Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells

Incorporation of graphene oxide into collagenous biomaterials attenuates scar-forming phenotype transition of reactive astrocytes in vitro

The integrin-mediated interaction between collagen type I and reactive astrocytes was recently shown to induce a detrimental, scar-forming phenotype transformation following spinal cord injury (SCI), which severely limits the therapeutic potential of commonly used collagen-based biomaterials. Graphene oxide (GO) is a promising candidate to disrupt the collagen-integrin interaction, since it is capable of altering the surface topography of biomaterials applied as SCI treatment. Moreover, free GO contributes towards potassium and glutamate transport, which is often implicated following SCI. However, it remains unclear whether both the integrin-mediated binding and astrocytic transport of potassium and glutamate are affected by GO, when inserted into collagenous biomaterials. Therefore, in the current study GO was incorporated into collagen-based hydrogels in an attempt to prevent the scar-forming phenotype transition and promote the expression of astrocytic potassium channels and glutamate transporters. Primary astrocytes were cultured either on top of or embedded within GO-enriched collagen type I or adipose tissue-derived extracellular matrix (ECM) gels. The impact of GO incorporation on integrin β1-mediated binding, astrocyte phenotype and potassium and glutamate transport was assessed by gene expression analysis and immunofluorescence studies. Upon GO incorporation into ECM gels, expression of integrin β1 and N-cadherin was significantly decreased. Moreover, GO decreased proteoglycan-associated gene expression by four-fold. Finally, GO incorporation led to a decrease in expression of both potassium channels and glutamate transporters. In conclusion, the incorporation of GO into collagen-based materials attenuated the transition of reactive astrocytes into a scar-forming phenotype.

Angiotensin II-Induced Hypertrophy in H9c2 Cells Reveals Severe Cytotoxicity of Graphene Oxide

This study investigates the differential cytotoxicity of reduced graphene oxide (RGO) and graphene oxide (GO) particles using an angiotensin II (Ang II)-induced hypertrophy model in H9c2 cells. Herein, GO particles were synthesized from graphite, and subsequent reduction was carried out to obtain RGO particles. To ensure a thorough assessment of particle size, functionalization, and purity, the particles were characterized by using UV-vis absorbance spectroscopy, dynamic light scattering, X-ray photoelectron spectroscopy, FTIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. Comprehensive characterization revealed that the transformation from GO (∼21.6% content of oxygen) to RGO (∼13.3% content of oxygen) results in an enrichment in the proportion of sp2 carbon. Additionally, rat cardiac myoblasts of the H9c2 cell line were subjected to Ang II to induce cellular hypertrophy, leading to cytoskeleton remodeling, increased cardiac myocyte surface area, extracellular matrix alterations, and collagen type 1a upregulation. To evaluate cytotoxicity, H9c2 cells were treated with RGO and GO suspensions at concentrations ranging from 1 to 10,000 μg/mL, and metabolic viability was assessed in both concentration- and time-dependent assays. GO and RGO reduced the viability of H9c2 cells; however, the metabolic viability assays showed that the half-maximal inhibitory concentration (IC50) values for GO and RGO were significantly lower in hypertrophic cardiomyocytes, with GO exhibiting an IC50 of 12.6 ± 10.7 μg/mL and RGO exhibiting an IC50 of 86.3 ± 12.9 μg/mL, compared to control cells (676.0 ± 80.3 μg/mL for GO and 152.9 ± 40.1 μg/mL for RGO). These results demonstrate that under hypertrophic conditions, there is a significant increase of cytotoxicity for GO (50-fold increase) in comparison to RGO (1.7-fold increase). It was demonstrated that GO particles create a pro-oxidative environment that ultimately leads to mechanistic impairments and cell death. Vulnerable populations predisposed to cardiac damage may be at increased risk of experiencing toxicity caused by the use of GO particles in potential bioapplications.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective

Two-dimensional (2D) materials have attracted tremendous interest ever since the isolation of atomically thin sheets of graphene in 2004 due to the specific and versatile properties of these materials. However, the increasing production and use of 2D materials necessitate a thorough evaluation of the potential impact on human health and the environment. Furthermore, harmonized test protocols are needed with which to assess the safety of 2D materials. The Graphene Flagship project (2013-2023), funded by the European Commission, addressed the identification of the possible hazard of graphene-based materials as well as emerging 2D materials including transition metal dichalcogenides, hexagonal boron nitride, and others. Additionally, so-called green chemistry approaches were explored to achieve the goal of a safe and sustainable production and use of this fascinating family of nanomaterials. The present review provides a compact survey of the findings and the lessons learned in the Graphene Flagship.

