UK: Science Feature - Nanotechnology

INTRODUCTION

Nanotechnology is "the design, characterisation, production and application of structures, devices and systems by controlling shape and size at nanometre scale."¹ One nanometre (nm) is one billionth of a metre. By controlling matter at such a scale, materials with new properties and uses can be created. These nanomaterials have a relatively large surface area to volume ratio when compared to the same mass of material produced in bulk form, which can make the nanomaterial more chemically reactive and affect its physical and chemical properties. At such a scale the electrons in the material are subjected to quantum mechanical effects, rather than the classical physics effects seen in materials at larger scale, affecting the optical, electrical and magnetic properties of nanomaterials.

The production of nanomaterials often requires new processes and new approaches to manufacturing. However, nanotechnology is not a new science, as the semiconductor industry has been working at the nanometre scale for many years, in the development of ever smaller transistors for computer chips. Currently, the manufacturing standard for a feature on a memory chip is 90 nm, but it is predicted that by 2016 this will have fallen to 22 nm.

The natural world also contains many examples of nanoscale structures, such as milk (a nanoscale colloidal suspension), and nanosized and nanostructured proteins. However, it is only relatively recently that it has been possible to accurately manipulate matter at the nanoscale level. This typically takes one of two approaches. The first, so called "top-down" technique, involves starting with a bulk material and etching it down to the desired shape. The second, "bottom-up" technique, involves the assembly of smaller sub-units (atoms or molecules) to form a larger structure.

Nanotechnology has the potential to bring huge benefits in areas such as drug development, communication technologies, new materials, medical devices, and environmental decontamination and remediation. The technology has already been exploited in medicine to powerful effect: the breast cancer drug Herceptin is a nanoscale antibody, and the anti-leukaemia drug Mylotarg is based on nanotechnology.

One widely quoted estimate puts the annual value for all nanotechnology related products at $1 trillion by 2011-2015.² Current funding in Europe for nanotechnology research & development is €1 billion, two-thirds of which comes from national and regional programmes. In 2003, the UK launched its nanotechnology strategy, pledging £45 million per year from 2003 to 2009. The USA's 21st Century Nanotechnology Research and Development Act, passed in 2003, allocated nearly $3.7 billion to nanotechnology from 2003-2008.

Nanotechnology has already been used to good effect in a wide variety of industry sectors

• Nanotechnology has been used in the fields of diagnostic techniques ("lab-on-a-chip" diagnostic kits, used, for example, in testing for viruses and bacteria), pharmaceuticals (using nanoparticle technology to deliver drugs and prostheses/implants with surfaces modified at the nanoscale (enabling increased colonisation by host cells and better camouflage from the host immune response)). Nanoscale modification of the implant surface also allows better binding of bioactive molecules, for instance in stents and catheters. Dendrimers (spherical polymeric molecules) can act as carrier molectules and are being investigated as carriers in drug delivery
• One dimensional nanomaterials such as thin films and nano-engineered surfaces have been used in the manufacture of electronic devices, in chemistry and in engineering. In the semiconductor industry, many devices rely on thin films which are deposited on substrates (surfaces) with extreme precision (sometimes a single atom or molecule thick). Chemical catalysts and fuel cells use surfaces specifically engineered to have a large surface area for reactivity. Nanoengineered surfaces have been used in implanted medical devices to reduce immunoreactivity and provide controlled release of active ingredients
• Carbon nanotubes (CNTs) are extended tubes of rolled sheets of carbon atoms. They are of particular interest as nanomaterials as they exhibit novel chemical and physical properties. They are extremely strong, flexible and can conduct electricity, giving CNTs a range of possible applications as sensors, in reinforced composite materials, display devices and nanoscale electronic devices
• Nanowires are ultra-fine wires made from a variety of materials and have demonstrated unique optical, electronic and magnetic properties. Nanowires have potential applications in communications technology, high density data storage, metallic interconnects and sensors
• Nanoparticles form the raw material for other manufactured products, or are used as ingredients or additives in existing products. Nanoparticles are often included in products such as cosmetics and sunscreens which are applied directly to the skin, raising issues concerning their health effects. Nanoparticles also have the potential to react with chemical contaminants in soil and convert them into harmless by-products. However, the release of active nanoparticles into the environment raises a number of concerns, such as uncontrollable proliferation - the "grey goo" scenario.³
• Dendrimers are used in conventional applications such as paints and inks. Dendrimers could also find uses in environmental remediation as they are able to bind heavy metals, for instance lead and cadmium pollutants in water, and can then be removed by filtration, either due to the formation of a suspension in the treated water or by using microfiltration.

