The discovery of numerous nanomaterials has added a new dimension to the rapid development of nanotechnology. Consequently, the professional and public exposure to nanomaterials is supposed to increase dramatically in the coming years. Especially, carbon-based nanomaterials (CBNs) are currently considered to be one of the key elements in nanotechnology. Their potential applications range from biomedicine through nanoelectronics to mechanical engineering. Thus, it is primordial to know the health hazards related to their exposure. As the public calls for safety studies get louder more and more researchers begin to study the potential toxicity of nanomaterials. Especially carbon-based nanomaterials, due to their numerous and wide-ranging applications and increasing real life usage, get nanotoxicological attention. Scientists in Switzerland studied the toxicity of carbon- based nanomaterials (nanotubes, nanofibers and nanowires) as a function of their aspect ratio and surface chemistry. Their work clearly indicates that these materials are toxic while the hazardous effect is size-dependent.
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.
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.
Imagine a toothpaste that not only seeks out but actually repairs damage to tooth enamel. For those who dread their annual visit to the dentist, this may sound like science fiction. For people in Japan, it is a reality. Using nanoparticles, Japan's Sangi Company, Ltd., has sold more than 50 million tubes - and continues to expand its line of products containing nanoparticles. Scientists have learned to synthesize hydroxyapatite, a key component of tooth enamel, as nanosized crystals. When nano-hydroxyapatite is used in toothpaste, it forms a protective film on tooth enamel, and even restores the surface in damaged areas. Availability of similar products that claim to actually repair cavities is just around the corner. Unlikely as it seems at first blush, the $200 billion global cosmetics industry is one of the major players in the emerging field of nanotechnology. According to the Centre for the Study of Environmental Change at Lancaster University in Britain, the cosmetics industry already holds the largest number of patents for nanoparticles - and be it toothpaste, sunscreen, shampoo, hair conditioner, lipstick, eye shadow, after shave, moisturizer or deodorant, the industry is leading the way.
All major powers are making efforts to research and develop nanotechnology- based materials and systems for military use. Asian and European countries, with the exception of Sweden (Swedish Defence Nanotechnology Programme), do not run dedicated programs for defense nanotechnology research. Rather, they integrate several nanotechnology- related projects within their traditional defense-research structures, e.g., as materials research, electronic devices research, or bio-chemical protection research. Not so the U.S. military. Stressing continued technological superiority as its main strategic advantage, it is determined to exploit nanotechnology for future military use and it certainly wants to be No. 1 in this area. The U.S. Department of Defense (DoD) is a major investor, spending well over 30% of all federal investment dollars in nanotechnology. Of the $352m spent on nanotech by the DoD in 2005, $1m, or roughly 0.25%, went into research dealing with potential health and environmental risks. In 2006, estimated DoD nanotechnology expenditures will be $436m - but the risk-related research stays at $1m.
Building construction and operation is estimated to be a trillion dollar per year industry worldwide. And it is one that is ripe for the innovations offered by nanotechnology and nanomaterials. Already, dozens of building materials incorporate nanotechnology, from self-cleaning windows to flexible solar panels to wi-fi blocking paint. Many more are in development, including self-healing concrete, materials to block ultraviolet and infrared radiation, smog-eating coatings and light-emitting walls and ceilings. Nanotech is also starting to make the smart home a reality. Nanotech-enabled sensors are available today to monitor temperature, humidity, and airborne toxins. The nanosensor market is expected to reach $17.2 billion by 2012. Soon, inexpensive sensors will be available to monitor vibration, decay and other performance concerns in building components from structural members to appliances. Nanotechnology is also rapidly improving the batteries and wireless components used in these sensors. In the not-too-distant future, sensors will be ubiquitous in buildings, gathering data about the environment and building users. Building components will be intelligent and interactive. Nanosensors and nano building materials raise questions for building designers, builders, owners and users. What will the consequences be as buildings become increasingly intelligent and nanomaterials become an everyday part of the buildings that surround us?
Particulate nanocarriers have been praised for their advantageous drug delivery properties in the lung, such as avoidance of macrophage clearance mechanisms and long residence times. However, instilled non-biodegradable polystyrene nanospheres with small diameters and thus large surface areas have been shown to induce pulmonary inflammation. New evidence suggests that biodegradable polymeric nanoparticles designed for pulmonary drug delivery may not induce the same inflammatory response as non-biodegradable polystyrene particles of comparable size.
Carbon nanomaterials have been studied as superior sorbents for their potential environmental applications to remove pollutants such as organic pollutants, metals, fluorides and radionuclides. Most of these studies focused on the adsorption process and few dealt with the interfacial interactions of organic contaminants with carbon nanomaterials in aqueous media. However, understanding their desorption behavior as well is critical to evaluating environmental and health impacts of carbon nanomaterials. New research looks at the high adsorption capacity and reversible adsorption of PAHs (polycyclic aromatic hydrocarbons), many of which are suspected carcinogens, on CNTs. The findings imply the potential release of PAHs if PAH-adsorbed CNTs are inhaled by animals and humans, leading to a high environmental and public health risk.