Lifeng Dong

Cytotoxicity Effects of Different Surfactant Molecules Conjugated to Carbon Nanotubes on Human Astrocytoma Cells

Phase contrast and epifluorescence microscopy were utilized to monitor morphological changes in human astrocytoma cells during a time-course exposure to single-walled carbon nanotube (SWCNT) conjugates with different surfactants and to investigate sub-cellular distribution of the nanotube conjugates, respectively. Experimental results demonstrate that cytotoxicity of the nanotube/surfactant conjugates is related to the toxicity of surfactant molecules attached on the nanotube surfaces. Both sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) are toxic to cells. Exposure to CNT/SDS conjugates (0.5 mg/mL) for less than 5 min caused changes in cell morphology resulting in a distinctly spherical shape compared to untreated cells. In contrast, sodium cholate (SC) and CNT/SC did not affect cell morphology, proliferation, or growth. These data indicate that SC is an environmentally friendly surfactant for the purification and dispersion of SWCNTs. Epifluorescence microscopy analysis of CNT/DNA conjugates revealed distribution in the cytoplasm of cells and did not show adverse effects on cell morphology, proliferation, or viability during a 72-h incubation. These observations suggest that the SWCNTs could be used as non-viral vectors for diagnostic and therapeutic molecules across the blood–brain barrier to the brain and the central nervous system.

Structures and properties of nano-particles prepared by hydrogen arc plasma method

A hydrogen arc plasma method for preparing nano-particles was introduced. A method which possesses higher production rate, lower energy consumption and is suitable for preparation of nano-particles of metals with high melting point. The microstructures and properties of the nano-particles prepared by this method were reported.

Direct imaging of copper catalyst migration inside helical carbon nanofibers

By using a double-aberration-corrected (scanning) transmission electron microscope (STEM/TEM) at an acceleration voltage of only 80 kV, we demonstrate that, due to the low solubility of copper (Cu) in carbon and its affinity with oxygen (O), single-crystal Cu catalysts dissociate into small cuprous oxide (Cu2O) nanoparticles after the growth of carbon nanofibers, and Cu2O nanoparticles ultimately localize on the fiber surfaces. This new finding is a step toward a better understanding of the interactions between Cu catalysts and carbon nanomaterials and could suggest a simple and effective method for eliminating Cu impurities from the fibers.

Association of Poly I:C RNA and Plasmid DNA onto MnO Nanorods Mediated by PAMAM

In this study, manganese oxide (MnO) nanorods and its association with polyamidoamine dendrimer (PAMAM) and macromolecular RNA were analyzed. Because manganese is found naturally in cells and tissues and binds proteins and nucleic acids, nanomaterials derived from manganese, such as first generation MnO, may have potential as a biocompatible delivery agent for therapeutic or diagnostic biomedical applications. Nucleic acids have a powerful influence over cell processes, such as gene transcription and RNA processing; however, macromolecular RNA is particularly difficult to stabilize as a nanoparticle and to transport across cell membranes while maintaining structure and function. PAMAM is a cationic, branching dendrimer known to form strong complexes with nucleic acids and to protect them from degradation and is also considered to be a cell penetrating material. There is currently much interest in polyinosinic:polycytidylic RNA (poly I:C) because of its potent and specific immunogenic properties and as a solo or combination therapy. In order to address this potential, here, as a first step, we used PAMAM to attach poly I:C onto MnO nanorods. Morphology of the MnO nanorods was examined by field emission scanning electron microscopy (FESEM) and their composition by energy dispersive X-ray microanalysis (EDX). Evidence was generated for RNA:PAMAM:MnO nanorod binding by a gel shift assay using gel electrophoresis, a sedimentation assay using UV spectroscopy, and zeta potential shifts using dynamic laser light scattering. The data suggest that RNA was successfully attached to the MnO nanorods using PAMAM, and this suggestion was supported by direct visualization of the ternary complexes with FESEM characterizations. In order to confirm that the associations were biocompatible and taken up by cells, MTT assays were carried out to assess the metabolic activity of HeLa cells after incubation with the complexes and appropriate controls. Subsequently, we performed transfection assays using PAMAM:MnO complexes with pDNA encoding a green fluorescent protein reporter gene instead of RNA. The results suggest that the complexes had minimal impact on metabolic activity and were readily taken up by cells, and the fluorescent protein was expressed. From the evidence, we conclude that complexes of PAMAM:MnO interact with nucleic acids to form associations that are well-tolerated and readily taken up by cells.

