Hard corona composition and cellular toxicities of the graphene sheets

Advancing Albumin Isolation from Human Serum with Graphene Oxide and Derivatives: A Novel Approach for Clinical Applications

This study introduces a novel, environmentally friendly albumin isolation method using graphene oxide (GO). GO selectively extracts albumin from serum samples, leveraging the unique interactions between GO's oxygen-containing functional groups and serum proteins. This method achieves high purification efficiency without the need for hazardous chemicals. Comprehensive characterization of GO and reduced graphene oxide (rGO) through techniques such as X-ray diffraction (XRD) analysis, Raman spectroscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) confirmed the structural and functional group transformations crucial for protein binding. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry analyses demonstrated over 95% purity of isolated albumin, with minimal contamination from other serum proteins. The developed method, optimized for pH and incubation conditions, showcases a green, cost-effective, and simple alternative for albumin purification, promising broad applicability in biomedical research and clinical applications.

Graphene Oxide Nanosheets Toxicity in Mice Is Dependent on Protein Corona Composition and Host Immunity

Two-dimension graphene oxide (GO) nanosheets with high and low serum protein binding profiles (high/low hard-bound protein corona/HChigh/low) are used in this study as model materials and screening tools to investigate the underlying roles of the protein corona on nanomaterial toxicities in vivo. We proposed that the in vivo biocompatibility/nanotoxicity of GO is protein corona-dependent and host immunity-dependent. The hypothesis was tested by injecting HChigh/low GO nanosheets in immunocompetent ICR/CD1 and immunodeficient NOD-scid II2rγnull mice and performed histopathological and hematological evaluation studies on days 1 and 14 post-injection. HClow GO induced more severe acute lung injury compared to HChigh GO in both immunocompetent and immunodeficient mice, with the effect being particularly pronounced in immunocompetent animals. Additionally, HClow GO caused more significant liver injury in both types of mice, with immunodeficient mice being more susceptible to its hepatotoxic effects. Moreover, administration of HClow GO resulted in increased hematological toxicity and elevated levels of serum pro-inflammatory cytokines in immunocompromised and immunocompetent mice, respectively. Correlation studies were conducted to explore the impact of distinct protein corona compositions on resulting toxicities in both immunocompetent and immunodeficient mice. This facilitated the identification of consistent patterns, aligning with those observed in vitro, thus indicating a robust in vitro-in vivo correlation. This research will advance our comprehension of how hard corona proteins interact with immune cells, leading to toxicity, and will facilitate the development of improved immune-modulating nanomaterials for therapeutic purposes.

Perilous paradigm of graphene oxide and its derivatives in biomedical applications: Insight to immunocompatibility

With advancements in nanotechnology and innovative materials, Graphene Oxide nanoparticles (GONP) have attracted lots of attention among the diverse types of nanomaterials owing to their distinctive physicochemical characteristics. However, the usage at scientific and industrial level has also raised concern to their toxicological interaction with biological system. Understanding these interactions is crucial for developing guidelines and recommendations for applications of GONP in various sectors, like biomedicine and environmental technologies. This review offers crucial insights and an in-depth analysis to the biological processes associated with GONP immunotoxicity with multiple cell lines including human whole blood cultures, dendritic cells, macrophages, and multiple cancer cell lines. The complicated interactions between graphene oxide nanoparticles and the immune system, are highlighted in this work, which reveals a range of immunotoxic consequences like inflammation, immunosuppression, immunostimulation, hypersensitivity, autoimmunity, and cellular malfunction. Moreover, the immunotoxic effects are also highlighted with respect to in vivo models like mice and zebrafish, insighting GO Nanoparticles' cytotoxicity. The study provides invaluable review for researchers, policymakers, and industrialist to understand and exploit the beneficial applications of GONP with a controlled measure to human health and the environment.

Understanding interactions between biomolecules and two-dimensional nanomaterials using in silico microscopes

Two-dimensional (2D) nanomaterials such as graphene are increasingly used in research and industry for various biomedical applications. Extensive experimental and theoretical studies have revealed that 2D nanomaterials are promising drug delivery vehicles, yet certain materials exhibit toxicity under biological conditions. So far, it is known that 2D nanomaterials possess strong adsorption propensities for biomolecules. To mitigate potential toxicity and retain favorable physical and chemical properties of 2D nanomaterials, it is necessary to explore the underlying mechanisms of interactions between biomolecules and nanomaterials for the subsequent design of biocompatible 2D nanomaterials for nanomedicine. The purpose of this review is to integrate experimental findings with theoretical observations and facilitate the study of 2D nanomaterial interaction with biomolecules at the molecular level. We discuss the current understanding and progress of 2D nanomaterial interaction with proteins, lipid membranes, and DNA based on molecular dynamics (MD) simulation. In this review, we focus on the 2D graphene nanosheet and briefly discuss other 2D nanomaterials. With the ever-growing computing power, we can image nanoscale processes using MD simulation that are otherwise not observable in experiment. We expect that molecular characterization of the complex behavior between 2D nanomaterials and biomolecules will help fulfill the goal of designing effective 2D nanomaterials as drug delivery platforms.

