Electrochemical generation of H2O2 using immobilized carbon nanotubes on graphite electrode fed with air: Investigation of operational parameters

Three cathode materials (i.e. bare graphite, activated carbon immobilized onto graphite surface (AC/graphite) and carbon nanotubes immobilized onto graphite surface (CNTs/graphite)) were investigated for electrochemical generation of hydrogen peroxide. The amount of electrogenerated H₂O₂ using CNTs/graphite fed with air was nearly three times higher than that of AC/graphite and seven times higher than that of bare graphite. The effect of some operational parameters such as applied current, supporting electrolyte concentration, air flow rate and pH on the generation of H₂O₂ was investigated. Results indicated that the optimal conditions for H₂O₂ generation were applied current of 100 mA (2.5 mA/cm²), air flow rate of 2.5 L/min, and pH = 3. After eight times reuse, electrochemical generated hydrogen peroxide concentration dropped from 118.65 μM to 114.63 μM, indicating a decay of 3.6%. This fact indicates that the present system can be useful for the in situ electrochemical generation of hydrogen peroxide.     

MWNT/Nafion composite modified glassy carbon electrode as the voltammetric sensor for sensitive determination of 8-hydroxyquinoline in cosmetic

In this paper, a multiwall carbon nanotube/Nafion composite modified glassy carbon electrode (MWNT/Nafion/GCE) was used as a voltammetric sensor to determine 8-hydroxyquinoline (8-HQ) in cosmetic. This voltammetric sensor exhibited strong catalytic effect toward the oxidation of 8-HQ and caused an anodic peak at 0.97 V in HAc-NaAc buffer solution (0.2 M, pH 3.6). Under the optimized condition, the anodic peak current was linear with the concentration of 8-HQ in the range of 2 × 10⁻⁸ M–1.0 × 10⁻⁵ M. The detection limit was 9 × 10⁻⁹ M. The practical application of MWNT/Nafion/GCE was carried out for determining 8-HQ in cosmetic sample with satisfactory results. The electrode reaction mechanism was studied by cyclic voltammetry and UV–vis spectra.     

TIMP1 promotes multi-walled carbon nanotube-induced lung fibrosis by stimulating fibroblast activation and proliferation

Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) may cause fibrosing lesions in animal lungs, raising health concerns about such exposure in humans. The mechanisms underlying fibrosis development remain unclear, but they are believed to involve the dysfunction of fibroblasts and myofibroblasts. Using a mouse model of MWCNT exposure, we found that the tissue inhibitor of metalloproteinase 1 (Timp1) gene was rapidly and highly induced in the lungs by MWCNTs in a time- and dose-dependent manner. Concomitantly, a pronounced elevation of secreted TIMP1 was observed in the bronchoalveolar lavage (BAL) fluid and serum. Knockout (KO) of Timp1 in mice caused a significant reduction in fibrotic focus formation, collagen fiber deposition, recruitment of fibroblasts and differentiation of fibroblasts into myofibroblasts in the lungs, indicating that TIMP1 plays a critical role in the pulmonary fibrotic response to MWCNTs. At the molecular level, MWCNT exposure significantly increased the expression of the cell proliferation markers Ki-67 and PCNA and a panel of cell cycle-controlling genes in the lungs in a TIMP1-dependent manner. MWCNT-stimulated cell proliferation was most prominent in fibroblasts but not myofibroblasts. Furthermore, MWCNTs elicited a significant induction of CD63 and integrin β1 in lung fibroblasts, leading to the formation of a TIMP1/CD63/integrin β1 complex on the surface of fibroblasts in vivo and in vitro, which triggered the phosphorylation and activation of Erk1/2. Our study uncovers a new pathway through which induced TIMP1 critically modulates the pulmonary fibrotic response to MWCNTs by promoting fibroblast activation and proliferation via the TIMP1/CD63/integrin β1 axis and ERK signaling.     

Intraperitoneal administration of tangled multiwalled carbon nanotubes of 15 nm in diameter does not induce mesothelial carcinogenesis in rats

Multiwalled carbon nanotubes (MWCNTs) have attracted public attention not only for their potential applications in engineering and materials science but also for possible environmental risks. MWCNTs share similar properties with asbestos, a definite human carcinogen causing malignant mesothelioma (MM), in that they are both biopersistent thin fibers with a high aspect ratio. Certain types of MWCNTs do induce MM in animal experiments. Though there are many different types of MWCNTs awaiting use in industry, there is little evidence about what types of MWCNTs present a high risk for MM in vivo. We have previously shown that the diameter of MWCNTs is one of the critical factors for mesothelial injury, which eventually leads to MM. Because of the extensive commercial use of MWCNTs, the properties of MWCNTs that determine carcinogenic activity should be clarified. Here we report that a high dose (10 mg) of a tangled form of pristine MWCNT (with a diameter of 15 nm) did not induce MM after intraperitoneal administration in rats, which were followed for up to 3 years after injection. This observation strengthens our previous finding that the rigidity, diameter, length and surface properties of MWCNTs are important factors in MM induction in vivo.     

