Culture Medium-Associated Physicochemical Insights on the Cytotoxicity of Carbon Nanomaterials

Application of cellulose nanocrystals in water treatment membranes: A review

Nanomaterials have brought great changes to human society, and development has gradually shifted the focus to environmentally friendly applications. Cellulose nanocrystals (CNCs) are new one-dimensional nanomaterials that exhibit environmental friendliness and ensure the biological safety of water environment. CNCs have excellent physical and chemical properties, such as simple preparation process, nanoscale size, high specific surface area, high mechanical strength, good biocompatibility, high hydrophilicity and antifouling ability. Because of these characteristics, CNCs are widely used in ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes to solve the problems hindering development of membrane technology, such as insufficient interception and separation efficiency, low mechanical strength and poor antifouling performance. This review summarizes recent developments and uses of CNCs in water treatment membranes and discusses the challenges and development prospects of CNCs materials from the perspectives of ecological safety and human health by comparing them with traditional one-dimensional nanomaterials.

The Application of Carbon Nanomaterials in Sensing, Imaging, Drug Delivery and Therapy for Gynecologic Cancers: An Overview

Gynecologic cancers are one of the main health concerns of women throughout the world, and the early diagnosis and effective therapy of gynecologic cancers will be particularly important for the survival of female patients. As a current hotspot, carbon nanomaterials have attracted tremendous interest in tumor theranostics, and their application in gynecologic cancers has also been developed rapidly with great achievements in recent years. This Overview Article summarizes the latest progress in the application of diverse carbon nanomaterials (e.g., graphenes, carbon nanotubes, mesoporous carbon, carbon dots, etc.) and their derivatives in the sensing, imaging, drug delivery, and therapy of different gynecologic cancers. Important research contributions are highlighted in terms of the relationships among the fabrication strategies, architectural features, and action mechanisms for the diagnosis and therapy of gynecologic cancers. The current challenges and future strategies are discussed from the viewpoint of the real clinical application of carbon-based nanomedicines in gynecologic cancers. It is anticipated that this review will attract more attention toward the development and application of carbon nanomaterials for the theranostics of gynecologic cancers.

The Blanket Effect: How Turning the World Upside Down Reveals the Nature of Graphene Oxide Cytocompatibility

Extensive cytocompatibility testing of 2D nanocarbon materials including graphene oxide (GO) has been performed, but results remain contradictory. Literature has yet to account for settling-although sedimentation is visible to the eye and physics suggests that even individual graphenic flakes will settle. To investigate settling, a series of functional graphenic materials (FGMs) with differing oxidation levels, functionalities, and physical dimensions are synthesized. Though zeta potential indicates colloidal stability, significant gravitational settling of the FGMs is theoretically and experimentally demonstrated. By creating a setup to culture cells in traditional and inverted orientations in the same well, a "blanket effect" is demonstrated in which FGMs settle out of solution and cover cells at the bottom of the well, ultimately reducing viability. Inverted cells protected from the blanket effect are unaffected. Therefore, these results demonstrate that settling is a crucial factor that must be considered for FGM cytocompatibility experiments.

Antioxidant Graphene Oxide Nanoribbon as a Novel Whitening Agent Inhibits Microphthalmia-Associated Transcription Factor-Related Melanogenesis Mechanism

In the melanin synthesis process, oxidative reactions play an essential role, and it is a good strategy to inhibit melanin production by reducing oxidative stress. Fullerene and its derivatives, or the complexes, were considered as strong free-radical scavengers, and we further applied multilayered sp² nanocarbons to discover melanin synthesis inhibitory mechanisms. In the present study, we used novel nanomaterials, such as multiwalled carbon nanotubes (MWCNTs), short-type MWCNTs, graphene oxide nanoribbons (GONRs), and short-type GONRs, as anti-oxidative agents to regulate melanin production. The results showed that GONRs had better anti-oxidative capabilities in intracellular and extracellular oxidative stress analysis platforms than others. We proposed that GONRs have oxygen-containing functional groups. In the 2',7'-dichlorodihydrofluorescein diacetate assay, we found out GONR could chelate metal ions to scavenge reactive oxygen species. In the molecular insight view, we observed that these nanomaterials downregulated the melanin synthesis by decreasing microphthalmia-associated transcription factor-related gene expressions, and there were similar consequences in protein expressions. To sum up, GONRs is a potential agent as a novel antioxidant and skin-whitening cosmetology material.

