Current Nanoscience - Volume 4, Issue 3, 2008

In many in vitro cultures, cells may change their morphology, probably caused by adherence to the surface of the culture dish. Since a fractal alkyl ketene dimer (AKD) surface provides super water-repellency with a contact angle of 174° , we considered that it might provide an improved surface environment for the growth and differentiation of cells by preventing intimate adhesion. C6 glioma cells which were selected to test the effects of the fractal surface, were cultured on a conventional surface, a smooth AKD surface or a fractal AKD surface. On the conventional and smooth AKD surfaces, cells developed bipolar or multipolar shapes with enlarged cell bodies and neurite-like processes. In contrast, cells cultured on the fractal AKD surface presented fine filopodium-like processes like protoplasmic astrocytes in vivo, and higher morphological complexity was revealed by fractal analysis. Reconstruction of three-dimensional shape indicated that cells on the fractal surface were globular, whereas those on the conventional surface were rather flat. Our results suggest that C6 glioma cells on a fractal AKD surface show features of natural astrocytes with their elaborate morphology. The fractal surface thus may provide a new and natural culture environment for experimental assessment of glial structure and function.

We investigate functional capabilities of large arrays of gold and silver nanorods as elements of plasmonic devices. The samples were fabricated by electron beam lithography and lift-off techniques on glass substrates. The areas patterned by the nanorods or other nanoparticles can be large, with dimensions of up to about one centimeter. Structural and optical characterization has allowed confirmation of a high homogeneity of the fabricated ensembles of nanorods, and a high sensitivity of their longitudinal extinction bands to the variations of the nanorod length and the refractive index of the environment. Applications of nanorods as refractive-index sensors is discussed.

SnO2 micron rods were prepared via a simple solution phase precursor route and modified with 1 wt% of Au. The products are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The gas sensing properties of the materials were tested in an organic glass chamber by mixing target gas into air. The results revealed that the product consists of SnO2 micron rods with diameters of ∼1-3 μm and lengths of ∼15-25 μm. SnO2 micron rods gas sensors exhibit good sensitivity and stability. Compared with pure SnO2 powders, the surface Au sensitization can improve the sensitivity and selectivity of the sensors. The role of Au in SnO2 gas sensor belongs to electronic sensitization. Large-scale synthesis and good sensitivities of SnO2 micron rods indicate the potential applications in gas sensors at the industry level.

To promote the applications of namomaterials, the potential toxicity of multi-walled carbon nanotubes (MWCNTs) and their derivates to environment have been studied. With γ-ray irradiation, MWCNTs were modified chemically with glucosamine and decylamine to obtain glucosamine-MWCNTs (g-MWCNTs) and decylamine-MWCNTs (d-MWCNTs). Their toxicological experiments were carried out with Tetrahymena pyriformis. The results illustrate that d-MWCNTs show a dose-dependent growth inhibition to the cells, due to the increasing concentration of toxic decylamine. This was attributed to the biological function performed by the decylamine after it was carried into the cell interior by the tubes. The results have a certain reference value for the applications of MWCNTs used as drug delivery system. Both glucosamine and purified MWCNTs (p-MWCNTs) alone show little biological activity, but g-MWCNTs exhibit a dose-dependent growth stimulation. This is due to the fact that the increasing hydrophilicity of g-MWCNTs promotes the conjugation of nanotubes with soluble peptone in culture medium via noncovalent binding. Uptake of the g-MWCNTs-peptone conjugates with various concentration of peptone by the cells is responsible for the dose-dependent growth stimulation. Consequently we propose the effects of concentration of functional groups, hydrophilicity of functionalized nanotubes as well as sequential nonspecific interaction between nanotubes with some components in culture medium on living system should be taken into account in the study of cytotoxicity of carbon nanotubes.

The effects of the tested factors including pH value, NaCl concentration, ODN concentration and charge ratio on the size and zeta potentials of nanoparticles (ODN-PLL, PLL: poly(l-lysine)s) were investigated by use of uniform design and NGR peptides were used to modify the nanoparticles, indicating that none of the tested factors was correlated with nanoparticles' size, however, a linear correlation (r = 0.8505) was found between charge ratio and zeta potential. A nanosize delivery system (ODN-PLL-NGR) with the function of targeting to tumor cells was developed by use of PLL to condense oligonucleotide into nanoparticles coated with peptide containing NGR motif. The ODN-PLL-NGR had the ability to protect ODN against nuclease degradation, and its cell uptake increased with time increment after incubation at 37°C for 40, 50 and 60 min.

