Functionalized Single-Wall Carbon Research Articles

In vitro and in vivo studies of pirarubicin-loaded SWNT for the treatment of bladder cancer

Intravesical chemotherapy is an important part of the treatment for superficial bladder cancer. However, the response to it is limited and its side effects are extensive. Functional single-walled carbon nanotubes (SWNT) have shown promise for tumor-targeted accumulation and low toxicity. In the present study, we performed in vivo and in vitro investigations to determine whether SWNT-based drug delivery could induce high tumor depression in rat bladder cancer and could decrease the side effects of pirarubicin (tetrahydropyranyl-adriamycin, THP). We modified SWNT with phospholipid-branched polyethylene glycol and constructed an SWNT-THP conjugate via a cleavable ester bond. The cytotoxicity of SWNT-THP against the human bladder cancer cell line BIU-87 was evaluated in vitro. Rat bladder cancer in situ models constructed by N-methyl-N-nitrosourea intravesical installation (1 g/L, 2 mg/rat once every 2 weeks for 8 weeks) were used for in vivo evaluation of the cytotoxicity of SWNT and SWNT-THP. Specific side effects in the THP group including urinary frequency (N = 12), macroscopic hematuria (N = 1), and vomiting (N = 7) were identified; however, no side effects were observed with SWNT-THP treatment. Flow cytometry was used to assess the cytotoxicity in vitro and in vivo. Results showed that SWNT alone did not yield significant tumor depression compared to saline (1.74 ± 0.56 and 1.23 ± 0.42%) in vitro. SWNT-THP exhibited higher tumor depression than THP-saline in vitro (74.35 ± 2.56 and 51.24 ± 1.45%) and in vivo (52.46 ± 2.41 and 96.85 ± 0.85%). The present findings indicate that SWNT delivery of THP for the treatment of bladder cancer leads to minimal side effects without loss of therapeutic efficacy. Therefore, this nanotechnology may play a crucial role in the improvement of intravesical treatment of bladder cancer. Key words: Single-walled carbon nanotubes; Bladder cancer; Drug vehicle; THP; Intravesical chemotherapy

Theoretical Investigation on the Solubilization in Water of Functionalized Single-Wall Carbon Nanotubes

An important technique to increase the solubility and reactivity of carbon nanotube is through functionalization. In this study, the effects of functionalization of some single-walled carbon nanotubes (SWCNTs) were investigated with the aid of density functional theory. The SWCNT model used in the study consists of a finite, (5, 0) zigzag nanotube segment containing 60 C atoms with hydrogen atoms added to the dangling bonds of the perimeter carbons. There are three water-dispersible SWCNTs used in this study that were functionalized with (a) formic acid, as a model of carboxylic acid, (b) isophthalic acid, as a model aromatic dicarboxylic acid, and (c) benzenesulfonic acid, as a model aromatic sulfonic acid. Binding energies of the organic radicals to the nanotubes are calculated, as well as the HOMO-LUMO gaps and dipole moments of both nanotubes and functionalized nanotubes. Binding was found out to be thermodynamically favorable. The functionalization increases the electrical dipole moments and results in an enhancement in the solubility of the nanotubes in water manifested through favorable changes in the free energies of solvation. This should lower the toxicity of nanotubes and improve their biocompatibility.

Esterification of Chemical Functional Single-Wall Carbon Nanotubes

Two kinds of chemical functional single-wall carbon nanotubes (SWNTs) are covalently coupled into special V-type superstructure by the esterification in pyridine medium. Both SWNTs bundles and individual SWNTs can be bound effectively through the deacidification path. The esterification between different kinds of modified SWNTs takes place on their ends and the crystallinity of SWNTs are well remained during the course. Interestingly, the inclinations between coupled SWNTs are very closely to the ester bond angle (109o18’). Furthermore, the formation mechanism about the peculiar structure has been proposed in the paper. The results suggest that selected connection bonds will determine the different angles of coupled SWNTs.

