Graphene Family Nanomaterials Research Articles

Tetrel bonding on graphene

Many experimental detections and theoretical calculations have shown that the small molecules CO2, N2, CO, H2O and NH3 can be adsorbed on the graphene-family nanomaterials. The molecule CO2 can form tetrel bonds with N2, CO, H2O and NH3, respectively. Hence, it is significant to study the adsorption behavior of the tetrel bonding on graphene. In this work, the van der Waals-corrected density functional theory calculations have been carried out to study the adsorption behavior of the tetrel-bonded complexes CO2∙∙∙N2, CO2∙∙∙CO, CO2∙∙∙H2O and CO2∙∙∙NH3 on graphene. The results clearly show that, from a free state to the state on graphene, the length of the tetrel bond becomes longer and the strength of the tetrel bond becomes weaker, although the changes are not very large for both quantities. The energy decomposition analysis reveals that the effects of graphene on the tetrel bonds are largely dependent on both electrostatic and dispersion type interactions.

Graphene oxide induces p62/SQSTM-dependent apoptosis through the impairment of autophagic flux and lysosomal dysfunction in PC12 cells

Graphene oxide (GO), as a two-dimensional carbon nanosheet, has been extensively studied for potential biomedical applications due to its notable properties. Although a growing number of studies have investigated the adverse effects of GO nanosheets, the available toxicity data concerning GO’s effect on the neuronal cells remain highly limited. In this work, we systematically investigated the toxic responses of commercially available GO on a rat pheochromocytoma-derived PC12 cell line, which was an ideal in vitro model to study the neurotoxicity of GO. GO exerted a significant toxic effect on PC12 cells in a dose- and time-dependent manner. GO treatments under doses of 40, 50, and 60 μg/mL triggered an autophagic response and the blockade of autophagic flux via disrupting lysosome degradation capability. Caspase 9-mediated apoptosis was also observed in GO-treated cells. Moreover, GO-induced apoptosis was relevant to the aberrant accumulation of autophagy substrate p62/SQSTM. Inhibitionofthe accumulation of autophagic substrate alleviated GO-caused apoptotic cell death. Our findings raise a concern for the putative biomedical applications of GO in the form of diagnostic and therapeutic tools, where its systematic biocompatibility should be thoroughly explored. Statement of significanceGraphene oxide (GO) has attracted considerable interests in biomedical fields, which also resulted in numerous safety risks to human bodies. It is urgently required to establish a paradigm for accurately evaluating their adverse effects in biological systems. This study thoroughly explored the neurotoxicity of GO in PC12 cells. We found GO triggered an increased autophagic response and the impairment of autophagic flux, which was functionally involved in cell apoptosis. Inhibitionofexcessive accumulation of autophagic cargo attenuated apoptotic cell death. Our findings highlight deep considerations on the regulation mechanism of autophagy-lysosomes-apotosis-axis, which will contribute to a better understanding of the neurotoxicity of graphene-family nanomaterials, and provide a new insight in the treatment of cancer cells at nanoscale levels.

Electroactive Scaffolds for Neurogenesis and Myogenesis: Graphene-Based Nanomaterials.

One of the major issues in tissue engineering is constructing a functional scaffold to support cell growth and also provide proper synergistic guidance cues. Graphene-based nanomaterials have emerged as biocompatible and electroactive scaffolds for neurogenesis and myogenesis, due to their excellent tunable chemical, physical, and mechanical properties. This review first assesses the recent investigations focusing on the fabrication and applications of graphene-based nanomaterials for neurogenesis and myogenesis, in the form of either 2D films, 3D scaffolds, or composite architectures. Besides, because of their outstanding electrical properties, graphene family materials are particularly suitable for designing electroactive scaffolds that could provide proper electrical stimulation (i.e., electrical or photo stimuli) to promote the regeneration of excitable neurons and muscle cells. Therefore, the effects and mechanism of electrical and/or photo stimulations on neurogenesis and myogenesis are followed. Furthermore, studies on their biocompatibilities and toxicities especially to neural and muscle cells are evaluated. Finally, the future challenges and perspectives in facilitating the development of clinical translation of graphene-family nanomaterials in treating neurodegenerative and muscle diseases are discussed.

