Activity and stability comparison of immobilized NADH oxidase on multi-walled carbon nanotubes, carbon nanospheres, and single-walled carbon nanotubes

Sodium insertion/extraction from single-walled and multi-walled carbon nanotubes: The differences and similarities

Over the last decade, rapid progress in the field of nanoscience has been increasingly driving the attention of the scientific community as well as society at large on the corresponding technological applications, which are the object of so-called nanotechnology. A strong interest in assessing the current state of the art of this fast growing field, as well as stimulating research networking, prompted the organization of the International School and Workshop 'Nanoscience & Nanotechnology (n&n2007)', under the patronage of the Italian Institute for Nuclear Physics (INFN), the University of Rome Tor Vergata, the Tor Vergata Polyclinic, and the Catholic University of Rome, with generous sponsorship from 3M, 2M Strumenti, MTS, Ape Research, Crisel Instruments, Veeco and Amira. The aims of this event were as follows:

A latex-based concept for making carbon nanotube/polymer nanocomposites

Carbon nanotubes have shown great potential as effective adsorbents for hydrophobic organic contaminants in water treatment. The present study investigated the influence of aqueous solution chemistry on the adsorption of tetracycline to carbon nanotubes. Specifically, the effects of ionic strength (NaCl and CaCl(2) ) and presence of Cu(2+) ion (7.5 mg/L) or dissolved soil or coal humic acids (50 mg/L) on adsorption of tetracycline to single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT), and nonporous pure graphite as a model of the graphite surface were systematically estimated. The presence of humic acids suppressed tetracycline adsorption on graphite and MWNT prominently, with stronger effects observed on graphite, but only slightly affected tetracycline adsorption on SWNT. The relatively large humic acid components could not readily access the small interstitial spaces of SWNT and thus were less competitive with tetracycline adsorption. The presence of Cu(2+) ion increased tetracycline adsorption to both SWNT and MWNT through the mechanism of cation bridging, with much larger effects observed on MWNT. This was probably because when compared with the Cu(2+) ions complexed on the surface of SWNT, those on the surface of MWNT having larger mesoporous interstices were more accessible to the relatively bulky tetracycline molecule. Increasing the ionic strength from 10 mM to 100 mM decreased tetracycline adsorption on both SWNT and MWNT, which was attributed to electronic shielding of the negatively charged surface sites. These results show that aqueous solution chemistry is important to tetracycline adsorption on carbon nanotubes.

Summary form given only. As carbon nanotubes (CNTs) are becoming the most promising material for nanoelectronic devices, interests on their high-frequency properties are being further increased. Recently, many active researches characterizing single-wall or multi-wall CNTs have been reported. Here, we fabricate the device with a bundle of single-wall CNT (SWCNT) captured between two signal electrodes of a coplanar waveguide (CPW), and report its radio-frequency (RF) characterization and equivalent circuit modeling. The article shows an SEM image of the SWCNT bundle captured between two signal electrodes of the CPW with the gap of 700 nm. First of all, the CPW for GSG measurement was fabricated on the high resistivity Si wafer by photolithography and lift-off process. Further electron beam lithography made the CPW has sharp signal electrodes to alleviate the drastic impedance mismatching with the SWCNT and to minimize the parasitic capacitance between two signal electrodes. The bundle of SWCNTs was captured between two signal electrodes of the CPW by dielectrophoresis alignment. Then, we made the ohmic contact between the SWCNT and the CPW by using Au electroplating and subsequent thermal annealing. This electroplating process does not require one more step of lithography. The article shows the measured transmission (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> ) and reflection (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) characteristics of the CPWs with/without SWCNT at frequencies of 0.1 ~ 40 GHz. The transmission of the CPW with SWCNT is 1 dB larger than that of the CPW without SWCNT at 10 GHz. The difference denotes the amount of the transmission through SWCNT, and it is added to the transmission through the parasitic capacitance between two signal electrodes of the open CPW. The reflection of the CPW with SWCNT is maximum 1.7 dB smaller than that of the CPW without SWCNT at 38 GHz. Figure 3 shows the equivalent circuit model of the CPW combined with SWCNT. The parasitic parameter values of the open CPW were extracted from the measurement data of the CPW without SWCNT by ADS optimization. The parasitic values are follows; L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> = 0.006 nH, L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 0.005 nH, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , = 8 Omega, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 10.7 Omega, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> = 0.04 pF, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 0.05 pF, and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> = 0.07 fF. Then, we extracted the other parameter values (due to SWCNT) from the measurement data of the CPW with SWCNT, keeping the parasitic values of the open CPW. The values are follows; R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 4.1 kOmega, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">el</sub> = 0.9 fF, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CNT</sub> = 1.04 kOmega, and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> = 1.2 nH. We completed the total equivalent circuit model of the CPW with SWCNT by using ADS optimization since the de-embedding of CPW pads may result in overestimation due to contact resistance. The article shows the magnitude and phase of the impedance (Z) obtained from the measurement and from the equivalent circuit of the CPW with SWCNT. The measured data are consistent with the modeled data within a reasonable accuracy. In summary, we have captured SWCNT between two signal electrodes of the CPW and presented its high-frequency characterization. From the de-embedding process using the equivalent circuit, we successfully obtain the resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CNT</sub> = 1 -04 kOmega) and the inductance (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> = 1.2 nH) of the SWCNT bundle.

