization, and testing as a PFAS equilibrium passive sampler. The graphene monoliths were self-assembled by hydrothermal treatment from graphene oxide (GO) aqueous dispersions to produce free standing cylinders of ~563 mm3 volume consisting of ~4 wt-% thin-walled porous graphene and ~96 wt-% water. The uptake of 23 PFAS was measured on the as-produced monoliths, and equilibrium partition coefficients (KSW), were derived for longer chain (C≥8) perfluoroalkyl acids (PFAA) and neutral precursors such as sulfonamides (log KSW range 1.9 - 3.6). To increase the KSW for shorter chain PFAA, the monoliths were chemically modified by a new diazonium-based grafting reaction that introduces positive surface charge without damage to the graphenic backbone. Introduction of benzylamine moieties through the diazonium intermediate switches zeta potential at pH 7 from -45mV (as-produced graphene) to + 5mV. This modification increased the sorption of short and middle chain PFAA by ten-fold (e.g. log KSW for PFBA increased from 1.3 to 2.2), thereby improving the functionality of the passive sampler device for a wider range of PFAS. Field deployments demonstrated that the graphene monoliths were capable of detecting key PFAS in the Delaware River.

Smart graphene-based hydrogel promotes recruitment and neural-like differentiation of bone marrow derived mesenchymal stem cells in rat skin.

Strategies to direct the differentiation of endogenous bone marrow derived mesenchymal stem cells (BMSCs) in vivo following recruitment to the injured site are critical to realizing the potential of stem cell-based therapies. But the differentiation efficiency of BMSCs remains limited without direction. Here we demonstrated a novel strategy to promote neuronal differentiation of BMSCs using cross-linked polyethylenimine (PEI) grafted graphene oxide (GO) as the enzyme responsive vector for delivering active genes to BMSCs. In vivo, a core-shell microfiber arrayed hydrogel with a chemokine (SDF-1α) and the cross-linked GO-PEI/pDNAs-bFGF microparticles incorporated into the shell and core, respectively, were constructed. The arrayed hydrogel was shown to recruit and stimulate the neural-like differentiation of BMSCs effectively by delivering the CXCL12 and GO-PEI/pDNAs-bFGF in a self-controlled manner. With this strategy, both in vitro and in vivo neuronal differentiation of BMSCs with function were accelerated significantly. The cross-linked GO-PEI mediated gene transfection together with a multi-functional microfiber arrayed hydrogel provide a translatable approach for endogenous stem cell-based regenerative therapy.

On-Demand Hydrophobic Drug Release Based on Microwave-Responsive Graphene Hydrogel Scaffolds.

Electromagnetically driven drug delivery systems stand out among stimulus-responsive materials due to their ability to release cargo on demand by remote stimulation, such as light, near infrared (NIR) or microwave (MW) radiation. MW-responsive soft materials, such as hydrogels, generally operate at 2.45 GHz frequencies, which usually involves rapid overheating of the scaffold and may affect tissue surrounding the target location. In contrast, 915 MHz MW penetrate deeper tissues and are less prone to induce rapid overheating. In order to circumvent these limitations, we present here for the first time a graphene-based hydrogel that is responsive to MW irradiation of ν=915 MHz. This system is a candidate soft scaffold to deliver a model hydrophobic drug. The graphene present in the hydrogel acts as a heat-sink and avoids overheating of the scaffold upon MW irradiation. In addition, the microwave trigger stimulates the in vitro delivery of the model drug, thus suggesting a remote and deep-penetrating means to deliver a drug from a delivery reservoir. Moreover, the MW-triggered release of drug was observed to be enhanced under acidic conditions, where the swelling state is maximum due to the swelling-induced pH-responsiveness of the hydrogel. The hybrid composite described here is a harmless means to deliver remotely a hydrophobic drug on demand with a MW source of 915 MHz. Potential use in biomedical applications were evaluated by cytotoxicity tests.

Study on Cost-Efficient Carbon Aerogel to Remove Antibiotics from Water Resources.

