Dispersed graphene materials of biomedical interest and their toxicological consequences

Photodynamic therapy of cancer using graphene nanomaterials

INTRODUCTION

High incidence and fatality rates of cancer remain a global challenge. The success of conventional treatment modalities is being questioned on account of adverse effects. Photodynamic therapy (PDT) is a potential alternative. It utilizes a combination of photosensitizer (PS), light and oxygen to target the tissues locally, thereby minimizing the damage to neighboring healthy tissues. Conventional PSs suffer from poor selectivity, high hydrophobicity and sub-optimal yield of active radicals. Graphene nanomaterials (GNs) exhibit interesting particulate and photophysical properties in the context of their use in PDT.

AREA COVERED

We focus on describing the mechanistic aspects of PDT-mediated elimination of cancer cells and the subsequent development of adaptive immunity. After covering up-to-date literature on the significant enhancement of PDT capability with GNs, we have discussed the probability of combining PDT with chemo-, immuno-, and photothermal therapy to make the treatment more effective.

EXPERT OPINION

GNs can be synthesized in various size ranges, and their biocompatibility can be improved through surface functionalization and doping. These can be used as PS to generate ROS or conjugated with other PS molecules for treating deep-seated tumors. With increasing evidence on biosafety, such materials offer hope as antitumor therapeutics.

Properties of a Dental Adhesive Containing Graphene and DOPA-Modified Graphene

Graphene is a promising biomaterial. However, its dispersion in aqueous medium is challenging. This study aimed to modify graphene nanoparticles with L-dopa to improve the properties of experimental dental adhesives. Adhesives were formulated with 0% (control), 0.25%, 0.5%, and 0.75% of graphene, modified or not. Particle modification and dispersion were microscopically assessed. Degree of conversion was tested by Fourier-transform infrared spectroscopy. Flexural strength and modulus of elasticity were evaluated by a 3-point flexural test. Bond strength was tested by shear. To test water sorption/solubility, samples were weighed during hydration and dehydration. Antibacterial activity was tested by Streptococcus mutans colony-forming units quantification. Cytotoxicity on fibroblasts was evaluated through a dentin barrier test. The modification of graphene improved the particle dispersion. Control presented the highest degree of conversion, flexural strength, and bond strength. In degree of conversion, 0.25% of groups were similar to control. In bond strength, groups of graphene modified by L-dopa were similar to Control. The modulus of elasticity was similar between groups. Cytotoxicity and water sorption/solubility decreased as particles increased. Compared to graphene, less graphene modified by L-dopa was needed to promote antibacterial activity. By modifying graphene with L-dopa, the properties of graphene and, therefore, the adhesives incorporated by it were enhanced.

Graphene in 3D Bioprinting

Three-dimensional (3D) bioprinting is a fast prototyping fabrication approach that allows the development of new implants for tissue restoration. Although various materials have been utilized for this process, they lack mechanical, electrical, chemical, and biological properties. To overcome those limitations, graphene-based materials demonstrate unique mechanical and electrical properties, morphology, and impermeability, making them excellent candidates for 3D bioprinting. This review summarizes the latest developments in graphene-based materials in 3D printing and their application in tissue engineering and regenerative medicine. Over the years, different 3D printing approaches have utilized graphene-based materials, such as graphene, graphene oxide (GO), reduced GO (rGO), and functional GO (fGO). This process involves controlling multiple factors, such as graphene dispersion, viscosity, and post-curing, which impact the properties of the 3D-printed graphene-based constructs. To this end, those materials combined with 3D printing approaches have demonstrated prominent regeneration potential for bone, neural, cardiac, and skin tissues. Overall, graphene in 3D bioprinting may pave the way for new regenerative strategies with translational implications in orthopedics, neurology, and cardiovascular areas.