Hysteresis effect in carbon nanotube field-effect transistors can be commonly employed to construct the nonvolatile memory devices of single-wall carbon nanotubes. In this paper, we investigate in detail the programming/erasing characteristics of such memory devices, which may present great importance for their availabilities. In order to write and erase the memory devices with reproducibility and stability, it is essential to set the writing and erasing time appropriately. The writing and erasing process of such memory devices is, in general, found to be much slower compared with traditional CMOS memory devices, typically operating on a time scale of the order of a second, which may pose a serious challenge to their practical exploitation. Furthermore, the stability of charge storage in such memories is slightly affected by temperature. A model based on electric polarization of surface-bound water molecules on SiO2 insulator has also been proposed to explain qualitatively the hysteresis and memory effect of these devices.

In semiconductor industry, process control and physical failure analysis were dominated by light and electron microscopy as well as surface analysis techniques including X-ray photoelectron spectroscopy (XPS) until the end of the last century. During the past decade, X-ray diffraction (XRD) and X-ray reflectivity (XRR) have been successfully applied in out-of-fab analytical labs. In addition to XRF and TXRF, some additional X-ray techniques - e.g. XRD, XRR and XPS - have been moved or are in the process to be moved from lab-based studies to in-line applications, using cleanroom compatible thin film characterization tools in wafer fabs. Lab-based smallangle X-ray scattering (SAXS) tools are applicable for pore size characterization in porous thin films. Advanced transmission X-ray microscopy (TXM) and X-ray computed tomography (XCT) systems with sub-100 nm resolution are currently being evaluated for their use in out-of-fab analytical labs. Apart from the on-site use of laboratory X-ray sources, synchrotron-radiation sources have been used in all fields of X-ray techniques: diffraction (SR-XRD), spectroscopy (SR-XPS, XAFS) and microscopy (SR-TXM/XCT). The high brightness and collimation of SR beams provide unique possibilities, e.g. for in-situ X-ray microdiffraction, photoelectron emission microscopy (PEEM) and in-situ TXM/XCT. In this paper, we demonstrate the high potential of the X-ray techniques for semiconductor industry, we describe potential implementations of these techniques for current and future applications, particularly for advanced process development and process monitoring, and we provide an outlook showing that we are living in a decade which is characterized by a breakthrough in the industrial application of Xray techniques. The application focus of this review is on the study of two types of nanostructures with typical dimensions less than 100 nm: artificial nanolayers and nanostructures caused by thin film deposition and patterning (litho/etch) processes as well as nanostructured materials, i. e. thin film materials with a “sub-structure” on sub-100 nm length scale.

The present study was aimed at developing and exploring the use of long circulating biocompatible PEGylated PPI 5.0G dendrimers for delivery of an anti-inflammatory drug, Aceclofenac. The PPI 5.0G dendrimers were synthesized and PEGylated using Nhydroxysuccinimide- activated dicarboxylic acid PEG 2000 (COOH-PEG-COOH). PEGylation was confirmed by IR, NMR and MASS spectra. The Aceclofenac was loaded in PEGylated dendritic system and various parameters like, hemolytic toxicity, drug entrapment, pH dependent in vitro drug release and in vivo blood-level were determined. The PEGylated dendritic system has shown increased drugloading capacity and reduced hemolytic toxicity as compared to non-PEGylated system. The in vitro release, in vivo blood level and tissue distribution studies in albino rats demonstrated suitability of PEGylated PPI 5.0G dendrimer for prolonged delivery of Aceclofenac. The carrageenan induced paw edema in albino rats revealed 69.41±0.7% and 77.08±0.4% inhibition of paw edema at 3rd and 7th hr, respectively that were maintained upto 52.17±0.9% until 48th hr from drug-PEGylated dendrimer complex. However, for plain drug the percentage of inhibition were found to be 66. 35±0.4% at 3rd hr, which was reduced to 28.44±0.3 % by 7th hr. PEGylation is considered to be suitable for amendment of PPI dendrimers for reducing of drug leakage and hemolytic toxicity, improving drug-loading capacity and stabilizes the system in body. The results suggested that, such PEGylated dendrimeric system is suitable for sustained delivery of Aceclofenac.