DNA-templated synthesis of Pt nanoparticles on single-walled carbon nanotubes

A series of electron microscopy characterizations demonstrate that single-stranded deoxyribonucleic acid (ssDNA) can bind to nanotube surfaces and disperse bundled single-walled carbon nanotubes (SWCNTs) into individual tubes. The ssDNA molecules on the nanotube surfaces demonstrate various morphologies, such as aggregated clusters and spiral wrapping around a nanotube with different pitches and spaces, indicating that the morphology of the SWCNT/DNA hybrids is not related solely to the base sequence of the ssDNA or the chirality or the diameter of the nanotubes. In addition to serving as a non-covalent dispersion agent, the ssDNA molecules bonded to the nanotube surface can provide addresses for localizing Pt(II) complexes along the nanotubes. The Pt nanoparticles obtained by a reduction of the Pt2+-DNA adducts are crystals with a size of < or =1-2 nm. These results expand our understanding of the interactions between ssDNA and SWCNTs and provide an efficient approach for positioning Pt and other metal particles, with uniform sizes and without aggregations, along the nanotube surfaces for applications in direct ethanol/methanol fuel cells and nanoscale electronics.

Applications of Nanomaterials in Biology and Medicine

1 College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China 2 Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, USA 3 Department of Biomedical Sciences, Missouri State University, Springfield, MO 65897, USA 4 School of Nano and Advanced Materials Engineering, Gyeongsang National University, Gyeongnam 660-701, Republic of Korea 5 National Center for Nanoscience and Technology, Beijing 100190, China

Tipping the Proteome with Gene-Based Vaccines: Weighing in on the Role of Nanomaterials

Since the first generation of DNA vaccines was introduced in 1988, remarkable improvements have been made to improve their efficacy and immunogenicity. Although human clinical trials have shown that delivery of DNA vaccines is well tolerated and safe, the potency of these vaccines in humans is somewhat less than optimal. The development of a gene-based vaccine that was effective enough to be approved for clinical use in humans would be one of, if not the most important, advance in vaccines to date. This paper highlights the literature relating to gene-based vaccines, specifically DNA vaccines, and suggests possible approaches to boost their performance. In addition, we explore the idea that combining RNA and nanomaterials may hold the key to successful gene-based vaccines for prevention and treatment of disease.

Photoelectrochemical Properties of Carbon Nanotube/SnO 2 Nanostructures Prepared by Three Different Methods

In this work, we employed three different methods to fabricate solar cell structures on indium tin oxide (ITO) substrates. For the first method, multi-layered structures were prepared by using single walled carbon nanotubes (SWCNTs) and tin oxide (SnO 2 ). First, a SWCNT layer was deposited on the ITO substrate; and photoactive material was then coated on the top of the SWCNT layer. For the second method, photoactive particles were added to a solution of SWCNTs. The SWCNT/SnO 2 solution was mechanically stirred and then deposited on the ITO substrate. For the third method, we synthesized photoactive particles on SWCNTs through a chemical-solution routine using SnCl 4 as a precursor. We characterized the morphology and structure of the SWCNTs coated with SnO 2 nanoparticles prepared with the three different methods by using a field emission scanning electron microscope equipped with an X-ray energy dispersive spectrometer. We characterized the photoelectrochemical properties of all electrodes by using an electrochemical station; mainly, we examined the photocurrent generated under periodic illumination. Our results indicate that there are significant differences in the photocurrent in the presence of SWCNTs. We propose the following hypothetical mechanism: without carbon nanotubes, generated electrons (when light is absorbed by SnO 2 particles) must cross the particle network to reach an electrode. Many electrons never escape this network to generate an electrical current. The carbon nanotubes “collect” the electrons and provide, therefore, a more direct route to the electrode, thus improving the efficiency of the solar cells.

Electron Spectroscopic Imaging of DNA Molecules along Carbon Nanotubes by Aberration-Corrected Transmission Electron Microscopy

Single-stranded DNA molecules (ssDNA) can effectively disperse bundled carbon nanotubes into individuals in aqueous solution for the synthesis of carbon-nanotube-supported platinum catalysts [1], and carbon nanotubes can be used as transporters for the delivery of DNA molecules into cells [2]. For these and other potential applications, it is critical to understand structure-property correlations of the nanotube/DNA hybrids. However, there remains a lack of systematic observations regarding the interfacial structure between the DNA and the nanotube surface. In this study, we used aberration-corrected transmission electron microscopy (TEM) to investigate the morphology and interfacial structures of the nanotube/DNA hybrids using energy-filtered TEM (EFTEM) and electron energy-loss spectroscopy (EELS).

DEFECT OF NANOCRYSTALLINE COPPER AND SILVER

Nanoscale copper and silver were synthesized by the H2+Ar arc plasma method. During the synthesis, hydrogen molecules were dissociated into hydrogen atoms and stored in the particles. At the same time, nanometer copper and silver particles were prepared by the inert gas condensation method whose power is about identical with the hydrogen arc plasma method. Various specimens were annealed respectively at low temperature. The particle size was measured by a transmission electron microscopy. A proper temperature was chosen to prepare the standard specimen.