Respiratory Toxicology of Graphene-Based Nanomaterials: A Review

Graphene-based nanomaterials (GBNs) consist of a single or few layers of graphene sheets or modified graphene including pristine graphene, graphene nanosheets (GNS), graphene oxide (GO), reduced graphene oxide (rGO), as well as graphene modified with various functional groups or chemicals (e.g., hydroxyl, carboxyl, and polyethylene glycol), which are frequently used in industrial and biomedical applications owing to their exceptional physicochemical properties. Given the widespread production and extensive application of GBNs, they can be disseminated in a wide range of environmental mediums, such as air, water, food, and soil. GBNs can enter the human body through various routes such as inhalation, ingestion, dermal penetration, injection, and implantation in biomedical applications, and the majority of GBNs tend to accumulate in the respiratory system. GBNs inhaled and substantially deposited in the human respiratory tract may impair lung defenses and clearance, resulting in the formation of granulomas and pulmonary fibrosis. However, the specific toxicity of the respiratory system caused by different GBNs, their influencing factors, and the underlying mechanisms remain relatively scarce. This review summarizes recent advances in the exposure, metabolism, toxicity and potential mechanisms, current limitations, and future perspectives of various GBNs in the respiratory system.

Disturbing cytoskeleton by engineered nanomaterials for enhanced cancer therapeutics

Cytoskeleton plays a significant role in the shape change, migration, movement, adhesion, cytokinesis, and phagocytosis of tumor cells. In clinical practice, some anti-cancer drugs achieve cytoskeletal therapeutic effects by acting on different cytoskeletal protein components. However, in the absence of cell-specific targeting, unnecessary cytoskeletal recombination in organisms would be disastrous, which would also bring about severe side effects during anticancer process. Nanomedicine have been proven to be superior to some small molecule drugs in cancer treatment due to better stability and targeting, and lower side effects. Therefore, this review summarized the recent developments of various nanomaterials disturbing cytoskeleton for enhanced cancer therapeutics, including carbon, noble metals, metal oxides, black phosphorus, calcium, silicon, polymers, peptides, and metal-organic frameworks, etc. A comprehensive analysis of the characteristics of cytoskeleton therapy as well as the future prospects and challenges towards clinical application were also discussed. We aim to drive on this emerging topic through refreshing perspectives based on our own work and what we have also learnt from others. This review will help researchers quickly understand relevant cytoskeletal therapeutic information to further advance the development of cancer nanomedicine.

Green and Sustainable Ultrasound-Assisted Anodic Electrochemical Preparation of Graphene Oxide Dispersions and Their Antioxidant Properties

A fast method for preparing aqueous graphene oxide (GO) dispersions by electrochemical oxidation of a graphite anode without preliminary intercalation with oxidizing agents is proposed. Ultrasonic probing was used in the modulation mode of ultrasonic waves (work/rest) for more efficient graphite oxidation-exfoliation. It is shown that the 4/2 s mode of ultrasonic modulation is the most effective due to the probe material's low corrosion while maintaining the optimum synthesis temperature not exceeding 30-35 °C and achieving the best characteristics of the resulting product. Three cases of anodic oxidation of graphite to obtain graphene oxide were considered: (1) a combined cathode-anode compartment, (2) a split cathode-anode salt-bridged compartment, and (3) separated anode compartment with a 3.5 kDa dialysis membrane. It was determined that the approach to synthesis with a divided cathode-anode compartment makes it possible to obtain GO sheets with fewer defects compared to chemical methods or methods with a combined cathode-anode compartment and makes it possible to control the oxidation degree of the material (C:O ratio) by varying the current density. The prepared samples showed good stability for more than six months. The spectral and morphological characteristics were studied. Using chemiluminometry in the luminol/Co(II)/H₂O₂ system, the antioxidant properties concerning three key reactive oxygen species (H₂O₂, superoxide anion radical, and hydroxyl radical) were demonstrated. It was also shown that the prepared GO dispersions do not induce lipid and phospholipid peroxidation.