Synthesis and Characterization of Boron Azadipyrromethene Single-Wall Carbon Nanotube Electron Donor−Acceptor Conjugates

The preparation of a novel donor-acceptor material, consisting of a red/near-infrared (NIR) absorbing boron azadipyrromethene donor covalently attached to a highly functionalized single-wall carbon nanotube (SWNT) acceptor, which bears great potential in the field of organic photovoltaics, has been demonstrated. Both purification and covalent functionalization of SWNTs have been demonstrated using a number of complementary characterization techniques, including atomic force microscopy, Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, and NIR-photoluminescence spectroscopy, and a functionalization density of approximately 1 donor molecule per 100 SWNT atoms has been estimated by XPS. The redox behavior of the fluorophore has been investigated by electrochemistry and spectroelectrochemistry as well as by pulse radiolysis. The donor-acceptor properties of the material have been characterized by means of various spectroscopic techniques, such as UV-vis NIR absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and time-resolved transient absorption spectroscopy. Charge transfer from the photoexcited donor to the SWNT acceptor has been confirmed with a radical ion pair state lifetime of about 1.2 ns.

ESR Investigations on Polyethylene–Fluorine Functionalized Single Wall Carbon Nanotubes Composites

Electron spin resonance investigations on nanocomposites obtained by dispersing fluorinated single walled carbon nanotubes within polyethylene are reported. Three resonance lines assigned to uncoupled electronic spins confined within magnetic impurities, amorphous carbon, and single wall carbon nanotubes have been observed. The temperature dependence of these lines is analyzed in detail and used to assign each component of the as-recorded ESR spectrum to a precise component of the nanocomposite. Magnetic impurities are originating from catalysts residues (in our case, Fe impurities). Surprisingly, the narrowest line is due to paramagnetic defects (amorphous carbon) while the broad line originates from electrons delocalized over conducting nanotubes. The broadening of this line reflects a bottleneck in the relaxation mechanism, triggered by the interaction of the uncoupled electrons localized on carbon nanotubes with the magnetic impurities.

The Adsorption Properties ofBacillus atrophaeusSpore on Functionalized Carbon Nanotubes

An equilibrium study ofBacillus atrophaeus(B.a) spores on functionalized Single-Wall Carbon Nanotubes (SWCNTs) has been performed in order to characterize the adsorption properties of the spores/nanotubes complex. The carbon nanotubes here investigated were subjected to a two-step purification and functionalization treatment in order to introduce chemical groups on their basal planes. The inclusion of carboxyl functional groups on the nanotubes was corroborated by Raman and infrared spectroscopy. These carboxyl groups appear to enhance the nanotube-B.a.interaction by reacting with the proteinaceous pili appendages present on the spore surface. The adsorption data demonstrate that bacillus spores diffuse faster on functionalized carbon nanotubes than on as-received and purified nanomaterials. Transmission Electron Microscopy also shows that the chemically treated nanotubes resulted in a swollen nano-network which seems to further enhance the bacillus adsorption due to a more extensive spore-nanotube contact area.

Functional single-walled carbon nanotubes based on an integrinαvβ3 monoclonal antibody for highly efficient cancer cell targeting

The application of single-walled carbon nanotubes (SWNTs) in the field of biomedicine is becomingan entirely new and exciting topic. In this study, a novel functional SWNT based on an integrinαvβ3 monoclonal antibody was developed and was used for cancer cell targeting in vitro. SWNTswere first modified by phospholipid-bearing polyethylene glycol (PL–PEG). The PL–PEGfunctionalized SWNTs were then conjugated with protein A. A SWNT–integrinαvβ3 monoclonal antibody system (SWNT–PEG–mAb) was thus constructedby conjugating protein A with the fluorescein labeled integrinαvβ3 monoclonal antibody. In vitro study revealed that SWNT–PEG–mAb presented a high targeting efficiency onintegrin αvβ3-positive U87MG cells with low cellular toxicity, while for integrinαvβ3-negative MCF-7 cells, the system had a low targeting efficiency, indicating that thehigh targeting to U87MG cells was due to the specific integrin targeting of themonoclonal antibody. In conclusion, SWNT–PEG–mAb developed in this research isa potential candidate for cancer imaging and drug delivery in cancer targetingtherapy.