Progress in the Development of Graphene-Based Biomaterials for Tissue Engineering and Regeneration

Over the last few decades, tissue engineering has become an important technology for repairing and rebuilding damaged tissues and organs. The scaffold plays an important role and has become a hot pot in the field of tissue engineering. It has sufficient mechanical and biochemical properties and simulates the structure and function of natural tissue to promote the growth of cells inward. Therefore, graphene-based nanomaterials (GBNs), such as graphene and graphene oxide (GO), have attracted wide attention in the field of biomedical tissue engineering because of their unique structure, large specific surface area, good photo-thermal effect, pH response and broad-spectrum antibacterial properties. In this review, the structure and properties of typical GBNs are summarized, the progress made in the development of GBNs in soft tissue engineering (including skin, muscle, nerve and blood vessel) are highlighted, the challenges and prospects of the application of GBNs in soft tissue engineering have prospected.

Nano-bio interfaces effect of two-dimensional nanomaterials and their applications in cancer immunotherapy

The field of two-dimensional (2D) nanomaterial-based cancer immunotherapy combines research from multiple subdisciplines of material science, nano-chemistry, in particular nano-biological interactions, immunology, and medicinal chemistry. Most importantly, the "biological identity" of nanomaterials governed by bio-molecular corona in terms of bimolecular types, relative abundance, and conformation at the nanomaterial surface is now believed to influence blood circulation time, bio-distribution, immune response, cellular uptake, and intracellular trafficking. A better understanding of nano-bio interactions can improve utilization of 2D nano-architectures for cancer immunotherapy and immunotheranostics, allowing them to be adapted or modified to treat other immune dysregulation syndromes including autoimmune diseases or inflammation, infection, tissue regeneration, and transplantation. The manuscript reviews the biological interactions and immunotherapeutic applications of 2D nanomaterials, including understanding their interactions with biological molecules of the immune system, summarizes and prospects the applications of 2D nanomaterials in cancer immunotherapy.

Formation and biological effects of protein corona for food-related nanoparticles

The rapid development of nanoscience and nanoengineering provides new perspectives on the composition of food materials, and has great potential for food biology research and applications. The use of nanoparticle additives and the discovery of endogenous nanoparticles in food make it important to elucidate in vivo safety of nanomaterials. Nanoparticles will spontaneously adsorb proteins during transporting in blood and a protein corona can be formed on the nanoparticle surface inside the human body. Protein corona affects the physicochemical properties of nanoparticles and the structure and function of proteins, which in turn affects a series of biological reactions. This article reviewed basic information about protein corona of food-related nanoparticles, elucidated the influence of protein corona on nanoparticles properties and protein structure and function, and discussed the effect of protein corona on nanoparticles in vivo. The effects of protein corona on nanoparticles transport, cellular uptake, cytotoxicity, and immune response were reviewed, and the reasons for these effects were also discussed. Finally, future research perspectives for food protein corona were proposed. Protein corona gives food nanoparticles a new identity, which makes proteins bound to nanoparticles undergo structural transformations that affect their recognition by receptors in vivo. It can have positive or negative impacts on cellular uptake and toxicity of nanoparticles and even trigger immune responses. Understanding the effects of protein corona have potential in evaluating the fate of the food-related nanoparticles, providing physicochemical and biological information about the interaction between proteins and foodborne nanoparticles. The review article will help to evaluate the safety of protein coronas formed on nanoparticles in food, and may provide fundamental information for understanding and controlling nanotoxicity.

MTT assay dataset of polyethylenimine coated graphenoxide nanosheets on breast cancer cell lines (MCF7, MDA-MB-231, MDA-MB-468)

Graphen oxide has emerged as a promising tool in medical biotechnology due to its outstanding properties applicable in several fields as well as cell imaging, drug and gene delivery. Monolayer structure and high surface area of Graphen benefits elevated loading capacity of drugs rather than other nanomaterials. However Graphen oxide in physiological solutions has unfavourable reactions which confine it's application in biomedical field without additional surface functionalization. Coating of graphenoxide by polyethylenimine is an approach to enhance biocompatibility of graphen oxide and also provides desirable physicochemical features for oligonucleotides delivery. The data presented here is related to graphenoxide-PEI characterisation and it's cytotoxicity assay on variouse breast cancer cell lines including MDA-MB-468 and MDA-MB-231 and MCF7 by MTT assay.

Modulation of Cancer Cell Autophagic Responses by Graphene-Based Nanomaterials: Molecular Mechanisms and Therapeutic Implications

Simple Summary

Graphene-based nanomaterials (GNM) are one-to-several carbon atom-thick flakes of graphite with at least one lateral dimension <100 nm. The unique electronic structure, high surface-to-volume ratio, and relatively low toxicity make GNM potentially useful in cancer treatment. GNM such as graphene, graphene oxide, graphene quantum dots, and graphene nanofibers are able to induce autophagy in cancer cells. During autophagy the cell digests its own components in organelles called lysosomes, which can either kill cancer cells or promote their survival, as well as influence the immune response against the tumor. However, a deeper understanding of GNM-autophagy interaction at the mechanistic and functional level is needed before these findings could be exploited to increase GNM effectiveness as cancer therapeutics and drug delivery systems. In this review, we analyze molecular mechanisms of GNM-mediated autophagy modulation and its possible implications for the use of GNM in cancer therapy.

