Showing papers by "Taihong Wang published in 2006"

The enhanced ethanol sensing properties of multi-walled carbon nanotubes/SnO2 core/shell nanostructures

Abstract: Multi-walled carbon nanotubes/SnO2 (CNT/SnO2) core/shell nanostructures were synthesized by a simple wet-chemical method The thickness of the SnO2 shell was about 10 nm and the diameters of the SnO2 particles were 2–8 nm Sensors based on the core/shell heterostructures exhibited enhanced ethanol sensing properties The sensitivity to 50 ppm ethanol was up to 245, and the response time and recovery time were about 1 and 10 s, respectively In addition, the fluctuation of the sensitivity was less than ± 3% on remeasurement after 3 months These results indicate that the core/shell nanostructures are potentially new sensing materials for fabricating gas sensors

Carbon nanotube delivery of the GFP gene into mammalian cells.

Abstract: Exogenous-gene expression and manipulation in mammalian cells has become a mainstay of biomedical research. Consequently, improving methods for efficient gene transfer to a broad range of cell types is of great interest and remains a high priority. Several classes of transfection methods have been developed, which include traditional cationic moleculemediated agents, such as Lipofectamine 20000 and FuGENE 6, viral-vector systems, and the “gene gun” approach. With the rapid development of nanobiotechnology, a variety of new materials, such as gold nanoparticles, silica nanoparticles, polymers, nanogels, and dendrimers have been investigated as biocompatible transporters. Recently, carbon nanotube—a well-studied nanomaterial— have been investigated for their ability to interact with and affect living systems. For instance, carbon nanotubes have been found to enhance DNA amplification in PCR and affect the growth pattern of neurons. Pantarotto et al. have reported the internalization of fluorescein isothiocynate (FITC) labeled nanotubes and nanotube delivery of the gene that encodes b-galactosidase into cells, with no apparent toxic effects. Kam et al. have studied the mechanism of protein-conjugated carbon nanotube uptake into cells via the endocytic pathway. Here we present our finding that amino-functionalized multiwalled carbon nanotubes (NH2-MWCNTs) are able to interact with plasmid DNA and deliver the green fluorescence protein (GFP) gene into cultured human cells. Our data strongly suggest that carbon nanotubes can be considered as a new carrier for the delivery of biomolecules, such as DNA, proteins, and peptides into mammalian cells. Therefore, this novel system might have potential applications in biology and therapy, including vaccine and gene delivery. In order to increase their biocompatibility, we introduced amino-, carboxyl-, hydroxyl-, and alkyl groups onto the surface of MWCNTs. COOH-MWCNTs were first prepared by nitric / sulfuric acid oxidation, and then NH2and CH3CH2CH2-groups were added. Finally, we obtained four types of MWCNTs with different chemical groups on their surface. Functionalized MWCNTs were observed under an electron microscope and were found to be 60–70 nm in diameter and 1–2 mm in length. Although we did not find a significant difference in size between the NH2-MWCNTs and NH2-MWCNT–DNAs, the latter appeared to have the tendency to aggregate (Figure 1B). In order to test the DNA-binding ability of amino-, carboxyl-, hydroxyl-, and alkyl-group-modified MWCNTs, we incubated them with pEGFPN1-plasmid DNA, and MWCNT–DNA mixtures were analyzed by agarose-gel electrophoresis. The results show that only NH2-MWCNT bound to DNA (Figure 2); since the NH2-MWCNT–DNA complex was too big to run into the

Three-dimensional functionalized tetrapod-like ZnO nanostructures for plasmid DNA delivery.

Abstract: Due to their special electrical, optical, and magnetic properties, materials less than 100 nm in size are very promising for biosensors, bio-separation, and drug delivery. In recent years liposomes and polymers have been used as carriers for transfections. Certain inorganic materials such as silica nanoparticles, carbon nanotubes, and silica nanotubes have been used as transporters with little toxicity in mammalian-cell transfections. These zero-dimensional nanoparticles and one-dimensional nanotubes suggest that nanomaterials, if modified properly, can be used as carriers for transfections. However, the application of three-dimensional nanostructures as biomolecule carriers is less well-studied. Here, we report three-dimensional functionalized tetrapod-like ZnO nanostructures as novel carriers for mammalian cell transfections. In this work, silica-coated amino-modifed nanostructures were prepared. Through electrostatic interactions, ZnO tetrapods could be bound to plasmid DNA. When mixed with cells, the tetrapods attached to cell membranes. Just as phages stand on cells with six legs suitable for gene delivery, ZnO nanostructures stand on the cells with three needle-shaped legs for DNA delivery as a result of their tetrapodal shape. With three tips located on the cell surfaces, the opportunity of internalization of the tips by cells should be increased. In addition, the geometry of the tetrapods imply a much larger steric hindrance, which makes it difficult for the tetrapods to pass wholly through the cell membranes. Just as phages insert genes into cells without entering them, tetrapods delivered plasmid DNA into the cells while standing on the cell membrane. This result is helpful in decreasing any cytotoxic effects. These results demonstrate a novel application of tetrapod-like nanostructures for gene delivery. Three-dimensional ZnO nanostructures were synthesized by thermal evaporation at 900 8C. The nanostructures consisted of four needle-shaped tetrahedrally arranged legs connected at the center, forming a tetrapod-like ZnO structure. The legs were single-crystalline and stable in air, with a mean diameter of 80 nm and a length of 5–10 mm. As shown in Figure 1A, one of the needle-shaped legs was per-