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Nanoparticles can also cross the blood–brain barrier, which could make them useful for delivering drugs that target brain tumours or diseases that affect the central nervous system.
Fundamentally, nanotechnology is about making things on the scale of atoms. By manipulating matter on the atomic and molecular scale, it is possible to create new materials and devices that can be smaller, stronger or faster; for example carbon nanotubes possess extraordinary strength and unique electrical properties, and have been described as 'the most important material in nanotechnology today'.1
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Nature also works on the molecular scale. Naturally occurring molecular assemblies that regulate and control biological systems are the most complex and highly functional nanoscale processes we know. The volume of a single molecule biodevice, such as a protein, is between one-millionth and one-billionth of the volume of an individual cell. If these natural processes were fully understood it might be possible to influence or interact with them, opening a new path to innovative pharmaceuticals. It could also be possible to stimulate the body to successfully repair diseased or damaged tissues.
However, predicting the impact of new technologies is difficult and there are many concerns regarding the use of nanotechnology, including what unintended and unwanted effects it could have on the environment and human health.
Nanotechnology can be defined in a number of ways, but is usually accepted as 'the ability to do things — measure, see, predict and make — on the scale of atoms and molecules, and exploit the novel properties found at that scale'.2 The units of measurement involved are difficult to comprehend. A single nanometer is equivalent to one thousandth of a micron or one billionth of a metre, which has been likened to comparing the size of a marble to the size of the Earth.3
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Although open to interpretation, the nanoscale is generally said to comprise anything measuring 1–100 nm. At this scale, materials often exhibit different physical, chemical and biological properties; for example, the melting point of a substance may change because of the change in surface area, chemical activity may increase or a substance may acquire the ability to cross tissue barriers. This creates new possibilities to optimize drug targeting and delivery. In what is reminiscent of a science fiction novel, researchers have also speculated that it could be possible to use nanorobots that patrol the body diagnosing and treating ailments.4
Many of these medical and pharmaceutical applications may not be possible for many years, as any product would have to be subjected to strict testing and validation procedures. However, there are already hundreds of products on the market that utilize nanotechnology, many of which we use in our daily lives including batteries, computers, kitchenware, clothing, cosmetics, toothpastes, sun creams and paints. It has been estimated that nanotechnology consumer products are coming on the market at a rate of 3–4 per week.5 Nanotechnology is also used in some pharmaceuticals, such as Abraxine, which was recently launched in India by Biocon (India) and Abraxis BioScience (CA, USA),6 and is available in more than 30 countries. The drug is administered as albumin-bound particles of approximately 130 nm.
The first documented introduction to nanotechnology is Richard Feynman's lecture entitled "There's Plenty of Room at the Bottom", which he gave at an American Physical Society meeting in 1959. Although the term nanotechnology was not used then, Feynman spoke about the possibility of manipulating matter on the atomic scale. However, nanotechnology and nanoparticles had unintentionally been used long before this by glaziers in medieval forges who produced colours with gold nanoparticles of different sizes to decorate glass.
It wasn't until 1974 that the term 'nanotechnology' was used by Norio Taniguchi from the Tokyo Science University (Japan) to describe precision micromachining, and discussions regarding the topic didn't really take place until 1980s. That decade saw the invention of the scanning tunnelling microscope, publication of the first nanotechnology book, Kim Eric Drexler's Engines of Creation: The Coming Era of Nanotechnology, and the formation of the Foresight Nanotech Institute (CA, USA) — the first organization dedicated to educate society about the benefits and risks of nanotechnology. At the end of the decade, it was also discovered that the scanning tunnelling microscope could be used to move single atoms when IBM scientist, Don Eigler, moved individual atoms of xenon gas to spell out the IBM logo. The ability to accurately position individual atoms led to other new discoveries; for example, Eigler's team later created a wall of iron atoms to study how electrons behaved in tightly constrained spaces.
Nanomedicine is a relatively new concept that was first used in1999 when Robert A. Freitas Jr.'s book Nanomedicine, Volume I: Basic Capabilities was published, describing the potential medical applications of nanotechnology and nanorobotics. In a more recent review, there are said to be three major potential uses for nanotechnology in medicine: delivering the exact dose of a drug to the intended location, providing new ways to grow and repair body tissues, and detecting single molecules in diagnosis.7
Drug delivery. Nanotechnology is already aiding drug delivery by improving bioavailability. Many of the current 'nano' drug delivery systems are considered to be remnants of conventional drug delivery systems that happen to be in the nanometer range, such as liposomes, polymeric micelles, nanoparticles, dendrimers and nanocrystals.8 For example, in 2007 Johnson & Johnson Pharmaceutical R&D (NJ, USA) submitted an application to FDA for a long-acting injectable paliperidone palmitate that uses Elan's Nanocrystal technology.9 The Nanocrystals enhance the older drug's solubility by reducing particle size.
Nanoparticles can also cross the blood–brain barrier, which could make them useful for delivering drugs that target brain tumours or diseases that affect the central nervous system. Further research must still be conducted as it is yet unknown whether there are any potentially negative side-effects of using nanoparticles.