Stabilization of lysozyme in aqueous dispersion of graphene oxide sheets

This study examines the effect of surface oxygen groups upon ability of graphene oxide (GO) sheets in suppressing the fibrillation of lysozyme (LYZ). Graphite was oxidized using 6 and 8 wt equivalents of KMnO₄, and as produced sheets were abbreviated as GO-06 and GO-08, respectively. Particulate characteristics of sheets were characterized by light scattering and electron microscopic techniques, and their interaction with LYZ was analysed by circular dichroism (CD) spectroscopy. After ascertaining acid-driven conversion of LYZ to fibrillary form, we have shown that the fibrillation of dispersed protein can be prevented by adding GO sheets. Inhibitory effect could be attributed to binding of LYZ over the sheets via noncovalent forces. A comparison between GO-06 and GO-08 samples showed superior binding affinity of the latter. Higher aqueous dispersibility and density of oxygenated groups in GO-08 sheets would have facilitated the adsorption of protein molecules, thus making them unavailable for aggregation. Pre-treatment of GO sheets with Pluronic 103 (P103, a nonionic triblock copolymer), caused reduction in the adsorption of LYZ. P103 aggregates would have rendered the sheet surface unavailable for the adsorption of LYZ. Based on these observations, we conclude that fibrillation of LYZ can be prevented in association with graphene oxide sheets.

Microstructures, mechanical and corrosion properties of graphene nanoplatelet-reinforced zinc matrix composites for implant applications

Zinc (Zn)-based alloys and composites are gaining increasing interest as promising biodegradable implant materials due to their appropriate biodegradation rates and biological functionalities. However, the inadequate mechanical strength and ductility of pure Zn have restricted its application. In this study, Zn matrix composites (ZMCs) reinforced with 0.1-0.4 wt.% graphene nanoplatelets (GNP) fabricated via powder metallurgy were investigated as potential biodegradable implant materials. The microstructures, mechanical properties, and corrosion behaviors of the GNP-reinforced ZMCs were characterized using optical microscopy, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, Raman spectroscopy, compression testing, and electrochemical and immersion testing in Hanks' balanced salt solution (HBSS). The microstructural study revealed that the GNP was uniformly dispersed in the ZMCs after ball milling and sintering at 420°C for 6 h. The microhardness, compressive yield strength, ultimate compressive strength, and compressive strain of the ZMC-0.2GNP were 69 HV, 123 MPa, 247 MPa, and 23 %, respectively, improvements of ∼ 18 %, 50%, ∼ 28%, and ∼ 15% compared to pure Zn. The corrosion rate of the ZMCs were lower than that of the pure Zn in HBSS, and the ZMC-0.2GNP composite exhibited the lowest corrosion rate of 0.09 mm/y as measured by electrochemical testing. Biocompatibility assessment indicated that the diluted extracts of pure Zn and GNP-reinforced ZMCs with concentrations of 12.5% and 6.25% exhibited no cytotoxicity after cell culturing for up to 5 days, and the diluted extracts of ZMC-0.2 GNP composite revealed more than 90% cell viability after cell culturing of 3 days, showing the satisfying cytocompatibility. STATEMENT OF SIGNIFICANCE: Biodegradable Zn is a promising candidate material for orthopedic implant applications. Nonetheless, the inadequate mechanical strength and ductility of pure Zn limited its clinical application. In this study, Zn matrix composites (ZMCs) reinforced with 0.1-0.4 wt.% graphene nanoplatelets (GNP) were developed via powder metallurgy, and the reinforcing efficacy of GNP on their mechanical properties was investigated. The addition of GNP significantly improved the compressive properties of ZMCs, with the Zn-0.2GNP composite exhibiting the best compressive properties, including 123 MPa compressive yield strength, 247 MPa ultimate compressive strength, and 22.9% compressive strain. Further, the 12.5% concentration extract of the ZMCs exhibited no cytotoxicity after cell culturing for 5 d toward SaOS2 cells.

Detection and modulation of neurodegenerative processes using graphene-based nanomaterials: Nanoarchitectonics and applications

Neurodegenerative disorders (NDDs) are caused by progressive loss of functional neurons following the aggregation and fibrillation of proteins in the central nervous system. The incidence rate continues to rise alarmingly worldwide, particularly in aged population, and the success of treatment remains limited to symptomatic relief. Graphene nanomaterials (GNs) have attracted immense interest on the account of their unique physicochemical and optoelectronic properties. The research over the past two decades has recognized their ability to interact with aggregation-prone neuronal proteins, regulate autophagy and modulate the electrophysiology of neuronal cells. Graphene can prevent the formation of higher order protein aggregates and facilitate the clearance of such deposits. In this review, after highlighting the role of protein fibrillation in neurodegeneration, we have discussed how GN-protein interactions can be exploited for preventing neurodegeneration. A comprehensive understanding of such interactions would contribute to the exploration of novel modalities for controlling neurodegenerative processes.

Oxidation state of graphene oxide nanosheets drives their interaction with proteins: A case of bovine serum albumin

In the present study, we explored the interaction of bovine serum albumin (BSA) with oxidized graphene oxide (GO) nanosheets. Nanosheets, synthesized with 4, 6, 8, 10 and 12 wt equivalents of KMnO₄ as oxidant, were coded as GO-4, GO-6, GO-8, GO-10 and GO-12, respectively. After incubating sheets with a fixed concentration of BSA at room temperature, interactions were monitored with time. The analysis is based on UV-vis spectroscopy, fluorescence quenching, dynamic light scattering (DLS), small angle neutron scattering (SANS), Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) techniques. Binding of BSA over sheets was recorded in the following order; GO-04 >> GO-06 > GO-08 > GO-10 ≈ GO-12. Our observations suggest that these interactions are largely regulated by the availability of pure graphitic domains and density of oxygen functionalities on sheet surface. This led us to the conclusion that GO-protein interactions can be minimized by modulating the extent of sheet oxidation. Moreover, we show that adsorption of proteins as colloidal aggregates contributes to improved biosafety of sheets. The protein molecule did not exhibit depletive changes in its conformation. However, from the viewpoint of drug delivery applications, density of oxygen groups must be optimized for maximizing the loading efficiency of oxidized sheets.

Development of Graphene-Based Materials in Bone Tissue Engineaering

Bone regeneration-related graphene-based materials (bGBMs) are increasingly attracting attention in tissue engineering due to their special physical and chemical properties. The purpose of this review is to quantitatively analyze mass academic literature in the field of bGBMs through scientometrics software CiteSpace, to demonstrate the rules and trends of bGBMs, thus to analyze and summarize the mechanisms behind the rules, and to provide clues for future research. First, the research status, hotspots, and frontiers of bGBMs are analyzed in an intuitively and vividly visualized way. Next, the extracted important subjects such as fabrication techniques, cytotoxicity, biodegradability, and osteoinductivity of bGBMs are presented, and the different mechanisms, in turn, are also discussed. Finally, photothermal therapy, which is considered an emerging area of application of bGBMs, is also presented. Based on this approach, this work finds that different studies report differing opinions on the biological properties of bGBMS due to the lack of consistency of GBMs preparation. Therefore, it is necessary to establish more standards in fabrication, characterization, and testing for bGBMs to further promote scientific progress and clinical translation.

Accurate construction of cell membrane biomimetic graphene nanodecoys via purposeful surface engineering to improve screening efficiency of active components of traditional Chinese medicine

Biomimetic nanoengineering presents great potential in biomedical research by integrating cell membrane (CM) with functional nanoparticles. However, preparation of CM biomimetic nanomaterials for custom applications that can avoid the aggregation of nanocarriers while maintaining the biological activity of CM remains a challenge. Herein, a high-performance CM biomimetic graphene nanodecoy was fabricated via purposeful surface engineering, where polyethylene glycol (PEG) was used to modifying magnetic graphene oxide (MGO) to improve its stability in physiological solution, so as to improve the screening efficiency to active components of traditional Chinese medicine (TCM). With this strategy, the constructed PEGylated MGO (PMGO) could keep stable at least 10 days, thus improving the CM coating efficiency. Meanwhile, by taking advantage of the inherent ability of HeLa cell membrane (HM) to interact with specific ligands, HM-camouflaged PMGO showed satisfied adsorption capacity (116.2 mg/g) and selectivity. Finally, three potential active components, byakangelicol, imperatorin, and isoimperatorin, were screened from Angelica dahurica, whose potential antiproliferative activity were further validated by pharmacological studies. These results demonstrated that the purposeful surface engineering is a promising strategy for the design of efficient CM biomimetic nanomaterials, which will promote the development of active components screening in TCM.

PEGylated Graphene Quantum Dot Improved Cardiac Function in Rats with Myocardial Infarction: Morphological, Oxidative Stress, and Toxicological Evidences

Introduction

The biocompatibility and potential application of graphene-based nanomaterials in biomedicine have been documented. The effects of polyethylene glycol-graphene quantum dots (GQDs-PEG) on cardiac function in rats with myocardial infarction (MI) were examined.