Three female Crl:CD(SD) rats/group were dosed with single wall carbon nanotube (SWCNT) or multi wall carbon nanotube (MWCNT) four times by gavage at a total of 50 mg/kg bw or 200 mg/kg bw (four equally divided doses at one-hour intervals). Acute oral doses of SWCNT and MWCNT caused neither death nor toxicological effects, and thus the oral LD<inf>50 </inf>values for SWCNT and MWCNT were considered to be greater than 50 mg/kg bw and 200 mg/kg bw, in rats respectively. Five or ten Crl:CD(SD) rats/sex were dosed with SWCNT once daily by gavage at a dose of 0 (control), 0.125, 1.25 or 12.5 mg/kg bw/day for 28 days with a 14-day recovery period (0 and 12.5 mg/kg bw/day groups). Six or twelve Crl:CD(SD) rats/sex were dosed with MWCNT once daily by gavage at a dose of 0 (control), 0.5, 5.0 or 50 mg/kg bw/day for 28 days with a 14-day recovery period (0 and 50 mg/kg bw/day groups). Based on no toxicological effects, the no observed adverse effect levels (NOAELs) of repeated dose toxicity of SWCNT and MWCNT were considered to be 12.5 mg/kg bw/day and 50 mg/kg bw/day (the highest dose tested), respectively. It was suggested that SWCNT and MWCNT dosed by gavage reached the gastro-intestinal tract as agglomerates and were mostly excreted via feces.

The crosstalk effects in single walled carbon nanotube (SWCNT) bundle and multi-walled carbon-nanotube (MWCNT) interconnect architectures are investigated for global interconnect lengths under sub threshold conditions. The crosstalk induced time delay and the peak crosstalk voltage on victim wire of multi wire SWCNT bundle and MWCNT interconnect configurations are derived and compared to those of the copper (Cu) wire counterparts for the global interconnects for three different technologies (32-, 22- and 16nm). It is observed that, compared with the Cu, and SWCNT bundle the MWCNT interconnect can lead to a reduction of crosstalk-induced time delay and it becomes more significant with increasing interconnect length, while the peak voltage of the crosstalk-induced glitch in MWCNT interconnects is slightly greater than SWCNT bundle and that of Cu wires. Because of considerable improvement in time delay, MWCNT interconnect will be more suitable for the next generation of interconnect technology as compared with the SWCNT bundle and Cu counterpart.

This study investigated the genotoxic effects of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) on Chlorella vulgaris under controlled laboratory conditions. SWCNTs (1–2 nm diameter) and MWCNTs (10–20 nm diameter) were used, and toxicity assessments followed the OECD standardized protocol. DNA damage in exposed algal cells was evaluated using the Comet Assay (CAM), observed under a fluorescence microscope, and analyzed with CASP software. The specific growth rate of C. vulgaris increased at concentrations up to 12.5 mg/L for both types of carbon nanotubes but declined at higher concentrations. Chlorophyll content decreased progressively with increasing SWCNT concentrations and exposure duration. Comet Assay results were statistically significant (p < 0.05), confirming notable genotoxic effects. Both SWCNTs and MWCNTs caused reductions in cell number and chlorophyll concentration, with SWCNTs demonstrating a greater impact. Nuclear structural changes were observed in all treatments, but more pronounced damage was associated with SWCNT exposure. Tail moment (TM) values showed significant differences between CNT-treated samples and controls across various concentrations, indicating a concentration-dependent toxicity. These findings suggest that carbon nanotubes, particularly SWCNTs, can significantly affect algal health and genetic integrity, highlighting the need for careful environmental risk assessments of nanomaterials.

Band Engineering of Carbon Nanotubes for Device Applications

Comparative analysis of single-walled and multi-walled carbon nanotubes for electrochemical sensing of glucose on gold printed circuit boards

Carbon nanotubes are the building blocks for future electronics, materials, health care devices etc. In order to explore the health care applications of nanotubes in diagnosis and drug delivery, it is important to understand their toxicity. In the present study the in vitro responses were seen when carbon nanotubes were exposed to human cell lines. It typically involves dispersion of multiwall and single walled carbon nanotubes, as well as carbon black and quartz as reference material within the cell culture medium followed by their subsequent addition to human cell lines. MTT 3-(4, 5 dimethylthiazol-2 yl) 2, 5-diphenyl tetrazolium bromide, a tetrazole assay was performed; cell viability was measured by observing their absorbance using ELISA (enzyme-linked immunosorbent assay) reader. Cell viabilities at different concentrations i.e. 50, 10, 5, 3, 1 μg mL−1 were studied. In MTT assay, it was observed that cell viability increases with decrease in concentration of single walled and multiwall carbon nanotubes. We found that both behave almost in the same manner in terms of viability in case of MTT assay. Cellular uptake of FITC (fluorescein isothiocyanate) labeled carbon nanotubes were imaged using confocal microscopy and transmission electron microscope.

