Where scalpel cannot reach

Nanotechnology could revolutionise medicine - despite the potential health hazards. E&T examines its potential to treat and diagnose disease.

We've been putting nano-sized particles into our bodies for thousands of years to try and cure ailments. The drugs, contained in plants, boiled into a poultice or carefully constructed in laboratories, all use elements on the nanoscale. The proponents of nanotechnology claim that it will give doctors greater levels of control while leaving the patients some control over their condition too. Dr Leonard Fass, director of academic relations at GE Healthcare, says that much of medical science has not changed a lot in the last few decades. We still cut cancers out of bodies, for instance, or blast an area with radiation. We ingest drugs wherever the ultimate source of the illness may be. The scalpel is a fine tool, but it is still a sledgehammer when you look at the scale at which diseases operate. Much of the hype around nanomedicine has involved little robot doctors roaming the body carrying out miniature surgery. The reality is likely to be different - but no less effective. Think about micro amounts of drugs released as close to the problem as possible. Or perhaps tiny monitoring devices powered through piezoelectrics. Nanomedicine is about seeing better and treating accurately. It's also about tapping into a multi-billion pound market that is driving developments. Investment is pouring into R&D because of potential for profit. Not only are those to be found in primary care and better surgery techniques, but also in patient-led diagnosis. Devices that people can use to diagnose themselves are a growth area. Care is being devolved from the hospital to the GP, to the high street and the home. It's a new market which investors believe nanotechnology can create. But what specific kinds of devices either at home or in the hospital are being looked at?

Quantum dots

A constant theme in nanomedicine is better targeting, i.e. being able to influence at the most effective place. Quantum dots are a crystalline compound between two and ten nanometers wide with electrical and optical properties. They could help refine the way that surgeons identify and remove damaged tissue. Some cancerous tissues can be hard to differentiate from healthy ones without extensive and repeated MRI scans. This is both impractical and expensive. The result is that surgeons err on the side of caution when removing tissue which can mean repeat intervention later on. Scientists have found that quantum dots can be made to cluster around certain types of damaged tissue. They emit infra-red rays when excited by normal light allowing a very accurate map to be targeted.

The quantum dots offer a long lasting and definitive signal.

Nanoshells

Another application that could treat cancer are nanoshells. Like quantum dots, scientists have exploited their optical properties to create miniature cancer-killers. Nanoshells are essentially glass particles inside a metal shell. The silica at the centre has an added chemical which makes different metals stick to the silica, and this is encouraged to spread until the shell is formed. Depending on the size of the nanoshell and the metal surrounding it, they can absorb or scatter different colours. By altering these, the shell can be 'tuned' from the visible to the infra-red band. When infra-red light hits it, a gold nanoshell acts like a lens, concentrating the light around it and converting it into heat. Experiments have shown that such nanoshells can be inserted into the bloodstream and wriggle their way into cancerous blood cells. When infra-red light is shone on them, they can burn away the surrounding cell. Again, the intervention is at a very localised level. Typical cancer drugs can leave a trail of destruction as they head towards their target. With nanoshells, the work begins 'on site'.

Nanorods

With a growing elderly population, billions of dollars are being spent on new hips. Nanorods are exactly what they sound like - organically grown tubes. One application is to use them to better bond replacement hips to the joint, much like the metal cores that run through concrete buildings. If this process is started early, the rod has a better chance of being accepted by the body.

Lab on a chip

Scientists have been able to create pumps, valves and filters at an incredibly small scale on microfluidic chips. These squares can sift and dissemble fluids allowing analysis of problems and detection of infectious agents. It is thought to be one of the strongest applications that will find its way on to the high street - after tests on the battlefield. America's Defense Advanced Research Projects Agency has been taking a particular interest in a lab on a chip technology as a battlefield treatment platform. The potential for instant self-diagnosis means many companies are investigating how they can be refined for use by the public. Biochips offer similar opportunities and could be powered using body's own heat or through piezoelectricity.

Nanospheres

Drug delivery procedures could be revolutionised through nano applications. At the moment, the most popular method is to take drugs orally, but this isn't the most efficient way of getting to the root of the problem Slow-release systems are already very well advanced. For instance, the Intellidrug fits inside a tooth. It contains a reservoir for the drug and an electrical timing mechanism that releases it in controlled amounts.

The device is relatively large but the principal of a controlled release could be replicated at a much smaller scale. Researchers at the University of Texas in Austin have described a means of using nanospheres for oral drug delivery. These nanosphere carriers are derived from hydrogels, which are highly stable organic compounds that swell when their environment becomes more acidic. They have been successfully formulated into controlled-release tablets and capsules, which release active compounds when the hydrogel body swells. Another drug delivery option is using liposomes. These carry particular drugs, which are diffused through the membrane over a period of time.

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