Abstract

Graphene-based nanomaterials (GNM) are plausible candidates for cancer therapeutics and drug delivery systems. Pure graphene and graphene oxide nanoparticles, as well as graphene quantum dots and graphene nanofibers, were all able to trigger autophagy in cancer cells through both transcriptional and post-transcriptional mechanisms involving oxidative/endoplasmic reticulum stress, AMP-activated protein kinase, mechanistic target of rapamycin, mitogen-activated protein kinase, and Toll-like receptor signaling. This was often coupled with lysosomal dysfunction and subsequent blockade of autophagic flux, which additionally increased the accumulation of autophagy mediators that participated in apoptotic, necrotic, or necroptotic death of cancer cells and influenced the immune response against the tumor. In this review, we analyze molecular mechanisms and structure–activity relationships of GNM-mediated autophagy modulation, its consequences for cancer cell survival/death and anti-tumor immune response, and the possible implications for the use of GNM in cancer therapy.

Comparison of the Toxicity of Pristine Graphene and Graphene Oxide, Using Four Biological Models

There are numerous applications of graphene in biomedicine and they can be classified into several main areas: delivery systems, sensors, tissue engineering and biological agents. The growing biomedical field of applications of graphene and its derivates raises questions regarding their toxicity. We will demonstrate an analysis of the toxicity of two forms of graphene using four various biological models: zebrafish (Danio rerio) embryo, duckweed (Lemna minor), human HS-5 cells and bacteria (Staphylococcus aureus). The toxicity of pristine graphene (PG) and graphene oxide (GO) was tested at concentrations of 5, 10, 20, 50 and 100 µg/mL. Higher toxicity was noted after administration of high doses of PG and GO in all tested biological models. Hydrophilic GO shows greater toxicity to biological models living in the entire volume of the culture medium (zebrafish, duckweed, S. aureus). PG showed the highest toxicity to adherent cells growing on the bottom of the culture plates—human HS-5 cells. The differences in toxicity between the tested graphene materials result from their physicochemical properties and the model used. Dose-dependent toxicity has been demonstrated with both forms of graphene.

Time-dependent study of graphene oxide-trypsin adsorption interface and visualization of nano-protein corona

Understanding of interactions of nanomaterials with biomolecules (especially proteins) is of great importance to the area of nanobiotechnology. Graphene and its derivative such as graphene oxide (GO), are two-dimensional (2-D) nanomaterials with remarkable physical and chemical properties and have been broadly explored in biotechnology and biomedical application. Here, we have reported the nature of adsorption of trypsin on the GO surface, considering its biomedical implications. A simple incubation of trypsin on GO surface exhibits varying resistance to autolysis. The structural morphology of trypsin on the GO surface was studied by using atomic force microscopy (AFM), circular dichroism (CD), fluorescence, and total internal reflection fluorescence (TIRF) microscopies. Results suggest that the trypsin follows the Freundlich Isotherm. By the Langmuir model, the maximum adsorption capacity was found to be 100 mg/g. From protein assay results we have concluded that the native trypsin exhibits the highest catalytic efficiency (33.97*10⁴ L mol^-1 min^-1) in comparison to other Trp-GO constructs. We have further visualized morphological change on GO-trypsin interface throughout the adsorption process by taking samples at definite time intervals, which suggests that the interaction of trypsin with GO is an example of the soft corona. Our findings may be implicated in enzyme engineering as well as enzyme-based bio-sensing applications.

Graphene Oxide Nanosheets Tailored With Aromatic Dipeptide Nanoassemblies for a Tuneable Interaction With Cell Membranes

Engineered graphene-based derivatives are attractive and promising candidates for nanomedicine applications because of their versatility as 2D nanomaterials. However, the safe application of these materials needs to solve the still unanswered issue of graphene nanotoxicity. In this work, we investigated the self-assembly of dityrosine peptides driven by graphene oxide (GO) and/or copper ions in the comparison with the more hydrophobic diphenylalanine dipeptide. To scrutinize the peptide aggregation process, in the absence or presence of GO and/or Cu²⁺, we used atomic force microscopy, circular dichroism, UV-visible, fluorescence and electron paramagnetic resonance spectroscopies. The perturbative effect by the hybrid nanomaterials made of peptide-decorated GO nanosheets on model cell membranes of supported lipid bilayers was investigated. In particular, quartz crystal microbalance with dissipation monitoring and fluorescence recovery after photobleaching techniques were used to track the changes in the viscoelastic properties and fluidity of the cell membrane, respectively. Also, cellular experiments with two model tumour cell lines at a short time of incubation, evidenced the high potential of this approach to set up versatile nanoplatforms for nanomedicine and theranostic applications.

The interaction between nanoparticles-protein corona complex and cells and its toxic effect on cells

Once nanoparticles (NPs) contact with the biological fluids, the proteins immediately adsorb onto their surface, forming a layer called protein corona (PC), which bestows the biological identity on NPs. Importantly, the NPs-PC complex is the true identity of NPs in physiological environment. Based on the affinity and the binding and dissociation rate, PC is classified into soft protein corona, hard protein corona, and interfacial protein corona. Especially, the hard PC, a protein layer relatively stable and closer to their surface, plays particularly important role in the biological effects of the complex. However, the abundant corona proteins rarely correspond to the most abundant proteins found in biological fluids. The composition profile, formation and conformational change of PC can be affected by many factors. Here, the influence factors, not only the nature of NPs, but also surface chemistry and biological medium, are discussed. Likewise, the formed PC influences the interaction between NPs and cells, and the associated subsequent cellular uptake and cytotoxicity. The uncontrolled PC formation may induce undesirable and sometimes opposite results: increasing or inhibiting cellular uptake, hindering active targeting or contributing to passive targeting, mitigating or aggravating cytotoxicity, and stimulating or mitigating the immune response. In the present review, we discuss these aspects and hope to provide a valuable reference for controlling protein adsorption, predicting their behavior in vivo experiments and designing lower toxicity and enhanced targeting nanomedical materials for nanomedicine.

