Water-soluble Multi-walled Carbon Nanotubes Research Articles

Partially oxidized polyvinyl alcohol + functionalized water soluble multiwalled carbon nanotubes: A new conductive nanocomposite material with promising implications for neuroregeneration

Carbon nanotubes (CNT) are promising electroconductive nano-scale materials for neuroregeneration. Herein, we report on a new electroconductive composite scaffold made of the polymer 1% oxidized polyvinyl alcohol (OxPVA) combined with functionalized water soluble multiwalled CNT (OxPVA + MWCNT-S) (diazotization reaction). Preliminarily, MWCNT-S were characterized to evaluate the reaction outcome, the degree of functionalization and the dispersibility in water. Thereafter, OxPVA + MWCNT-S nanocomposite membranes were fabricated and analyzed for physicochemical properties (Raman spectroscopy, thermal decomposition, calorimetric properties, electroconductivity), macroscopic appearance and ultrastructure, mechanical behavior, in vitro cytotoxicity and in vivo biocompatibility. In parallel, OxPVA + MWCNT-S membranes with a linear pattern were also developed and analyzed for interaction with SH-SY5Y cells. Compared to OxPVA, the presence of MWCNT-S (only 0.016 wt%) significantly increased polymer conductivity and imparted a certain porosity without altering mechanical behaviour, as corroborated by uniaxial tensile tests. Neither cytotoxicity nor local signs of inflammation were detected in vitro and after subcutaneous implantation (14 and 42 days), proving composite material biocompatibility. OxPVA + MWCNT-S nanocomposite revealed as promising for future electroconductive conduits free from toxic effects amenable to CNT agglomeration within the polymer. Ideally, nerve lesions with wide gaps, may be effectively supported by those “active” devices, overcoming limitations of the available ones. Despite preliminary data, the presence of a linear pattern confirmed to have a beneficial effect over the scaffold/cells interaction.

Facile preparation of water-soluble multiwalled carbon nanotubes bearing phosphorylcholine groups for heat generation under near-infrared irradiation

In the present study, water-soluble molecular complexes between carboxylic acid-functionalized multiwalled carbon nanotubes (MWCNTs) and biocompatible poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were prepared by hand grinding. MWCNTs could be solubilized in phosphate-buffered saline using this simple method. The suspended concentration of MWCNTs was found to increase with increasing polymer concentration and pH of the solution. Heat generation from the complexes was studied upon irradiation with near-infrared (NIR) radiation at a wavelength of 808 nm. The results demonstrated that MWCNTs absorbed light and generated heat when the molecular complex was irradiated by NIR. The solution temperature increased with increasing MWCNT concentration and irradiation time. This study presents a facile method for preparation of water-soluble molecular complexes between carboxylic acid-functionalized multiwalled carbon nanotube and poly(2-methacryloyloxyethyl phosphorylcholine) (MWCNTs/PMPC) by hand grinding. MWCNTs could be solubilized in aqueous environment with higher suspended concentrations when increasing polymer concentration and pH of the solution. MWCNTs/PMPC adsorbed light and induced heat generation to reach the temperature required for photothermal therapy (PTT) when the complexes were irradiated by near-infrared (NIR) at a wavelength of 808 nm. The water-soluble MWCNT complex covered by biocompatible PMPC is a promising candidate for PTT application.

Cytotoxicity Effects of Water-Soluble Multi-Walled Carbon Nanotubes Decorated with Quaternized Hyperbranched Poly(ethyleneimine) Derivatives on Autotrophic and Heterotrophic Gram-Negative Bacteria.