Because of pharmaceutical-emerging contaminants in water resources, there has been a significant increase in the antibiotic resistance in bacteria. Therefore, the removal of antibiotics from water resources is essential. Various antibiotics have been greatly studied using many different carbon-based materials including graphene-based hydrogels and aerogels. In this study, carbon aerogels (CAs) were synthesized from waste paper sources and their adsorption behaviors toward three antibiotics (hygromycin B, gentamicin, and vancomycin) were investigated, for which there exist a limited number of reports in the literature. The prepared CAs were characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and micro-computerized tomography (μ-CT). According to the μ-CT results, total porosity and open porosity were calculated as 90.80 and 90.76%, respectively. The surface area and surface-to-volume ratio were found as 795.15 mm2 and 16.79 mm–1, respectively. The specific surface area of the CAs was found as 104.2 m2/g. A detailed adsorption study was carried out based on different pH values, times, and analyte concentrations. The adsorption capacities were found as 104.16, 81.30, and 107.52 mg/g for Hyg B, Gen, and Van, respectively. For all three antibiotics, the adsorption behavior fits the Langmuir model. The kinetic studies showed that the system fits the pseudo-second-order kinetic model. The production of CAs, within the scope of this study, is safe, facile, and cost-efficient, which makes these green adsorbents a good candidate for the removal of antibiotics from water resources. This study represents the first antibiotic adsorption study based on CAs obtained from waste paper.

Construction of stretchable supercapacitors using graphene hybrid hydrogels and corrosion-resistant silver nanowire current collectors

For wearable electronics applications, developing stretchable materials and energy storages is crucial. Without improving the contact between components of an energy device, maintaining its electrochemical performance during large deformations is challenging. Here, our development of stretchable and chemically stable supercapacitors is introduced using (i) graphene-based hydrogels and (ii) silver-nanowire-based current collector (investing the percolation effect). The stretchable hydrogels are created via a green hydrothermal process using graphene oxide (GO) functionalized with a diol oligomer (enabling stretchability) and PEDOT:PSS (increasing conducitivity and capacitance). Importantly, the stretchable current collector is formed by an alternating sequence of spray-coating silver nanowires (Ag NWs) and GO nanoflakes to not only improve its stability towards elongation and acid corrosion in 0.5 M H3PO4 electrolyte (up to 3 days), but also decrease materials costs (<0.1 USD cm−2). The significance of our supercapacitor electrodes composed of the hydrogels and the current collector with H3PO4 electrolyte is their (i) specific capacitance of 75–108 F g−1 and (ii) notably retention of 70% after a cyclic stretching test (~10000 cycles, 40% elongation) and 60% after an additional cyclic charge-discharge test (3000 cycles). The results suggest that our stretchable hydrogels and corrosion-resistant current collector are promising for developing wearable energy devices.

Siloxene-reduced graphene oxide composite hydrogel for supercapacitors

• 3D oxygen-rich graphene-based hydrogel is developed for supercapacitors. • Layered siloxene is used to tailor the architecture and chemical nature of graphene. • Superior capacitance performance with excellent cycling stability is achieved. The electrochemical properties of graphene-based supercapacitor electrode materials are closely related to their architecture and chemical nature. Herein, the siloxene-reduced graphene oxide composite hydrogel (SGH) with modified three-dimensional (3D) hierarchical architecture and increased oxygen-containing functional groups are developed via intercalating small amount of layered siloxene between the reduced graphene oxide sheets by a one-step hydrothermal process. Siloxene serves as the “spacers” to form a three-dimensional structure with graphene, resulting in increased specific surface area. More importantly, siloxene is used to modify the surface chemical nature of graphene sheets by introducing additional oxygen-containing functional groups. The abundant oxygen-containing functional groups on SGH contribute to the pseudocapacitance and improve the wettability. Consequently, the proposed SGH exhibits a high specific capacitance of 520 F g −1 at 1 A g −1 in a three-electrode system in 1 M H 2 SO 4 electrolyte, which can be maintained for 76.9% even as the discharging current density increases up to 100 A g −1 . Moreover, excellent stability is achieved for SGH with approximately 96.3% retention of the initial specific capacitance value after 15,000 cycles at a high current density of 50 A g −1 . Furthermore, the assembled symmetrical supercapacitor of SGH//SGH delivers a high energy density of 24.5 Wh kg −1 at the power density of 399.6 W kg −1 . These imply that the siloxene-reduced graphene oxide composite hydrogel may be a promising electrode material for high-performance supercapacitors.

