Dental implant failure possibly attributed to embedded pencil graphite: first clinical report.

Implant failures have been associated with a diversity of etiologic processes, predominately arising from bone loss (peri-implantitis) due to inadequate maintenance of oral hygiene or excess luting agents. The aim of this article is to report a novel case of the apparent failure of a dental implant to undergo osseointegration in the presence of submerged pencil graphite. Practitioners are advised to carefully evaluate the clinical and radiographic site of a proposed implant for occult foreign substances. Embedded pencil graphite in the jawbone may promote a foreign body reaction and should be considered in the list of possible contributing factors to dental implant complications.

Case study: risk associated to wearing silver or graphene nanoparticle-coated facemasks for protection against COVID-19.

The world is living a pandemic situation derived from the worldwide spreading of SARS-CoV-2 virus causing COVID-19. Facemasks have proven to be one of the most effective prophylactic measures to avoid the infection that has made that wearing of facemasks has become mandatory in most of the developed countries. Silver and graphene nanoparticles have proven to have antimicrobial properties and are used as coating of these facemasks to increase the effectivity of the textile fibres. In the case of silver nanoparticles, we have estimated that in a real scenario the systemic (internal) exposure derived from wearing these silver nanoparticle facemasks would be between 7.0 × 10-5 and 2.8 × 10-4 mg/kg bw/day. In addition, we estimated conservative systemic no effect levels between 0.075 and 0.01 mg/kg bw/day. Therefore, we estimate that the chronic exposure to silver nanoparticles derived form facemasks wearing is safe. In the case of graphene, we detected important gaps in the database, especially regarding toxicokinetics, which prevents the derivation of a systemic no effect level. Nevertheless, the qualitative approach suggests that the risk of dermal repeated exposure to graphene is very low, or even negligible. We estimated that for both nanomaterials, the risk of skin sensitisation and genotoxicity is also negligible.

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.

Biomimetic reduced graphene oxide coated collagen scaffold for in situ bone regeneration.

A variety of bone-related diseases and injures and limitations of traditional regeneration methods require new tissue substitutes. Tissue engineering and regeneration combined with nanomedicine can provide different natural or synthetic and combined scaffolds with bone mimicking properties for implantation in the injured area. In this study, we synthesized collagen (Col) and reduced graphene oxide coated collagen (Col-rGO) scaffolds, and we evaluated their in vitro and in vivo effects on bone tissue repair. Col and Col-rGO scaffolds were synthesized by chemical crosslinking and freeze-drying methods. The surface topography, and the mechanical and chemical properties of scaffolds were characterized, showing three-dimensional (3D) porous scaffolds and successful coating of rGO on Col. The rGO coating enhanced the mechanical strength of Col-rGO scaffolds to a greater extent than Col scaffolds by 2.8 times. Furthermore, Col-rGO scaffolds confirmed that graphene addition induced no cytotoxic effects and enhanced the viability and proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) with 3D adherence and expansion. Finally, scaffold implantation into rabbit cranial bone defects for 12 weeks showed increased bone formation, confirmed by Hematoxylin-Eosin (H&E) and alizarin red staining. Overall, the study showed that rGO coating improves Col scaffold properties and could be a promising implant for bone injuries.

Graphene Family Nanomaterials in Ocular Applications: Physicochemical Properties and Toxicity.

Graphene family nanomaterials (GFNs) are rapidly emerging for ocular applications due to their outstanding physicochemical properties. Since the eyes are very sensitive organs and the contact between the eyes and GFNs in eye drops, contact lenses, intraocular drug delivery systems and biosensors and even the workers handling these nanomaterials is inevitable, it is necessary to investigate their ocular toxicities and physiological interactions with cells as well as their toxicity mechanisms. The toxicity of GFNs can be extremely affected by their physicochemical properties, including composition, size, surface chemistry, and oxidation level as well as dose and the time of exposure. Up to now, there are several studies on the in vitro and in vivo toxicity of GFNs; however, a comprehensive review on ocular toxicity and applications of GFNs is missing, and a knowledge about the health risks of eye exposure to the GFNs is predominantly unspecified. This review highlights the ocular applications of GFNs and systematically covers the most recent advances of GFNs' physicochemical properties, in vitro and in vivo ocular toxicity, and the possible toxicity mechanisms as well as provides some perspectives on the potential risks of GFNs in material development and biomedical applications.

Enhanced Hemocompatibility of a Direct Chemical Vapor Deposition-Derived Graphene Film.

A wide range of biomedical devices are being used to treat cardiovascular diseases, and thus they routinely come into contact with blood. Insufficient hemocompatibility has been found to impair the functionality and safety of these devices through the activation of blood coagulation and the immune system. Numerous attempts have been made to develop surface modification approaches of the cardiovascular devices to improve their hemocompatibility. However, there are still no ideal "blood-friendly" coating materials, which possess the desired hemocompatibility, tissue compatibility, and mechanical properties. As a novel multifunctional material, graphene has been proposed for a wide range of biomedical applications. The chemical inertness, atomic smoothness, and high durability make graphene an ideal candidate as a surface coating material for implantable devices. Here, we evaluated the hemocompatibility of a graphene film prepared on quartz glasses (Gra-glasses) from a direct chemical vapor deposition process. We found that the graphene coating, which is free of transfer-mediating polymer contamination, significantly suppressed platelet adhesion and activation, prolonged coagulation time, and reduced ex vivo thrombosis formation. We attribute the excellent antithrombogenic properties of the Gra-glasses to the low surface roughness, low surface energy (especially the low polar component of the surface energy), and the negative surface charge of the graphene film. Given these excellent hemocompatible properties, along with its chemical inertness, high durability, and molecular impermeability, a graphene film holds great promise as an antithrombogenic coating for next-generation cardiovascular devices.

Graphene oxide aggravated dextran sulfate sodium-induced colitis through intestinal epithelial cells autophagy dysfunction.

Graphene oxide (GO) is one of the most promising nanomaterials used in biomedicine. However, studies about its adverse effects on the intestine in state of inflammation remain limited. This study aimed to explore the underlying effects of GO on intestinal epithelial cells (IECs) in vitro and colitis in vivo. We found that GO could exert toxic effects on NCM460 cells in a dose- and time-dependent manner and promote inflammation. Furthermore, GO caused lysosomal dysfunction and then blockaded autophagy flux. Moreover, pharmacological autophagy inhibitor 3-Methyladenine could reverse GO-induced LC3B and p62 expression levels, reduce expression levels of IL-6, IL-8, TLR4, and CXCL2, and increase the level of IL-10. In vivo, C57BL/6 mice were treated with 2.5% dextran sulfate sodium (DSS) in drinking water for five consecutive days to induce colitis. Then, GO at 60 mg/kg dose was administered through the oral route every two days from day 2 to day 8. These results showed that GO aggravated DSS-induced colitis, characterized by shortening of the colon and severe pathological changes, and induced autophagy. In conclusion, GO caused the abnormal autophagy in IECs and exacerbated DSS-induced colitis in mice. Our research indicated that GO may contribute to the development of intestinal inflammation by inducing IECs autophagy dysfunction.

Investigating biological effects of multidimensional carboxylated carbon-based nanomaterials on human lung A549 cells revealed via non-targeted metabolomics approach.

The biological responses of multidimensional carboxylated carbon-based nanomaterials (c-CBNs), including carboxylated graphene, carbon nanotube, and fullerene, on human lung A549 cells were investigated by using metabolomics technology. The structure and components of c-CBNs were characterized, and their biological effects were evaluated through cell apoptosis and viability analysis. Additionally, the metabolomics analysis of the nanomaterial-cell interaction system was performed using the established platform combining liquid chromatography-mass spectrometry (LC-MS) with the bioinformatics system. Results revealed that all tested c-CBNs demonstrated some biological effects in our cell model. However, significant metabolomic alterations induced by c-CBNs were also observed mainly in amino acids, organic acids, glycerophospholipids, and glycerolipids. Further, under the tested concentrations, the multiple dimensions of c-CBNs played a major role in determining the metabolic process in various interaction modes. This study provides an advanced alternative for evaluating metabolic effects of multidimensional nanomaterials through metabolomics technology considering the association between dimension and metabolic characteristics.