Comparison of cytotoxicity and membrane efflux pump inhibition in HepG2 cells induced by single-walled carbon nanotubes with different length and functional groups

Environmental risk of single-walled carbon nanotubes (SWCNTs) is receiving increasing attentions owing to their wide study and application. However, little is known on the influence of length and functional groups on SWCNT cytotoxicity. In this study, six types of SWCNTs with different functional groups (pristine, carboxyl group and hydroxyl group) and lengths (1-3 μm and 5-30 μm) were chosen. Cytotoxicities in human hepatoma HepG2 cells induced by these SWCNTs were compared based on cell viability, oxidative stress, plasma membrane fluidity and ABC transporter activity assays. Results showed that all the SWCNTs decreased cell viability of HepG2, increased intracellular reactive oxygen species (ROS) level, and damaged plasma membrane in a concentration-dependent manner. Long SWCNTs had stronger cytotoxic effects than short SWCNTs, which might be due to weaker aggregation for the long SWCNTs. Functionalization changed the toxic effects of the SWCNTs, and different influence was found between long SWCNTs and short SWCNTs. Moreover, the six types of SWCNTs at low concentrations changed plasma membrane fluidity, inhibited transmembrane ABC transporter (efflux pump) activity, and acted as chemosensitizer to improve the sensitivity of cells to arsenic, indicating the chemosensitive effect should be considered as toxic endpoint of SWCNTs. Comparison of different toxic endpoints among the six types of SWCNTs showed that short hydroxyl-SWCNT might be safer than other SWCNTs. This study provides insights into toxicities of SWCNTs, which is of great value for the risk assessment and application of SWCNTs.

Adsorption of Plasma Proteins on Single-Walled Carbon Nanotubes Reduced Cytotoxicity and Modulated Neutrophil Activation

Proteins in the bloodstream bind to carbon nanotubes (CNTs) through noncovalent interactions to form a protein corona, thereby effectively influencing the biological properties and blood biocompatibility of the CNTs. Here, we investigated the binding of common plasma proteins (i.e., human immunoglobulin G (IgG), human serum albumin (HSA), and fibrinogen (FG)) to carboxylated single-walled CNTs (SWCNTs), and evaluated the effects of these different protein coronas on cytotoxicity to endothelial cells and immune response to neutrophils in the bloodstream. Measurements of adsorption parameters revealed tight binding of proteins to SWCNTs, and the SWCNTs adsorption capacities followed the order FG > HSA > IgG. In addition, the basic residues (Arg, Lys, His) were found to play an important role in the formation of protein-SWCNTs corona complexes and determine their adsorption capacity. Consistent with the higher protein adsorption capacity, FG more significantly reduced the cytotoxicity of CNTs to human umbilical vein endothelial cells than the other two proteins. However, only treatment of SWCNTs with IgG resulted in the enhancement of CNT-induced myeloperoxidase (MPO) release (i.e., neutrophil activation) in neutrophils, while MPO-dependent degradation of CNTs induced less cytotoxicity than initial nanomaterials. Consistent with these effects of protein coronas, the presence of serum attenuated the cytotoxicity of CNTs and CNTs could induce neutrophil activation in human blood plasma. Our study demonstrates the ability of adsorbed plasma proteins to influence cytotoxicity and neutrophil response caused by CNTs in the bloodstream.