Hemocompatibility of Carbon Nanostructures

Carbon nanostructures (CNs), such as carbon nanotubes, fullerenes, carbon dots, nanodiamonds as well as graphene and its derivatives present a tremendous potential for various biomedical applications, ranging from sensing to drug delivery and gene therapy, biomedical imaging and tissue engineering. Since most of these applications encompass blood contact or intravenous injection, hemocompatibility is a critical aspect that must be carefully considered to take advantage of CN exceptional characteristics while allowing their safe use. This review discusses the hemocompatibility of different classes of CNs with the purpose of providing biomaterial scientists with a comprehensive vision of the interactions between CNs and blood components. The various complex mechanisms involved in blood compatibility, including coagulation, hemolysis, as well as the activation of complement, platelets, and leukocytes will be considered. Special attention will be paid to the role of CN size, structure, and surface properties in the formation of the protein corona and in the processes that drive blood response. The aim of this review is to emphasize the importance of hemocompatibility for CNs intended for biomedical applications and to provide some valuable insights for the development of new generation particles with improved performance and safety in the physiological environment.

Dispersed graphene materials of biomedical interest and their toxicological consequences

Graphene is one-atom thick nanocarbon displaying a unique honeycomb structure and extensive conjugation. In addition to high surface area to mass ratio, it displays unique optical, thermal, electronic and mechanical properties. Atomic scale tunability of graphene has attracted immense research interest with a prospective utility in electronics, desalination, energy sectors, and beyond. Its intrinsic opto-thermal properties are appealing from the standpoint of multimodal drug delivery, imaging and biosensing applications. Hydrophobic basal plane of sheets can be efficiently loaded with aromatic molecules via non-specific forces. With intense biomedical interest, methods are evolving to produce defect-free and dispersion stable sheets. This review summarizes advancements in synthetic approaches and strategies of stabilizing graphene derivatives in aqueous medium. We have described the interaction of colloidal graphene with cellular and sub-cellular components, and subsequent physiological signaling. Finally, a systematic discussion is provided covering toxicological challenges and possible solutions on utilizing graphene formulations for high-end biomedical applications.

Potential clinical applications of the personalized, disease-specific protein corona on nanoparticles

Nanoscale objects lose their original identity once in contact with biological fluids and get a new biological identity, referred to as a protein corona (PC). The PC modifies many of the physicochemical properties of nanoparticles (NPs), including surface charge, size, and aggregation state. These changes, in turn, affect the biological fate of NPs, including their biodistribution, pharmacokinetics, and therapeutic efficacy. It is well known that even small differences in the composition of a protein source (e.g., plasma and serum) can considerably change the composition of the corona formed on the surface of the same NPs. Recently, it has been shown that the PC is intensely affected by the patient's specific disease. Consequently, the same nanomaterial incubated with proteins of biological fluids belonging to patients with different pathologies adsorbs protein coronas with different compositions, giving rise to the concept of the personalized protein corona (PPC). Herein, we review recent advances on the topic of PPC, with a particular focus on their clinical significance.

Adsorption of Human Serum Albumin on Graphene Oxide: Implications for Protein Corona Formation and Conformation

The influence of solution chemistry on the adsorption of human serum albumin (HSA) proteins on graphene oxide (GO) was investigated through batch adsorption experiments and the use of a quartz crystal microbalance with dissipation (QCM-D). The conformation of HSA layers on GO was also examined with the QCM-D. Our results show that an increase in ionic strength under neutral pH conditions resulted in stronger binding between HSA and GO, as well as more compact HSA layers on GO, emphasizing the key role of electrostatic interactions in controlling HSA-GO interactions. Calcium ions also facilitated HSA adsorption likely through charge neutralization and bridging effect. At physiological ionic strength conditions (150 mM), maximum HSA adsorption was observed at the isoelectric point of HSA (4.7). Under acidic conditions, the adsorption of HSA on GO led to the formation of protein layers with a high degree of fluidity due to the extended conformation of HSA. Finally, the attachment of GO to a supported lipid bilayer that was composed of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine, a model for cell membranes, was reduced in the presence of protein coronas. This reduction in GO attachment was influenced by the conformation of the protein coronas on GO.

Interaction of graphene oxide with cell culture medium: Evaluating the fetal bovine serum protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions

The interaction of single-layer graphene oxide (SLGO) and multi-layered graphene oxide (MLGO) with a cell culture medium (i.e. DMEM) was studied by evaluating fetal bovine serum (FBS) protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions. SLGO and MLGO exhibited different colloidal behavior in the culture medium, which was visualized by cryogenic transmission electron microscopy in situ analysis. Exploring proteomics and bioinformatics tools, 394 and 290 proteins were identified on the SLGO and MLGO hard corona compositions, respectively. From this amount, 115 proteins were exclusively detected on the SLGO and merely 11 on MLGO. SLGO enriched FBS proteins involved in metabolic processes and signal transduction, while MLGO enriched proteins involved in cellular development/structure, and lipid transport/metabolic processes. Such a distinct corona profile is due to differences on surface chemistry, aggregation behavior and the surface area of GO materials. Hydrophilic interactions were found to play a greater role in protein adsorption by MLGO than SLGO. Our results point out implications for in vitro studies of graphene oxide materials concerning the effective dose delivered to cells and corona bioactivity. Finally, we demonstrated the importance of integrating conventional and modern techniques thoroughly to understand the GO-FBS complexes towards more precise, reliable and advanced in vitro nanotoxicity assessment.

