Role of carbon nanotubes (CNTs) in transgenic plant development

Carbon nanotubes (CNTs) are nanostructures, allotropes of carbon which are made up of graphene sheets wrapped around it forming cylindrical structures. CNTs have been regarded to have interesting and attractive physical and chemical properties and have been tremendously used in genetic engineering. Understanding the role of CNTs in development of transgenic plants, review of research papers in the field was done. CNTs are classified into two categories: the single-walled and multiwalled (MWCNTs) structures. They are valuable vectors in various biomedicine fields such as Gene delivery, Drug delivery, Immunotherapy, Tissue engineering, and Biomedical imaging and also, they deliver the DNA without damaging the cells. Based on recent studies, the functionalization of CNTs when combined with some other suitable molecules can drastically subside their toxic effects. Having unique properties such as small size, larger surface area is useful in delivering DNA into mammalian cells as well. Modifications in CNTs can make nucleic acids adhere to them even more efficiently. Also, MWCNTs are crucial in delivery DNA into the cytoplasm. Based on other methods, the CNTs-DNA are a preferred choice and the inclination toward double-stranded DNA is used over single-stranded DNA in gene delivery shows effective results. The only downside of CNTs is that they are hydrophobic and are difficult to form an aqueous solution, thus limiting their applicability. This review will aid you in comprehending useful knowledge related to a general overview of topics related to CNTs.     

Proteomic investigation on bio-corona of functionalized multi­walled carbon nanotubes

Background

The formation of bio-corona, due to adsorption of biomolecules onto carbon nanotubes (CNTs) surface in a physiological environment, may lead to a modified biological “identity” of CNTs, contributing to determination of their biocompatibility and toxicity.

ROS and NF-κB are involved in upregulation of IL-8 in A549 cells exposed to multi-walled carbon nanotubes

Carbon nanotubes (CNTs) have potential applications in biosensors, tissue engineering, and biomedical devices because of their unique physico-chemical, electronic and mechanical properties. However, there is limited literature data available concerning the biological properties and toxicity of CNTs. This study aimed to assess the toxicity exhibited by multi-walled CNTs (MWCNTs) and to elucidate possible molecular mechanisms underlying the biological effects of MWCNTs in A549 cells. Exposing A549 cells to MWCNTs led to cell death, changes in cell size and complexity, reactive oxygen species (ROS) production, interleukin-8 (IL-8) gene expression and nuclear factor (NF)-κB activation. Treatment of A549 cells with antioxidants prior to adding MWCNTs decreased ROS production and abrogated expression of IL-8 mRNA. Pretreatment of A549 cells with NF-κB inhibitors suppressed MWCNTs-induced IL-8 mRNA expression. These results indicate that MWCNTs are able to induce expression of IL-8 in A549 cells, at least in part, mediated by oxidative stress and NF-κB activation.     

A rapid assay for assessment of sphingosine kinase inhibitors and substrates

The effect of incorporating carbon nanotubes (CNTs) in the gel matrix on the electrophoretic mobility of proteins based on their molecular weight differences was investigated using sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). More specifically, a reduction in standard deviation in the molecular weight calibration plots by 55% in the case of multiwalled carbon nanotubes (MWCNTs) and by 34% in the case of single-walled carbon nanotubes (SWCNTs) compared with that of pristine polyacrylamide gels was achieved after incorporating an insignificant amount of functionalized CNTs into the gel matrix. A mechanism based on a more uniform pore size distribution in CNT modified polyacrylamide gel matrix is proposed. Furthermore, the impact of SWCNTs and MWCNTs on the mobility of proteins in different molecular weight regimes at a given acrylamide concentration offers a tunable gel matrix in terms of the selection of molecular weight ranges of proteins. The robustness and excellent reproducibility of the CNT–PAGE protocol are expected to have a significant impact on the molecular weight determination of newly isolated proteins.     