Scalable Functional Group Engineering of Carbon Nanotubes by Improved One-Step Nitrene Chemistry

A facile, green, low cost and efficient one-step technology to synthesize highly dispersible functional single-walled and multiwalled carbon nanotubes (f-SWNTs and f-MWNTs) up to supergrams is reported. Large-scale (up to hundreds of grams) synthesis of functional azides was developed at first, and various reactive groups (i.e., −OH, −NH2, −COOH, and −Br) were then introduced onto the convex surfaces of CNTs in merely one reaction of nitrene addition under a relatively mild condition without causing significant damage to nanotubes. The contents of the functional moieties can be easily controlled by adjusting the feed ratio of the azide compounds to CNTs. In order to demonstrate the reactivity and functions of the immobilized organic moieties, different chemical reactions, including surface-initiated polymerizations, amidation, and reduction of metal ions, were performed on the functional CNTs, affording various CNT-polymer and CNT-Pt nanohybrids. The resulting materials were characterized by various measurements, such as TGA, Raman, XPS, FTIR, NMR, XRD, SEM, TEM, and HRTEM. The presented one-step methodology opens the avenue for industrial production of functional CNTs.

Two-Phonon Combination Raman Modes in Covalently Functionalized Single-Wall Carbon Nanotubes

Single-wall carbon nanotubes covalently functionalized with chloro-phenyl groups were investigated by Raman spectroscopy. We examine the features observed in the spectral ranges 350−1200, 1650−2000, and 2400−3200 cm−1. The Raman modes associated with the presence of defects, strongly enhanced by the functionalization are clearly distinguished from those defect independent. We indicate that some features highly enhanced by the electron−phonon coupling are very sensitive to charge transfers between the nanotubes and functional groups. A feature at ∼2900 cm−1 is observed in the spectra of functionalized nanotubes, and its origin is explained here as a combination of two disorder-induced modes.

Facile Decoration of Functionalized Single-Wall Carbon Nanotubes with Phthalocyanines via “Click Chemistry”

We describe the functionalization of single-wall carbon nanotubes (SWNTs) with 4-(2-trimethylsilyl)ethynylaniline and the subsequent attachment of a zinc-phthalocyanine (ZnPc) derivative using the reliable Huisgen 1,3-dipolar cycloaddition. The motivation of this study was the preparation of a nanotube-based platform which allows the facile fabrication of more complex functional nanometer-scale structures, such as a SWNT-ZnPc hybrid. The nanotube derivatives described here were fully characterized by a combination of analytical techniques such as Raman, absorption and emission spectroscopy, atomic force and scanning electron microscopy (AFM and SEM), and thermogravimetric analysis (TGA). The SWNT-ZnPc nanoconjugate was also investigated with a series of steady-state and time-resolved spectroscopy experiments, and a photoinduced communication between the two photoactive components (i.e., SWNT and ZnPc) was identified. Such beneficial features lead to monochromatic internal photoconversion efficiencies of 17.3% when the SWNT-ZnPc hybrid material was tested as photoactive material in an ITO photoanode.

Effective electrical conductivity of functional single-wall carbon nanotubes in aqueous fluids

In this paper, for the first time, we have used a coaxial fixture to successfully obtain the relatively low and precise electrical conductivity values of nanofluids based on functional sulfonated carbon nanotubes. From 0 to 0.5 wt.% nanotube loading, the conductivity increased approximately 13 times. However, no percolation threshold phenomenon is observed. The linear conductivity increase versus the weight percentage indicates that the dominant conduction mechanism might be the ionic conduction, which is in agreement with the chemical structure of functional SWNT (anion SO 3 − group).

