Nano-this and nano-that. These days it seems you need the prefix "nano" for products or applications if you want to be either very trendy or incredibly scary. This "nanotrend" has assumed "mega" proportions: Patent offices around the world are swamped with nanotechnology-related applications; investment advisors compile nanotechnology stock indices and predict a coming boom in nanotechnology stocks with misleading estimates floating around of a trillion-dollar industry within 10 years; pundits promise a new world with radically different medical procedures, manufacturing technologies and solutions to environmental problems; nano conferences and trade shows are thriving all over the world; scientific journals are awash in articles dealing with nanoscience discoveries and nano- technology breakthroughs. Nanotechnology has been plagued by a lot of hype, but cynicism and criticism have not been far behind. Science fiction writers exploit fears of nanorobots turning into killers; the media can run amok when news about potential health problems with nanoproducts surface (as happened last year with a product recall for a bathroom cleaner in Germany). Some see doomsday scenarios of molecular self-assembly turning the world into "grey goo." The emerging polarization of opinions on nanotechnology is reminiscent of controversies about genetically modified plants or nuclear energy. Vague promises of a better life are met by equally vague, generalized fears about a worse future. These debates have some aspects in common: the subject is complex and not easy to explain; there is no consensus on risks and benefits; scientists and corporations seem able to proceed unchecked, and it is unclear who is in control.
It seems that with every new study on the toxicity of nanomaterials there remain more questions afterwards than before. Environmental, occupational and public exposure to engineered nanoparticles will increase dramatically in the near future as a result of the widespread use of nanoparticles for consumer and industrial products. The extent of future exposure to nanoparticles associated with these new products is still unknown. So far only limited data is available regarding carbon nanotube (CNT) toxicity. As a result still not much is known about their impact on biological systems including humans. Discussions regarding the potential risks of their widespread use, as well as their possible positive impact are just beginning to take place. In order to provide a basis for comparison to existing epidemiological data, a group of researchers in Switzerland and Germany have investigated CNTs at various degrees of agglomeration using an in vitro cytotoxicity study with human cancer cells. The cytotoxic effects of well-dispersed CNT were compared with that of conventionally purified rope-like agglomerated CNTs and asbestos as a reference. While suspended CNT-bundles were less cytotoxic than asbestos, rope-like agglomerates induced more pronounced cytotoxic effects than asbestos fibers at the same concentrations. The study underlines the need for thorough materials characterization prior to toxicological studies and corroborates the role of agglomeration in the cytotoxic effect of nanomaterials.
Obtaining an understanding, at the atomic level, of the interaction of nanomaterials with biological systems has recently become an issue of great research interest. Nanomaterials can exhibit drastically different characteristics compared to their bulk counterparts. Although the use of such materials in biological systems opens avenues for the creation of novel biosensing and alternative nanomedical technologies, these nanomaterials can also be highly toxic. A greater understanding of the interaction of nanomaterials with biological systems, especially of the interaction of nanomaterials with cell membranes, will enable scientists to take full advantage of the unique properties of nanomaterials while minimizing their adverse effects. Fullerenes and their derivatives are an important subset of nanomaterials. Fullerenes have been used as robust oxygen scavengers, anti-HIV drugs, X-ray contrast agents, and transporters for delivering antibodies. While experimental studies suggest that the toxicity of nanomaterials depends critically on their surface properties, it was also found that, in the case of fullerenes, functionalizing the molecules can reduce their toxicity notably. New work by U.S. researchers offers a mechanistic view on the different cytotoxicity of fullerenes and their functionalized derivatives - a first in this important field of nanotoxicity. The major finding is that pristine fullerene can readily jump into a lipid bilayer while the translocation of a functionalized fullerene is severely hindered due to its surface charge, leading to a much reduced toxicity.
The study of adverse health effects of nanosized particles is nothing new. Particle toxicology is a mature science, dealing with the exposure to airborne nanosized (or ultrafine) particles that either occur naturally or have increasingly been introduced through human activities or industrial products such as materials that include asbestos fibers and coal dust. Research on ultrafine particles has laid the foundation for the emerging field of nanotoxicology, with the goal of studying the biokinetics of engineered nanomaterials and their potential for causing adverse effects. Most, if not all, toxicological studies on nanoparticles rely on current methods, practices and terminology as gained and applied in the analysis of micro- and ultrafine particles and mineral fibers. Together with recent studies on nanoparticles, this provides an initial basis for evaluating the primary issues in a risk assessment framework for nanomaterials. Given the many parameters involved, nanotoxicology requires an interdisciplinary team approach, even more so than classical toxicology, in order to arrive at an appropriate risk assessment. As a still-maturing science, nanotoxicology will expand the boundaries of traditional toxicology from a testing and auxiliary science to a new discipline where toxicological knowledge of nanomaterials can be put to constructive use in therapeutics as well as the development of new and better biocompatible materials.
The potential benefits of Nanofoods - foods produced using nanotechnology - are astonishing. Advocates of the technology promise improved food processing, packaging and safety; enhanced flavor and nutrition; 'functional foods' where everyday foods carry medicines and supplements, and increased production and cost-effectiveness. In a world where thousands of people starve each day, increased production alone is enough to warrant worldwide support. For the past few years, the food industry has been investing millions of dollars in nanotechnology research and development. Some of the world's largest food manufacturers, including Nestle, Altria, H.J. Heinz and Unilever, are blazing the trail, while hundreds of smaller companies follow their lead. Yet, despite the potential benefits, compared with other nanotechnology arenas, nanofoods don't get a lot of publicity. The ongoing debate over nanofood safety and regulations has slowed the introduction of nanofood products, but research and development continue to thrive - though, interestingly, most of the larger companies are keeping their activities quiet (when you search for the term 'nano' or nanotechnology' on the websites of Kraft, Nestle, Heinz and Altria you get exactly zero results). Although the risks associated with nanotechnology in other areas, such as cosmetics and medicine, are equally blurry, it seems the difference is that the public is far less apt to jump on the nanotechnology bandwagon when it comes to their food supply.
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.