Adsorption of Essential Micronutrients by Carbon Nanotubes and the Implications for Nanotoxicity Testing

Division of Engineering Brown University, Providence, RI 02912, USA.
Small (Impact Factor: 8.37). 06/2008; 4(6):721-7. DOI: 10.1002/smll.200700754
Source: PubMed


A study used biochemical profiling techniques and ultraviolet (UV) visible spectroscopy, to demonstrate that single-walled nanotubes (SWNTs) caused dose-dependent adsorption and depletion of more than 14 amino acids and vitamins from RPMI cell culture medium. It was found that HepG2 cells cultured through these techniques, showed significantly reduced viability that can be restored by replenishment of folate. The study demonstrated a new mechanism through which hydrophobic nanotube formulations influenced cell behavior indirectly. The study involved the dispersion of SWNTs in RPMI cell culture medium at different doses and sonicating for 30 minutes, to conduct investigations.

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Available from: Annette von dem Bussche, Mar 28, 2014
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    • "In the same way, CNTs reduce mobility and micro-limiting effect on the bioavailability of nutrients present in the aqueous medium (Oleszczuk et al., 2011). Guo et al. proved that there is an unambiguous correlation between concentration of SWCNTs and concentration of critical small molecules in the culture medium (Guo et al., 2008). This relationship, based on hydrophobic and p–p interactions between backbones of aminoacids , folic acid and other vitamins, was found as responsible for the indirect cytotoxicity of SWCNTs since the nutrients were only weakly specifically adsorbed by nanotubes. "
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    ABSTRACT: Due to their unique molecular architecture translating into numerous every-day applications, carbon nanotubes (CNTs) will be ultimately an increasingly significant environmental contaminant. This work reviews qualitative/quantitative analyses of interactions of various types of CNTs and their chemically modified analogues with aqueous/aquatic media containing organic and inorganic contaminants and selected organisms of aquatic ecosystems. A special emphasis was placed on physicochemical interactions between CNTs as adsorbents of heavy metal cations and aromatic compounds (dyes) with its environmental consequences. The studies revealed CNTs as more powerful adsorbents of aromatic compounds (an order of magnitude higher adsorption capacity) than metal cations. Depending on the presence of natural organic matter (NOM) and/or co-contaminants, CNTs may act as Trojan horse while passing through biological membranes (in the absence of NOM coordinating metal ions). Nanotubes, depending on flow conditions and their morphology/surface chemistry, may travel with natural waters or sediment with immobilized PAHs or metals and/or increase cyto- and ecotoxicity of PAHs/metal ions by their release via competitive complexation, or cause synergic ecotoxicity while adsorbing nutrients. Additionally, toxicity of CNTs against exemplary aquatic microorganisms was reviewed. It was found for Daphnia magna that longer exposures to CNTs led to higher ecotoxicity with a prolonged CNTs excretion. SWCNTs were more toxic than MWCNTs, while hydrophilization of CNTs via oxidation or anchoring thereto polar/positively charged polymer chains enhanced stability of nanotubes dispersion in aqueous media. On the other hand, bioavailability of functionalized CNTs was improved leading to more complex both mechanisms of uptake and cytotoxic effects. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · May 2015 · Chemosphere
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    • "Therefore, a systematic study is required to investigate the interactions between amino acids and CNTs in aqueous solution . Additionally, Guo et al. experimentally showed that CNTs caused adsorption and depletion of essential micronutrients (including 14 amino acids and vitamins) in cell culture medium and significantly reduced HepG2 cell viability, which revealed a novel mechanism of the indirect nanotoxicity of CNTs [37]. This experimental study also calls for a simulation study to provide more molecular-level details. "
