| The latest buzzword in the scientific community is nanotechnology.
A report by the Economic and Social Research Council entitled “The
social and economic challenges of nanotechnology” was published
last month and draws attention to the increasing controversy over the
possible effects of this emerging technology.
Some of its more extreme critics fear this scientific discipline will
wreak havoc on the world, turning the surface of the earth into a gooey
grey mess. But its most fervent supporters predict it will change the
world for the better — making the development of innovative products
possible and the production of goods cheaper.
|
Nanotechnology
Nanotechnology makes use of particles at the nano-length
scale — a nanometer is one billionth of a metre. The technology
can be approached in one of two ways — from the bottom up
or the top down. The top-down approach refers to the construction
of nanoscale structures using machining and etching techniques.
The bottom-up approach (often referred to as molecular nanotechnology)
refers to the creation of structures “atom-by-atom” or “molecule-by-molecule”.
|
What is nanotechnology?
Ottilia Saxl, chief executive officer of the Institute of Nanotechnology,
based at the University of Stirling Innovation Park, says nanotechnology
can be considered an extension of miniaturisation. Essentially, it
is the creation of materials, devices and systems at the nanometer
scale (see Panel).
Nanotechnology is offering us the ability to design materials with totally
new characteristics. In other words, nanotechnology will fundamentally
change the things we make and the way we make them,” she says.
But pharmaceutical scientists have been creating small particles for
many years. Indeed, Professor Graham Buckton, in his Science Chairman’s
address (PDF 110K) at this week’s British Pharmaceutical Conference, refers
to nanotechnology as “a trendy term for the microparticles that
many have been making for years” (see p377). So what has changed?
Dr Saxl points out that the development of advanced analytical techniques
means that scientists can now see what they are doing and this is allowing
matter to be manipulated in precise ways.
Changing drug characteristics
In terms of application to medicine, nano-technology looks set to have
considerable impact. One company using nanotechnology to manipulate
drug particle characteristics is Elan. The company’s nanocrystal
milling process has allowed drugs like Wyeth’s sirolimus (Rapamune)
to be developed from an oral solution formulation (requiring relatively
complicated administration) to a tablet formulation.
Dr Joseph Fix is executive vice-president of NanoSystems, the drug delivery
business unit of Elan. “By making smaller particles we improved
the disssolution rate [of sirolimus] enough that we could formulate it
as a tablet. The driving force was dosing convenience for patients,” he
says.
Commercially, this milling technology can only really be applied to poorly
soluble drugs but Dr Fix estimates that somewhere between 40 and 50 per
cent of all new chemical entities coming out of discovery fit into this
category. Furthermore, up to 10 per cent of drugs that are already marketed
have some performance issues related to solubility.
Nanotechnology is also permitting drugs such as peptides, conventionally
administered by injection to avoid metabolism in the gut, to be delivered
in ways that may be more acceptable to patients.
Xstal Bio, a company affiliated to Strathclyde and Glasgow universities,
develops protein-coated crystals. Marie Claire Parker, chief executive
of Xstal Bio, explains: “Most conventional technologies start with
big particles and break them down. Our technology creates the small particle
so there isn’t any further processing required.”
The company is developing an inhaleable formulation of insulin. “Patients
simply take a puff of a dry powder formulation of insulin or another
protein.”
For this route to be effective — and this is where the technology
comes in — the particles on which the drug is delivered have to
be small enough to avoid clogging up the lungs but large enough to avoid
being exhaled. So far, Xstal Bio has taken its inhaleable insulin through
the proof of
concept stage, but it has yet to be tested in humans.
Nanotechnology is also being applied to earlier, simpler disease detection,
improved imaging, and rapid assessment of potential drug candidates,
according to Dr Saxl.
The authors of the ESRC report, Professor Stephen Wood and colleagues
from the ESRC Centre for Organisation and Innovation, Sheffield, are
optimistic about the potential of nanotechnology.
They highlight several medical applications arising from nanoscale science,
such as the creation of artificial organs and implants, laboratory-on-a-chip
technology for quicker diagnosis and personal health monitors, and advanced
drug delivery. “The ultimate combination of the laboratory-on-a-chip
and advanced drug delivery technologies would be a device that was implantable
in the body, which would continuously monitor the level of various biochemicals
in the bloodstream and in response would release appropriate drugs,” they
say.
Gene therapy
Another possible application for nanotechnology is in the delivery of
gene therapy. Current vectors — modified viruses — are
associated with immune reactions so research is focused on building
nanostructures that can carry genes to the required delivery site.
Other delivery and targeting techniques are being investigated to maximise
drug action and minimise side effects. In a report published by the Institute
of Nanotechnology (www.nano.org.uk), Dr Saxl explains that light-activated
coatings can be applied to particulate drugs used to treat bone conditions. “The
drugs remain insoluble due to the coating, becoming preferentially concentrated
at the joints. The coatings are dissolved by exposure to light, allowing
the drugs to be released exactly where needed,” she says. Studies
are also focusing on using magnetic particles to guide and position drugs
at target sites. Coating nano-sized drug particles with polymers such
as polyethylene glycol is another technique used to direct drugs to target
tissues. This changes the surface characteristics of the drug particles,
allowing them to avoid uptake in the liver. “This avenue of research
will shortly result in therapeutic procedures,” says Dr Saxl.
Nanotechnology may be a trendy term for an established scientific disipline
but that should not detract from its potential. |
