Showing Spotlights 1665 - 1672 of 2340 in category All (newest first):
The toxicity issues surrounding carbon nanotubes (CNTs) are highly relevant for two reasons: Firstly, as more and more products containing CNTs come to market, there is a chance that free CNTs get released during their life cycles, most likely during production or disposal, and find their way through the environment into the body. Secondly, and much more pertinent with regard to potential health risks, is the use of CNTs in biological and medical settings. CNTs interesting structural, chemical, electrical, and optical properties are explored by numerous nanomedicine research groups around the world with the goal of drastically improving performance and efficacy of biological detection, imaging, and therapy applications. In many of these envisaged applications, CNTs would be deliberately injected or implanted in the body. While it has been shown that carbon nanotubes can indeed act as a means for drug delivery, negative effects such as unusual and robust inflammatory response, oxidative stress and formation of free radicals, and the accumulation of peroxidative products have also been found as a result of carbon nanotubes and their accumulated aggregates. As a possible solution, scientists have provided compelling evidence of the biodegradation of carbon nanotubes by horseradish peroxidase and hydrogen peroxide over the period of several weeks. This marks a promising possibility for nanotubes to be degraded by horseradish peroxidase in environmentally relevant settings.
Nov 10th, 2008
Developed originally for the surface finishing industry, diamond nanoparticles are now finding new and far-reaching applications in modern biomedical science and biotechnologies. Due to its excellent biocompatibility, diamond has been called the Biomaterial of the 21st Century and medical diamond coatings are already heavily researched for implants and prostheses. Nanoscale diamond is also being discussed as a promising cellular biomarker and a non-toxic alternative to heavy metal quantum dots. Further extending the nanomedical use of diamond, researchers now have demonstrated a nanodiamond-embedded device that could be used to deliver chemotherapy drugs locally to sites where cancerous tumors have been surgically removed.
Nov 7th, 2008
Mesoporous materials, i.e. materials with pores that measure less than 50 nanometers in size, have been researched extensively for at least 20 years now. Especially mesoporous silicates, due to their large surface area, their uniform pore size, and the accessibility of these pores, have become very popular as catalyst materials and excellent dug delivery candidates. Despite of the long research history of mesoporous silica materials and their biomedical potential, there have been only few reports on actual in vivo applications. Although the theory looks good, there are several practical obstacles for mesoporous silica materials to be used as drug carriers or for instance as in vivo cancer targeting agents. Researchers who tried making small mesoporous silica particles with sizes of around 100 nm often ended up with much larger lumps of aggregated particles. These larger chunks cannot be used because, due to their size, they are easily trapped in the body's defense mechanism, the reticuloendothelial system (RES). Researchers in South Korea have now reported the fabrication of discrete, monodisperse, and precisely size-controllable core?shell nanoparticles that are smaller than 100 nm, by using single magnetite nanocrystals as core and a mesoporous silica shell.
Nov 6th, 2008
DNA, the fundamental building block of our genetic makeup, has become an intense nanotechnology research field. DNA molecules can serve as precisely controllable and programmable scaffolds for organizing functional nanomaterials in the design, fabrication, and characterization of nanometer scale electronic devices and sensors. The reason why DNA could be useful in nanotechnology for the design of electric circuits is the fact that it actually is the best nanowire in existence - it self-assembles, it self-replicates and it can adopt various states and conformations. The most basic and simplest form of DNA mechanical devices that are expected to be the first to demonstrate some close-to-reality functions are DNA tweezers. This concept was first introduced in 2000 by scientists at Bell Labs and Oxford University. To keep this type of tweezers running, two fuel DNA strands are alternately added to a buffered solution that contains the tweezers. These fuels are basically two stretches of complementary DNA, one of which closes the tweezers and the other opens them. The exciting potential applications for DNA tweezers include their use in constructing various molecular devices dedicated to repairing a functional unit in a cell, harnessing the delivery of drug molecules to pathogenic cells, or assembling nanoscale devices.
Nov 5th, 2008
Bone grafts are second only to blood transfusions on the list of transplanted materials. With bone grafts, a surgeon replaces missing bone with material from the patient's own body, or a synthetic or natural substitute. Traditional tissue repair techniques, especially with synthetic materials, may lead to poor integration with the existing bone or tissue structure, potentially transfers dangerous pathogens into the body, and sometimes lead to a complete rejection of the graft. To minimize these harmful side effects, researchers are developing sophisticated tissue engineering techniques based on the construction of three-dimensional scaffolds out of biomaterials to provide mechanical support and guide cell growth into new tissues or organs. In the quest to make bone, joint and tooth implants almost as good as nature's own version, scientists are turning to nanotechnology. They have found that the response of host organisms to nanomaterials is different than that observed with conventional materials. The surface nano-characteristics of biomaterials are increasingly recognized as crucial factors with regard to tissue acceptance and cell behaviors. While this new field of nanomedical implants is in its very early stage, it holds the promise of novel and improved implant materials.
Nov 4th, 2008
Forget boxy loudspeakers. Researchers have now found that just a piece of carbon nanotube thin film could be a practical magnet-free loudspeaker simply by applying an audio frequency current through it. These loudspeakers - which are only tens of nanometers thick, transparent, flexible, and stretchable - can be tailored into many shapes and mounted on a variety of insulating surfaces, such as room walls, ceilings, pillars, windows, flags, and clothes without area limitations. The scientists demonstrated that their CNT loudspeakers can generate sound with wide frequency range, high sound pressure level, and low total harmonic distortion. Another advantage compared to conventional loudspeakers is that the CNT loudspeakers don't vibrate and are damage tolerant. They will work even if part of the thin film is torn or damaged.
Nov 3rd, 2008
Modern fuel cells have the potential to revolutionize transportation. Like battery-electric vehicles, fuel cell vehicles are propelled by electric motors. But while battery electric vehicles use electricity from an external source and store it in a battery, fuel cells onboard a vehicle are electrochemical devices that convert a fuel's chemical energy directly to electrical energy with high efficiency and without combustion. One of the leading fuel cell technologies developed, in particular for transportation applications, is the proton exchange membrane (PEM) fuel cell, also known as polymer electrolyte membrane fuel cells - both resulting in the same acronym PEMFC. These fuel cells are powered by the electrochemical oxidation reaction of hydrogen and by the electroreduction of the oxygen contained in air. Presently, platinum-based electrocatalysts are the most widely used in PEM fuel cell prototypes. However, this metal is expensive due to its limited supply and its price is highly volatile. This creates one of the major barriers preventing commercialization of PEMFCs - the lack of suitable materials to make them affordable. Nanotechnology provides solutions to this problem.
Oct 31st, 2008
Crystalline nanoporous compounds have attracted the attention of scientists and materials engineers because of the interest in creating nanoscale spaces and the novel phenomena in them. Nanoporous materials find applications in many chemical processes such as separation and catalysis and are also heavily researched as storage materials, for instance in hydrogen fuel cells. Researchers still lack a complete understanding of the mechanism that leads to, and occurs during, crystal growth. Only once scientists achieve full control of properties such as composition, structure, size, morphology, and the presence and form of defects within the crystals can they fully exploit the benefits of crystalline nanoporous materials for the fabrication of novel materials. Researchers in the UK have now presented definitive real-time evidence of the crystal growth mechanism in what appears to be the first high-resolution observation of in-situ crystal growth of a crystalline nanoporous material monitored using atomic force microscopy (AFM).
Oct 30th, 2008