Non-functionalized Single-walled Carbon Nanotubes Research Articles

Effect of polyethylene glycol surface charge functionalization of SWCNT on the in vitro and in vivo nanotoxicity and biodistribution monitored noninvasively using MRI

The current study evaluated in vitro and in vivo toxicity of carboxyl or amine polyethylene glycol (PEG) surface functionalization of single-walled carbon nanotubes (SWCNTs). Assessments of cytotoxicity, genotoxicity, immunotoxicity, and oxidative stress were performed in vitro and in vivo (in a 1-month follow-up study). The SWCNT biodistribution was investigated using noninvasive magnetic resonance imaging (MRI). Results confirmed the enhanced biocompatibility of PEG-functionalized SWCNTs compared to non-functionalized materials with significant decreases (p < 0.05) in the percentage of cell viability and increases in ROS generation, mitochondrial membrane potential, cell apoptosis, oxidative stress generation, and oxidative DNA damage in vitro. PEG-functionalized SWCNTs with amine terminals were found to induce prominent increases in ROS generation, mitochondrial membrane potential, and oxidative stress compared to carboxy functionalization. No significant difference in the biodistribution of either functionalized SWCNTs was observed in MRI. In vivo assessments revealed a statistically significant increase (p < 0.05) in oxidative stress as early as 24 h in serum and liver; however, all values normalized at 2 weeks’ investigation time point. DNA damage was minimal with either PEG-COOH or PEG-NH2 functionalized SWCNTs after 2 weeks’ exposure. The negatively charged SWCNTs caused lesser DNA damage compared to positively charged samples. Carboxy-functionalized SWCNTs did not cause substantial changes in inflammatory mediators and were found to be significantly safer than non-functionalized SWCNTs and may pave the way for novel biomedical applications in cancer diagnosis and therapy.

Hollow carbon spheres trigger inflammasome-dependent IL-1β secretion in macrophages

It is disputed whether inflammasome activation leading to secretion of pro-inflammatory interleukin (IL)-1β in macrophages transpires independently of cell death or whether the two processes are linked. Here, we synthesized hollow carbon spheres (HCS) and investigated their effects on primary human monocyte-derived macrophages (HMDM); short (500 nm) non-functionalized single-walled carbon nanotubes (SWCNT) were included for comparison. HCS (250 nm) were readily taken up by HMDM and induced ROS production, but did not trigger a loss of cell viability. However, a dose- and time-dependent release of IL-1β was detected in lipopolysaccharide (LPS)-primed macrophages upon exposure to HCS, while SWCNT-induced secretion of IL-1β was less pronounced. HCS-triggered IL-1β secretion was cathepsin B- and caspase-1-dependent, and was accompanied by a reduction in intracellular K+. Furthermore, cytokine secretion was reduced following treatment with the antioxidant, N-acetylcysteine, and cytochalasin D, an inhibitor of actin polymerization. HCS also triggered IL-1β release in LPS-primed THP.1 cells, but not in THP.1 cells with silencing of ASC, NLRP3, or caspase-1 expression, providing evidence that IL-1β was elicited through NLRP3 inflammasome activation. These studies shed light on the effects of HCS on primary macrophages, and show that spherical carbon-based nanoparticles are potent inflammasome activators.

Salinity-dependent toxicity of water-dispersible, single-walled carbon nanotubes to Japanese medaka embryos.

To investigate the effects of salinity on the behavior and toxicity of functionalized single-walled carbon nanotubes (SWCNTs), which are chemical modified nanotube to increase dispersibility, medaka embryos were exposed to non-functionalized single-walled carbon nanotubes (N-SWCNTs), water-dispersible, cationic, plastic-polymer-coated, single-walled carbon nanotubes (W-SWCNTs), or hydrophobic polyethylene glycol-functionalized, single-walled carbon nanotubes (PEG-SWCNTs) at different salinities, from freshwater to seawater. As reference nanomaterials, we tested dispersible chitin nanofiber (CNF), chitosan-chitin nanofiber (CCNF) and chitin nanocrystal (CNC, i.e. shortened CNF). Under freshwater conditions, with exposure to 10 mg l-1 W-SWCNTs, the yolk sacks of 57.8% of embryos shrank, and the remaining embryos had a reduced heart rate, eye diameter and hatching rate. Larvae had severe defects of the spinal cord, membranous fin and tail formation. These toxic effects increased with increasing salinity. Survival rates declined with increasing salinity and reached 0.0% in seawater. In scanning electron microscope images, W-SWCNTs, CNF, CCNF and CNC were adsorbed densely over the egg chorion surface; however, because of chitin's biologically harmless properties, only W-SWCNTs had toxic effects on the medaka eggs. No toxicity was observed from N-SWCNT and PEG-SWCNT exposure. We demonstrated that water dispersibility, surface chemistry, biomedical properties and salinity were important factors in assessing the aquatic toxicity of nanomaterials. Copyright © 2016 John Wiley & Sons, Ltd.