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    ABSTRACT: The adsorption of 20 standard amino acids on (6,6) carbon nanotube (CNT) at a concentration of 0.17 M and neutral pH has been studied by molecular dynamics simulations, to assess the suitability of amino acids for CNT aqueous dispersions. Simulation results show that among the 20 amino acids, phenylalanine, tyrosine, tryptophan and arginine exhibit the strongest affinity for CNT(6,6) in terms of adsorption amount and interaction energy. These amino acids adsorb to CNT(6,6) and form very stable aggregates, covering about half of the tube surface. Phenylalanine, tyrosine and tryptophan interact with the tube via the strong π–π stacking of their aromatic rings. Interestingly, the strong attraction of arginine to CNT(6,6) mainly attributes to its guanidinium group, which strongly interacts with the tube and forms multiple salt bridges. The negatively charged carboxylate and positively charged ammonium groups of these adsorbed amino acids extend away from the tube surface and point towards aqueous solution, which facilitates the solubilization of CNTs in water, and may be able to provide electrostatic repulsion forces to prevent CNT agglomeration. The results of this work provide a theoretical support for using amino acids as novel CNT dispersing agents and help to understand CNT–protein interactions.
    Full-text · Article · Sep 2014 · Carbon
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    • "Earlier studies have suggested generation of ROS one of the important mechanisms of cytotoxicity of graphene.40,42 Many studies suggest that the mechanisms of toxicity is by direct-contact interaction of extremely sharp edges of graphene nanowalls with wall membrane, Akhavan et al6 proposed mechanisms of toxicity of graphene materials and the other mechanism involves the potential for graphene to block the delivery of nutrients to cancer cells by adhering to cell membranes through cell membrane surface receptors.69,75 Taking the literature and the present study into account, we suggest that ROS generation could be one of the important mechanisms of cell death, both in bacteria and eukaryotic cells. "
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    ABSTRACT: Recently, graphene and graphene-related materials have attracted much attention due their unique properties, such as their physical, chemical, and biocompatibility properties. This study aimed to determine the cytotoxic effects of graphene oxide (GO) that is reduced biologically using Ganoderma spp. mushroom extracts in MDA-MB-231 human breast cancer cells. Herein, we describe a facile and green method for the reduction of GO using extracts of Ganoderma spp. as a reducing agent. GO was reduced without any hazardous chemicals in an aqueous solution, and the reduced GO was characterized using a range of analytical procedures. The Ganoderma extract (GE)-reduced GO (GE-rGO) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, dynamic light scattering, scanning electron microscopy, Raman spectroscopy, and atomic force microscopy. Furthermore, the toxicity of GE-rGO was evaluated using a sequence of assays such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation in human breast cancer cells (MDA-MB-231). The preliminary characterization of reduction of GO was confirmed by the red-shifting of the absorption peak for GE-rGO to 265 nm from 230 nm. The size of GO and GE-rGO was found to be 1,880 and 3,200 nm, respectively. X-ray diffraction results confirmed that reduction processes of GO and the processes of removing intercalated water molecules and the oxide groups. The surface functionalities and chemical natures of GO and GE-rGO were confirmed using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface morphologies of the synthesized graphene were analyzed using high-resolution scanning electron microscopy. Raman spectroscopy revealed single- and multilayer properties of GE-rGO. Atomic force microscopy images provided evidence for the formation of graphene. Furthermore, the effect of GO and GE-rGO was examined using a series of assays, such as cell viability, membrane integrity, and reactive oxygen species generation, which are key molecules involved in apoptosis. The results obtained from cell viability and lactate dehydrogenase assay suggest that GO and GE-rGO cause dose-dependent toxicity in the cells. Interestingly, it was found that biologically derived GE-rGO is more toxic to cancer cells than GO. We describe a simple, green, nontoxic, and cost-effective approach to producing graphene using mushroom extract as a reducing and stabilizing agent. The proposed method could enable synthesis of graphene with potential biological and biomedical applications such as in cancer and angiogenic disorders. To our knowledge, this is the first report using mushroom extract as a reducing agent for the synthesis of graphene. Mushroom extract can be used as a biocatalyst for the production of graphene.
    Full-text · Article · Apr 2014 · International Journal of Nanomedicine
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