Methods

Wistar rats were randomly assigned to two main groups, each consisting of sham-Veh., MI-Veh., and MI+GQDs-PEG at doses of 5, 10, and 20 mg/kg. MI was induced by the closure of the left anterior descending (LAD) coronary artery. After MI, GQDs-PEG were injected at different doses IP every other day for two weeks. In the end, hemodynamic and heart contractility indices were assessed. The levels of myocardial MDA (malondialdehyde), SOD (superoxide dismutase), GPX (glutathione peroxidase), and TAC (total antioxidant capacity) were measured by the ELISA method. The serum ALP, ALT, AST, creatinine, and urea levels were measured using the photometric method. The infarct size was assessed by TTC staining.

Results

GQDs-PEG decreased the infarct size at doses of 10 and 20 mg/kg and recovered the MI-induced reductions of +dp/dt max and -dp/dt max in the study groups. GQDs-PEG normalized systolic blood pressure and left ventricular systolic pressure reduction at the dose of 20 mg/kg in the MI group. Heart SOD, GPX, and TAC increased in the GQDs-PEG 10 and 20 groups. Almost no signs of toxic effects due to GQDs-PEG administration were observed on the liver and kidneys.

Conclusions

The results provided clear evidence that GQDs-PEG improve cardiac performance and hemodynamic parameters in rats with MI by reducing oxidative stress. GQDs-PEG is proposed as a therapeutic target for the treatment of MI.

Effects of graphite, graphene, and graphene oxide on the anaerobic co-digestion of sewage sludge and food waste: Attention to methane production and the fate of antibiotic resistance genes

This study explored and compared the influence of graphite, graphene, and graphene oxide (GO) on the performance of anaerobic co-digestion fed with sewage sludge and food waste, the variations of antibiotic resistance genes (ARGs), and the evolution of microbial community. Graphene exhibited the best performance for improving methane production and organic degradation, which increased by 36.09% and 23.07% compared with control group. The experimental results showed that graphene had the greatest influence on the removal efficiency of blaOXA-1, macrolide resistance genes (ermF and ermB), and some tetracycline resistance genes (tetQ and tetX); however, the removal efficiency of sulfonamide resistance genes (sul1 and sul2), intI1, and some tetracycline resistance genes (tetM, tetO, and tetW) were highest when GO was added. Network analysis indicated that the host cells of mefA, ermB, and tetO were different from other ARG host cells; moreover, graphene controlled the horizontal transfer of ARGs between microbial communities.

Graphene and its derivatives: understanding the main chemical and medicinal chemistry roles for biomedical applications

Over the past few years, there has been a growing potential use of graphene and its derivatives in several biomedical areas, such as drug delivery systems, biosensors, and imaging systems, especially for having excellent optical, electronic, thermal, and mechanical properties. Therefore, nanomaterials in the graphene family have shown promising results in several areas of science. The different physicochemical properties of graphene and its derivatives guide its biocompatibility and toxicity. Hence, further studies to explain the interactions of these nanomaterials with biological systems are fundamental. This review has shown the applicability of the graphene family in several biomedical modalities, with particular attention for cancer therapy and diagnosis, as a potent theranostic. This ability is derivative from the considerable number of forms that the graphene family can assume. The graphene-based materials biodistribution profile, clearance, toxicity, and cytotoxicity, interacting with biological systems, are discussed here, focusing on its synthesis methodology, physicochemical properties, and production quality. Despite the growing increase in the bioavailability and toxicity studies of graphene and its derivatives, there is still much to be unveiled to develop safe and effective formulations.