Multiwall Carbon Nanotubes Induce More Pronounced Transcriptomic Responses in Pseudomonas aeruginosa PG201 than Graphene, Exfoliated Boron Nitride, or Carbon Black

Carbonaceous and boron nitride (BN) nanomaterials have similar applications and hydrophobic properties suggesting common release pathways and exposure to bacteria. While high nanomaterial concentrations can be bactericidal or growth-inhibitory, little is known regarding bacterial transcriptional responses to non-growth-inhibitory nanomaterial concentrations. Here, using one strain of Pseudomonas aeruginosa-a clinically and environmentally important bacterial taxon-we analyzed the comparative transcriptomic response to carbonaceous or BN nanomaterials. We show that, at non-growth-inhibitory, equal mass concentrations (10 mg/L), multiwall carbon nanotubes (MWCNTs) induced differential regulation of 111 genes in P. aeruginosa, while graphene, BN, and carbon black caused differential regulation of 44, 26, and 25 genes, respectively. MWCNTs caused the upregulation of genes encoding general stress response (9 genes), sulfur metabolism (15), and transport of small molecules (7) and downregulation of genes encoding flagellar basal-body rod proteins and other virulence-related factors (6), nitrogen metabolism (7), and membrane proteins (12), including a two-component regulatory system CzcS/R. Because two-component systems are associated with antibiotic resistance, the antibiotic susceptibility of P. aeruginosa was tested following MWCNT exposure. In MWCNT-treated cultures, the minimal inhibitory concentrations (MICs) of meropenem and imipenem decreased from 0.06 to 0.03 μg/mL and from 0.25 to 0.125 μg/mL, respectively. Taken together, whole genome analysis indicated that, in the absence of growth inhibition, nanomaterials can alter bacterial physiology and metabolism. For MWCNTs, such alterations may include downregulation of antibiotic resistance pathways, suggesting that pre-exposure to MWCNTs could potentially render bacteria more susceptible to carbapenems which are often the last resort for the globally concerning, highly antibiotic resistant P. aeruginosa.

Graphene Oxide Quantum Dots as Novel Nanozymes for Alcohol Intoxication

Alcohol overconsumption as a worldwide issue results in alcoholic liver disease (ALD), such as steatosis, alcoholic hepatitis, and cirrhosis. The treatment of ALD has been widely investigated but remains challenging. In this work, the protective effects of graphene oxide quantum dots (GOQDs) as novel nanozymes against alcohol overconsumption are discovered, and the specific mechanisms underlying these effects are elucidated via omics analysis. GOQDs dramatically alleviate the reduction of cell viability induced by ethanol and can act as nanozymes to accelerate ethanol metabolism and avoid the accumulation of toxic intermediates in cells. Mitochondrial damage and the excessive generation of free radicals were mitigated by GOQDs. The mechanisms underlying the cellular protective effects were also related to alterations in metabolic and protein signals, especially those involved in lipid metabolism. The moderately increased autophagy induced by GOQDs explained the removal of accumulated lipids and the subsequent elimination of excessive GOQDs. These findings suggest that GOQDs have an antagonistic capacity against the adverse effects caused by ethanol and provide new insights into the direct applications of GOQDs. In addition to traditional antioxidation, this work also establishes metabolomics and proteomics techniques as effective tools to discover the multiple functions of nanozymes.

Functional Graphene Nanomaterials Based Architectures: Biointeractions, Fabrications, and Emerging Biological Applications

Functional graphene nanomaterials (FGNs) are fast emerging materials with extremely unique physical and chemical properties and physiological ability to interfere and/or interact with bioorganisms; as a result, FGNs present manifold possibilities for diverse biological applications. Beyond their use in drug/gene delivery, phototherapy, and bioimaging, recent studies have revealed that FGNs can significantly promote interfacial biointeractions, in particular, with proteins, mammalian cells/stem cells, and microbials. FGNs can adsorb and concentrate nutrition factors including proteins from physiological media. This accelerates the formation of extracellular matrix, which eventually promotes cell colonization by providing a more beneficial microenvironment for cell adhesion and growth. Furthermore, FGNs can also interact with cocultured cells by physical or chemical stimulation, which significantly mediate their cellular signaling and biological performance. In this review, we elucidate FGNs-bioorganism interactions and summarize recent advancements on designing FGN-based two-dimensional and three-dimensional architectures as multifunctional biological platforms. We have also discussed the representative biological applications regarding these FGN-based bioactive architectures. Furthermore, the future perspectives and emerging challenges will also be highlighted. Due to the lack of comprehensive reviews in this emerging field, this review may catch great interest and inspire many new opportunities across a broad range of disciplines.