Graphene oxide touches blood: in vivo interactions of bio-coronated 2D materials

Graphene oxide is the hot topic in biomedical and pharmaceutical research of the current decade. However, its complex interactions with human blood components complicate the transition from the promising in vitro results to clinical settings. Even though graphene oxide is made with the same atoms as our organs, tissues and cells, its bi-dimensional nature causes unique interactions with blood proteins and biological membranes and can lead to severe effects like thrombogenicity and immune cell activation. In this review, we will describe the journey of graphene oxide after injection into the bloodstream, from the initial interactions with plasma proteins to the formation of the "biomolecular corona", and biodistribution. We will consider the link between the chemical properties of graphene oxide (and its functionalized/reduced derivatives), protein binding and in vivo response. We will also summarize data on biodistribution and toxicity in view of the current knowledge of the influence of the biomolecular corona on these processes. Our aim is to shed light on the unsolved problems regarding the graphene oxide corona to build the groundwork for the future development of drug delivery technology.

A Review on Graphene-Based Nanomaterials in Biomedical Applications and Risks in Environment and Health

Graphene-based nanomaterials (GBNs) have attracted increasing interests of the scientific community due to their unique physicochemical properties and their applications in biotechnology, biomedicine, bioengineering, disease diagnosis and therapy. Although a large amount of researches have been conducted on these novel nanomaterials, limited comprehensive reviews are published on their biomedical applications and potential environmental and human health effects. The present research aimed at addressing this knowledge gap by examining and discussing: (1) the history, synthesis, structural properties and recent developments of GBNs for biomedical applications; (2) GBNs uses as therapeutics, drug/gene delivery and antibacterial materials; (3) GBNs applications in tissue engineering and in research as biosensors and bioimaging materials; and (4) GBNs potential environmental effects and human health risks. It also discussed the perspectives and challenges associated with the biomedical applications of GBNs.

Cytotoxicity and Efflux Pump Inhibition Induced by Molybdenum Disulfide and Boron Nitride Nanomaterials with Sheetlike Structure

Sheetlike molybdenum disulfide (MoS₂) and boron nitride (BN) nanomaterials have attracted attention in the past few years due to their unique material properties. However, information on adverse effects and their underlying mechanisms for sheetlike MoS₂ and BN nanomaterials is rare. In this study, cytotoxicities of sheetlike MoS₂ and BN nanomaterials on human hepatoma HepG2 cells were systematically investigated at different toxic end points. Results showed that MoS₂ and BN nanomaterials decreased cell viability at 30 μg/mL and induced adverse effects on intracellular ROS generation (≥2 μg/mL), mitochondrial depolarization (≥4 μg/mL), and membrane integrity (≥8 μg/mL for MoS₂ and ≥2 μg/mL for BN). Furthermore, this study first found that low exposure concentrations (0.2-2 μg/mL) of MoS₂ and BN nanomaterials could increase plasma membrane fluidity and inhibit transmembrane ATP binding cassette (ABC) efflux transporter activity, which make both nanomaterials act as a chemosensitizer (increasing arsenic toxicity). Damage to plasma membrane and release of soluble Mo or B species might be two reasons that both nanomaterials inhibit efflux pump activities. This study provides a systematic understanding of the cytotoxicity of sheetlike MoS₂ and BN nanomaterials at different exposure levels, which is important for their safe use.

Insights into key factors controlling GO stability in natural surface waters

The effects of pH, cations (Na⁺, K⁺, Mg²⁺, Ca²⁺ and Al³⁺), and anions (Cl^-, HCO₃^-, HPO₄^2- and SO₄^2-) on graphene oxide (GO) stability were investigated to address the current limitations in the knowledge regarding the stability of GO in natural surface water and its underlying mechanism. The threshold values of cations that destabilize GO were obtained and affected by both pH and anions. By employing elemental mapping and studying the effects of polyacrylic acid (PAA) on GO sedimentation and the re-dispersion of GO aggregates, we find that the GO aggregates induced by Na⁺ and K⁺ via electric double layer suppression and by Ca²⁺ and Al³⁺ via strong complxing are difficult to re-disperse completely. Specifically, more PAA is needed to re-disperse GO aggregates than to stabilize GO, which suggests that after GO binds with heavy metal ions. It is less likely to be transported over a long distance even in natural water that are rich in natural organic matter. Finally, we find that the key factor controlling GO sedimentation in natural surface waters is its binding with Mg²⁺ and Ca²⁺. This study is expected to provide critical knowledge to more accurately predict the fate of GO in natural surface aquatic environments.

