1,721,048 research outputs found
Non-destructive decoration of full-length multi-walled carbon nanotubes with variable amounts of silica gel nanoparticles
No full textA non-destructive strategy for the synthesis of full-length multi-walled carbon nanotube-silica gel nanobead (flCNT-SNB) composite material, was illustrated. The SNB were grown onto silylated full-length CNT through the hydrophobic adsorption of pyrenyl groups onto the surface of CNT via π-π interactions. For transmission electron microscopy (TEM) a drop of dispersion of nanoparticles in MeOH was allowed to evaporate on a 300-mesh copper grid. The results show that the nanoassemblies exhibit various valuable features including high versatility of the silica and the bare graphitic surfaces
Biomedical platforms based on composite nanomaterials and cellular toxicity
No full textCarbon nanotubes possess unique chemical, physical, optical, and magnetic properties, which make them suitable for many uses in industrial products and in the field of nanotechnology, including nanomedicine. We describe fluorescent nanocomposites for use in biosensors or nanoelectronics. Then we describe recent results on the issue of cytotoxicity of carbon nanotubes obtained in our labs. Silica nanoparticles have been widely used for biosensing and catalytic applications due to their large surface area-to-volume ratio, straightforward manufacture, and the compatibility of silica chemistry with covalent coupling of biomolecules. Carbon nanotubes-composite materials, such as those based on Carbon nanotubes bound to nanoparticles, are suitable, in order to tailor Carbon nanotubes properties for specific applications. We present a tunable synthesis of Multi Wall Carbon nanotubes-Silica nanoparticles. The control of the nanotube morphology and the bead size, coupled with the versatility of silica chemistry, makes these structures an excellent platform for the development of biosensors (optical, magnetic and catalytic applications). We describe the construction and characterization of supramolecular nanostructures consisting of ruthenium-complex luminophores, directly grafted onto short oxidized single-walled carbon nanotubes or physically entrapped in silica nanobeads, which had been covalently linked to short oxidized single-walled carbon nanotubes or hydrophobically adsorbed onto full-length multi-walled carbon nanotubes. These structures have been evaluated as potential electron-acceptor complexes for use in the fabrication of photovoltaic devices, and for their properties as fluorescent nanocomposites for use in biosensors or nanoelectronics. Finally, we compare the toxicity of pristine and oxidized Multi Walled Carbon nanotubes on human T cells - which would be among the first exposed cell types upon intravenous administration of Carbon nanotubes in therapeutic and diagnostic nanodevices. Our results suggest that carbon nanotubes indeed can be very toxic and induce massive loss of cell viability through programmed cell death at sufficiently high concentrations (>1ng/cell). The cytotoxicity of Carbon nanotubes does depend on many other factors than concentration, including their physical form, diameter, length, and the nature of attached molecules or nanomaterials: carbon black, for instance, is less toxic than pristine CNTs (what shows the relevance of structure and topology); oxidized CNTs are more toxic than pristine CNTs. © 2007 IOP Publishing Ltd
Dispersion of pristine single-walled carbon nanotubes in water by a thiolated organosilane: application in supramolecular nanoassemblies
No full textWe report a novel technique to disperse pristine single-walled carbon nanotubes in water by ultrasonication in the presence of a thiolated organosilane and subsequent ultracentrifugation. As revealed by the sharp features in the visible range of the absorption spectrum and by transmission electron microscopy, the collected supernatant fraction was composed of small bundles of nanotubes coated by a thin layer of organosilane molecules. We hypothesized and demonstrated that the organosilane adsorbed onto the nanotubes through the thiol group leaving the silane group extruding out. The pristine properties of the nanotubes and the versatile chemistry available for sol-gel materials make the reported dispersed nanotubes an excellent scaffold for the realization of supramolecular nanoassemblies suitable for different applications. As examples, we decorated them with silica nanobeads, by using a water-in-oil nanoemulsion system, and with gold nanoparticles, by a previous derivatization with a second layer of thiolated organosilane providing exposed thiol groups
Role of PTPN22 in type 1 diabetes and other autoimmune diseases
No full textWe recently discovered that a single-nucleotide polymorphism (SNP) in the lymphoid tyrosine phosphatase (LYP), encoded by the PTPN22 gene on chromosome lp13, correlates strongly with the incidence of type 1 diabetes (T1D) in two independent populations. This findings has now been verified by numerous studies and it has been expanded to rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, Graves' disease, generalized vitiligo and other autoimmune disease. Here we review the genetics of the SNP and its association with autoimmunity, discuss the function of the phosphatase in signaling, the biochemistry of the disease-predisposing allele, and the possible mechanisms by which PTPN22 contributes to the development of human disease. (C) 2006 Elsevier Ltd. All rights reserved
Adsorption of streptavidin onto single-walled carbon nanotubes: application in fluorescent supramolecular nanoassemblies
No full textWe report the solubilization of full-length single-walled carbon nanotubes into a physiological buffer by sonication in presence of streptavidin. Transmission electron microscopy showed that the resultant dispersion was enriched of individual/small ropes of nanotubes. By the analysis of the crystal structure of tetrameric streptavidin and of the tryptophan emission of adsorbed proteins we hypothesized that proteins adsorbed onto SWNT sidewalls through their amine functionalities. Our results suggested using streptavidin as an interlinker between carbon nanotubes and semiconducting nanocrystals. We fabricated a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by optical fluorescent microscopies
Biomedical applications of carbon nanotubes find the related cellular toxicity
No full textWe present a tunable synthesis of Carbon nanotubesSilica Nanoparticles Composites and illustrate their potential uses in Biomedicine. We also compare the cytotoxicity of pristine and oxidized Multi Walled Carbon nanotubes on human T cells - which would be among the first exposed cell types upon intravenous administration of Carbon nanotubes in therapeutic and diagnostic nanodevices
Full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots as multivalent intracellular fluorescent nanoprobes
No full textWe report the formation of a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length, single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The supramolecular luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by both optical and confocal fluorescent microscopies. Jurkat T leukemia cells were able to internalize the nanoassembly by multivalent CD3 receptor-mediated endocytosis (adsorption by cell). Once internalized by cells, the nanoassembly was found to be transported to lysosomes. These properties should make this supramolecular luminescent nanoassembly an excellent building block for the construction of intracellular polyvalent nanoprobes, mimicking natural viral delivery entities with enhanced loading capacity compared to small molecules
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