Showing Spotlights 2057 - 2064 of 2284 in category All (newest first):
Thermolysis (from thermo- meaning heat and -lysis meaning break down) is a chemical process by which a substance is decomposed into other substances by use of heat. In photothermolysis the transfer of laser energy is used to generate the required heat. And finally, nanophotothermolysis is the process where nanoparticles, when irradiated by short laser pulses, get hot so quickly that they explode. This thermal explosion of nanoparticles (nanobombs) may be accompanied by optical plasma, generation of shock waves with supersonic expansion and particle fragmentation with fragments of high kinetic energy, all of which can contribute to the killing of cancer cells they are attached to. By engineering the laser wavelength, pulse duration and particle size and shape, this technology can provide highly localized damage in a controlled manner, potentially varying from a few nanometers (for DNA) to tens of microns (the size of a single cancer cell) without damaging the surrounding tissue.
Jan 12th, 2007
If you had brain tumor, would you rather receive your medicine through an injection in the arm or have a hole drilled in your skull? Even if you opted for the 'hole-in-the-skull' method, brain cancers are often inoperable due to their location within critical brain regions or because they are too small to detect. Nanotechnology offers a vision for a 'smart' drug approach to fighting tumors: the ability of nanoparticles to locate cancer cells and destroy them with single-cell precision. One of the most important applications for such nanoparticulate drug delivery could be the delivery of the drug payload into the brain. However, crossing the brains protective shield, the blood-brain barrier, is a considerable challenge. Novel targeted nanoparticulate drug delivery systems that are able to cross this barrier bring us closer to this vision of brain cancer destroying drugs.
Jan 11th, 2007
The success of nanorobotics requires the precise placement and subsequent operation of specific nanomechanical devices at particular locations, thereby leading to a diversity of structural states. The structural programmability of DNA makes it a particularly attractive system for nanorobotics. A large number of DNA-based nanomechanical devices have been described, controlled by a variety of methods. These include pH changes and the addition of other molecular components, such as small molecule effectors, proteins and DNA strands. The most versatile of these devices are those that are controlled by DNA strands. This versatility results because they can be addressed specifically by strands with particular sequences. Researchers at New York University have developed a framework that contains a binding site ‚?? a cassette ‚?? that allows insertion of a rotary device into a specific site of a DNA array, allowing for the motion of a nanorobotic arm. Changing the cassette‚??s control sequences or insertion sequences allows the researchers to manipulate the array or insert it at different locations.
Jan 10th, 2007
A control over spin-electron interactions is vital for development of spintronic devices and for quantum computation. When a magnetic impurity is surrounded by free electrons, a realignment of the electron spins occurs below a critical temperature due to spin-electron interactions; this causes an increase in resistivity of the material - a phenomenon known as the "Kondo" effect. The Kondo effect has been observed in a wide range of systems including single atoms/molecules, quantum-dots, and carbon nanotubes, however two-dimensional molecular Kondo systems have yet to be explored. Molecules with magnetic properties recently have great appeal as they offer an ideal platform to advance the fundamental understanding of spin related mechanisms, and can act as templates for molecular spintronic device fabrication due to their propensity for spontaneous self assembly. By manipulating nearest-neighbor molecules with a scanning tunneling microscope tip researchers now were able to tune the spin-electron coupling of the center molecule inside a small hexagonal molecular assembly in a controlled step-by-step manner. This variation of Kondo effect might be useful for instance for storing or manipulating data in spintronic memory devices.
Jan 9th, 2007
Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. The importance of carbon nanomaterials in biological applications has been recently recognized. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. Researchers now have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types.
Jan 8th, 2007
Nanoparticles exhibit unique properties that make them ideal for a wide-variety of applications. Also unique, and largely unknown, are the interactions that occur between the biological environment and nanoparticles. On the upside, the ability of quantum dots and fullerenes to penetrate intact skin provides potential benefits for the development of nanomaterial applications involving drug delivery. On the downside, this ability poses potential risks associated with manufacturing and handling such nanoparticles. A new study now confirms that fullerene-based peptides can penetrate intact skin and that mechanical stressors, such as those associated with a repetitive flexing motion, increase the rate at which these particles traverse into the dermis. These results are important for identifying external factors that increase the risks associated with nanoparticle exposure during manufacturing or consumer processes. Future assessments of nanoparticle safety should recognize and take into account the effect that repetitive motion and mechanical stressors have on nanoparticle interactions with the biological environment. Additionally, these results could have profound implications for the development of nanoparticle use in drug delivery, specifically in understanding mechanisms by which nanoparticles penetrate intact skin.
Jan 5th, 2007
Novel and robust networks, tailored from nanostructures as building blocks, are the foundations for constructing nano- and microdevices. However, assembling nanostructures into ordered micronetworks remains a significant challenge in nanotechnology. The most suitable building blocks for assembling such networks are nanoparticle clusters, nanotubes and nanowires. Unfortunately, little is known regarding the different ways networks can be created and their physicochemical properties as a function of their architecture. It is expected that, when 1D nanostructures are connected covalently, the resulting assemblies possess mechanical, electronic, and porosity properties that are strikingly different from those of the isolated 1D blocks. In extensive theoretical studies, researchers now have shown that the properties of 2D and 3D networks built from 1D units are dictated by the specific architecture of these arrays. Specifically, they demonstrate that one could join nanotubes and make supernetworks that exhibit different properties when compared to the individual building blocks (i.e. the nanotubes). Besides the unique and unusual mechanical and electronic properties, the porosity of these systems makes them good candidates for exploring novel catalysts, sensors, filters, or molecular storage properties. The crystalline 2D and 3D networks are also expected to present unusual optical properties, in particular when the pore periodicity approaches the wavelength of different light sources, such as optical photonic crystals.
Jan 4th, 2007
Bacteria are ubiquitous in the earth's surface, subsurface, fresh water, and oceanic environment. Bacteria are remarkable in that they are capable of respiring aerobically and anaerobically using a variety of compounds, including metals, as terminal electron acceptors. Metal reducing bacteria can significantly affect the geochemistry of aquatic sediments, submerged soils, and the terrestrial subsurface. Microbial dissimilatory reduction of metals is a globally important biogeochemical process driving the cycling of iron and manganese, associated trace metals, and organic matte. Microbial metal reduction is of significant interest among scientists who are researching remediation of environmental contaminants. However, little is known about the biochemical or molecular mechanisms underlying bacterial metal reduction. Conducting research with toxic metal reducing bacteria, researchers discovered that bacteria produce electrically conductive nanowires in response to electron-acceptor limitation. These findings could be used to bioengineer electrical devices such as microbial fuel cells.
Jan 3rd, 2007