Functionalization of graphene family nanomaterials for application in cancer therapy.

Graphene family nanomaterials' (GFN) ability to interact with near-infrared light has propelled their application in cancer photothermal therapy. Furthermore, the graphitic lattice of GFN can adsorb different types of molecules, which has motivated their use in cancer drug delivery. However, the direct application of GFN in cancer therapy is severely hindered by their poor colloidal stability, sub-optimal safety, inefficient tumor uptake and non-selectivity towards cancer cells. To overcome these limitations, GFN have been functionalized with different types of materials. This review is focused on the different functionalizations used in the design of GFN aimed for application in cancer therapy, disclosing their role on surpassing the critical issues related to GFN-based therapies.

Biomedical Applications of Graphene Nanomaterials and Beyond.

Graphene nanomaterials have been considered as a novel class of nanomaterials that show exceptional structural, optical, thermal, electrical, and mechanical properties. As a consequence, it has been extensively studied in various fields including electronics, energy, catalysis, sensing, and biomedical fields. In the previous couple of years, a significant number of studies have been done on graphene-based nanomaterials, where it is utilized in a wide range of bioapplications that includes delivery of small molecule drugs/genes, biosensing, tissue engineering, bioimaging, and photothermal and photodynamic therapies because of its excellent aqueous processability, surface functionalizability, outstanding electrical and mechanical properties, tunable fluorescence properties, and surface-enhanced Raman scattering (SERS).Therefore, it is necessary to get detailed knowledge about it. In this review, we will highlight the various synthesis procedures of graphene family nanomaterials including graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs) as well as their biomedical applications. We will also highlight the biocompatibity of graphene nanomaterials as well as its possible risk factors for bioapplications. In conclusion, we will outline the future perspective and current challenges of graphene nanomaterials for clinical applications.

Detection and Quantification of Graphene-Family Nanomaterials in the Environment.

An increase in production of commercial products containing graphene-family nanomaterials (GFNs) has led to concern over their release into the environment. The fate and potential ecotoxicological effects of GFNs in the environment are currently unclear, partially due to the limited analytical methods for GFN measurements. In this review, the unique properties of GFNs that are useful for their detection and quantification are discussed. The capacity of several classes of techniques to identify and/or quantify GFNs in different environmental matrices (water, soil, sediment, and organisms), after environmental transformations, and after release from a polymer matrix of a product is evaluated. Extraction and strategies to combine methods for more accurate discrimination of GFNs from environmental interferences as well as from other carbonaceous nanomaterials are recommended. Overall, a comprehensive review of the techniques available to detect and quantify GFNs are systematically presented to inform the state of the science, guide researchers in their selection of the best technique for the system under investigation, and enable further development of GFN metrology in environmental matrices. Two case studies are described to provide practical examples of choosing which techniques to utilize for detection or quantification of GFNs in specific scenarios. Because the available quantitative techniques are somewhat limited, more research is required to distinguish GFNs from other carbonaceous materials and improve the accuracy and detection limits of GFNs at more environmentally relevant concentrations.

Aqueous aggregation and stability of graphene nanoplatelets, graphene oxide, and reduced graphene oxide in simulated natural environmental conditions: complex roles of surface and solution chemistry.

Graphene-family nanomaterials (GFNs) exhibit universal applications and consequently will inevitably enter aquatic systems. However, both the fate and behavior of GFNs in aquatic environments have not been completely explored at field relevant conditions. Herein, we have systematically investigated the aqueous aggregation and stability of graphene nanoplatelets (GNPs), graphene oxide (GO), and reduced graphene oxide (RGO) under varied solution chemistry parameters (pH, divalent cations, and dissolved organic carbon (DOC)) during 21days of incubation in simulated natural environmental conditions. Results indicate that pH values from 6 to 9 had a notable impact on the aqueous behaviors of the three GFNs. Divalent cations (Ca2+ and Mg2+) at the concentrations of 2.5 and 10mM remarkably increased the extent of aggregation of the three GFNs and resulted in severe sedimentation, independently of surface chemical functionalization. The presence of only DOC ranging from 0.5 to 2mg C/L significantly elevated the dispersion stability of GNPs and RGO in a dose-dependent manner, whereas no effects were observed on GO. Furthermore, DOC at the studied concentrations and surface functionality were insufficient to counterbalance the impact of the divalent cations. Direct visual and in situ observations further supported the conclusions on the effects of divalent cations or/and DOC. These findings further underline that the environmental behaviors of GFNs are controlled by the complex interplay between water chemistry parameters and GFN surface properties.

