Graphene is a single-atom thick, two-dimensional sheet of hexagonally arranged carbon atoms isolated from its three-dimensional parent material, graphite. Related materials include few-layer-graphene (FLG), ultrathin graphite, graphene oxide (GO), reduced graphene oxide (rGO), and graphene nanosheets (GNS). This review proposes a systematic nomenclature for this set of Graphene-Family Nanomaterials (GFNs) and discusses specific materials properties relevant for biomolecular and cellular interactions. We discuss several unique modes of interaction between GFNs and nucleic acids, lipid bilayers, and conjugated small molecule drugs and dyes. Some GFNs are produced as dry powders using thermal exfoliation, and in these cases, inhalation is a likely route of human exposure. Some GFNs have aerodynamic sizes that can lead to inhalation and substantial deposition in the human respiratory tract, which may impair lung defense and clearance leading to the formation of granulomas and lung fibrosis. The limited litera...

Biological Interactions of Graphene-Family Nanomaterials: An Interdisciplinary Review

In vitro toxicity evaluation of graphene oxide on A549 cells

MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti3C2Tx (MXene) has been recently explored for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti3C2Tx MXene flakes in colloidal solution. The antibacterial properties of Ti3C2Tx were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti3C2Tx shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentratio...

Antibacterial Activity of Ti3C2Tx MXene

We have for the first time developed a simple plasma-etching technology to effectively generate metal-free particle catalysts for efficient metal-free growth of undoped and/or nitrogen-doped single-walled carbon nanotubes (CNTs). Compared with undoped CNTs, the newly produced metal-free nitrogen-containing CNTs were demonstrated to show relatively good electrocatalytic activity and long-term stability toward oxygen reduction reaction (ORR) in an acidic medium. Owing to the highly generic nature of the plasma etching technique, the methodology developed in this study can be applied to many other substrates for efficient growth of metal-free CNTs for various applications, ranging from energy related to electronic and to biomedical systems.

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Highly efficient metal-free growth of nitrogen-doped single-walled carbon nanotubes on plasma-etched substrates for oxygen reduction.

The innovation on the low dimensional nanomaterials brings the rapid growth of nano community. Developing the controllable production and commercial applications of nanomaterials for sustainable society is highly concerned. Herein, carbon nanotubes (CNTs) with sp(2) carbon bonding, excellent mechanical, electrical, thermal, as well as transport properties are selected as model nanomaterials to demonstrate the road of nanomaterials towards industry. The engineering principles of the mass production and recent progress in the area of CNT purification and dispersion are described, as well as its bulk application for nanocomposites and energy storage. The environmental, health, and safety considerations of CNTs, and recent progress in CNT commercialization are also included. With the effort from the CNT industry during the past 10 years, the price of multi-walled CNTs have decreased from 45 000 to 100 $ kg(-1) and the productivity increased to several hundred tons per year for commercial applications in Li ion battery and nanocomposites. When the prices of CNTs decrease to 10 $ kg(-1) , their applications as composites and conductive fillers at a million ton scale can be anticipated, replacing conventional carbon black fillers. Compared with traditional bulk chemicals, the controllable synthesis and applications of CNTs on a million ton scale are still far from being achieved due to the challenges in production, purification, dispersion, and commercial application. The basic knowledge of growth mechanisms, efficient and controllable routes for CNT production, the environmental and safety issues, and the commercialization models are still inadequate. The gap between the basic scientific research and industrial development should be bridged by multidisciplinary research for the rapid growth of CNT nano-industry.

The Road for Nanomaterials Industry: A Review of Carbon Nanotube Production, Post‐Treatment, and Bulk Applications for Composites and Energy Storage

Nanotoxicology and nanomedicine make extensive use of in vitro cellular assays that were developed prior to the nanotechnology era. The introduction of nanomaterials to these standard assays causes problems that are currently limiting progress in the field.[1] Nanoparticles are often difficult to disperse;[2] they can interfere with optical measurements through light absorption, and they can interact with dyes used as molecular probes of cellular integrity.[3] In some cases the resulting artifacts can lead to gross misinterpretation of effects on cell viability and cytotoxicity.[4] Because sp2-hybridized carbon materials are near-universal sorbents for organic compounds in aqueous phases, and in light of a recent report of favorable noncovalent interactions between small-aromatic-molecule therapeutic agents and single-walled carbon nanotubes (SWNTs),[5] we hypothesize that SWNTs will adsorb a wide variety of small organic solutes from biological media, not limited to indicator dyes or their water-insoluble reduction products.

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Adsorption of essential micronutrients by carbon nanotubes and the implications for nanotoxicity testing.

The ultimate success of many nanotechnologies will depend on our ability to understand and manage nanomaterial health risks. Carbon nanotubes are now primarily fabricated by catalytic routes and typically contain significant quantities of transition metal catalyst residues. Iron-catalyzed free-radical generation has been hypothesized to contribute to oxidative stress and toxicity upon exposure to ambient particulate, amphibole asbestos fibers, and single-wall carbon nanotubes. A key issue surrounding nanotube iron is bioavailability, which has not been systematically characterized, but is widely thought to be low on the basis of electron microscope observations of metal encapsulation by carbon shells. Here, we validate and apply simple acellular assays to show that toxicologically significant amounts of iron can be mobilized from a diverse set of commercial nanotube samples in the presence of ascorbate and the chelating agent ferrozine. This mobilized iron is redox active and induces single-strand breaks ...

Iron Bioavailability and Redox Activity in Diverse Carbon Nanotube Samples

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Carbon nanomaterials are among the best known and most promising products of the nanotechnology movement. Some early studies suggest that fullerenes and nanotubes may pose significant health risks, and this has given rise to an emerging literature on carbon nanotoxicology. This young field has now begun to yield insight into toxicity mechanisms and the specific material features involved in those mechanisms. This paper explores the potential to alter those material features through post-processing or reformulation with the goal of reducing or eliminating carbon nanomaterial health risks. The paper emphasizes the important roles of metal content and bioavailability, carbon surface chemistry, and nanomaterial aggregation state. The nanotechnology movement has been given a unique "window of opportunity" to systematically investigate the toxicity of nanotechnology products and to develop ways to manage health risks before large scale manufacturing becomes widespread.

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A Window of Opportunity: Designing Carbon Nanomaterials for Environmental Safety and Health

There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.

Lin Guo

Papers

Adsorption of essential micronutrients by carbon nanotubes and the implications for nanotoxicity testing.

Iron Bioavailability and Redox Activity in Diverse Carbon Nanotube Samples

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

A Window of Opportunity: Designing Carbon Nanomaterials for Environmental Safety and Health

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes