Taihong Wang

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

Nanoparticles containing magnetic materials, such as magnetite (Fe3O4), are particularly useful for imaging and separation techniques. As these nanoparticles are generally considered to be biologically and chemically inert, they are typically coated with metal catalysts, antibodies or enzymes to increase their functionality as separation agents. Here, we report that magnetite nanoparticles in fact possess an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, which are widely used to oxidize organic substrates in the treatment of wastewater or as detection tools. Based on this finding, we have developed a novel immunoassay in which antibody-modified magnetite nanoparticles provide three functions: capture, separation and detection. The stability, ease of production and versatility of these nanoparticles makes them a powerful tool for a wide range of potential applications in medicine, biotechnology and environmental chemistry.

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

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 24.5, 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.

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

Functionalized tetrapod-like ZnO nanostructures for plasmid DNA purification, polymerase chain reaction and delivery

Functionalized tetrapodal ZnO nanostructures are tested in plasmid DNA experiments (1) as a solid-phase adsorbent for plasmid DNA purification, (2) as improving reagents in a polymerase chain reaction (PCR) and (3) as novel carriers for gene delivery. The amino-modification, the tetrapod-like shape of the nanostructure and its high biocompatibility all contribute to measurements showing promise for applications. A sol-gel method is used for silica coating and amino-modification. Plasmid DNA is purified through reversible conjugations of amino-modified ZnO tetrapods with DNA. Also, as additional reagents, functionalized tetrapods are shown to improve the amount of PCR product. For transfection, ZnO tetrapods provide some protection against deoxyribonuclease cleavage of plasmid DNA and deliver plasmid DNA into cells with little cytotoxicity.

Formation and orientation control of Y2O3 inclusions in pulsed laser deposited YBa2Cu3O7−δ films by using a melt-textured target

The formation and orientation Of Y2O3 inclusions in pulsed laser deposited YBa2Cu3O7-delta films by using Y2BaCuO5-containing melt-textured target have been studied by X-ray diffractometry and transmission electron microscopy. The results show that Y2O3 inclusions, rather than the Y2BaCuO5 phase contained in the target, are formed in the films. [1 1 1]- and [10 0]-oriented Y2O3 inclusions have been found in the YBa2Cu3O7-delta films. The orientation Of Y2O3 inclusions is dependent on the deposition temperature. If the deposition temperature is high enough, [I I 1]-oriented Y2O3 can be inhibited. The reasons for the formation Of Y2O3 inclusions and their orientation are discussed