Conductive polymers for cardiac tissue engineering and regeneration

Cardiovascular diseases, such as myocardial infarction, are considered a significant global burden and the leading cause of death. Given the inability of damaged cardiac tissue to self-repair, cell-based tissue engineering and regeneration may be the only viable option for restoring normal heart function. To maintain the normal excitation-contraction coupling function of cardiac tissue, uniform electronic and ionic conductance properties are required. To transport cells to damaged cardiac tissues, several techniques, including the incorporation of cells into conductive polymers (CPs) and biomaterials, have been utilized. Due to the complexity of cardiac tissues, the success of tissue engineering for the damaged heart is highly dependent on several variables, such as the cell source, growth factors, and scaffolds. In this review, we sought to provide a comprehensive overview of the electro CPs and biomaterials used in the engineering and regeneration of heart tissue.

Harnessing graphene oxide nanocarriers for siRNA delivery in a 3D spheroid model of lung cancer

Gene therapy has been recently proposed as an effective strategy for cancer treatment. A significant body of literature proved the effectiveness of nanocarriers to deliver therapeutic agents to 2D tumour models, which are simple but not always representative of the in vivo reality. In this study, we analyze the efficiency of 3D spheroids combined with a minimally modified graphene oxide (GO)-based nanocarrier for siRNA delivery as a new system for cell transfection. Small interfering RNA (siRNA) targeting cluster of differentiation 47 (CD47; CD47_siRNA) was used as an anti-tumour therapeutic agent to silence the genes expressing CD47. This is a surface marker able to send a "don't eat me" signal to macrophages to prevent their phagocytosis. Also, we report the analysis of different GO formulations, in terms of size (small: about 100 nm; large: >650 nm) and functionalization (unmodified or modified with polyethylene glycol (PEG) and the dendrimer PAMAM), aiming to establish the efficiency of unmodified GO as a nanocarrier for the transfection of A549 lung cancer spheroids. Small modified GO (smGO) showed the highest transfection efficiency values (>90%) in 3D models. Interestingly, small unmodified GO (sGO) was found to be promising for transfection, with efficiency values >80% using a higher siRNA ratio (i.e., 3 : 1). These results demonstrated the higher efficiency of spheroids compared to 2D models for transfection, and the high potential of unmodified GO to carry siRNA, providing a promising new in vitro model system for the analysis of anticancer gene therapies.

Synthesis and Characterization of Rutile TiO2 Nanoparticles for the Toxicological Effect on the H9c2 Cell Line from Rats

The widespread use of titanium dioxide (TiO₂) has raised concerns about potential health risks associated with its cytotoxicity in the cardiovascular system. To evaluate the cytotoxicity of TiO₂ particles, the H9c2 rat cardiomyoblasts were used as a biological model, and their toxicological susceptibility to TiO₂-anatase and TiO₂-rutile particles was studied in vitro. The study examined dose and time exposure responses. The cell viability was evaluated based on metabolic inhibition and membrane integrity loss. The results revealed that both TiO₂-anatase and TiO₂-rutile particles induced similar levels of cytotoxicity at the inhibition concentrations IC₂₅ (1.4-4.4 μg/cm²) and IC₅₀ (7.2-9.3 μg/cm²). However, at more significant concentrations, TiO₂-rutile appeared to be more cytotoxic than TiO₂-anatase at 24 h. The study found that the TiO₂ particles induced apoptosis events, but necrosis was not observed at any of the concentrations of particles used. The study considered the effects of microstructural properties, crystalline phase, and particle size in determining the capability of TiO₂ particles to induce cytotoxicity in H9c2 cardiomyoblasts. The microstress in TiO₂ particles was assessed using powder X-ray diffraction through Williamson-Hall and Warren-Averbach analysis. The analysis estimated the apparent crystallite domain and microstrain of TiO₂-anatase to be 29 nm (ε = 1.03%) and TiO₂-rutile to be 21 nm (ε = 0.53%), respectively. Raman spectroscopy, N₂ adsorption isotherms, and dynamic light scattering were used to identify the presence of pure crystalline phases (>99.9%), comparative surface areas (10 m²/g), and ζ-potential values (-24 mV). The difference in the properties of TiO₂ particles made it difficult to attribute the cytotoxicity solely to one variable.