The characterisation of natural aquatic nanoparticles (especially in relation to flocculation processes, contaminant transport and biogeochemistry) has become an important field of environmental science. Ubiquitous colloid-size microbes and their nanoscale extracellular components affect the chemistry and physical properties of their surroundings in all habitable environments on Earth, thus affecting fundamentally the planet's geochemical systems. The adverse health effects of airborne particles, and the atmospheric deposition of particulate contaminants into surface waters, are well recognised environmental issues, with serious questions being posed about the biomedical effects of the nanoparticle component. There is a growing public health concern about nanoparticles in general, as a result of biomedical findings which reveal that atmospheric nanoparticles can present unanticipated toxicity and mechanisms for entering biological cells. The evolving analytical needs, issues, concerns and new facts call for improved means to detect and characterise environmental nanoparticles. Transmission electron microscopy (TEM) is making a major contribution. With foci on aquatic and airborne examples, this review presents literature highlighting nanoparticle relevance to environmental and public health. Common “species” of nanoparticles are described, while characterisation by TEM is considered in terms of apparatus, artifact minimisation and standard protocols for isolation and concentration. Evolving correlative microscopical approaches to characterisation are outlined, along with successful case studies involving heterogeneous environmental samples. Diverse activities of aquatic nanoparticles are featured, with reference to planetary-scale biogeochemical processes and water treatment. Informed speculation is presented on upcoming improvements to nanoparticle characterisation.

Owing to vast technological advances, hemodialysis (HD) has become a mature modality significantly increasing the survival of end-stage renal disease (ESRD) patients. However, many HD complications still exist that mainly relate to the nature of middlemolecular- weight and/or protein-bound toxins that both low- and high-flux dialysers cannot efficiently remove. For instance, hyperhomocysteinemia and amyloidosis are two dialysis-related disorders that motivate serious health complications. Here, we introduce a new method for the selective removal of specific toxins that is based on the preparation of Ferromagnetic Nanoparticle-Targeted Binding Substance Conjugates (FN-TBS Cs) constituted of biocompatible FNs and a specifically designed TBS that must have high affinity for the respective Target Toxin Substance (TTS). The FN-TBS Cs should be administered to the patient timely prior to the dialysis session so that they will be able to bind with the specific TTS owing to their free circulation in the bloodstream. The complex FN-TBS-TTS can be selectively removed from the ESRD patient during the HD session by means of a magnetic dialyser (MD). For the in vitro evaluation of this proposal we employed highly biocompatible Fe3O4 and Bovine Serum Albumin (BSA) as constituents of the FN-TBS Cs and an array of permanent magnets placed along the circulation line as a simple MD. We have evaluated the binding affinity and capacity of both bare Fe3O4 FNs and Fe3O4-BSA Cs by employing homocysteine (Hcy) as a model TTS. We investigate Hcy concentrations ranging from mild to severe hyperhomocysteinemia. Most importantly, we investigate the effectiveness of low concentrations of Fe3O4 that are within the safety levels established from the treatment of iron-deficiency anemia, thus making a preliminary evaluation of future in vivo applications. We observed that Hcy is readily adsorbed onto both bare Fe3O4 FNs and Fe3O4-BSA Cs. The obtained results prove the successful in vitro applicability of the proposed method since pathological Hcy concentrations may be adequately handled by relatively low Fe3O4 concentrations, thus making feasible future in vivo applications.

Nano-engineered multilayer microshells (microcapsules) as nano/microreactors are expected to expand the capabilities of confined photoreaction occurring in shell walls and in shell interiors and to explore new functionalities of application. The basis for optical reactions in multilayer microshells is their tailored wall components and particular properties originated from the permeability and stability of shell walls in response to external stimuli. This review aims at describing recent developments on the photochemical behaviors of photofunctionalized shell walls, mainly focusing on photocontrollable wall permeability by visible illumination. Apart from these, the photocatalytic reaction in spatially confined microshells is also reviewed, with an emphasis on recent advances in the visible lightassisted degradation of defined dye pollutants in the homogeneous or heterogeneous photo-Fenton system. The photoreaction mechanism occurring in the shells is also discussed. Finally, we have addressed some of the perspectives and challenges for the potential future development of microshells as photoreactors and applications based on these systems.