Tube length and cell type-dependent cellular responses to ultra-short single-walled carbon nanotube

This paper presents a detailed study on the cellular responses to PEGylated ultra-short (<80 nm) single-walled carbon nanotube (US-SWNT). The experimental results show clearly the tube length and cell-type dependent cellular uptake, intracellular localization, excretion of US-SWNT, as well as US-SWNT partitioning at cell division. Confocal fluorescence imaging and flow cytometry analysis of three cell types (HeLa, human hepatoma, and HUVEC) indicate that PEGylated SWNT below 35 nm might not be suitable for active targeting but could find alternative applications in gene transfection due to the ability to spontaneously traverse the nuclear membrane. While US-SWNT with an average length of 30 nm were rapidly excreted by non-polarized HeLa and hepatoma cells, lysosomal retention was observed by HUVEC, a polarized cell line. Further, HUVEC transferred intracellular US-SWNT to subsequent generations through asymmetric partitioning. These results could have significant implications for the rational design of SWNT carriers for drug delivery, as contrast agents, and for other new niche applications.     

多壁碳纳米管与甘草苷和异甘草苷的选择性吸附作用

碳纳米管作为一种特殊的纳米材料,具有中空结构,高强度韧性及良好的化学和热力学稳定性。对人体毒性小,有良好的生物相容性,一直被期望作为药物传送系统的运输载体[1~4]。在碳纳米管与生物体系相互作用研究中发现碳纳米管是一种高效地向细胞内输送药物的载体。沈海军[5]利用MM     

Specific thermal ablation of tumor cells using single‐walled carbon nanotubes targeted by covalently‐coupled monoclonal antibodies

CD22 is broadly expressed on human B cell lymphomas. Monoclonal anti‐CD22 antibodies alone, or coupled to toxins, have been used to selectively target these tumors both in SCID mice with xenografted human lymphoma cell lines and in patients with B cell lymphomas. Single‐walled carbon nanotubes (CNTs) attached to antibodies or peptides represent another approach to targeting cancer cells. CNTs convert absorbed near‐infrared (NIR) light to heat, which can thermally ablate cells that have bound the CNTs. We have previously demonstrated that monoclonal antibodies (MAbs) noncovalently coupled to CNTs can specifically target and kill cells in vitro. Here, we describe the preparation of conjugates in which the MAbs are covalently conjugated to the CNTs. The specificity of both the binding and NIR‐mediated killing of the tumor cells by the MAb‐CNTs is demonstrated by using CD22⁺CD25^? Daudi cells, CD22^?CD25⁺ phytohemagglutinin‐activated normal human peripheral blood mononuclear cells, and CNTs covalently modified with either anti‐CD22 or anti‐CD25. We further demonstrate that the stability and specificity of the MAb‐CNT conjugates are preserved following incubation in either sodium dodecyl sulfate or mouse serum, indicating that they should be stable for in vivo use. © 2009 UICC     

Establishment of an in vivo simulating co‐culture assay platform for genotoxicity of multi‐walled carbon nanotubes

Engineered nanomaterials (ENM) are now used in a wide variety of fields, and, thus, their safety should urgently be assessed and secured. It has been suggested that inflammatory responses via the phagocytosis of ENM by macrophages is a key mechanism for their genotoxicity. The present study was conducted to establish a mechanism‐based assay to evaluate the genotoxicity of ENM under conditions simulating an in vivo situation, featuring a co‐culture system of murine lung resident cells (GDL1) and immune cells (RAW264.7). GDL1 were cultured with or without RAW264.7, exposed to a multi‐walled carbon nanotube (MWCNT), and then analyzed for mutagenicity and underlying mechanisms. Mutation frequencies induced in GDL1 by the MWCNT were significantly greater with the co‐existence of RAW264.7 than in its absence. Mutation spectra observed in GDL1 co‐cultured with RAW264.7 were different from those seen in GDL1 cultured alone, but similar to those observed in the lungs of mice exposed to the MWCNT in vivo. Inflammatory cytokines, such as IL‐1β and TNF‐α, were produced from RAW264.7 cells treated with the MWCNT. The generation of reactive oxygen species and the formation of 8‐oxodeoxyguanosine in GDL1 exposed to the MWCNT were greater in the co‐culture conditions than in the single culture conditions. Based on these findings, it is indicated that inflammatory responses are involved in the genotoxicity of MWCNT, and that the presently established, novel in vitro assay featuring a co‐culture system of tissue resident cells with immune cells is suitable to evaluate the genotoxicity of ENM.     

Photothermic regulation of gene expression triggered by laser-induced carbon nanohorns

The development of optical methods to control cellular functions is important for various biological applications. In particular, heat shock promoter-mediated gene expression systems by laser light are attractive targets for controlling cellular functions. However, previous approaches have considerable technical limitations related to their use of UV, short-wavelength visible (vis), and infrared (IR) laser light, which have poor penetration into biological tissue. Biological tissue is relatively transparent to light inside the diagnostic window at wavelengths of 650-1,100 nm. Here we present a unique optical biotechnological method using carbon nanohorn (CNH) that transforms energy from diagnostic window laser light to heat to control the expression of various genes. We report that with this method, laser irradiation within the diagnostic window resulted in effective heat generation and thus caused heat shock promoter-mediated gene expression. This study provides an important step forward in the development of light-manipulated gene expression technologies.