Easy and Versatile Synthesis of Bulk Quantities of Highly Enriched 13C-Graphene Materials for Biological and Safety Applications

The preparation of bulk quantities of ¹³C-labeled graphene materials is relevant for basic investigations and for practical applications. In addition, ¹³C-labeled graphene materials can be very useful in biological and environmental studies, as they may allow the detection of graphene or its derivatives in cells or organs. In this paper, we describe the synthesis of ¹³C-labeled graphene materials (few-layer graphene, FLG, and graphene oxide, GO) on a tens of mg scale, starting from ¹³C-labeled methane to afford carbon fibers, followed by liquid-phase exfoliation (FLG) or oxidation (GO). The materials have been characterized by several analytical and microscopic techniques, including Raman and nuclear magnetic resonance spectroscopies, thermogravimetric analysis, X-ray photoelectron spectroscopy, and X-ray powder diffraction. As a proof of concept, the distribution of the title compounds in cells has been investigated. In fact, the analysis of the ¹³C/¹²C ratio with isotope ratio mass spectrometry (IRMS) allows the detection and quantification of very small amounts of material in cells or biological compartments with high selectivity, even when the material has been degraded. During the treatment of ¹³C-labeled FLG with HepG2 cells, 4.1% of the applied dose was found in the mitochondrial fraction, while 4.9% ended up in the nuclear fraction. The rest of the dose did not enter into the cell and remained in the plasma membrane or in the culture media.

Delivery of Melittin as a Lytic Agent via Graphene Nanoparticles as Carriers to Breast Cancer Cells

Melittin, as an agent to lyse biological membranes, may be a promising therapeutic agent in the treatment of cancer. However, because of its nonspecific actions, there is a need to use a delivery method. The conducted research determined whether carbon nanoparticles, such as graphene and graphene oxide, could be carriers for melittin to breast cancer cells. The studies included the analysis of intracellular pH, the potential of cell membranes, the type of cellular transport, and the expression of receptor proteins. By measuring the particle size, zeta potential, and FT-IT analysis, we found that the investigated nanoparticles are connected by electrostatic interactions. The level of melittin encapsulation with graphene was 86%, while with graphene oxide it was 78%. A decrease in pHi was observed for all cell lines after administration of melittin and its complex with graphene. The decrease in membrane polarization was demonstrated for all lines treated with melittin and its complex with graphene and after exposure to the complex of melittin with graphene oxide for the MDA-MB-231 and HFFF2 lines. The results showed that the investigated melittin complexes and the melittin itself act differently on different cell lines (MDA-MB-231 and MCF-7). It has been shown that in MDA-MD-231 cells, melittin in a complex with graphene is transported to cells via caveolin-dependent endocytosis. On the other hand, the melittin-graphene oxide complex can reach breast cancer cells through various types of transport. Other differences in protein expression changes were also observed for tumor lines after exposure to melittin and complexes.

Graphene oxide induced dynamic changes of autophagy-lysosome pathway and cell apoptosis via TFEB dysregulation in F98 cells

The extensive application of graphene oxide (GO) nanomaterials increases the risk of their release into the environment, thus posing a threat to the human body. Multiple studies indicate that GO could lead to neurotoxicity, while the intricate biological effects of GO in astrocytes remain unclear. The autophagic disorder was considered an important part of the exposure risk of GO in the application of neuromedicine. This study explored the key regulators mediating the autophagic process in rat astroglioma-derived F98 cells caused by GO, especially the dynamic changes in the cellular physiological state over time. We identified transcription factor EB (TFEB), a critical regulator of the autophagy-lysosome pathway (ALP), as a crucial factor in GO-induced autophagy flux blockade and cell apoptosis. Specifically, the prolonged exposure to GO increased the amount of its cellular internalization, which gradually prevented TFEB from entering the nucleus, thereby leading to the subsequent ALP dysfunction and excessive cell apoptosis. Furthermore, STIP1 homology and U-Box containing protein 1 (STUB1), an E3 ubiquitin ligase, was responsible for GO-triggered TFEB dysregulation, and overexpression of STUB1 helped alleviate GO cytotoxicity. Our study highlights that impaired TFEB activity underlies compromised autophagy flux in GO-induced apoptosis and opens up new avenues for the application of GO-based nanotherapeutics with specific autophagy-regulating properties in the central nervous system.