Physicochemical properties of functionalized carbon-based nanomaterials and their toxicity to fishes

Chemical functionalization to tailor surface properties of nanomaterials (NMs) is expected to broaden their scope of potential applications but may also be used to modify NM toxicity. We have examined the physicochemical properties of single-walled carbon nanotubes (SWCNTs) with varying degrees of carboxylic acid group functionalization, two types of lignin-wrapped SWCNTs, as well as nonfunctionalized SWCNTs. Zebrafish (Danio rerio) embryos were exposed to 1, 10, 50, 100 or 200 mg/L functionalized and nonfunctionalized SWCNTs for up to 72 h; measured endpoints included survival, hatching success, and alteration in gene expression. We have also characterized carboxylated cellulose nanocrystals (CNCs) and examined their effects both in vivo using zebrafish and in vitro using three channel catfish (Ictalurus punctatus) cell lines. While nonfunctionalized SWCNTs did not affect survival or hatch of embryos, carboxylic acid functionalized SWCNTs accelerated hatching and lignin-wrapped SWCNTs both decreased survival and delayed hatch at all time points tested. Carboxylated CNC exposure decreased the viability of 1G8 and 28S.3 catfish cells. We suggest that surface functionality affects SWCNT characteristics and plays a key role in determining their toxicity.

Novel design of non-enzymatic sensor for rapid monitoring of hydrogen peroxide in water matrix

A simple and reliable design of the non-enzymatic sensor capable of instant detection of broad range of hydrogen peroxide (H2O2) concentrations in various water-based matrixes has been presented. Manufacturing of the sensor was based on the manganese dioxide (MnO2)-non-functionalized single walled carbon nanotubes (SWCNTs) - Nafion nanocomposite modified glassy carbon electrode (MnO2/SWCNTs-Nf/GCE). The electrochemical behavior of hydrogen peroxide at this sensitive platform was verified by the cyclic voltammetry and amperometry. The obtained results have demonstrated that the modified GCE exhibited an excellent electrocatalytic activity towards hydrogen peroxide. The parameters related to this sensor, such as amount of MnO2, applied potential and pH value were optimized to attain a broad working linear range 5.0×10−6 to 3.0×10−3M, with detection limit of 0.52×10−6M (17.7ppb) of detection H2O2. Developed electrode was tested for stability and accuracy measurements in environmental/biological conditions, such as pH and interference of common ions, namely calcium, magnesium, nickel, copper, bicarbonate and citrate, showing an excellent stability and repeatability in tested ranges.

Reactive oxygen species generation and dispersant-dependent electron transfer through single-walled carbon nanotubes in water

Although induction of oxidative stress is widely accepted as one of the major cytotoxic effects of carbon nanotubes (CNTs), there is no solid understanding of how biological redox reactions are affected and how reactive oxygen species (ROS) are generated by CNTs, especially when they are coated with various dispersing agents. In this study, we investigated electron transfer from biological reducing agents through nonfunctionalized single-walled carbon nanotubes (SWCNTs) to molecular oxygen, generating ROS in the process. Electron transfer rates in the colloidal SWCNT suspensions depended on the dispersant used to stabilize them, with six dispersants examined. Oxidation of both nicotinamide adenine dinucleotide (NADH) and dithiothreitol was catalyzed by SWCNTs coated with either cetyltrimethylammonium bromide (CTAB) or Suwannee River natural organic matter (SRNOM). SWCNTs coated with other types of surfactants showed only slight effect. In the presence of NADH or dithiothreitol, generation of ROS also was dispersant-dependent, with CTAB- and SRNOM-coated SWCNTs generating significant amounts of superoxide anion and hydrogen peroxide. In systems containing xanthine and xanthine oxidase, accumulated charge on the SWCNTs appeared to be transferred to superoxide anion, resulting in indirect disproportionation of superoxide anion, forming more hydrogen peroxide.