Exfoliated graphene nanosheets: pH-sensitive drug carrier and anti-cancer activity

A straightforward and facile method for the exfoliation of graphene sheets using poly(vinylpyrrolidone) nanoparticles of an average size of 42nm was developed and their dual role as pH-sensitive drug carrier and anti-cancer agent was evaluated. The cytotoxic impact of the exfoliated nanosheets (GRP-PVP-NP) was examined on various cells (HCT-116, HeLa, SCC-9, NIH-3T3 and HEK-293cells) by a series of assays. Their cytotoxic nature was attributed to affecting the mitochondrial enzyme activity, proliferation capability, and the formation of tight junctions in cancer cells. The endocytosis was found to be internalization mechanism for the cellular uptake of nanosheets. The generation of reactive oxygen species and elicitation of caspase-3 activity which was undoubtedly associated with triggering of oxidative stress speculated to be the dominant cause of the cytotoxic pattern of nanosheets against cancer cells. Additionally, the results also showed the role of the nanosheets as a pH-sensitive drug carrier through drug loading by supramolecular interaction. The efficient release of doxorubicin was seen at low pH and in an environment with a low oxygen concentration, thus under conditions mimicking the typical tumor microenvironment. Therefore, these findings provide the first evidence for a dual function of exfoliated graphene sheets and also elucidate the cytotoxic mechanism responsible for the cancer cell death.

Antibacterial mechanisms of graphene-based composite nanomaterials

Pathogenic bacteria are gaining resistance to conventional antibiotics at an alarming rate due to overuse and rapid transfer of resistance genes between bacterial populations. As bacterial resistance to antibiotics causes millions of fatalities worldwide, it is of urgent importance to develop a new class of antibiotic materials with both broad-spectrum bactericidal activity and suitable biocompatibility. Graphene derivatives are rapidly emerging as an extremely promising class of antimicrobial materials due to their diverse bactericidal mechanisms and relatively low cytotoxicity towards mammalian cells. By combining graphene derivatives with currently utilized antibacterial metal and metal-oxide nanostructures, composite materials with exceptional bactericidal activity can be achieved. In this review, the antibacterial activities of graphene derivatives as well as their metal and metal-oxide composite nanostructures will be presented. The synthetic methodology for these various materials will be briefly mentioned, and emphasis will be placed on the evaluation of their mechanisms of action. This information will provide a valuable insight into the current understanding of the interactions governing the microbial toxicity of graphene-based composite nanostructures.

Superior coagulation of graphene oxides on nanoscale layered double hydroxides and layered double oxides

With the development and application of graphene oxides (GO), the potential toxicity and environmental behavior of GO has become one of the most forefront environmental problems. Herein, a novel nanoscale layered double hydroxides (glycerinum-modified nanocrystallined Mg/Al layered double hydroxides, LDH-Gl), layered double oxides (calcined LDH-Gl, LDO-Gl) and metallic oxide (TiO₂) were synthesized and applied as superior coagulants for the efficient removal of GO from aqueous solutions. Coagulation of GO as a function of coagulant contents, pH, ionic strength, GO contents, temperature and co-existing ions were studied and compared, and the results showed that the maximum coagulation capacities of GO were LDO-Gl (448.3 mg g^-1) > TiO₂ (365.7 mg g^-1) > LDH-Gl (339.1 mg g^-1) at pH 5.5, which were significantly higher than those of bentonite, Al₂O₃, CaCl₂ or other natural materials due to their stronger reaction active and interfacial effect. The presence of SO₃^2- and HCO₃^- inhibited the coagulation of GO on LDH-Gl and LDO-Gl significantly, while other cations (K⁺, Mg²⁺, Ca²⁺, Ni²⁺, Al³⁺) or anion (Cl^-) had slightly effect on GO coagulation. The interaction mechanism of GO coagulation on LDO-Gl and TiO₂ might due to the electrostatic interactions and strong surface complexation, while the main driving force of GO coagulation on LDH-Gl might be attributed to electrostatic interaction and hydrogen bond, which were further evidenced by TEM, SEM, FT-IR and XRD analysis. The results of natural environmental simulation showed that LDO-Gl, TiO₂ or other kinds of natural metallic oxides could be superior coagulants for the efficient elimination of GO or other toxic nanomaterials from aqueous solutions in real environmental pollution cleanup.

Interactions of graphene with mammalian cells: Molecular mechanisms and biomedical insights

Carbon-based functional nanomaterials have attracted immense scientific interest from many disciplines and, due to their extraordinary properties, have offered tremendous potential in a diverse range of applications. Among the different carbon nanomaterials, graphene is one of the newest and is considered the most important. Graphene, a monolayer material composed of sp²-hybridized carbon atoms hexagonally arranged in a two-dimensional structure, can be easily functionalized by chemical modification. Functionalized graphene and its derivatives have been used in diverse nano-biotechnological applications, such as in environmental engineering, biomedicine, and biotechnology. However, the prospective use of graphene-related materials in a biological context requires a detailed comprehension of these materials, which is essential for expanding their biomedical applications in the future. In recent years, the number of biological studies involving graphene-related nanomaterials has rapidly increased. These studies have documented the effects of the biological interactions between graphene-related materials and different organizational levels of living systems, ranging from biomolecules to animals. In the present review, we will summarize the recent progress in understanding mainly the interactions between graphene and cells. The impact of graphene on intracellular components, and especially the uptake and transport of graphene by cells, will be discussed in detail.

Synthesis, toxicity, biocompatibility, and biomedical applications of graphene and graphene-related materials

Graphene is a two-dimensional atomic crystal, and since its development it has been applied in many novel ways in both research and industry. Graphene possesses unique properties, and it has been used in many applications including sensors, batteries, fuel cells, supercapacitors, transistors, components of high-strength machinery, and display screens in mobile devices. In the past decade, the biomedical applications of graphene have attracted much interest. Graphene has been reported to have antibacterial, antiplatelet, and anticancer activities. Several salient features of graphene make it a potential candidate for biological and biomedical applications. The synthesis, toxicity, biocompatibility, and biomedical applications of graphene are fundamental issues that require thorough investigation in any kind of applications related to human welfare. Therefore, this review addresses the various methods available for the synthesis of graphene, with special reference to biological synthesis, and highlights the biological applications of graphene with a focus on cancer therapy, drug delivery, bio-imaging, and tissue engineering, together with a brief discussion of the challenges and future perspectives of graphene. We hope to provide a comprehensive review of the latest progress in research on graphene, from synthesis to applications.