Cellular and subcellular interactions of graphene-based materials with cancerous and non-cancerous cells

Despite significant advances in early detection and personalized treatment, cancer is still among the leading causes of death globally. One of the possible anticancer approaches that is presently receiving a lot of attention is the development of nanocarriers capable of specific and efficient delivery of anticancer drugs. Graphene-based materials are promising nanocarriers in this respect, due to their high drug loading capacity and biocompatibility. In this review, we present an overview on the interactions of graphene-based materials with normal mammalian cells at the molecular level as well as cellular and subcellular levels, including plasma membrane, cytoskeleton, and membrane-bound organelles such as lysosomes, mitochondria, nucleus, endoplasmic reticulum, and peroxisome. In parallel, we assemble the knowledge about the interactions of graphene-based materials with cancerous cells, that are considered as the potential applications of these materials for cancer therapy including metastasis treatment, targeted drug delivery, and differentiation to non-cancer stem cells. We highlight the influence of key parameters, such as the size and surface chemistry of graphene-based materials that govern the efficiency of internalization and biocompatibility of these particles in vitro and in vivo. Finally, this review aims to correlate the key parameters of graphene-based nanomaterials specially graphene oxide, such as size and surface modifications, to their interactions with the cancerous and non-cancerous cells for designing and engineering them for bio-applications and especially for therapeutic purposes.

Graphene oxide nanoflackes prevent reperfussion injury of Langerdorff isolated rat heart providing antioxidative activity in situ

Carbon materials possess powerful antioxidant activity that might be promising for the development of new generation treatment of cardiovascular diseases, ischemic conditions, and reperfusion injury. The present study aimed to characterize the structure of nanosized graphene oxide (GrO) sample and evaluate the antioxidant efficacy of GrO in situ models of oxidative stress widely used in pre-clinical studies. The structure and surface chemistry of the initial samples were analyzed via LDS, RAMAN, LDI, TPD-MS, and FTIR methods. The GrO showed a strong ability to scavenge DPPH, hydroxyl, and superoxide anion free radicals and have a total antioxidant capacity. The DFT quantum-chemical calculation demonstrated the radical scavenging effect of GrO proceeding due to the physical adsorption of the free radical on the surface. For evaluation of the antioxidant effect of GrO in situ, we used the model of ischemia-reperfusion (I/R) of Langendorff isolated rat heart. We revealed that intravenous pretreatment of Wistar male rats with GrO significantly increased resistance of myocardium to I/R, improved restoration of heart function, prevented non-effective oxygen utilization, and I/R induced reactive oxygen species production in cardiac tissue. Thus, our data demonstrate the perspective of further use of GrO for the development of antiischemic therapy.

Differential modulation of endothelial cytoplasmic protrusions after exposure to graphene-family nanomaterials

Engineered nanomaterials offer the benefit of having systematically tunable physicochemical characteristics (e.g., size, dimensionality, and surface chemistry) that highly dictate the biological activity of a material. Among the most promising engineered nanomaterials to date are graphene-family nanomaterials (GFNs), which are 2-D nanomaterials (2DNMs) with unique electrical and mechanical properties. Beyond engineering new nanomaterial properties, employing safety-by-design through considering the consequences of cell-material interactions is essential for exploring their applicability in the biomedical realm. In this study, we asked the effect of GFNs on the endothelial barrier function and cellular architecture of vascular endothelial cells. Using micropatterned cell pairs as a reductionist in vitro model of the endothelium, the progression of cytoskeletal reorganization as a function of GFN surface chemistry and time was quantitatively monitored. Here, we show that the surface oxidation of GFNs (graphene, reduced graphene oxide, partially reduced graphene oxide, and graphene oxide) differentially affect the endothelial barrier at multiple scales; from the biochemical pathways that influence the development of cellular protrusions to endothelial barrier integrity. More oxidized GFNs induce higher endothelial permeability and the increased formation of cytoplasmic protrusions such as filopodia. We found that these changes in cytoskeletal organization, along with barrier function, can be potentiated by the effect of GFNs on the Rho/Rho-associated kinase (ROCK) pathway. Specifically, GFNs with higher surface oxidation elicit stronger ROCK2 inhibitory behavior as compared to pristine graphene sheets. Overall, findings from these studies offer a new perspective towards systematically controlling the surface-dependent effects of GFNs on cytoskeletal organization via ROCK2 inhibition, providing insight for implementing safety-by-design principles in GFN manufacturing towards their targeted biomedical applications.