Direct electrochemistry of glucose oxidase and electrochemical biosensing of glucose on quantum dots/carbon nanotubes electrodes

Because of their unique chemical, physical and electronic properties, Quantum dots (QDs) and carbon nanotubes (CNTs) are now extremely attractive and important nanomaterials in bioanalytical applications. In this work, CdTe QDs with the size of about 3 nm were prepared and a novel electrochemical biosensing platform of glucose based on CdTe/CNTs electrode was explored. This CdTe/CNTs electrode was prepared by first mixing CdTe QDs, CNTs, Nafion, and glucose oxidase (GOD) in appropriate amounts and then modifying this mixture on the glass carbon electrode (GC). Transmission electron microscopy (TEM) was used to observe the dispersion of CdTe QDs on carbon nanotubes and cyclic voltammetry (CV) was used to investigate the electrochemical behavior of the CdTe/CNTs electrode. A pair of well-defined quasi-reversible redox peaks of glucose oxidase were obtained at the CdTe/CNTs based enzyme electrode by direct electron transfer between the protein and the electrode. The immobilized glucose oxidase could retain bioactivity and catalyze the reduction of dissolved oxygen. Due to the synergy between the CdTe QDs and CNTs, this novel biosensing platform based on QDs/CNTs electrode responded even more sensitively than that based on GC electrode modified by CdTe QDs or CNTs alone. The inexpensive, reliable and sensitive sensing platform based on QDs/CNTs electrode provides wide potential applications in clinical, environmental, and food analysis.     

Carbon nanotubes provoke inflammation by inducing the pro-inflammatory genes IL-1β and IL-6

Carbon nanotubes (CNTs) are largely produced and widely used because of their novel features, and the annual yield is expected to increase dramatically in the near future. Meanwhile, adverse health influences from exposure to CNTs are widely concerned, partially due to their asbestoid characteristics. In the current study, to assess the inflammatory responses and related mechanisms, we established a mouse model of chronic exposure to CNTs using intraperitoneal injection of single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). Our results demonstrated the fibre-like pathogenic behaviors of CNTs, reflected by increased total protein content in the lavageate from peritoneal cavities and increased serum levels of inflammatory cytokines, IL-1β and IL-6. The pro-inflammatory effects of CNTs were further validated with exposure to in vitro cultured monocyte-macrophage cells, J774A.1, as SWNTs and MWNTs significantly increased the expression levels of pro-inflammatory genes IL-1β and IL-6. Collectively, our data demonstrate that SWNTs and MWNTs provoke considerable inflammation presumably due to their fibre-like shape, and further confirm the length- and size-related structure-activity relationship for CNTs in stimulating inflammatory responses.     

Biosafety of non-surface modified carbon nanocapsules as a potential alternative to carbon nanotubes for drug delivery purposes

Background

Carbon nanotubes (CNTs) have found wide success in circuitry, photovoltaics, and other applications. In contrast, several hurdles exist in using CNTs towards applications in drug delivery. Raw, non-modified CNTs are widely known for their toxicity. As such, many have attempted to reduce CNT toxicity for intravenous drug delivery purposes by post-process surface modification. Alternatively, a novel sphere-like carbon nanocapsule (CNC) developed by the arc-discharge method holds similar electric and thermal conductivities, as well as high strength. This study investigated the systemic toxicity and biocompatibility of different non-surface modified carbon nanomaterials in mice, including multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), carbon nanocapsules (CNCs), and C₆₀ fullerene (C₆₀). The retention of the nanomaterials and systemic effects after intravenous injections were studied.

Methodology and Principal Findings

MWCNTs, SWCNTs, CNCs, and C₆₀ were injected intravenously into FVB mice and then sacrificed for tissue section examination. Inflammatory cytokine levels were evaluated with ELISA. Mice receiving injection of MWCNTs or SWCNTs at 50 µg/g b.w. died while C₆₀ injected group survived at a 50% rate. Surprisingly, mortality rate of mice injected with CNCs was only at 10%. Tissue sections revealed that most carbon nanomaterials retained in the lung. Furthermore, serum and lung-tissue cytokine levels did not reveal any inflammatory response compared to those in mice receiving normal saline injection.

Conclusion

Carbon nanocapsules are more biocompatible than other carbon nanomaterials and are more suitable for intravenous drug delivery. These results indicate potential biomedical use of non-surface modified carbon allotrope. Additionally, functionalization of the carbon nanocapsules could further enhance dispersion and biocompatibility for intravenous injection.     