Graphene-Functionalized Biomimetic Scaffolds for Tissue Regeneration.

Graphene is a two-dimensional atomic layer of graphite, where carbon atoms are assembled in a honeycombed lattice structure. Recently, graphene family nanomaterials, including pristine graphene, graphene oxide and reduced graphene oxide, have increasingly attracted a great deal of interest from researchers in a variety of science, engineering and industrial fields because of their unique structural and functional features. In particular, extensive studies have been actively conducted in the biomedical and related fields, including multidisciplinary and emerging areas, as their stimulating effects on cell behaviors have been becoming an increasing concern. Herein, we are attempting to summarize some of recent findings in the fields of tissue regeneration concerning the graphene family nanomaterial-functionalized biomimetic scaffolds, and to provide the promising perspectives for the possible applications of graphene family nanomaterial.

An in vitro cytotoxicity assessment of graphene nanosheets on alveolar cells

The collection of intrinsic properties possessed by graphene family nanomaterials (GFNs) results in their continuous exploitation for biomedical applications. The materials biomedical potential has motivated an upsurge in green preparation routes for the production of graphene like materials with limited toxicity. A number of bio-friendly reducing agents have been utilized for the preparation of chemically reduced graphene oxide (GO), and their resulting cytotoxic effects examined. However, the toxicology effects of one of the first biomolecules implemented for the reduction of GO, ascorbic acid (AA) has yet to be investigated. Herein, the toxicity of three distinct GFNs; GO, hydrazine reduced GO (H.rGO) and AA.rGO, prepared through diverse chemical routes are studied, to demonstrate the cytotoxic activity of a green reducer, in comparison to an established reduction method using hydrazine hydrate. The variation in atomic structure of GO, H.rGO and AA.rGO resulting from different synthesis techniques demonstrates the dependence of toxicity on particle shape and size. All GFNs induced high levels of alveolar cell toxicity. Interaction of AA.rGO with the A549 human lung epithelial carcinoma cell line resulted in increased leakage of lactate dehydrogenase, indicative of diminished cell membrane integrity. The uncharacteristic shape of the AA.rGO may be responsible for this proliferated release of the essential protein. The presented data therefore demonstrates that modification of synthetic processes significantly alter the biological activities of GFNs.

Cytotoxicity and genotoxicity of graphene-family nanomaterials in RAW 264.7 mouse macrophages

Cytotoxicity and genotoxicity of graphene-family nanomaterials in RAW 264.7 mouse macrophages

Photocatalytic Generation of H2O2 by Graphene Oxide in Organic Electron Donor-Free Condition under Sunlight

Graphene family nanomaterials are emerging, two-dimensional photocatalysts consisting of Earth-abundant elements. This study evaluated the potential of graphene oxide (GO) toward photocatalytic H2O2 production in water driven by renewable sunlight and visible light without synthetic organic electron donors. We reported for the first time that GO can efficiently photocatalyze the generation of H2O2 to millimolar levels under simulated sunlight in a few hours. The concentration of H2O2 produced is among the greatest values reported in current photocatalytic systems without organic electron donors. We showed that dissolved O2 played a pivotal role in the photoproduction of H2O2 by GO and that superoxide (O2•–) was not involved. A 2-fold increase in H2O2 photoproduction can be readily achieved by raising pH from 3 to 7. The addition of oxalate as the electron donor only enhanced H2O2 photoproduction at low pH, but not at high pH where GO suffered greater photocorrosion. As a result, GO had a greater long-term...