Development of injectable graphene oxide/laponite/gelatin hydrogel containing Wharton's jelly mesenchymal stem cells for treatment of oxidative stress-damaged cardiomyocytes

In the initial stage of myocardial infarction (MI), cardiomyocyte necrosis activates aninflammatory response and increases the reactive oxygen species (ROS) content. Graphene oxide (GO) possesses potential antioxidant properties and can provide the adequate mechanical support for cell growth. The clinical studies showed that direct injection of Wharton's jelly mesenchymal stem cells (WJ-MSCs) into infarcted areas of myocardium can reduce apoptosis and fibrosis. Gelatin is a natural polymer and can promote cell attachment. Nanoclay laponite with shear-thinning properties can be injected and gelled in-situ without chemical triggers. In the study, injectable GO/laponite/gelatin (GO-LG) hydrogel was developed and characterized. The results of cell viability showed that the optimal concentration of GO flasks (200 to 300 nm) to treat cells was 100 μg/ml. Addition of nanosized GO to the laponite/gelatin (LG) hydrogel could increase the mechanical strength and have both hemocompatibility and cytocompatibility. The release of GO from LG hydrogel could inhibit the H2O2-induced oxidative stress. The GO-LG hydrogel containing WJ-MSCs could decrease inflammation and apoptosis level and increase the cell viability of cardiomyocytes under oxidative stress. We believe that utilizing this newly developed GO-LG hydrogel containing WJ-MSCs may have potential applications in the future for treatment of MI.

Hydroxyapatite Nanoparticles in Drug Delivery: Physicochemistry and Applications

Hydroxyapatite (HAP) has been the gold standard in the biomedical field due to its composition and similarity to human bone. Properties such as shape, size, morphology, and ionic substitution can be tailored through the use of different synthesis techniques and compounds. Regardless of the ability to determine its physicochemical properties, a conclusion for the correlation with the biological response it is yet to be found. Hence, a special focus on the most desirable properties for an appropriate biological response needs to be addressed. This review provides an overview of the fundamental properties of hydroxyapatite nanoparticles and the characterization of physicochemical properties involved in their biological response and role as a drug delivery system. A summary of the main chemical properties and applications of hydroxyapatite, the advantages of using nanoparticles, and the influence of shape, size, functional group, morphology, and crystalline phase in the biological response is presented. A special emphasis was placed on the analysis of chemical and physical interactions of the nanoparticles and the cargo, which was explained through the use of spectroscopic and physical techniques such as FTIR, Raman, XRD, SEM, DLS, and BET. We discuss the properties tailored for hydroxyapatite nanoparticles for a specific biomolecule based on the compilation of studies performed on proteins, peptides, drugs, and genetic material.

Dependence of Graphene Oxide (GO) Toxicity on Oxidation Level, Elemental Composition, and Size

The mass production of graphene oxide (GO) unavoidably elevates the chance of human exposure, as well as the possibility of release into the environment with high stability, raising public concern as to its potential toxicological risks and the implications for humans and ecosystems. Therefore, a thorough assessment of GO toxicity, including its potential reliance on key physicochemical factors, which is lacking in the literature, is of high significance and importance. In this study, GO toxicity, and its dependence on oxidation level, elemental composition, and size, were comprehensively assessed. A newly established quantitative toxicogenomic-based toxicity testing approach, combined with conventional phenotypic bioassays, were employed. The toxicogenomic assay utilized a GFP-fused yeast reporter library covering key cellular toxicity pathways. The results reveal that, indeed, the elemental composition and size do exert impacts on GO toxicity, while the oxidation level exhibits no significant effects. The UV-treated GO, with significantly higher carbon-carbon groups and carboxyl groups, showed a higher toxicity level, especially in the protein and chemical stress categories. With the decrease in size, the toxicity level of the sonicated GOs tended to increase. It is proposed that the covering and subsequent internalization of GO sheets might be the main mode of action in yeast cells.

Graphene oxide disrupted mitochondrial homeostasis through inducing intracellular redox deviation and autophagy-lysosomal network dysfunction in SH-SY5Y cells

Graphene oxide (GO) nanomaterials have significant advantages for drug delivery and electrode materials in neural science, however, their exposure risks to the central nervous system (CNS) and toxicity concerns are also increased. The current studies of GO-induced neurotoxicity remain still ambiguous, let alone the mechanism of how complicated GO chemistry affects its biological behavior with neural cells. In this study, we characterized the commercially available GO in detail and investigated its biological adverse effects using cultured SH-SY5Y cells. We found that ultrasonic processing in medium changed the oxidation status and surface reactivity on the planar surface of GO due to its hydration activity, causing lipid peroxidation and cell membrane damage. Subsequently, ROS-disrupted mitochondrial homeostasis, resulting from the activation of NOX2 signaling, was observed following GO internalization. The autophagy-lysosomal network was initiated as a defensive reaction to obliterate oxidative damaged mitochondria and foreign nanomaterials, which was ineffective due to reduced lysosomal degradation capacity. These sequential cellular responses exacerbated mitochondrial stress, leading to apoptotic cell death. These data highlight the importance of the structure-related activity of GO on its biological properties and provide an in-depth understanding of how GO-derived cellular redox signaling induces mitochondrion-related cascades that modulate cell functionality and survival.