Improved blood biocompatibility of composite film of chitosan/carbon nanotubes complex

Single-walled carbon nanotubes are novel molecular-scale wires having excellent anti-adhesion properties with regard to platelets. On the other hand, chitosan is a partially de-acetylated derivative of chitin that has a critical role in cell attachment and growth. The aim of this study was to investigate how carbon nanotubes improve the blood biocompatibility of chitosan film. We prepared composite films with various concentrations of chitosan/carbon nanotubes (CS/CNTs) (1.3–6.3 wt%). The sample surfaces were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements. The surface characterization revealed that the surface of the CS/CNTs composite film became more hydrophobic with increasing amounts of CNTs. Cell attachment tests using bovine aortic endothelial cells (BAECs) indicated that CS/CNTs composite films retained their cell adhesion ability. The blood compatibility of the CS/CNTs composite films was evaluated using the blood platelet adhesion and activation tests in vitro. Platelet adhesion results confirmed that platelet adhesion and the formation of a platelet network were inhibited on composite films with higher concentrations of CNTs (5.1 wt%). Our experimental results show that the novel composite film containing CS/CNTs possesses two paradoxical characteristics, namely, good adherence of endothelial cells and minimum adherence and activation of platelets, making this film a promising antithrombogenic material for use in the biomedical field.     

The covalent bioconjugate of multiwalled carbon nanotube and amino‐modified linearized plasmid DNA for gene delivery

Carbon nanotubes (CNTs) are allotropes of carbon, which have unique physical, mechanical, and electronic properties. Among various biomedical applications, CNTs also attract interest as nonviral gene delivery systems. Functionalization of CNTs with cationic groups enables delivery of negatively charged DNA into cells. In contrast to this well‐known strategy for DNA delivery, our approach included the covalent attachment of linearized plasmid DNA to carboxylated multiwalled CNTs (MWCNTs). Carboxyl groups were introduced onto MWCNTs by oxidative treatment, and then the carboxyl groups were activated by 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC). The whole pQE‐70 vector including the gene encoding green fluorescent protein (GFP) was subjected to polymerase chain reaction (PCR) using the modified nucleotide N6‐(6‐Amino)hexyl‐2′‐deoxyadenosine‐5′‐triphosphate. Hence, free amino groups were introduced onto the linearized plasmid. Covalent bonding between the amino‐modified plasmid DNA and the carboxylated MWCNTs was achieved via EDC chemistry. The resulting bioconjugate was successfully transformed into chemically competent Escherichia coli cells, without necessity of a heat‐shock step at 42°C. The presence of Ca²⁺ in transformation medium was required to neutralize the electrostatic repulsion between DNA and negatively charged outer layer of E. coli. The transformants, which were able to express GFP were inspected manually on ampicillin agar plates. Our study represents a novelty with respect to other noncovalent CNT gene delivery systems. Considering the interest for delivery of linear DNA fragments, our study could give insights into further studies. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:224–232, 2014     

Effects of single and multi walled carbon nanotubes on macrophages: cyto and genotoxicity and electron microscopy

Production of nanotechnology-based materials is increasing worldwide: it is essential to evaluate their potential toxicity. Among these nanomaterials, carbon nanotubes (CNTs) have tremendous potential in many areas of research and applications. We have investigated the cyto- and genotoxic effects of single and multi-walled CNTs (SWCNTs, MWCNTs) and carbon black (CB) on the mouse macrophage cell line RAW 264.7. Specifically we have investigated inflammatory response, release of tumor necrosis factor-α (TNF-α), intracellular reactive oxygen species (ROS) production, cell death (both necrosis and apoptosis), chromosomal aberrations and cellular ultrastructural alteration caused by CB, MWCNTs and SWCNTs. Our data confirm that both CNTs and CB are cyto and geno-toxic to RAW 264.7 mouse macrophages. CNTs exposure induced ROS release, necrosis and chromosomal aberrations but did not cause an inflammatory response. In addition CNTs induce ultrastructural damage and apoptosis. CNTs penetrate the cell membrane and individual MWCNTs are seen associated with the nuclear envelope.     

Appreciating the role of carbon nanotube composites in preventing biofouling and promoting biofilms on material surfaces in environmental engineering: A review

The ability of carbon nanotubes (CNTs) to undergo surface modification allows them to form nanocomposites (NCs) with materials such as polymers, metal nanoparticles, biomolecules, and metal oxides. The biocidal nature, protein fouling resistance, and fouling release properties of CNT-NCs render them the perfect material for biofouling prevention. At the same time, the cytotoxicity of CNT-NCs can be reduced before applying them as substrates to promote biofilm formation in environmental biotechnology applications. This paper reviews the potential prospects of CNT-NCs to accomplish two widely varying objectives in environmental engineering applications: (i) preventing biofouling, and (ii) promoting the formation of desirable biofilms on materials surface. This paper addresses practical issues such as costs, risks to human health, and ecological impacts that are associated with the application, development and commercialization of CNT-NC technology.     