Photoelectrochemical Devices Comprised of Covalently Functionalized Single-Walled Carbon Nanotubes

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An inlaying ultra-thin carbon paste electrode modified with functional single-wall carbon nanotubes for simultaneous determination of three purine derivatives

A functional single-wall carbon nanotube film electrode (SWNTE) was constructed on the surface of inlaying ultra-thin carbon paste electrode (IUTCPE). The precursor film was formed by direct inlaying carbon paste onto nichrome substrate. Scanning electron microscope (SEM) was employed to characterize the electrode surface. The electrochemical behavior of SWNT/IUTCPE for xanthine (Xa), hypoxanthine (Hxa) and uric acid (UA) was investigated by various electrochemical techniques. The SWNT/IUTCPE exhibited an excellent electrocatalysis and enhancement of the current response for the purine derivatives. Three well-defined oxidation peaks of Xa, Hxa and UA were appeared at the electrode. The proposed electrode can be applied to determine Xa, Hxa and uric acid in human urine simultaneously without any pretreatment.

Biological Interactions of Functionalized Single-Wall Carbon Nanotubes in Human Epidermal Keratinocytes

Carbon nanotube-based nanovectors, especially functionalized nanotubes, have shown potential for therapeutic drug delivery. 6-Aminohexanoic acid-derivatized single-wall carbon nanotubes (AHA-SWNTs) are soluble in aqueous stock solutions over a wide range of physiologically relevant conditions; however, their interactions with cells and their biological compatibility has not been explored. Human epidermal keratinocytes (HEKs) were dosed with AHA-SWNTs ranging in concentration from 0.00000005 to 0.05 mg/ml. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability decreased significantly (p < .05) from 0.00005 to 0.05 mg/ml after 24 h. The proinflammatory mediators of inflammation cytokines interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-alpha, IL-10, and IL-1beta were also assessed. Cytokine analysis did not show a significant increase in IL-6 and IL-8 in the medium containing 0.000005 mg/ml of AHA-SWNTs from 1 to 48 h. IL-6 increased in cells treated with 0.05 mg/ml of AHA-SWNTs from 1 to 48 h, whereas IL-8 showed a significant increase at 24 and 48 h. No significant difference (p < .05) was noted with TNF-alpha, IL-10, and IL-1beta expression at any time point. Transmission electron microscopy of HEKs treated with 0.05 mg/ml AHA-SWNTs for 24 h depicted AHA-SWNTs localized within intracytoplasmic vacuoles in HEKs. Treatment with the surfactant 1% Pluronic F127 caused dispersion of the AHA-SWNT aggregates in the culture medium and less toxicity. These data showed that the lower concentration of 0.000005 mg/ml of AHA-SWNTs maintains cell viability and induces a mild cytotoxicity, but 0.05 mg/ml of AHA-SWNTs demonstrated an irritation response by the increase in IL-8.

Rectifying Diodes from Asymmetrically Functionalized Single-Wall Carbon Nanotubes

Asymmetrically functionalized single-wall carbon nanotubes (SWNTs) have been prepared by a covalent reaction of an 11-mercaptoundecanol-modified Au surface with oxidized SWNT cylinders. While one end of the tubes is attached to gold substrate via ester groups, the free carboxylic substituents on the other end can be either ionized (CO2-) or esterified (CO2Et), creating a donor-acceptor asymmetric and acceptor-acceptor symmetric SWNT, respectively. Study of the SWNT monolayer conductance in Hg drop junction experiments reveals a pronounced diode-like behavior for donor-SWNT-acceptor junctions, while acceptor-SWNT-acceptor junctions are electrically symmetric.