Oxidized multi-walled carbon nanotubes (oxCNTs) were functionalized by a simple non-covalent modification procedure using quaternized hyperbranched poly(ethyleneimine) derivatives (QPEIs), with various quaternization degrees. Structural characterization of these hybrids using a variety of techniques, revealed the successful and homogenous anchoring of QPEIs on the oxCNTs’ surface. Moreover, these hybrids efficiently dispersed in aqueous media, forming dispersions with excellent aqueous stability for over 12 months. Their cytotoxicity effect was investigated on two types of gram(−) bacteria, an autotrophic (cyanobacterium Synechococcus sp. PCC 7942) and a heterotrophic (bacterium Escherichia coli). An enhanced, dose-dependent antibacterial and anti-cyanobacterial activity against both tested organisms was observed, increasing with the quaternization degree. Remarkably, in the photosynthetic bacteria it was shown that the hybrid materials affect their photosynthetic apparatus by selective inhibition of the Photosystem-I electron transport activity. Cytotoxicity studies on a human prostate carcinoma DU145 cell line and 3T3 mouse fibroblasts revealed that all hybrids exhibit high cytocompatibility in the concentration range, in which they also exhibit both high antibacterial and anti-cyanobacterial activity. Thus, QPEI-functionalized oxCNTs can be very attractive candidates as antibacterial and anti-cyanobacterial agents that can be used for potential applications in the disinfection industry, as well as for the control of harmful cyanobacterial blooms.

Gold Nanoparticle Conjugated Water Soluble Multiwall Carbon Nanotubes

The poor solubility and dispersibility of carbon nanotubes in both aqueous and organic solvents restrict their applications in biological science. Herein, a simple and cheap method for synthesizing and purification of water soluble multiwall carbon nanotubes from coal combustion fly ash and characterization of this water soluble multiwall carbon nanotubes after conjugation with gold nanoparticles has been described.

Three-Dimensional Electric Micro-Grid Network for High-Energy-Density Lithium-Ion Battery Cathodes

High-energy-density LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes are prepared by the reduction of carbon additive loading based on the self-organization of water-soluble multiwalled carbon nanotubes (MW-CNTs) into MW-CNT/NCM523 supramolecular assemblies. Field emission scanning electron microscopy reveals that the MW-CNTs homogeneously included NCM523 particles and formed a grid structure that bridges the NCM523 particles. These structural characteristics are quite different from conventional composite electrode systems in lithium-ion secondary batteries. The supramolecular assemblies enable the increase of the NCM523 particle concentration (up to 98 wt%) and tap density (up to 3.8 g cm-3), and eliminate the need for a binder. A higher C-rate capability and cyclability are achieved by improving the kinetic parameters in the composite electrode for the battery reactions. In particular, the maximum average discharge capacity based on the total mass of the composite is 171 mAh g-1 in the MW-CNT/NCM523 (98 wt%) composite electrode within the cut-off voltage range of 2.5–4.3 V (vs Li+/Li), which is much higher than that of conventional acetylene black systems (157 mAh g-1).

Functionalization of multi-walled carbon nanotubes by radiation-induced graft polymerization in aqueous solution

ABSTRACTA facile strategy for the preparation of water-soluble multi-walled carbon nanotubes (MWCNTs) in aqueous solution is proposed, where MWCNTs were treated by the concentrated mix acid and then functionalized by simultaneous radiation-induced graft polymerization of acrylic acid under the γ-ray. The structure of the grafted MWCNTs (denoted as MWCNT-g-PAAc) is characterized by means of FT-IR, lH NMR, Raman spectroscopies, TGA analysis, and TEM imaging. The degree of grafting was dependent on the reaction conditions such as the monomer concentration and the inhibitor concentration. The stability of the aqueous solution of MWCNT-g-PAAc is highly improved, where the solution is stable for more than 30 days at the concentration 1.5 g/L.

Three-dimensional electric micro-grid networks for high-energy-density lithium-ion battery cathodes

High-energy-density LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes are prepared by the reduction of carbon additive loading based on the self-organization of water-soluble multiwalled carbon nanotubes (MW-CNTs) into MW-CNT/NCM523 supramolecular assemblies.