Brittle ductile transition in carbon nanotube bundles

The superior strength and stiffness of carbon nanotubes (CNTs) make them attractive for many structural applications. Although the strength and stiffness of CNTs are extremely high, fibres of aligned CNTs have been found to date to be far weaker than the constituent CNTs. The intermolecular interactions between the CNTs in the fibres are governed by weak van der Waals forces, resulting in slippage between CNTs which occurs at tensions well below the breaking strength of the CNTs. Both theoretical and experimental studies show that by introducing chemical bonds between the CNTs increases load transfer and prevents the CNTs from slipping.     

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G'' bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.     

High-temperature calcined fullerene nanowhiskers as well as long needle-like multi-wall carbon nanotubes have abilities to induce NLRP3-mediated IL-1β secretion

Because multi-wall carbon nanotubes (MWCNTs) have asbestos-like shape and size, concerns about their pathogenicity have been raised. Contaminated metals of MWCNTs may also be responsible for their toxicity. In this study, we employed high-temperature calcined fullerene nanowhiskers (HTCFNWs), which are needle-like nanofibers composed of amorphous carbon having similar sizes to MWCNTs but neither metal impurities nor tubular structures, and investigated their ability to induce production a major proinflammatory cytokine IL-1β via the Nod-like receptor pyrin domain containing 3 (NLRP3)-containing flammasome-mediated mechanism. When exposed to THP-1 macrophages, long-HTCFNW exhibited robust IL-1β production as long and needle-like MWCNTs did, but short-HTCFNW caused very small effect. IL-1β release induced by long-HTCFNW as well as by long, needle-like MWCNTs was abolished by a caspase-1 inhibitor or siRNA-knockdown of NLRP3, indicating that NLRP3-inflammasome-mediated IL-1β production by these carbon nanofibers. Our findings indicate that the needle-like shape and length, but neither metal impurities nor tubular structures of MWCNTs were critical to robust NLRP3 activation.     

Water transport through carbon nanotubes with defects

Non-equilibrium molecular dynamics simulations are performed to investigate how changing the number of structural defects in the wall of a (7,7) single-walled carbon nanotube (CNT) affects water transport and internal fluid dynamics. Structural defects are modelled as vacancy sites (missing carbon atoms). We find that, while fluid flow rates exceed continuum expectations, increasing numbers of defects lead to significant reductions in fluid velocity and mass flow rate. The inclusion of such defects causes a reduction in the water density inside the nanotubes and disrupts the nearly frictionless water transport commonly attributed to CNTs.     

Interaction parameters between carbon nanotubes and water in Dissipative Particle Dynamics

Flow of water past an array of single-walled carbon nanotubes (SWNTs) is simulated in this work to determine the interaction parameters of carbon nanotubes (CNTs) and water using Dissipative Particle Dynamics (DPD). For this flow configuration, results from molecular dynamics simulations by Walther et al. are available and can be used for validation (Phys. Rev. E, 2004, 062201). The hydrodynamic properties for SWNT (32, 0) with diameter of 2.5 nm were determined in different Reynolds number flows. A set of appropriate DPD parameters was found so that the drag coefficients of the CNT agreed well with the Stokes–Oseen analytical solution and the fluid slip length on the CNT wall was comparable with the Walther et al. results. It was also found that it is feasible to apply these parameters in longer length and time scales by increasing the number of water molecules grouped into each DPD bead and still maintain the hydrodynamic properties of CNTs as well as their hydrophobic surface character.     

碳纳米管固定化纤维素酶的最佳工艺研究

纤维素酶在环保、医药、食品等领域都具有广泛的应用前景,但由于纤维素酶的生产成本较高,生物活性较低,使得纤维素酶的应用受到了限制。为了寻找一种固定化纤维素酶的方法,使酶可以重复多次使用,首次以多壁碳纳米管为载体固定化纤维素酶,研究功能化的多壁碳纳米管固定化纤维素酶的固定化条件,采用正交试验对酶固定化中的主要条件进行优化,并通过傅里叶变换红外光谱仪对多壁碳纳米管（multiwalled carbon nanotube,MWCNTs）、纤维素酶及固定化纤维素酶的结构进行表征。结果表明,固定化纤维素酶的最佳工艺条件为：酶浓度5 mg·mL-1,温度40 ℃,pH 5.0,固定化时间3 h;通过傅里叶变换红外光谱证实纤维素酶成功固定到多壁碳纳米管上。     