Peptidic vaccines: The new cure for heart diseases?

Cardiovascular disease continues to be the most common cause of death worldwide. The global burden is so high that numerous organizations are providing counseling recommendations and annual revisions of current pharmacological and non-pharmacological treatments as well as risk prediction for disease prevention and further progression. Although primary preventive interventions targeting risk factors such as obesity, hypertension, smoking, and sedentarism have led to a global decline in hospitalization rates, the aging population has overwhelmed these efforts on a global scale. This review focuses on peptidic vaccines, with the known and not well-known autoantigens in atheroma formation or acquired cardiac diseases, as novel potential immunotherapy approaches to counteract harmful heart disease continuance. We summarize how cancer immunomodulatory strategies started novel approaches to modulate the innate and adaptive immune responses, and how they can be targeted for therapeutic purposes in the cardiovascular system. Brief descriptions focused on the processes that start as either immunologic or non-immunologic, and the ultimate loss of cardiac muscle cell contractility as the outcome, are discussed. We conclude debating how novel strategies with nanoparticles and nanovaccines open a promising therapeutic option to reduce or prevent cardiovascular diseases.

Characterization of carotid endothelial cell proliferation on Au, Au/GO, and Au/rGO surfaces by electrical impedance spectroscopy

To the best of the authors' knowledge, testing the biocompatibility of graphene coatings can be considered as the first to demonstrate human carotid endothelial cell (HCtAEC) proliferation on Au, graphene oxide-coated Au (Au/GO), and reduced graphene oxide-coated Au (Au/rGO) surfaces. We hypothesized that stent material modified with graphene (G)-based coatings could be used as electrodes for electrical impedance spectroscopy (EIS) in monitoring cell cultures, i.e., endothelialization. Alamar Blue cell viability assay and cell staining and cell counting with optical images were performed. For EIS analysis, an EIS sensor consisting of Au surface electrodes was produced by the photolithographic technique. Surface characterizations were performed by considering scanning electron microscope (SEM) and water contact angle analyses. Results showed that GO and rGO coatings did not prevent neither the electrical measurements nor the cell proliferation and that rGO had a positive effect on HCtAEC proliferation. The rate of increase of impedance change from day 1 to day 10 was nearly fivefold for all electrode surfaces. Alamar Blue assay performed to monitor cell proliferation rates between groups, and rGO has shown the highest Alamar Blue reduction value of 43.65 ± 8.79%. Graphical abstract.

Do biomedical engineers dream of graphene sheets?

During the past few years, graphene has outstandingly emerged as a key nanomaterial for boosting the performance of commercial, industrial and scientific related technologies. The popularity of this novel nanomaterial in biomedical engineering is due to its excellent biological, electronic, optical and thermal properties that, as a whole, surpass the features of commonly used biomaterials and consequently open a wide range of applications so far within the reach of science fiction. In this minireview, the potential of graphene and its based materials in the expanding biomedical field is highlighted with focus on groundbreaking diagnostic, monitoring and therapeutic strategies. Some of the major challenges related to the synthesis and safety of graphene-based materials are also briefly discussed because of their critical importance in bringing this class of carbon materials closer to the clinic.

Graphene-Based Nanomaterials in Soil: Ecotoxicity Assessment Using Enchytraeus crypticus Reduced Full Life Cycle

Graphene-based nanomaterials (GBNs) possess unique physicochemical properties, allowing a wide range of applications in physical, chemical, and biomedical fields. Although GBNs are broadly used, information about their adverse effects on ecosystem health, especially in the terrestrial environment, is limited. Therefore, this study aims to assess the toxicity of two commonly used derivatives of GBNs, graphene oxide (GO) and reduced graphene oxide (rGO), in the soil invertebrate Enchytraeus crypticus using a reduced full life cycle test. At higher exposure concentrations, GO induced high mortality and severe impairment in the reproduction rate, while rGO showed little adverse effect up to 1000 mg/kg. Collectively, our body of results suggests that the degree of oxidation of GO correlates with their toxic effects on E. crypticus, which argues against generalization on GBNs ecotoxicity. Identifying the key factors affecting the toxicity of GBNs, including ecotoxicity, is urgent for the design of safe GBNs for commercial purposes.