Unravelling the Potential of Graphene Quantum Dots in Biomedicine and Neuroscience.

Quantum dots (QDs) are semiconducting nanoparticles that have been gaining ground in various applications, including the biomedical field, thanks to their unique optical properties. Recently, graphene quantum dots (GQDs) have earned attention in biomedicine and nanomedicine, thanks to their higher biocompatibility and low cytotoxicity compared to other QDs. GQDs share the optical properties of QD and have proven ability to cross the blood-brain barrier (BBB). For this reason, GQDs are now being employed to deepen our knowledge in neuroscience diagnostics and therapeutics. Their size and surface chemistry that ease the loading of chemotherapeutic drugs, makes them ideal drug delivery systems through the bloodstream, across the BBB, up to the brain. GQDs-based neuroimaging techniques and theranostic applications, such as photothermal and photodynamic therapy alone or in combination with chemotherapy, have been designed. In this review, optical properties and biocompatibility of GQDs will be described. Then, the ability of GQDs to overtake the BBB and reach the brain will be discussed. At last, applications of GQDs in bioimaging, photophysical therapies and drug delivery to the central nervous system will be considered, unraveling their potential in the neuroscientific field.

In vivo immunological response of exposure to PEGylated graphene oxide via intraperitoneal injection.

Polyethylene glycol functionalization is believed to have the capacity of endowing nanomaterials with stealth characteristics, which can diminish the arrest by macrophages and adverse immunological response. However, our previous study provided evidences that polyethylene glycol-functionalized graphene oxide (GOP) stimulated a strong immunological response to macrophages despite non-internalization in vitro, raising safety concerns and potential immunostimulation use of GOP. In light of this finding, we herein systematically study the in vivo immunological response upon the exposure to GOP via intraperitoneal injection. Taking cytokines production, cell types in the peritoneal fluid, biochemical index, hematology and histopathology as in vivo indicators, we demonstrate that GOP still remains the stealth-but-activating capacity on macrophages in a time and dose-dependent manner. Specifically, the immune response can be significantly elevated after a single high-dose injection, indicating that GOP can be a new candidate adjuvant for immunotherapy. For multiple low dose injections, the immune response is gentle, temporary, and tolerable, which manifests the biocompatibility of GOP in general drug delivery. The above results can thus provide guidance for safe and rational use of GOP for various biomedical applications.

Improved Biocompatibility of Amino-Functionalized Graphene Oxide in Caenorhabditis elegans.

Graphene oxide (GO) holds high promise for diagnostic and therapeutic applications in nanomedicine but reportedly displays immunotoxicity, underlining the need for developing functionalized GO with improved biocompatibility. This study describes adverse effects of GO and amino-functionalized GO (GONH2 ) during Caenorhabditis elegans development and ageing upon acute or chronic exposure. Chronic GO treatment throughout the C. elegans development causes decreased fecundity and a reduction of animal size, while acute treatment does not lead to any measurable physiological decline. However, RNA-Sequencing data reveal that acute GO exposure induces innate immune gene expression. The p38 MAP kinase, PMK-1, which is a well-established master regulator of innate immunity, protects C. elegans from chronic GO toxicity, as pmk-1 mutants show reduced tissue-functionality and facultative vivipary. In a direct comparison, GONH2 exposure does not cause detrimental effects in the wild type or in pmk-1 mutants, and the innate immune response is considerably less pronounced. This work establishes enhanced biocompatibility of amino-functionalized GO in a whole-organism, emphasizing its potential as a biomedical nanomaterial.

Effects of carbon nanotubes and derivatives of graphene oxide on soil bacterial diversity.

Carbon nanotubes (CNTs), reduced graphene oxide (rGO) and ammonia-functionalized graphene oxide (aGO), are nanomaterials with useful properties, such as high tensile strength, elasticity and thermal conductivity. However, following their use, their release into the environment is inevitable. While CNTs have been shown to influence soil bacterial diversity, albeit only at concentrations far exceeding predicted rates of release, the effects of rGO have only been examined using pure bacterial cultures, and those of aGO are unknown. Here, we investigated the effects of CNTs, rGO and aGO, at three time points (7, 14 and 30days), and over a range of concentrations (1ng, 1µg and 1mgkg dry soil-1), on soil bacterial diversity using 16S rRNA amplicon sequencing. Graphite was included to facilitate comparisons with a similar and naturally occurring carbon material, while the inclusion of GO allowed the effects of GO modification to be isolated. Bacterial community composition, but not alpha diversity, was altered by all treatments except the low GO, low rGO and high aGO treatments on day 14 only. In all cases, the nanomaterials led to shifts in community composition that were of similar magnitude to those induced by graphite and GO, albeit with differences in the taxa affected. Our study highlights that carbon nanomaterials can induce changes in soil bacterial diversity, even at doses that are environmentally realistic.

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.

Effects of graphene oxide and graphite on soil bacterial and fungal diversity.

Graphene oxide (GO) is an oxidized form of graphene that is relatively cheap and easy to produce. This has heralded its widespread use in a range of industries, with its likelihood of release into the environment increasing accordingly. In pure culture, GO has been shown to influence bacteria and fungi, but its effects on environmental microbial communities remain poorly characterized, despite the important ecosystem services that these organisms underpin. Here, we characterized the effects of GO and graphite, over time (7, 14 and 30 days) and at three concentrations (1 ng, 1 µg and 1 mg kg dry soil-1), on soil bacterial and fungal diversity using 16S rRNA and ITS2 gene amplicon sequencing. Graphite was included as a reference material as it is widely distributed in the environment. Neither GO or graphite had significant effects on the alpha diversity of microbial communities. The composition of bacterial and fungal communities, however, was significantly influenced by both materials at all doses. With the exception of the lowest GO dose on day 14, these effects were apparent for all treatments over the course of the experiment. Nonetheless, the effects of GO and graphite were of similar magnitude, albeit with some differences in the taxa affected.

Understanding the influence of carbon nanomaterials on microbial communities.

Carbon nanomaterials (CNMs) are widely used because of their unique advantages in recent years. At the same time, the influence of CNMs on the environment is becoming increasingly prominent. This review mainly introduces the research progress in the effects of fullerenes, multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs) and graphene on microorganisms and their toxicity mechanisms. On this basis, we have analyzed beneficial and adverse effects of fullerenes, graphene, MWCNTs and SWCNTs to microorganisms, and discussed the similarities of the toxicity mechanisms of different CNMs on microorganisms. This review helps provide ideas on how to protect microorganisms from the impacts of carbon nanomaterials, and it will be conductive to providing a strong theoretical basis for better application of carbon nanomaterials.

A Highly Efficient Tumor-Targeting Nanoprobe with a Novel Cell Membrane Permeability Mechanism.

Efficient tumor targeting has been a great challenge in the clinic for a very long time. The traditional targeting methods based on enhanced permeability and retention (EPR) effects show only an ≈5% targeting rate. To solve this problem, a new graphene-based tumor cell nuclear targeting fluorescent nanoprobe (GTTN), with a new tumor-targeting mechanism, is developed. GTTN is a graphene-like single-crystalline structure amphiphilic fluorescent probe with a periphery that is functionalized by sulfonic and hydroxyl groups. This probe has the characteristic of specific tumor cell targeting, as it can directly cross the cell membrane and specifically target to the tumor cell nucleus by the changed permeability of the tumor cell membranes in the tumor tissue. This new targeting mechanism is named the cell membrane permeability targeting (CMPT) mechanism, which is very different from the EPR effect. These probes can recognize tumor tissue at a very early stage and track the invasion and metastasis of tumor cells at the single cell level. The tumor-targeting rate is improved from less than 5% to more than 50%. This achievement in efficient and accurate tumor cell targeting will speed up the arrival of a new era of tumor diagnosis and treatment.

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.

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 SIGNIFICANCE: Graphene 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.