Significance of the Length of Carbon Nanotubes on the Bioelectrocatalytic Activity of Bilirubin Oxidase for Dioxygen Reduction

Bilirubin oxidase (BOD) catalyzes 4e−-reduction of O2 into H2O and is one of the enzymes allowing direct electron transfer (DET)-type bioelectrocatalysis. Mesoporous carbon materials are often used for constructing BOD-modified DET-type biocathodes. We have examined the performance of several multi-walled carbon nanotubes (MWCNTs) as cathode platforms for BOD-catalyzed bioelectrocatalytic O2 reduction. It has been found that the length of MWCNTs is a very important factor to control the performance. The π-π conjugated system with the carboxy groups on the surface of MWCNTs plays an important role in enhancing the DET-type bioelectrocatalytic activity of BOD. Water-soluble MWCNT with the length of as short as 1−4μm is the most suitable material among the MWCNTs examined, and they have been used to construct a mesoporous carbon electrode without any binder. The catalytic current density has reached a diffusion-controlled level for the first time for BOD at an electrode rotating rate of 4000rpm and at 25°C (8mAcm−2).

ATRP graft copolymerization of poly(N-isopropylacrylamide-co-acrylic acid) on multiwalled carbon nanotubes

The polymer functionalized multiwalled carbon nanotubes (MWCNT) have been prepared by atom transfer radical graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) monomers from their binary mixture at fixed feed molarity and composition (f NIPAAm ). The donor-acceptor interactions between acrylic acid and N-isopropylacrylamide have enhanced the activity of N-isopropylacrylamide for grafting onto MWCNT (52%) in comparison to individual grafting of N-isopropylacrylamide onto MWCNT (38%). The CuBr and N′N′N′N′N′-pentamethyldiethylenetriamine (PMDETA) were used as ATRP catalysts for graft copolymerization of N-isopropylacrylamide and acrylic acid onto multiwalled carbon nanotubes. The copolymers grafted onto MWCNT were of high molecular weight (42×103 g mol−1) with low molecular weight dispersity (1.13) at 0.1 M a feed molarity and feed composition (f NIPAAm ) of 0.6. The graft yield (%G), molecular weight (MW), and sequence length of N-isopropylacrylamide and acrylic acid monomers (mM1 an mM2) in the grafted chains varied significantly with varying feed composition (f NIPAAm ). The grafting produced highly water soluble multiwalled carbon nanotubes in comparison to pristine MWCNT. The grafted copolymer chain dispersity varied with solution temperature and pH due to the temperature and pH sensitivity of the monomers. The poly(N-isopropylacrylamide-co-acrylic acid) grafted chains were characterized by FT-IR and NMR techniques for their structures and thermal stability as determined by TGA.

Enhanced solid-phase photocatalytic degradation of polyethylene by TiO2–MWCNTs nanocomposites

In this work, a novel acid vapor method was introduced to prepare the water soluble multi-walled carbon nanotubes (MWCNTs) and the titanium dioxide (TiO2)–MWCNTs nanocomposites photocatalyst were successfully synthesized by sol–gel solvothermal method. Products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the anatase TiO2 particles were uniform deposited on MWCNTs surface. UV–vis diffuse reflectance spectroscopy (UV–vis) showed that composite photocatalyst had an obviously absorption band which covered the whole range of UV–vis region and exhibited a significant enhancement of optical absorption property. Based on above properties, we used the TiO2–MWCNTs composites as photocatalysts to degrade the polyethylene (PE) plastic. Solid-phase PE film photocatalytic degradation experiments were investigated through monitoring TiO2–MWCNTs–PE composite film's weight loss under mercury lamp irradiation. Results showed that the degradation efficiency could be tuned by changing the concentration of MWCNTs in photocatalyst. The photo-induced degradation of composite film was significantly higher than that of the pure PE film and the Degussa P25-PE film under the same UV irradiation. The weight loss of TiO2–MWCNTs (20 wt%)–PE sample reached 35% under 180 h UV-light irradiation. Our work could be extended to synthesize other MWCNTs based composite with the purpose of enhancing TiO2's activity and inspiring for the practical environmental pollution, especially for degradation of plastics.

Highly water-soluble multi-walled carbon nanotubes amine-functionalized by supercritical water oxidation

Multi-walled carbon nanotubes (MWNTs) have been amine-functionalized by eco-friendly supercritical water oxidation. The facilely functionalized MWNTs have high solubility (~84 mg L(-1)) in water and 78% transmittance at 30-fold dilution. The Tyndall effect is also shown for several liquids.