Effect of single-walled carbon nanotubes on morphology and mechanical properties of NBR/PVC blends

Dynamically vulcanized thermoplastic elastomer based on Nitrile butadiene-rubber (NBR)/PVC with functionalized single-walled carbon nanotubes (f-SWNTs) and non-functionalized single-walled carbon nanotubes (SWNTs) were prepared using a brabender internal mixer. Effects of two types of SWNTs (functionalized and non-functionalized) on morphology and mechanical properties of NBR/PVC blends were studied. Results showed that the mechanical properties of NBR/PVC/SWNTs nanocomposites improved with the increasing of SWNTs content and in particular with the increase of f-SWNTs content. Moreover, the enhancement of mechanical properties of NBR/PVC blends reinforced with functionalized SWNT was higher than that of NBR/PVC blends with non-functionalized SWNT. Dispersion of SWNTs and morphology of NBR/PVC/SWNT nanocomposites were determined by scanning electron microscopy and transmission electron microscopy (TEM) techniques. TEM images illustrated that f-SWNTs were dispersed uniformly in NBR/PVC matrix while non-functionalized SWNTs showed much aggregation. Dynamic mechanical thermal analysis of NBR/PVC/SWNTs nanocomposites was also studied. The outcomes indicated that in the case of f-SWNTs, the intensity of tan δ peak was lower than that in the case of non-functionalized SWNTs. Meanwhile, the intensity of tan δ peak reduced when the content of f-SWNTs was increased.

Derivatization of SWCNTs with cobalt phthalocyanine residues and applications in screen printed electrodes for electrochemical detection of thiocholine

Single-walled carbon nanotubes (SWCNTs) derivatized with cobalt phthalocyanine (CoPh) were applied onto screen-printed graphite electrodes (SPEs) to be used for the low-potential electrochemical oxidation of thiocholine (TCh). Covalent attachment of CoPh to SWCNTs via stable sulfonamide bonds was confirmed by Raman/FT-IR spectroscopy and thermogravimetric analysis (TGA) coupled with FT-IR detection. The resulting modified SPE surfaces (CoPh-SWCNT-SPEs) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) with the redox probe [F 3(CN) 6] 3−/4−. Detection of TCh was accomplished using cyclic voltammetry and amperometry; a lower overpotential (100 mV vs. Ag/AgCl pseudoreference electrode) was obtained using CoPh-SWCNT-SPEs as compared to unmodified SPEs and SPEs modified with non-functionalized SWCNTs (SWCNT-SPEs). The linear range for TCh detection was 0.077–0.45 mM, with a sensitivity of 5.11 × 10 −1 μA mM −1 and a limit of detection of 0.038 mM according to the 3 s/m definition.

Ground-Based Space Radiation Effects Studies on Single-Walled Carbon Nanotube Materials

ABSTRACTMaterials based on carbon nanotubes hold great promise for a variety of applications relevant to space exploration and the aerospace industry. Materials used for these applications will be subject to hostile environments including increased levels of high-energy particulate radiation. The type, energy range and fluence of the radiation will depend on the environment of the space mission. While it is not feasible to conduct an exhaustive study of the effects of space radiation on the earth's surface, ground-based experiments can be designed to simulate expected radiation environments using sources representing components of the relevant radiation environments. In this paper we present a compilation of results on materials based on singlewalled carbon nanotubes (SWNT) emphasizing nano-composites with raw (non-functionalized) and with 2–5% functionalized SWNTs in a polyethylene matrix. Materials such as these are promising candidates for multi-functional materials with good structural and radiation shielding characteristics. The radiation sources discussed here are relevant to the upper atmosphere (high energy neutrons), low earth orbit (medium energy protons) and interplanetary space (high energy protons and heavy ions). The samples are characterized before and after radiation with Raman spectroscopy which gives information on the structure of the SWNT and state of sidewall functionalization. Based on results from the SWNT papers (“buckypapers”) and the composites made from functionalized and non-functionalized SWNT, our data indicates that structural integrity and any sidewall functionalization of the SWNT in the nano-composite are radiation tolerant to radiation fluences commensurate with expected exposures on long-term spaceflight. More importantly, we find that the chemistry and material science of the processes used to produce the pristine and functionalized SWNT can affect the radiation characteristics of the nano-composites.