Graphene scaffolds in progressive nanotechnology/stem cell-based tissue engineering of the nervous system

Although graphene/stem cell-based tissue engineering has recently emerged and has promisingly and progressively been utilized for developing one of the most effective regenerative nanomedicines, it suffers from low differentiation efficiency, low hybridization after transplantation and lack of appropriate scaffolds required in implantations without any degrading in functionality of the cells. In fact, recent studies have demonstrated that the unique properties of graphene can successfully resolve all of these challenges. Among various stem cells, neural stem cells (NSCs) and their neural differentiation on graphene have attracted a lot of interest, because graphene-based neuronal tissue engineering can promisingly realize the regenerative therapy of various incurable neurological diseases/disorders and the fabrication of neuronal networks. Hence, in this review, we further focused on the potential bioapplications of graphene-based nanomaterials for the proliferation and differentiation of NSCs. Then, various stimulation techniques (including electrical, pulsed laser, flash photo, near infrared (NIR), chemical and morphological stimuli) which have recently been implemented in graphene-based stem cell differentiations were reviewed. The possibility of degradation of graphene scaffolds (NIR-assisted photodegradation of three-dimensional graphene nanomesh scaffolds) was also discussed based on the latest achievements. The biocompatibility of graphene scaffolds and their probable toxicities (especially after the disintegration of graphene scaffolds and distribution of its platelets in the body), which is still an important challenge, were reviewed and discussed. Finally, the initial recent efforts for fabrication of neuronal networks on graphene materials were presented. Since there has been no in vivo application of graphene in neuronal regenerative medicine, we hope that this review can excite further and concentrated investigations on in vivo (and even in vitro) neural proliferation, stimulation and differentiation of stem cells on biocompatible graphene scaffolds having the potential of degradability for the generation of implantable neuronal networks.

Coagulation Behavior of Graphene Oxide on Nanocrystallined Mg/Al Layered Double Hydroxides: Batch Experimental and Theoretical Calculation Study

Graphene oxide (GO) has attracted considerable attention because of its remarkable enhanced adsorption and multifunctional properties. However, the toxic properties of GO nanosheets released into the environment could lead to the instability of biological system. In aqueous phase, GO may interact with fine mineral particles, such as chloridion intercalated nanocrystallined Mg/Al layered double hydroxides (LDH-Cl) and nanocrystallined Mg/Al LDHs (LDH-CO3), which are considered as coagulant molecules for the coagulation and removal of GO from aqueous solutions. Herein the coagulation of GO on LDHs were studied as a function of solution pH, ionic strength, contact time, temperature and coagulant concentration. The presence of LDH-Cl and LDH-CO3 improved the coagulation of GO in solution efficiently, which was mainly attributed to the surface oxygen-containing functional groups of LDH-Cl and LDH-CO3 occupying the binding sites of GO. The coagulation of GO by LDH-Cl and LDH-CO3 was strongly dependent on pH and ionic strength. Results of theoretical DFT calculations indicated that the coagulation of GO on LDHs was energetically favored by electrostatic interactions and hydrogen bonds, which was further evidenced by FTIR and XPS analysis. By integrating the experimental results, it was clear that LDH-Cl could be potentially used as a cost-effective coagulant for the elimination of GO from aqueous solutions, which could efficiently decrease the potential toxicity of GO in the natural environment.

Applications and toxicity of graphene family nanomaterials and their composites

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

Personalized disease-specific protein corona influences the therapeutic impact of graphene oxide

The hard corona, the protein shell that is strongly attached to the surface of nano-objects in biological fluids, is recognized as the first layer that interacts with biological objects (e.g., cells and tissues). The decoration of the hard corona (i.e., the type, amount, and conformation of the attached proteins) can define the biological fate of the nanomaterial. Recent developments have revealed that corona decoration strongly depends on the type of disease in human patients from which the plasma is obtained as a protein source for corona formation (referred to as the 'personalized protein corona'). In this study, we demonstrate that graphene oxide (GO) sheets can trigger different biological responses in the presence of coronas obtained from various types of diseases. GO sheets were incubated with plasma from human subjects with different diseases/conditions, including hypofibrinogenemia, blood cancer, thalassemia major, thalassemia minor, rheumatism, fauvism, hypercholesterolemia, diabetes, and pregnancy. Identical sheets coated with varying protein corona decorations exhibited significantly different cellular toxicity, apoptosis, and uptake, reactive oxygen species production, lipid peroxidation and nitrogen oxide levels. The results of this report will help researchers design efficient and safe, patient-specific nano biomaterials in a disease type-specific manner for clinical and biological applications.