Stealth Immune Properties of Graphene Oxide Enabled by Surface-Bound Complement Factor H

With mounting evidence that nanomaterials can trigger adverse innate immune responses such as complement activation, there is increasing attention to the development of strategies that mask the complement-activating properties of nanomaterials. The current gold standard to reduce complement activation of nanomaterials is the covalent attachment of polymer coatings on nanomaterial surfaces, even though this strategy provides only moderate protection against complement activation. Akin to protein coronas that form on nanomaterial surfaces in physiological fluids, noncovalent strategies based on protein adsorption would offer a simplified, biomimetic approach to mitigate complement activation. Herein, we demonstrate that precoating graphene-based nanomaterials with purified, natural proteins enables regulatory control of nanomaterial-triggered complement activation. When the graphene-based nanomaterials were coated with complement factor H, nearly complete protection (>90% reduction) against complement activation (a "stealth effect") was achieved. By contrast, coating the nanomaterials with a passivating layer of bovine or human serum albumins achieved moderate protection (∼40% reduction), whereas immunoglobulin G amplified complement activation by several-fold. Taken together, our results demonstrate that surface-bound factor H, as well as serum albumins, can prevent graphene oxide-triggered complement activation, thereby offering a facile approach to inhibit complement activation completely down to naturally occurring levels.

Graphene oxide as a scaffold for bone regeneration

Graphene oxide (GO), the oxidized form of graphene, holds great potential as a component of biomedical devices, deriving utility from its ability to support a broad range of chemical functionalities and its exceptional mechanical, electronic, and thermal properties. GO composites can be tuned chemically to be biomimetic, and mechanically to be stiff yet strong. These unique properties make GO-based materials promising candidates as a scaffold for bone regeneration. However, questions still exist as to the compatibility and long-term toxicity of nanocarbon materials. Unlike other nanocarbons, GO is meta-stable, water dispersible, and autodegrades in water on the timescale of months to humic acid-like materials, the degradation products of all organic matter. Thus, GO offers better prospects for biological compatibility over other nanocarbons. Recently, many publications have demonstrated enhanced osteogenic performance of GO-containing composites. Ongoing work toward surface modification or coating strategies could be useful to minimize the inflammatory response and improve compatibility of GO as a component of medical devices. Furthermore, biomimetic modifications could offer mechanical and chemical environments that encourage osteogenesis. So long as care is given to assure their safety, GO-based materials may be poised to become the next generation scaffold for bone regeneration. WIREs Nanomed Nanobiotechnol 2017, 9:e1437. doi: 10.1002/wnan.1437 For further resources related to this article, please visit the WIREs website.

Comparative Study of Carbon Materials Synthesized "Greenly" for 2-CP Removal

Carbon nanotubes (CNTs), graphene (GA) and carbon nanospheres (CNSs) were prepared respectively using grass (Festucaarundinace) as the sole carbon resource by solvothermal method and characterized as adsorbent and photocatalyst for 2-chlorophenol (2-CP) removal in water. With H2O2/HNO3/H2SO4, the CNTs were firstly produced from grass (Festucaarundinace) at 300 °C by hydrolysis and oxidization, the CNTs were secondly opened to form the GA by oxidization at 400 °C, and the GA was lastly rolled-up to form the CNSs by oxidization at 500 °C. All adsorption equilibration of the CNTs, GA, and CNSs for 2-CP were achieved within 120 min, and 60.35%, 20.12%, and 76.22% of 2-CP (5 mg L(-1), pH = 6.3) were adsorbed, respectively. Furthermore, the high removal rates of 2-CP were about 88.23%, 92.90%, and 79.64% by the CNTs, GA, and CNSs, after 120 min adsorption and 160 min irradiation. On the basis of these results, the CNSs were suitable for removal 2-CP as adsorbent, and the GA was suitable as photocatalyst. The photooxidation of 2-CP was mainly initiated by O2(·-) or ·OH which was generated from the combine with simulated sunlight and the CNTs or GA, respectively. However, the CNTs was not suitable for removal 2-CP owing to the increasing toxicity.