Graphic abstract

Graphene-based nanomaterials for breast cancer treatment: promising therapeutic strategies

Breast cancer is the most common malignancy in women, and its incidence increases annually. Traditional therapies have several side effects, leading to the urgent need to explore new smart drug-delivery systems and find new therapeutic strategies. Graphene-based nanomaterials (GBNs) are potential drug carriers due to their target selectivity, easy functionalization, chemosensitization and high drug-loading capacity. Previous studies have revealed that GBNs play an important role in fighting breast cancer. Here, we have summarized the superior properties of GBNs and modifications to shape GBNs for improved function. Then, we focus on the applications of GBNs in breast cancer treatment, including drug delivery, gene therapy, phototherapy, and magnetothermal therapy (MTT), and as a platform to combine multiple therapies. Their advantages in enhancing therapeutic effects, reducing the toxicity of chemotherapeutic drugs, overcoming multidrug resistance (MDR) and inhibiting tumor metastasis are highlighted. This review aims to help evaluate GBNs as therapeutic strategies and provide additional novel ideas for their application in breast cancer therapy.

Antibacterial and antibiofilm properties of graphene and its derivatives

Infections resulting from bacteria and biofilms have become a huge problem threatening human health. In recent years, the antibacterial and antibiofilm effects of graphene and its derivatives have been extensively studied. However, there continues to be some controversy over whether graphene and its derivatives can resist infection and biofilms. Moreover, the antibacterial mechanism and cytotoxicity of graphene and its derivatives are unclear. In the present review, antibacterial and antibiofilm abilities of graphene and its derivatives in solution, on the surface are reviewed, and their toxicity and possible mechanisms are also reviewed. Furthermore, we propose possible future development directions for graphene and its derivatives in antibacterial and antibiofilm applications.

Adsorption of P103 Nanoaggregates on Graphene Oxide Nanosheets: Role of Electrostatic Forces in Improving Nanosheet Dispersion

Graphene oxide (GO) nanosheet suspension is not stable in physiological ionic fluids. To improve stability, surfactants such as Pluronic 103 (P103) have been tested. Going further, this work investigated whether conferring positive surface charge to the surfactant may improve the adsorption ability of P103 micelles on GO sheets. Positive charge on the surfactant was induced by adding dodecyltrimethylammonium bromide (DTAB, a cationic surfactant) in P103 micelles. Subsequent changes in aggregation parameters were investigated through dynamic light scattering and small-angle neutron scattering studies. DTAB incorporation was accompanied by a steady increase in the ζ potential and mixed micelle formation. At high surface charge density, the interaction between adjacent head groups was distorted, which led to dissociation of mixed micelles. Structural developments during the adsorption of mixed micelles on the sheet surface (mass fractal formation) were monitored in terms of changes in the scattering features of aggregates. These fractals emerged as a result of electrostatic interactions. Our observations point toward the existence of small-sized building blocks at low DTAB concentration (≤4 mM). With a superior adsorption, mixed micelles are expected to occupy the intersheet space and maintain a hydration layer. However, at a higher DTAB concentration (≥10 mM), micelles dissociate to produce DTAB-rich unimers and P103-rich loose aggregates. At this point, sheets tend to aggregate in the solvent, regardless of fractal formation.

Microstructure evolution and texture tailoring of reduced graphene oxide reinforced Zn scaffold

Zinc (Zn) possesses desirable degradability and favorable biocompatibility, thus being recognized as a promising bone implant material. Nevertheless, the insufficient mechanical performance limits its further clinical application. In this study, reduced graphene oxide (RGO) was used as reinforcement in Zn scaffold fabricated via laser additive manufacturing. Results showed that the homogeneously dispersed RGO simultaneously enhanced the strength and ductility of Zn scaffold. On one hand, the enhanced strength was ascribed to (i) the grain refinement caused by the pinning effect of RGO, (ii) the efficient load shift due to the huge specific surface area of RGO and the favorable interface bonding between RGO and Zn matrix, and (iii) the Orowan strengthening by the homogeneously distributed RGO. On the other hand, the improved ductility was owing to the RGO-induced random orientation of grain with texture index reducing from 20.5 to 7.3, which activated more slip systems and provided more space to accommodate dislocation. Furthermore, the cell test confirmed that RGO promoted cell growth and differentiation. This study demonstrated the great potential of RGO in tailoring the mechanical performance and cell behavior of Zn scaffold for bone repair.

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Zn/RGO composite scaffold was successfully fabricated by laser additive manufacturing.

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RGO refined the grains and significantly weakened the texture with random grain orientation.

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The uniformly distributed RGO simultaneously enhanced the strength and ductility of scaffold.

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The incorporated RGO exerted a positive effect on cell growth and differentiation.