A specific Tween-80-Rhodamine S-MWNTs phosphorescent reagent for the detection of trace calcitonin

The present study proposed a simple sensitive and specific immunoassay for the quantification of calcitonin (CT) in human serum with water-soluble multi-walled carbon nanotubes (MWNTs). The COOH group of MWNTs could react with the NH group of rhodamine S (Rhod.S) molecules to form Rhod.S-MWNTs, which could emit room temperature phosphorescence (RTP) on acetate cellulose membrane (ACM) and react with Tween-80 to form micellar compound. Tween-80-Rhod.S-MWNTs (TRM), as a phosphorescent labelling reagent, could dramatically enhance the RTP signal of the system. The developed TRM phosphorescent reagent was used to label anti-calcitonin antibody (AbCT) to form the TRM-AbCT labelling product, which could take high specific immunoreaction with CT, and the ΔIp (= Ip2−Ip1, Ip2 and Ip1 were the phosphorescence intensity of the test solution and the blank sample, respectively) of the system was linear to the content of CT. Hence, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) was established for the determination of CT in human serum. This sensitive (limit of quantification (LOQ) was 8.0×10−14gmL−1), accurate, selective and precise method has been applied to determine CT in human serum and predict primary osteoporosis and fractures, with the results in good agreement with those obtained by chemiluminescence immunoassay (CLIA). Simultaneously, the structure of MWNTs was characterized with scanning electron microscopy (SEM) and infrared spectroscopy (IR), and the reaction mechanisms of both labelling AbCT with TRM and SSRTPIA for the determination of trace CT were discussed.

Abstract 403: Interaction of carbon nanotubes with macrophages in tumor microenvironment

Abstract Macrophages take on different phenotypes and play different roles in tumor progress as well as anti-tumor therapy depending on the environmental signals that they receive. We have previously reported that subcutaneously injected oxidized multiwalled carbon nanotubes (o-MWCNTs) in normal BABL/c mice were largely engulfed by resident macrophages around the injection site, inducing complement activation and short-term upregulation of inflammatory cytokines [Jie Meng, Man Yang, Zhen Xu, Fumin Jia, Hua Kong, and Haiyan Xu. Immune responses of BALB/c mice to subcutaneously injected multi-walled carbon nanotubes. Nanotoxicology, 2010, DOI:10.3109/17435390.2010.523483]; subcutaneous injection of o-MWCNTs in tumor bearing BALB/c mice upregulated the expression of GM-CSF and IL12p70 in the serum over 2-fold increase and inhibited the tumor progression to a certain extent [Jie Meng, Man Yang, Fumin Jia, Hua Kong, Weiqi Zhang, ChaoyingWang, Jianmin Xing, Sishen Xie and Haiyan Xu. Subcutaneous injection of water-soluble multi-walled carbon nanotubes in tumor-bearing mice boosts the host immune activity. Nanotechnology 2010; 21: 145104]. When o-MWCNTs were used as a carrier of tumor lysate, subcutaneous injection of this conjugate in tumor-bearing mice effectively increased cytotoxicity of the lymphocytes to the tumor cells [Jie Meng, Jie Meng, Jinhong Duan, Hua Kong, Chen Wang, Sishen Xie, Shuchang Chen, Haiyan Xu and Xian-Da Yang. Carbon Nanotubes Conjugated to Tumor Lysate Protein Enhance the Efficacy of an Anti-tumor Immunotherapy. Small 2008; 4(9): 1364-1370]. These findings imply that the inhibitory effect of o-MWCNTs on tumor progression may be associated with their interactions with macrophages. The present work focused on the effect of o-MWCNTs on macrophages phenotypes and functions in the tumor environment. The o-MWCNTs were physicochemically characterized with SEM, DLS, FTIR, TGA, and UV-vis-NIR spectroscopy; and the effects on RWA 264.7 cell line or macrophages in breast cancer tumor-bearing mice were investigated using MTS assay, flow cytometry analysis, and histological and immunohistochemical observations. Experimental results showed that subcutaneously injected o-MWCNTs not only attracted resident macrophages in tissue and induced phagocytosis, but also competitively recruited macrophages from circulating monocytes, which led to reduction of macrophages and vessel density around the tumor mass and inhibition of tumor progression and metastasis in the lung. Additionally, o-MWCNTs inhibited the ability of alternatively activated RAW macrophages to promote tumor cells migration as well as decreased their proliferation rate. Acknowledgement: This work was supported by National Key Scientific Projects of China (2011CB933504, 2010CB934002) and Beijing Municipal Natural Science Foundation (2011022). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 403. doi:1538-7445.AM2012-403