Characteristics and toxicity assessment of electrospun gelatin/PCL nanofibrous scaffold loaded with graphene in vitro and in vivo

Background: Electrospun gelatin/polycaprolactone (Gt/PCL) nanofibrous scaffolds loaded with graphene are novel nanomaterials with the uniquely strong property of electrical conductivity, which have been widely investigated for their potential applications in cardiovascular tissue engineering, including in bypass tracts for atrioventricular block.

Purpose: Electrospun Gt/PCL/graphene nanofibrous mats were successfully produced. Scanning electron micrography showed that the fibers with graphene were smooth and homogeneous. In vitro, to determine the biocompatibility of the scaffolds, hybrid scaffolds with different fractions of graphene were seeded with neonatal rat ventricular myocytes. In vivo, Gt/PCL scaffolds with different concentrations of graphene were implanted into rats for 4, 8 and 12 weeks.

Results: CCK-8 assays and histopathological staining (including DAPI, cTNT, and CX43) indicated that cells grew and survived well on the hybrid scaffolds if the mass fraction of graphene was lower than 0.5%. After implanting into rats for 4, 8 or 12 weeks, there was no gathering of inflammatory cells around the nanomaterials according to the HE staining results.

Conclusion: The results indicate that Gt/PCL nanofibrous scaffolds loaded with graphene have favorable electrical conductivity and biological properties and may be suitable scaffolds for use in the treatment of atrioventricular block. These findings alleviate safety concerns and provide novel insights into the potential applications of Gt/PCL loaded with graphene, offering a solid foundation for comprehensive in vivo studies.

Thermal Reduction of Graphene Oxide Mitigates Its In Vivo Genotoxicity Toward Xenopus laevis Tadpoles

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H₂ atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg·L⁻¹). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate “safer-by-design” strategy for the development of a safer material for environment.

In vitro cardiotoxicity evaluation of graphene oxide

Graphene is a two-dimensional (2D) monolayer of carbon atoms, tightly packed, forming a honey comb crystal lattice, with physical, chemical, and mechanical properties greatly used for energy storage, electrochemical devices, and in nanomedicine. Many studies showed that nanomaterials have side-effects on health. At present, there is a lack of information regarding graphene and its derivatives including their cardiotoxic properties. The aim of the present study was to evaluate the toxicity of nano-graphene oxide (nano-GO) in the rat cardiomyoblast cell line H9c2 and the involvement of oxidative processes. The cell viability was evaluated with the fluorescein diacetate (FDA)/propidium iodide (PI) and in the trypan blue exclusion assay, furthermore mitochondrial membrane potential and production of free radicals were measured. Genotoxicity was evaluated in comet assay and low molecular weight DNA experiment. Reduction of cell viability with 20, 40, 60, 80, and 100 μg/mL nano-GO was observed after 24 h incubation. Besides, nano-GO induced a mitochondrial hyperpolarization and a significant increase of free radicals production in the same concentrations. DNA breaks were observed at 40, 60, 80, and 100 μg/mL. This DNA damage was accompanied by a significant increase in LMW DNA only at 40 μg/mL. In conclusion, the nano-GO caused cardiotoxicity in our in vitro model, with mitochondrial disturbances, generation of reactive species and interactions with DNA, indicating the importance of the further evaluation of the safety of nanomaterials.

The impact of processing on the cytotoxicity of graphene oxide

In-house prepared graphene oxide (GO) was processed via base washing, sonication, cleaning and combinations of these processing techniques to evaluate the impact on the flake morphology, composition and cytotoxicity of the material. The flakes of unprocessed GO were relatively planar, but upon base washing, the flakes became textured exhibiting many folds and creases observed by AFM. In addition to the pronounced effect on the topography, base washing increased the C/O ratio and increased the cytotoxicity of GO on all four cell lines studied determined via the WST-8 assay. Sonicating the unprocessed and base washed samples resulted in smaller flakes with a similar topography; the base washed flakes lost the texture previously observed upon sonication. The sonicated samples were more toxic than the unprocessed sample, attributed to the smaller flake size, but were interestingly less toxic than the base washed, unsonicated sample despite the base washed unsonicated sample having a larger flake size. This unexpected finding was confirmed by a second analyst using the same, and a different source of GO and resulted in the conclusion that the morphology of GO greatly impacts the cytotoxicity. Cleaning the GO reduced the amount of nitrogen and sulfur impurities in the sample but had no significant impact on the cytotoxicity of the material. It was observed that nutrient depletion via nanomaterial adsorption was not the route of cytotoxicity for the GO samples studied.