Performance of graphene-based hydrogel in oil removal using graphene oxide derived from powder and flake graphite

Graphene-based hydrogel had been formed by chemical reduction process of graphene oxide using ascorbic acid as a reducing agent in this study. Oil adsorption capacity of the hydrogels that were synthesized using different parameters, including type of graphene oxide feedstocks (powder or flake graphite), concentration of graphene oxide used (2 mg/mL or 5 mg/mL), as well as the amount of ascorbic acid added into the graphene oxide (5 grams or 8 grams), had been evaluated in this work. Fourier Transform Infrared Spectroscopy (FTIR) results showed that the oxygen-containing functional groups which were initially present in the graphene oxide could be removed or reduced to form the 3-dimensional π-π interactions hydrogel. In overall, hydrogel produced from flake graphene oxide with the use of higher concentration of graphene oxide (5 mg/mL) and the lower amount of ascorbic acid (5 g), showed the best performance in oil adsorption capacity. The hydrogel produced from these parameters showed the highest adsorption capacity of 7.90 g of oil adsorb per g of hydrogel. This study has provided useful information on the functional groups of graphene-based hydrogels in addition to their oil adsorption capability.

Stimuli-responsive graphene-based hydrogel driven by disruption of triazine hydrophobic interactions.

The study reported here concerns the preparation of a novel graphene-diaminotriazine (G-DAT) nanocomposite hydrogel for application in the drug delivery field. The hybrid nature of this material is founded on two key elements: the presence of the DAT backbone induced the formation of hydrophobic regions that allowed efficient loading of a series of drugs of increasing hydrophobicity (Metronidazole, Benzocaine, Ibuprofen, Naproxen and Imipramine), while simultaneously endowing swelling-induced pH-responsiveness to the hydrogel. Additionally, the incorporation of graphene was found to interfere with these hydrophobic domains through favourable non-covalent interactions, thus leading to the partial disruption of these aggregates. As a consequence, graphene facilitated and enhanced the release of model hydrophobic drug Imipramine in a synergistic manner with the pH trigger, and increased the swelling capacities and improved mechanical performance. This hybrid hydrogel can therefore be envisaged as a proof-of-concept system for the release of hydrophobic compounds in the field of drug delivery.

Three-Dimensional Graphene-Based Composite Hydrogel Materials for Flexible Supercapacitor Electrodes.

Three-dimensional (3D) graphene-based hydrogels have attracted great interest for applying in supercapcacitors electrodes, owing to their intriguing properties that combine the structural interconnectivities and the outstanding properties of graphene. However, the pristine graphene hydrogel can not satisfy the high-performance demands, especial in high specific capacitance. Consequently, novel graphene-based composite hydrogels with increased electrochemical properties have been developed. In this mini review, a brief summary of recent progress in the research of the three-dimensional graphene-based composite hydrogel for flexible supercapacitors electrodes materials is presented. The latest progress in the graphene-based composite hydrogel consisting of graphene/metal, graphene/polymer, and atoms doped graphene is discussed. Furthermore, future perspectives and challenges in graphene-based composite hydrogel for supercapacitor electrodes are also expressed.

Preparation of composite graphene hydrogels adsorbent with special-shaped ZnO and TiO2

Graphene-based hydrogels (GH) have exhibited prominent performances in wastewater treatment. Herein, Special-shaped ZnO tetrapods and TiO2 nanosheets were introduced to the preparation of GH via a one-step hydrothermal reduction method. The ZnO-GH and TiO2-GH composite hydrogel with a uniform 3D network structure and good mechanical properties can be used as an adsorbent for printing and dyeing wastewater. The optimum doping amount of ZnO and TiO2 in the composite hydrogel and the adsorption regularity to rhodamine B (RhB) with different concentrations were discussed. The cyclic adsorption performance and adsorption kinetics were briefly discussed. When the doping ratio of ZnO to graphene oxide (GO) is 5:8, ZnO-GH has the best adsorption rate, which is 71.7%. The best degradation rate appears at a ZnO doping ratio of 1:2, which also shows the best total removal rate of RhB of approximately 82.20%. When the doping ratio of TiO2 to GO is 3:4, the photocatalytic degradation rate is 30.3%, and the total removal rate of RhB reaches 99.1%, which indicates that RhB can be almost completely removed by TiO2-GH through adsorption and degradation. After five cycles, the adsorption capacity of ZnO-GH and TiO2-GH for the low RhB concentration is still good. The addition of ZnO and TiO2 improves not only the adsorption and degradation properties of the composite hydrogel but also its recycling performance as a result of the increase in mechanical stability.