Improved stability of the carbon nanotubes-enzyme bioconjugates by biomimetic silicification

Nano-materials have been applied in many fields due to their excellent characteristics, such as the high surface area-to-volume ratio, excellent physicochemical properties and biological compatibility. In this study, multi-walled carbon nanotubes (MWCNTs) were utilized to prepare MWCNTs-papain bioconjugates and then realized the immobilization of papain. MWCNTs functionalized with carboxyl- and amine- groups on their surface were used as immobilization carriers. The immobilization of papain on the functionalized MWCNTs through physical absorption was examined. The conjugates were denoted as MWCNTs-papain bioconjugates. To improve the stability, the bioconjugates were further coated by silica through the biomimetic silicification process that induced by papain (denoted as silica-coated bioconjugates). The as-prepared MWCNTs-papain bioconjugates and the silica-coated bioconjugates were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The preliminary results showed that the bioconjugates could retain most of the initial activity of papain. Compared to free papain and MWCNTs-papain bioconjugates, the silica-coated bioconjugates exhibited significantly improved thermal, pH and recycling stability. Comparisons of the kinetic parameters between MWCNTs-papain bioconjugates and the silica-coated bioconjugates revealed that the K_m value of the immobilized papain experienced a slight increase after silica coating, which suggested that the silica coating did not significantly hinder papain's access to substrate or release of product.     

Effects of Functionalized and Raw Multi-Walled Carbon Nanotubes on Soil Bacterial Community Composition

Carbon nanotubes (CNTs) are widely used in industry, but their environmental impacts on soil microbial communities are poorly known. In this paper, we compare the effect of both raw and acid treated or functionalized (fCNTs) multi-walled carbon nanotubes (MWCNTs) on soil bacterial communities, applying different concentrations of MWCNTs (0 µg/g, 50 µg/g, 500 µg/g and 5000 µg/g) to a soil microcosm system. Soil DNA was extracted at 0, 2 and 8 weeks and the V3 region of the 16S rRNA gene was PCR-amplified and sequenced using paired-end Illumina bar-coded sequencing. The results show that bacterial diversity was not affected by either type of MWCNT. However, overall soil bacterial community composition, as illustrated by NMDS, was affected only by fMWCNT at high concentrations. This effect, detectable at 2 weeks, remained equally strong by 8 weeks. In the case of fMWCNTs, overall changes in relative abundance of the dominant phyla were also found. The stronger effect of fMWCNTs could be explained by their intrinsically acidic nature, as the soil pH was lower at higher concentrations of fMWCNTs. Overall, this study suggests that fMWCNTs may at least temporarily alter microbial community composition on the timescale of at least weeks to months. It appears, by contrast, that raw MWCNTs do not affect soil microbial community composition.     

Maternal exposure to multi-wall carbon nanotubes does not induce embryo-fetal developmental toxicity in rats

BACKGROUND: Although the potential risk of carbon nanotubes (CNTs) to humans has recently increased due to expanding production and widespread use, the potential adverse effects of CNTs on embryo–fetal development have not yet been determined. METHODS: This study investigated the potential effects of multi‐wall CNTs (MWCNTs) on pregnant dams and embryo–fetal development in rats. MWCNTs were administered to pregnant rats by gavage at 0, 40, 200, and 1,000 mg/kg/day. All dams were subjected to Cesarean section on day 20 of gestation, and the fetuses were examined for any morphological abnormalities. RESULTS: All animals survived to the end of the study. A decrease in thymus weight was observed in the high dose group in a dose‐dependent manner. However, maternal body weight, food consumption, and oxidant–antioxidant balance in the liver were not affected by treatment with MWCNTs. No treatment‐related differences in gestation index, fetal deaths, fetal and placental weights, or sex ratio were observed between the groups. Morphological examinations of the fetuses demonstrated no significant difference in incidences of abnormalities between the groups. CONCLUSIONS: The results show that repeated oral doses of MWCNTs during pregnancy induces minimal maternal toxicity and no embryo–fetal toxicity at 1,000 mg/kg/day in rats. The no‐observed‐adverse‐effect level of MWCNTs is considered to be 200 mg/kg/day for dams and 1,000 mg/kg/day for embryo–fetal development. In this study, the dosing formulation was not analyzed to determine the degree of reaggregation (or not), nor were blood levels of CNT's measured in the dosed animals to verify or characterize absorption. Birth Defects Res (Part B) 92:69–76, 2011. © 2011 Wiley‐Liss, Inc.