Few papers have been published on the effects of nanoparticles on the health of animals and none on the effects on humans, but concerns have been raised that the likely increased reactivity of nanoparticles and their ability to cross cell membranes (pass through the outer surface of the cell) may have adverse environmental and health effects. For instance, creams applied to the skin containing nanoparticles of sufficiently small size may allow the nanoparticles to pass though the outer layer of the skin, either through pores in the skin or through the surface of skin cells directly. The potential ability of nanoparticles to pass through the outer surface of cells also has implications for air-borne nanoparticles which may be inhaled and pass through the cells of the lung.

Concerns about nanotechnology have centred on the impact of manufactured nanomaterials on human health, non-human ecosystems and the environment. Exposure to nanoparticles may occur by inhalation, surface contact or ingestion. Use of nanoparticles in pharmaceutical preparations may result in these nanoparticles entering the body, where their effects are unknown and cannot be accurately predicted from studies of similar preparations containing non-nanoengineered particles.

Nanomaterials may accumulate in the environment and the food chain and cause direct damage to plants and animals. The toxicology of nanoparticles cannot be inferred from toxicity of the bulk material as the nanoparticles may have substantially different properties to the bulk material.

Carbon nanotubes typically have dimensions similar to those of asbestos fibres. Therefore there is a risk that carbon nanotubes could cause the same type of injuries as asbestos. This may leave nanotube manufacturers open to long term liability for injuries caused by inhaling nanotubes (30 or more years after the event).

At the end of March 2006, at least 77 people in Germany reported severe respiratory problems - including six who were hospitalised with pulmonary oedema (fluid in the lungs) - after using a "Magic Nano" cleaning product, leading to the product being recalled. The spray was meant to be used on glass and ceramic surfaces to make them dirt and water repellent. It is unclear what kind of nanomaterial was used in the spray and it has been suggested that the spray lacked engineered nanoparticles, but claimed to be "nano" to appeal to consumers for high-tech labour-saving products.⁴

Nanotechnology presents particular problems from a regulatory perspective because it spans many different technologies and it is therefore unlikely that a single regulatory regime will be able to properly regulate all aspects of it. Nor, given that the properties of nanomaterials may be substantially different from the bulk material, is it likely to be possible to simply adapt a combination of existing regulatory regimes. Safety tests performed on any bulk material will not necessarily be applicable to the derivative nanomaterial and the requirement for full hazard assessments will add to the cost of developing new nanomaterials.

Another barrier in the way of wider use of nanotechnology is the increasing use of the precautionary principle in framing legislation. New products and processes must be assessed to determine not only obvious risks but also possible future risks. However, with a technology such as nanotechnology, where products have properties which may be completely different from the properties of bulk materials, it may be exceedingly difficult to assess future risks of devices incorporating nanotechnology, simply because there is little to compare them against.

The science of nanotechnology has already brought benefits to consumers and businesses in a number of different product industries including medicine, electronics and cosmetics. With tangible proposals afoot for its widespread use in areas such as diagnostics and tissue engineering, it seems that only the surface of the capabilities of nanotechnology has been scratched. With every scientific advance comes potential health risks however, and there is already concern about the type and extent of the risks that development of the new technology might bring. With this in mind, industry, regulatory authorities and governments need to work together to develop appropriate strategies to regulate the development and safety of products that rely on nanotechnology in such a way that allows the science to be fully exploited, but also places priority on ensuring the safety of consumers affected by it.

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