Update on Carbon Nanotube Toxicity

Recently portable Raman probes have emerged into markets with a variety of applications including carbon nanotube (CNTs) characterization. Aqueous dispersed carbon nanotubes (CNTs) have shown a lot of promise towards biomedical application like drug / gene delivery vectors, photo-thermal therapy, and photoacoustic imaging. In this study we report the simultaneous detection and irradiation of carbon nanotubes in live cancer cells using a portable Raman probe. A portable handheld Raman instrument was utilized for dual purpose, as a CNT detector and as an irradiating laser source. Single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were dispersed in an aqueous solution using a lipid-polymer (LP) coat which formed highly stable dispersions both in buffer and cell media. The LP coated SWCNTs and MWCNTs aqueous dispersions were characterized by atomic force microscopy, transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy and Raman spectroscopy. The cellular uptake of the LP dispersed SWCNTs and MWCNTs was carried out using confocal microscopy, where the FITC labeled nanotube conjugates were found internalized by the breast cancer cells confirmed by Z-stack fluorescence confocal imaging. The in vitro biocompatibility of SWCNTs and MWCNTs, assessed using cell viability MTT assay, found that the nanotube dispersions did not hinder the cell proliferation of breast cancer cells at the dosages tested. Breast cancer cells treated with SWCNTs and MWCNTs were simultaneously detected and irradiated live in vitro using the portable Raman probe. Apoptotic TUNEL assay carried out on the breast cancer cells fixed after laser irradiation confirmed the cell death only in presence of the nanotube dispersions. For the first time we show that both SWCNTs and MWCNTs could be selectively irradiated by specifically detecting the CNTs in cancer cells using a simple handheld Raman instrument in three dimensionally grown cell culture. A combination of handheld Raman instrumentation used along with carbon nanomaterials could help treat various diseases like cancer.

The use of carbon nanotubes (CNTs) on the development of biomaterials has been motivated by their excellent mechanical properties that could improve synthetic bone materials. However, the toxicity of CNTs on the tissue/implant interface and their influence on the biomineralization process have some contradictions. We investigated the influence of CNTs on osteoblasts plated on titanium (Ti) discs or plastic surfaces. We evaluated osteoblasts viability, alkaline phosphatase (ALP) activity, and mineralized matrix formation in the different phases of osteoblasts growth in the presence of single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs). An increase in osteoblasts viability was observed at the 21st day for both CNTs on plastic surface, while viability increased for MWCNTs at the 7th and 14th days and at the 7th day for SWCNTs on Ti discs compared to control. ALP activity increased at the 14th and 21st days for MWCNTs on plastic surfaces. For cells incubated with SWCNTs, an increase in ALP activity at the 7th day for plastic surface and at the 14th day for both materials (plastic and Ti) was observed. The mineralized matrix formation increased at the 21st day on plastic surface with SWCNTs, and at the 14th and 21st days for both CNTs on Ti discs. In conclusion, both SWCNTs and MWCNTs are not toxic to osteoblasts at concentrations up to 5×10(-5) and 1.3×10(-2)mg/mL, respectively, either in Ti discs or plastic surfaces. In the long term, the cells grown in contact with both CNTs and Ti presented better results regarding bone-like nodules formation.

Human exposure to airborne carbon nanotubes (CNT) is increasing because of their applications in different sectors; therefore, they constitute a biological hazard. Consequently, developing studies on CNT toxicity become a necessity. CNTs can have different properties in term of length, size and charge. Here, we compared the cellular effect of multiwall (MWCNTs) and single wall CNTs (SWCNTs). MWCNTs consist of multiple layers of graphene, while SWCNTs are monolayers. The effects of MWCNTs and SWCNTs were evaluated by the water‐soluble tetrazolium salt cell proliferation assay on NR8383 cells, rat alveolar macrophage cell line (NR8383). After 24 hours of exposure, MWCNTs showed higher toxicity (50% inhibitory concentration [IC50] = 3.2 cm2/cm2) than SWCNTs (IC50 = 44 cm2/cm2). Only SWCNTs have induced NR8383 cells apoptosis as assayed by flow cytometry using the annexin V/IP staining test. The expression of genes involved in oxidative burst (Ncf1), inflammation (Nfκb, Tnf‐α, Il‐6 and Il‐1β), mitochondrial damage (Opa) and apoptotic balance (Pdcd4, Bcl‐2 and Casp‐8) was determined. We found that MWCNT exposure predominantly induce inflammation, while SWCNTs induce apoptosis and impaired mitochondrial function. Our results clearly suggest that MWCNTs are ideal candidates for acute inflammation induction. In vivo studies are required to confirm this hypothesis. However, we conclude that toxicity of CNTs is dependent on their physical and chemical characteristics.