Effects of Phosphoryl Choline Grafted Water Soluble Carbon Nanotubes Examined by Different Cytotoxicity Methods in 16-HEB Cells

The widespread explored application of water soluble carbon nanotubes makes it important to understand their potential toxic effects on health. This study investigates the effects of phosphoryl choline grafted water soluble multi-walled carbon nanotubes (MWCNTs-PC) on human bronchial epithelial (16-HBE) cells by different cytotoxicity methods in vitro. Various concentrations of MWCNTs-PC were incubated with 16-HBE cells, the effects of cell proliferation, cell apoptosis, cell cycle and DNA damage were detected by methyl thiazolyl tetrazolium (MTT) assay, flow cytometry, single cell gel electrophoresis assay (SCGE) and micronuclear assay, respectively. Compared with the control group, there were no significant differences in the changes of cell proliferation, cell apoptosis, cell cycle and DNA damage. Within the experimental concentrations of MWCNTs-PC, no obviously cytotoxicity and DNA damage was observed on 16-HBE cells in this study.

Carbon Nanotubes Containing Metal Nanoparticles-Graft-Hyperbranched Polyglycerols Nanocomposites

New water soluble multiwall carbon nanotubes (MWCNTs) containing silver nanoparticles-grafted-hyperbranched polyglycerols (HPG) nanocomposites were synthesized and characterized successfully. In this work, MWCNTs were opened using HNO3/H2SO4 mixture and filled by metal nanoparticles such as silver nanoparticles through wet chemcial method. Then MWCNTs containing silver nanoparticles (MWCNTs(Ag)) were used as macroinitiator for ring opening polymerization of glycidol and MWCNTs(Ag)-g-HPG nanocomposites were obtained. Structure of nanocomposites was evaluated by TEM, TGA and spectroscopy methods. With the solubility of MWCNTs(Ag)-g-HPG greatly improved, the new nanocomposites exhibit potential application in biomedicine and nanomedicine.

A Simple and Facile Approach to Synthesize Water-Soluble Multiwalled Carbon Nanotubes Wrapped by Poly(4-Vinylpyridine)

By simple grinding, water-soluble linear polymers poly(4-vinylpyridine) (PVP) wrapped around multiwalled carbon nanotubes (MWCNTs) and thus rendered them reversibly soluble in water, ethanol, and DMF. The structure and properties of the resulting nanocomposite, CNTs wrapped by PVP, were evaluated by SEM, AFM, TGA, and FTIR spectroscopy. Individual tubes are clearly observed after PVP-wrapped nanotubes were spin-coated onto a silicon wafer as determined by SEM and AFM. Subsequently, a novel and facile approach to attach high-density and uniform size gold nanoparticles on individual multiwalled carbon nanotubes was achieved by in situ reduction of HAuCl4 in the homogeneous aqueous solution of MWCNTs–PVP.

Facile synthesis of water-soluble multi-wall carbon nanotubes and polyaniline composites and their application in detection of small metabolites by matrix assisted laser desorption/ionization mass spectrometry

Multi-wall carbon nanotubes and polyaniline composites were synthesized via a simple hydrothermal reaction, and the as-made composites were successfully applied in the analysis of small molecular-weight metabolites as a novel matrix by matrix assisted laser desorption/ionization mass spectrometry.

Water Soluble Multi-Walled Carbon Nanotubes Enhance Peritoneal Macrophage Activity <I>In Vivo</I>

Due to their unique physical properties, carbon nanotubes are becoming promising novel materials in diverse areas like information technology, ultrastiff materials, biomedicine etc. The toxicological study of these materials is very imperative for the safety assessment in respect to their wide applications. The objective of the toxicity study was to find out whether water soluble multi-walled carbon nanotubes (S-MWNTs) would impair the phagocytic activity of macrophages, which play an important role in defenses against invading microbioles. The results showed that S-MWNTs did not impair the phagocytosis of macrophages; to our surprise, S-MWNT significantly enhanced this function. Increased activity of enzymes in lysosome also showed that S-MWNTs enhanced the lysosome function of macrophages. However, S-MWNTs can not influence nitric oxide secretion in macrophages and induce inflammation.