Consecutive evaluation of graphene oxide and reduced graphene oxide nanoplatelets immunotoxicity on monocytes

The biocompatibilities of graphene-family nanomaterials (GFNs) should be thoroughly evaluated before their application in drug delivery and anticancer therapy. The present study aimed to consecutively assess the immunotoxicity of graphene oxide nanoplatelets (GONPs) and reduced GONPs (rGONPs) on THP-1 cells, a human acute monocytic leukemia cell line. GONPs induced the expression of antioxidative enzymes and inflammatory factors, whereas rGONPs had substantially higher cellular uptake rate, higher levels of NF-κB expression. These distinct toxic mechanisms were observed because the two nanomaterials differ in their oxidation state, which imparts different affinities for the cell membrane. Because GONPs have a higher cell membrane affinity and higher impact on membrane proteins compared with rGONPs, macrophages (THP-1a) derived from GONPs treated THP-1cells showed a severer effect on phagocytosis. By consecutive evaluation the effects of GONPs and rGONPs on THP-1 and THP-1a, we demonstrated that their surface oxidation states may cause GFNs to behave differently and cause different immunotoxic effects.

Recent Developments of Phototherapy Based on Graphene Family Nanomaterials.

Graphene-based nanomaterials have drawn abundant interest in various fields such as biomedicine in recent years. Thanks to the ultra-high surface area of single-layered graphene, higher molecular loading is obtained. In addition, easy modifications were acquired because of its ample oxygen-content functional groups. Owing to its excellent physical- chemical properties, graphene-based nanomaterials have been widely explored as novel nanovectors for disease theranostics. In this article, we gave a comprehensive review of graphenebased nanomaterials, including introduction about different members of graphene family nanomaterials (GFNs), various modifications, toxicity and biomedical applications of graphene- based derivatives. More attentions were given to phototherapy in this paper. The mechanisms of photothermal and photodynamic therapy were also offered. Finally, the prospects and challenges of the graphene-based nanomaterials were discussed in this review.

Graphene-family nanomaterials assembled with cobalt oxides and cobalt nanoparticles as hybrid supercapacitive electrodes and enzymeless glucose detection platforms – CORRIGENDUM

Graphene-family nanomaterials assembled with cobalt oxides and cobalt nanoparticles as hybrid supercapacitive electrodes and enzymeless glucose detection platforms – CORRIGENDUM

Experimental and theoretical investigation of relative optical band gaps in graphene generations

Size and chemical functionalization dependant optical band gaps in graphene family nanomaterials were investigated by experimental and theoretical study using Tauc plot and density functional theory (DFT). We have synthesized graphene oxide through a modified Hummer’s method using graphene nanoplatelets and sequentially graphene quantum dots through hydrothermal reduction. The experimental results indicate that the optical band gap in graphene generations was altered by reducing the size of graphene sheets and attachment of chemical functionalities like epoxy, hydroxyl and carboxyl groups plays a crucial role in varying optical band gaps. It is further confirmed by DFT calculations that the π orbitals were more dominatingly participating in transitions shown by projected density of states and the molecular energy spectrum represented the effect of attached functional groups along with discreteness in energy levels. Theoretical results were found to be in good agreement with experimental results. All of the above different variants of graphene can be used in native or modified form for sensor design and optoelectronic applications.

Graphene-family nanomaterials assembled with cobalt oxides and cobalt nanoparticles as hybrid supercapacitive electrodes and enzymeless glucose detection platforms

Abstract

Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells

Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells. Herein, GO particles were produced from graphite using the Tour method and subsequent mild reduction was carried out to obtain low-reduced GO (LRGO) particles. A qualitative analysis of the viability, cellular uptake, and internalization of particles was carried out using GO (~54% content of oxygen) and LRGO (~37% content of oxygen) and graphite. GO and LRGO reduce the viability of cardiac cells at IC50 of 652.1±1.2 and 129.4±1.2μg/mL, respectively. This shows that LRGO particles produce a five-fold increase in cytotoxicity when compared to GO. The cell uptake pattern of GO and LRGO particles demonstrated that cardiac cells retain a similar complexity to control cells. Morphological alterations examined with electron microscopy showed that internalization by GO and LRGO-treated cells (100μg/mL) occurred affecting the cell structure. These results suggest that the viability of H9c2 cells can be associated with the surface chemistry of GO and LRGO, as defined by the amount of oxygen functionalities, the number of graphitic domains, and the size of particles. High angle annular dark-field scanning transmission electron microscopy, dynamic light-scattering, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies were used to characterize the as-prepared materials.