PEG-b-AGE Polymer Coated Magnetic Nanoparticle Probes with Facile Functionalization and Anti-fouling Properties for Reducing Non-specific Uptake and Improving Biomarker Targeting

Non-specific surface adsorption of bio-macromolecules (e.g. proteins) on nanoparticles, known as biofouling, and the uptake of nanoparticles by the mononuclear phagocyte system (MPS) and reticuloendothelial system (RES) lead to substantial reduction in the efficiency of target-directed imaging and delivery in biomedical applications of engineered nanomaterials in vitro and in vivo. In this work, a novel copolymer consisting of blocks of poly ethylene glycol and allyl glycidyl ether (PEG-b-AGE) was developed for coating magnetic iron oxide nanoparticles (IONPs) to reduce non-specific protein adhesion that leads to formation of "protein corona" and uptake by macrophages. The facile surface functionalization was demonstrated by using targeting ligands of a small peptide of RGD or a whole protein of transferrin (Tf). The PEG-b-AGE coated IONPs exhibited anti-biofouling properties with significantly reduced protein corona formation and non-specific uptake by macrophages before and after the surface functionalization, thus improving targeting of RGD-conjugated PEG-b-AGE coated IONPs to integrins in U87MG glioblastoma and MDA-MB-231 breast cancer cells that overexpress α_vβ₃ integrins, and Tf-conjugated PEG-b-AGE coated IONPs to transferrin receptor (TfR) in D556 and Daoy medulloblastoma cancer cells with high overexpression of transferrin receptor, compared to respective control cell lines. Magnetic resonance imaging (MRI) of cancer cells treated with targeted IONPs with or without anti-biofouling PEG-b-AGE coating polymers demonstrated the target specific MRI contrast change using anti-biofouling PEG-b-AGE coated IONP with minimal off-targeted background compared to the IONPs without anti-biofouling coating, promising the highly efficient active targeting of nanoparticle imaging probes and drug delivery systems and potential applications of imaging quantification of targeted biomarkers.

Effect of the protein corona on nanoparticles for modulating cytotoxicity and immunotoxicity

Although the cytotoxicity of nanoparticles (NPs) is greatly influenced by their interactions with blood proteins, toxic effects resulting from blood interactions are often ignored in the development and use of nanostructured biomaterials for in vivo applications. Protein coronas created during the initial reaction with NPs can determine the subsequent immunological cascade, and protein coronas formed on NPs can either stimulate or mitigate the immune response. Along these lines, the understanding of NP-protein corona formation in terms of physiochemical surface properties of the NPs and NP interactions with the immune system components in blood is an essential step for evaluating NP toxicity for in vivo therapeutics. This article reviews the most recent developments in NP-based protein coronas through the modification of NP surface properties and discusses the associated immune responses.

Toxicology of chemically modified graphene-based materials for medical application

This review article aims to provide an overview of chemically modified graphene, and graphene oxide (GO), and their impact on toxicology when present in biological systems. Graphene is one of the most promising nanomaterials due to unique physicochemical properties including enhanced optical, thermal, and electrically conductive behavior in addition to mechanical strength and high surface-to-volume ratio. Graphene-based nanomaterials have received much attention over the last 5 years in the biomedical field ranging from their use as polymeric conduits for nerve regeneration, carriers for targeted drug delivery and in the treatment of cancer via photo-thermal therapy. Both in vitro and in vivo biological studies of graphene-based nanomaterials help understand their relative toxicity and biocompatibility when used for biomedical applications. Several studies investigating important material properties such as surface charge, concentration, shape, size, structural defects, and chemical functional groups relate to their safety profile and influence cyto- and geno-toxicology. In this review, we highlight the most recent studies of graphene-based nanomaterials and outline their unique properties, which determine their interactions under a range of environmental conditions. The advent of graphene technology has led to many promising new opportunities for future applications in the field of electronics, biotechnology, and nanomedicine to aid in the diagnosis and treatment of a variety of debilitating diseases.

Personalized protein coronas: a "key" factor at the nanobiointerface

It is now well known that the primary interactions of biological entities (e.g., tissues and cells) with nanoparticles (NPs) are strongly influenced by the protein composition of the "corona" (i.e., the NP surface attached proteins). The composition of the corona strongly depends on the protein source (e.g., human plasma). Because the protein source determines the NP corona, it is reasonable to hypothesize that humans with specific disease(s) may have specific NP coronas. To test this hypothesis, we incubated two different hydrophobic/hydrophilic types of NPs (polystyrene and silica) with plasma from human subjects with different diseases and medical conditions (e.g., breast cancer, diabetes, hypercholesterolemia, rheumatism, fauvism, smoking, hemodialysis, thalassemia, hemophilia A and B, pregnancy, common cold and hypofibrinogenemia). Our results demonstrate that the type of disease has a crucial role in the protein composition of the NP corona. Based on these results, we introduce the concept of the "personalized protein corona" (PPC) as a determinant factor in nano-biomedical science. This study will help researchers rationally design experiments based on the "personalized protein corona" for clinical and biological applications.

Graphene-based materials functionalized with elastin-like polypeptides

Graphene-based materials commonly require functionalization for biological applications in order to control their physical/colloidal properties and to introduce additional capabilities, such as stimuli-responsiveness and affinity to specific biomolecules. Here, we functionalized CVD-grown graphene and graphene oxide with a genetically engineered elastin-like polypeptide fused to a graphene binding peptide and then showed that the resulting hybrid materials exhibit thermo- and photoresponsive behaviors. Furthermore, we demonstrate that our genetic engineering strategy allows for the facile introduction of bioactivity to reduced graphene oxide. The stimuli-responsiveness and genetic tunability of our graphene-protein nanocomposites are attractive for addressing future biomedical applications.