Disease treatment. There has been growing excitement about the potential of nanotechnology to help treat some of the most debilitating diseases, including cancer and Alzheimer's.10,11 Research has been conducted as to how nanotechnology may aid cartilage loss and even repair spinal cord injuries,12,13 but these developments are in the early stages and it will be many years before tests in humans are conceivable.
One promising treatment for cancer is nanoshells, which consist of a spherical core surrounded by a shell that is only a few nanometres wide. The shells can absorb or scatter specific wavelengths of light. Gold-encased nanoshells can convert these wavelengths into heat.7 In laboratory tests, scientists have used nanoshells to 'cook' tumour cells without harming surrounding healthy cells.14
Diagnosis. Much research has been conducted into improving the detection of cancer, and nanotechnology could offer a solution as it may help with the long-term tracking of cells and molecules. In 2005, researchers attached nanocrystals to antibodies and used them to identify the molecule p-glycoprotein,15 which makes cancer cells resistant to chemotherapy. The method meant that a single molecule of p-glycoprotein on the cell surface could be detected. Magnetic nanoparticles have also been used to help locate tumours in magnetic resonance imaging scans.
Nanotechnology could also offer advantages for medical implants as some nanomaterials, such as nanocrystalline ceramics, have properties that include hardness, wear resistance and biocompatibility. In the future, nanosized sensors could also be used, for example, to monitor blood sugar levels in diabetes.
In Drexler's Engines of Creation: The Coming Era of Nanotechnology, he introduces the possibility of scientists engineering synthetic life forms that could in turn generate self-replicating nanorobots that would spread around the Earth making life as we know it extinct. This "grey goo" scenario (as termed by the author) has triggered many of the doubts and fears that are commonly associated with nanotechnology.16
Advances in this field have often been unwelcome by public opinion because of concerns regarding toxicity and the ethical issues that surround it. With regard to toxicity, although there is no direct evidence to support this, it has been suggested that finely divided chemicals might be more toxic and more effective at getting into our bodies than the same chemicals as we normally use them. With regard to ethical issues, it is feared that society may lose control and blur the lines between man and machine by engineering synthetic forms of life that are better suited to living on Earth than equivalent living organisms.
How realistic is this? The answer is unrealistic. We should not worry about "grey goo" as it is unlikely that scientists will be able to produce better, more efficient nanoscale living forms than nature itself has already produced.
So what is the future of nanotechnology? It is difficult to say. Public opinion seems to be against it, but the technological advances that have been and will be made as a result of it are life changing. Currently, we have very little understanding of how biology operates and many of its processes remain a mystery; however, nanotechnology may help scientists paint a clearer picture by allowing certain processes and functions to be mimicked and studied. In the field of IT, cheap and powerful computing systems combined with mass storage and ultra-fast processing systems are forecast to revolutionize society.
Let's give nanotechnology the benefit of the doubt and not assume that it is dangerous. In the next 20 years it will be important to exploit and control the technology and keep the public well informed of the benefits and advantages it brings us.
Bibiana Campos-Seijo is Editor of Pharmaceutical Technology Europe.
Stephanie Sutton is Assistant Editor of Pharmaceutical Technology Europe.
1. P. Holister, The tiny revolution (2002). www.cientifica.com
2. UK Department of Trade and Industry — New Dimensions for Manufacturing. A UK Strategy for Nanotechnology, June 2002. www.innovateuk.org
3. J. Kahn, National Geographic (June, 2006) 98–119.
4. A. Cavalcanti et al.,Nanotechnology, 19(1), Article 015103 (2008).
5. The Project on Emerging Nanotechnologies, "An inventory of nanotechnology-based consumer products currently on the market" (2008). www.nanotechproject.org
6. Abraxis BioScience, "Biocon and Abraxis BioScience Launch ABRAXANE in India for Treatment of Breast Cancer" (2008). www.abraxisbio.com
7. M. Sharman, Exploring the World of Nano Medical Devices (May, 2006). www.devicelink.com
8. K. Park, PubMed Central, July 2007. www.pubmedcentral.nih.gov
9. Johnson & Johnson (2007). www.jnj.com
10. Going Small for Big Advances: using Nanotechnology to Advance Cancer Diagnosis, Prevention and Treatment (US Department of Health and Human Services, January 2004).
11. A. Nazim and G. Ali Mansoori, J. Alzheim. Dis., 13(2), 199–223 (2008).
12. Brown University, "Brown researchers work towards aiding cartilage loss" (2008). www.brown.edu
13. Northwestern University, "Promising new nanotechnology for spinal cord injury" (2008). www.northwestern.edu
14. A.P. Alivisatos, "Less is more," in Scientific American, Ed., Understanding Nanotechnology (Warner Books, New York, New York, USA, 2002) pp 56–69.
15. AICR, "Nanotechnology" (2005). www.aicr.org.uk
16. R. Jones, The Future of Nanotechnology, (2004). http://physicsworld.com