Mammalian pharmacokinetics of carbon nanotubes using intrinsic near-infrared fluorescence.
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Individualized, chemically pristine single-walled carbon nanotubes have been intravenously administered to rabbits and monitored through their characteristic near-infrared fluorescence. Spectra indicated that blood proteins displaced the nanotube coating of synthetic surfactant molecules within seconds. The nanotube concentration in the blood serum decreased exponentially with a half-life of 1.0 +/- 0.1 h. No adverse effects from low-level nanotube exposure could be detected from behavior or pathological examination. At 24 h after i.v. administration, significant concentrations of nanotubes were found only in the liver. These results demonstrate that debundled single-walled carbon nanotubes are high-contrast near-infrared fluorophores that can be sensitively and selectively tracked in mammalian tissues using optical methods. In addition, the absence of acute toxicity and promising circulation persistence suggest the potential of carbon nanotubes in future pharmaceutical applications. (+info)
As the leading nanodevice candidate, single-walled carbon nanotubes (SWNTs) have potential therapeutic applications in gene therapy and novel drug delivery. We found that SWNTs can inhibit DNA duplex association and selectively induce human telomeric i-motif DNA formation by binding to the 5'-end major groove under physiological conditions or even at pH 8.0. SWNT binding to telomeric DNA was studied by UV melting, NMR, S1 nuclease cleavage, CD, and competitive FRET methods. These results suggest that SWNTs might have the intriguing potential to modulate human telomeric DNA structures in vivo, like biologically relevant B-A and B-Z DNA transitions, which is of great interest for drug design and cancer therapy. (+info)
Conductance-controlled point functionalization of single-walled carbon nanotubes.
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We used covalent attachments to single-walled carbon nanotubes (SWNTs) to fabricate single-molecule electronic devices. The technique does not rely on submicrometer lithography or precision mechanical manipulation, but instead uses circuit conductance to monitor and control covalent attachment to an electrically connected SWNT. Discrete changes in the circuit conductance revealed chemical processes happening in real time and allowed the SWNT sidewalls to be deterministically broken, reformed, and conjugated to target species. By controlling the chemistry through electronically controlled electrochemical potentials, we were able to achieve single chemical attachments. We routinely functionalized pristine, defect-free SWNTs at one, two, or more sites and demonstrated three-terminal devices in which a single attachment controls the electronic response. (+info)
Comparison of multiwalled carbon nanotubes and a conventional absorbent on the enrichment of sulfonylurea herbicides in water samples.
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Recently, multiwalled carbon nanotubes (MWCNTs) have been at the center of attention because of their applications in many fields. Efforts to investigate the possibility of MWCNTs as SPE absorbents for the enrichment of environmental pollutants yielded positive results. The goal of the present work was to compare the enrichment power of MWCNTs with that of regular adsorbents, such as C18 silica for SPE of five sulfonylurea herbicides. The results indicated that multiwalled carbon nanotubes were very suitable for the preconcentration of sulfonylurea herbicides in complex water samples, yielding better recoveries. C18 gave a lightly lower enrichment performance, and could not enrich nicosulfuron in complex samples. All of these experimental results indicated that multiwalled carbon nanotubes could be used as a valuable alternative adsorbent for the SPE of sulfonylurea herbicides in many real water samples. (+info)
A direct electrochemical biosensing platform constructed by incorporating carbon nanotubes and gold nanoparticles onto redox poly(thionine) film.
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A direct electrochemical biosensing platform has been fabricated by covalent incorporation of carbon nanotubes (CNT) and gold nanoparticles (GNP) onto the poly(thionine) (PTH) film deposited by electropolymerization. With the synergic effects of the composite nanomaterials together with the excellent mediating redox polymer, the proposed platform could allow for faster electron transfer and higher enzyme immobilization efficiency than the platforms designed by using CNT or GNP alone. Comparison studies indicated that the as-developed H(2)O(2) sensor could show greatly improved performances of amperometric responses. (+info)
Biological effects of field emission-type X-rays generated by nanotechnology.
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Thermionic emission (TE)-type X-ray generators have been exclusively used in medicine, but there are many difficulties in making these X-ray sources compact. A field emission (FE)-type X-ray generator using carbon nanotubes is a newly-developed compact system that can be as small as several cm in length. Considering the compactness of the equipment, the FE-type X-ray generator may become a useful tool for endoscopic, intracavitary or intraoperative radiotherapy in the future. The aim of this study was to investigate the biological effects of X-rays generated by the FE-type X-ray source in comparison with those of conventional TE-type X-rays. Mouse thymic lymphoma 3SB cells were irradiated by an FE-type X-ray generator developed by our group and a conventional TE-type X-ray source under identical conditions. DNA damage after radiation was detected by foci formation of phospho-H2AX (gamma-H2AX). Effect on the cell cycle was analyzed by flow cytometry. Activation of the DNA damage checkpoint was analyzed by immunoblotting. Induction of apoptosis was studied using the TUNEL assay. In terms of induction of DNA damage (DNA double-strand breaks), activation of cell cycle checkpoints (p53 stabilization, p21 induction, Chk1 and Chk2 phosphorylations), and induction of apoptotic cell death, FE-type X-rays were as effective as TE-type X-rays, and FE-type X-rays appeared to be applicable to radiation therapy. (+info)
Angiogenesis is important for normal growth and wound healing processes. An imbalance of the growth factors involved in this process, however, causes the acceleration of several diseases including malignant, ocular, and inflammatory diseases. Inhibiting angiogenesis through interfering with its pathway is a promising methodology to hinder the progression of these diseases. Herein, we studied the anti-angiogenic effects of various carbon materials such as graphite, multiwalled carbon nanotubes and fullerenes in vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2)-induced angiogenesis evaluated in the chick chorioallantoic membrane (CAM) model. All the carbon materials tested showed substantial anti-angiogenic activity against either FGF2- or VEGF-induced angiogenesis in the CAM model. Those carbon materials did not have any significant effects on basal angiogenesis in the absence of the added growth factors. (+info)
Preparation of carbon nanotube-alginate nanocomposite gel for tissue engineering.
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A novel scaffold material based on an alginate hydrogel which contained carbon nanotubes (CNTs) was prepared, and its mechanical property and biocompatibility evaluated. Soluble CNTs were prepared with acid treatment and dispersed in sodium alginate solution as a cross-linker. After which, the mechanical property (elastic deformation), saline sorption, histological reaction, and cell viability of the resultant nanocomposite gel (CNT-Alg gel) were evaluated. The CNT-Alg gel showed faster gelling and higher mechanical strength than the conventional alginate gel. Saline sorption amount of freeze-dried CNT-Alg gel was equal to that of the alginate gel. In terms of histological evaluation and cell viability assay, CNT-Alg gel exhibited a mild inflammatory response and non-cytotoxicity. These results thus suggested that CNT-Alg gel could be useful as a scaffold material in tissue engineering with the sidewalls of CNTs acting as active sites for chemical functionalization. (+info)