Tailoring Aqueous Solubility of Functionalized Single-Wall Carbon Nanotubes over a Wide pH Range through Substituent Chain Length

Carboxylic acid-functionalized SWNTs prepared via the reaction of an amino acid, NH2(CH2)nCO2H, with fluoronanotubes show similar levels of sidewall functionalization; however, the solubility in water is controlled by the length of the hydrocarbon side chain (i.e., n). The 6-aminohexanoic acid derivative is soluble in aqueous solution (0.5 mg mL(-1)) between pH 4 and 11, whereas the glysine and 11-aminoundecanoic acid derivatives are insoluble across all pH values.

Polyethyleneimine Functionalized Single-Walled Carbon Nanotubes as a Substrate for Neuronal Growth

We report the synthesis of a single-walled carbon nanotube (SWNT) graft copolymer. This polymer was prepared by the functionalization of SWNTs with polyethyleneimine (PEI). We used this graft copolymer, SWNT-PEI, as a substrate for cultured neurons and found that it promotes neurite outgrowth and branching.

Photovoltaic Properties of Dye Functionalized Single-Wall Carbon Nanotube/Conjugated Polymer Devices

Photovoltaic properties of dye, N-(1-pyrenyl)maleimide (PM), functionalized single-walled carbon nanotubes (SWNT)−conjugated polymer, poly(3-octylthiophene) (P3OT), blend composites are reported. Devices were fabricated by drop or spin cast from the solution of composite onto ITO-coated glass. Improved performance was achieved by functionalizing the SWNT with dye molecules. Photovoltaic behavior with an open circuit voltage of 0.6−0.7 V was measured in diodes (Al/SWNT+PM−polymer/ITO). The short circuit current was found to increase by more than an order of magnitude compared to the SWNT−polymer diode without dye. Optical absorption spectra showed considerable ground-state interaction between SWNT+dye and the polymer. It is proposed that the main reason for the increase in short circuit current is due to efficient transfer of holes by dye molecules to P3OT at the dye/polymer interface and the rapid transfer of the generated electrons to the SWNTs at the dye/nanotube interface. It is shown that the dye functionalized SWNT−conjugated polymer composites represent an alternative class of organic semiconducting materials for dye-based organic photovoltaic cells.

Electrochemical Hydrogen Adsorption/Storage in Pure and Functionalized Single Wall Carbon Nanotubes

AbstractSelf-assembled sheets of single wall carbon nanotubes (SWNTs) were used as the working electrode for electrochemical hydrogen adsorption/storage in a three-electrode cell in 6M aqueous KOH or HNO3 solution. Hydrogen adsorption studies on pristine SWNTs, as well as SWNTs functionalized with electrodeposited nanoparticles of magnesium (Mg) and cobalt (Co), have been performed. The adsorbed hydrogen (uncorrected for possible water uptake via nanocapillarity) was measured to be 2.5 weight percent by thermogravimetric analysis (TGA) on a Mg-functionalized sample and 3.2 weight percent by Prompt-Gamma Activation Analysis (PGAA) for a pristine sample charged for 20 hrs. Weight loss occurs in the 105° to 125°C temperature range for both sample types. Hydrogen in Co-functionalized SWNTs and 6M HNO3 electrolyte appears to be strongly chemisorbed as indicated by the appearance of a C-H stretching line in the Fourier-transform infrared spectrum (FTIR) and absence of a desorption peak in the TGA data in the 25° to 600°C temperature range. Thermopower measurements scale with the TGA data and suggest that hydrogen uptake is associated with partial charge transfer. Ex-situ Raman spectroscopy shows a reproducible downshift of the SWNT tangential stretching mode consistent with charge transfer or chemisorption on electrochemical charging, and a substantial decrease under some conditions in resonance-enhanced intensity with increasing charging time. A SWNT sheet electrochemically coated with the conducting polymer polyaniline and then charged in 6M KOH shows possible hydrogen uptake of 1.5 weight % that desorbs at 70°C.