MoS2 flakes stabilized with DNA/RNA nucleotides: In vitro cell response

Two-dimensional transition metal dichalcogenides (TMDCs), such as MoS₂ and WS₂, have recently emerged as nanomaterials with potential use in biomedicine. An attractive means to favor their interaction with biological media is the use of proper biomolecules as exfoliating/dispersing agents. Here, MoS₂ flakes were stabilized with different small functional biomolecules such as adenosine monophosphate (AMP), guanosine monophosphate (GMP) and flavin mononucleotide (FMN) through the strong nucleotide-MoS₂ interaction of Lewis acid-base type, rather than just on the weak dispersive and hydrophobic forces commonly associated with the use of many surfactants. The impact of the nucleotide-stabilized MoS₂ flakes on the viability and cell proliferation, on the production of intracellular reactive oxygen species (ROS), and on the preosteoblast differentiation process (early stage) has been also evaluated, as well as the incorporation and intracellular localization of the nanomaterials by MC3T3-E1 and Saos-2 cells. The nucleotide-stabilized MoS₂ flakes were found to exhibit excellent biocompatibility. Furthermore, their incorporation did not affect the integrity of the cell plasma membrane, which makes them ideal candidates for delivering drug/gene directly into cells. The in vitro cell response of tumor cells to these nanomaterials differs from that of undifferentiated cells, which provides the basis for their potential use in cancer therapy.

Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment

Graphene and its derivatives are heralded as "miracle" materials with manifold applications in different sectors of society from electronics to energy storage to medicine. The increasing exploitation of graphene-based materials (GBMs) necessitates a comprehensive evaluation of the potential impact of these materials on human health and the environment. Here, we discuss synthesis and characterization of GBMs as well as human and environmental hazard assessment of GBMs using in vitro and in vivo model systems with the aim to understand the properties that underlie the biological effects of these materials; not all GBMs are alike, and it is essential that we disentangle the structure-activity relationships for this class of materials.

Systematic toxicity investigation of graphene oxide: evaluation of assay selection, cell type, exposure period and flake size

Understanding the toxicity of nanomaterials is essential for the safe and sustainable development of new applications. This is particularly true for a nanomaterial as widely used as graphene oxide (GO), which is utilized as films for electronics, membranes for filtration, drug carriers and more. Despite this, the current literature presents conflicting results on the overall toxicity of GO. Here, the cytotoxicity of three sizes of commercially available GO was investigated on six cell lines, as values of NOAEL/LOAEL. The effectiveness of four viability assays was also evaluated. The overall toxicity of GO greatly varied between cell lines; the suspension cells showed a greater response to the GO treatment compared to the adherent cell lines. Time dependent cytotoxicity was also cell line dependent, with only one cell line demonstrating obvious dependence. The six cell lines were also tested to evaluate their response to varying GO flake sizes: the suspension/phagocytic cells showed little variation in viability, while a difference was observed for the adherent/non-phagocytic cell lines. By systematically studying the effect of dose, GO size and treatment time for the six cell lines by using commercially available GO samples, we eliminate many of the variables which may result in the conflicting reports on the cytotoxicity of GO in the literature.

Nanomedicine for the cardiac myocyte: Where are we?

Biomedical achievements in the last few decades, leading to successful therapeutic interventions, have considerably improved human life expectancy. Nevertheless, the increasing load and the still suboptimal outcome for patients with cardiac dysfunction underlines the relevance of continuous research to develop novel therapeutics for these diseases. In this context, the field of nanomedicine has attracted a lot of attention due to the potential novel treatment possibilities, such as controlled and sustained release, tissue targeting, and drug protection from degradation. For cardiac myocytes, which constitute the majority of the heart by mass and are the contractile unit, new options have been explored in terms of the use of nanomaterials (NMs) for therapy, diagnosis, and tissue engineering. This review focuses on the advances of nanomedicine targeted to the cardiac myocyte: first presenting the NMs used and the principal cardiac myocyte-based afflictions, followed by an overview of key advances in the field, including NMs interactions with the cardiac myocyte, therapy delivery, diagnosis based on imaging, and tissue engineering for tissue repair and heart-on-a-chip devices.