Toxicity of Graphene Based Nanomaterials Towards Different Bacterial Strains: A Comprehensive Review

Nanomaterials including graphene and its derivatives have attained immense popularity among scientific community due to their unique properties. Graphene (G), graphene oxide (GO), reduced graphene oxide (rGO) and their nano-composites have shown to possess enormous potential in the field of nanomedicines. Graphene family nanomaterials (GFNs) have extensively being used in different fields including antibacterial formulations. Mechanisms underlying the toxicity of GFNs involve the interaction of sharp edges of graphene derivatives with the bacterial cell wall, charge transfer and formation of huge number of reactive oxygen species. The use of graphene derivatives including GO-Ag nanocomposites, polydopamine-graphene nanosheets, rGO-Iron oxide NPs, Pluronic-GO, G-Carbon Nanotubes-iron oxides, Ag-rGO-Fe3O4-polyethylenimine composites, ZnO-GO and Cystamine-GO has revealed a strong antibacterial action against a variety of bacteria. In this paper, an attempt has been made to comprise the latest approaches being put forward in various researches based on the antibacterial action of graphene based nanomaterials and their composites

Engineered nanomaterials exposure in the production of graphene

The objective of this study was to obtain the multi-metric occupational exposure assessment to graphene family nanomaterials (GFNs) particles of workers engaged in the large-scale production of graphene. The study design consisted of the combination of (i) direct-reading instruments, used to evaluate the total particle number concentrations relative to the background concentration (time series with spatial approach) and the mean size-dependent characteristics of particles (mean diameter and surface-area concentration) and (ii) filter-based air sampling for the determination of size-resolved particle mass concentrations. The data obtained from direct reading measurement were then used to estimate the 8-h time weighted average (8-h TWA) exposure to GFNs particles for workers involved in different working tasks. Workers were generally exposed to 8-h TWA GFNs particle levels lower than the proposed reference value (40,000 particle/cm3). Furthermore, despite high short-term exposure conditions were present during specific operations of the production process, the possibility of significant exposure peaks is not likely to be expected. The estimated 8-h TWA concentration showed differences between the unexposed (<100 particle/cm3; <0.05 µg/m3) and exposed subjects (mean concentration ranging from 909 to 6438 particle/cm3 and from 0.38 to 3.86 µg/m3). The research outcomes can be of particular interest because the exposure of workers in real working conditions was assessed with a multi-metric approach; in this regard, the study suggests that workers who are directly involved in some specific working task (material sampling for quality control) have higher potential for occupational exposure than operators who are in charge of routine production work.© 2016 American Association for Aerosol Research

Applications and toxicity of graphene family nanomaterials and their composites.

Graphene has attracted much attention of scientific community due to its enormous potential in different fields, including medical sciences, agriculture, food safety, cancer research, and tissue engineering. The potential for widespread human exposure raises safety concerns about graphene and its derivatives, referred to as graphene family nanomaterials (GFNs). Due to their unique chemical and physical properties, graphene and its derivatives have found important places in their respective application fields, yet they are being found to have cytotoxic and genotoxic effects too. Since the discovery of graphene, a number of researches are being conducted to find out the toxic potential of GFNs to different cell and animal models, finding their suitability for being used in new and varied innovative fields. This paper presents a systematic review of the research done on GFNs and gives an insight into the mode and action of these nanosized moieties. The paper also emphasizes on the recent and up-to-date developments in research on GFNs and their nanocomposites for their toxic effects.