Pulmonary Toxicity in Mice Exposed to Low and Medium Doses of Water-Soluble Multi-Walled Carbon Nanotubes

Carbon nanotubes (CNTs) are a class of new allotrope of carbon. Different functionalized CNTs may vary from their physical and chemical properties to the biological property. In this study, the toxicity of water-soluble taurine multi-walled CNTs (tau-MWNTs), raw MWNTs and positive control crystalline silicon dioxide particles on mouse lungs via intratracheal instillation (i.t.) was investigated. The dosages we used were 0.125, 0.25, 0.5 or 1 mg/kg of tau-MWNTs and raw MWNTs, and 1 mg/kg of silicon dioxide particles; Serum and lungs were collected at 1, 7, 14 or 28 days postexposure. The biochemical and cellular parameters were assessed, which include the ratio of the lung weight and body weight (lung indices), lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and angiotensin converting enzyme (ACE) in serum, and malondialdehyde (MDA), reduced glutathione (GSH), total sulfhydryl group (TSH) in lung tissue homogenates as well as the hydroxyproline in lungs. The characteristic recovery of the lung injury at 28 days postexposure was examined by the assessment of LDH, ALP, lung indices, and histopathology. ACE, MDA, GSH, TSH and histopathological changes showed that tau-MWNTs were less toxic than the raw MWNTs. Histopathological and ultrastructural investigation indicated that the acute pulmonary inflammation in lungs alleviated after 7d postexposure, and were greatly recovered within 28d. Meanwhile, the entrapment of tau-MWNTs reduced greatly by the 28d postexposure. Whereas the heavier pathologic changes induced by raw MWNTs lasted 7 days more than that of tau-MWNTs. Notably, no occurrence of granulomas and fibrosis were found in this study both in the two CNTs samples through 28d postexposure. Silicon dioxide particles, on the contrary, produced more severe damage to lungs than CNTs did in lung index, as well as other biochemical and cellular parameters. These findings indicate that water-soluble tau-MWNTs in low and medium doses induce slight and recoverable pulmonary inflammation in mice, and are less toxic than the insoluble raw MWNTs.

Carbon Nanotubes Induce Secondary Structure Changes of Bovine Albumin in Aqueous Phase

Interaction of nanomaterials to protein molecules is one of the most important issues to deeply understand the influences of the nanomaterials upon physiological processes and protein functions. So far most of investigations focused on the protein molecules adsorbed on the nanomaterials surface, less is known about those in the aqueous phase (not absorbed). In this work, luminescent spectroscopy analysis, circular dichroism measurement, atomic force microscopy, matrix-assisted laser desorption/ionization time of flight mass spectrometry, isoelectric focusing and sulfate polyacrylamide gel electrophoresis were used to investigate the influence of oxidized water-soluble multiwalled carbon nanotubes (CNT) dispersing in aqueous solution upon the structures of bovine serum albumin (BSA) through co-incubation. We focused on BSA molecules that stayed in the aqueous phase instead of those adsorbed by CNT. Experimental results show that the fractions of beta-sheet decreased from 33.3% to 29.8% and beta-turn increased from 2% to 5% in reference with native BSA. There was a slight increase of alpha-helix and a slight reduction of random coil. BSA molecules that had been encountered with CNT and were left in the solution formed a loose and flatten morphology on graphite substrates instead of their native tight and round morphology observed by AFM. The value of isoelectric point for BSA after exposed to CNT moved towards to a higher pH position compared with native BSA. All together, it was concluded that the oxidized water-soluble multiwalled carbon nanotubes not only adsorb bovine serum albumin molecules to their surface, but also induces albumin molecules in the aqueous solution undergo secondary structure changes, which lead to a conformation change.