The incredible shrinking laboratory or 'lab-on-a-chip'
Compared with a
conventional laboratory, greater sensitivity means a lab-on-a-chip
requires a much smaller test sample. Photograph: Reuters
When a doctor wants to carry out a test, she will probably prick
you with a needle, fill up several test tubes of your blood, label,
package and send them to some centralised hospital laboratory.
Technicians will then take the contents, perform the various biochemical
analyses needed, write up the results and send back the documentation
in a few weeks, perhaps longer if there's a backlog.
The process
is slow and labour-intensive. What if you could reduce the whole
business to a few minutes? What if, for the majority of ailments or
questions, the doctor only needed a drop of your blood and could test
you for viruses or cancers while you wait in her surgery? With a
lab-on-a-chip, that is already possible.
Quick tests are not a new
idea – pregnancy tests can be done at home and diabetics can quickly
and easily measure their blood sugar levels using only a drop of blood –
but complex diagnoses still need labs and technicians.
"With a
lab-on-a-chip you can do a quick diagnostic test and get information
right there, which is very useful when somebody's got a disease that's
got a very short timeline to be treated," says Mark Morrison, CEO of the
Institute of Nanotechnology
in Stirling, UK. "What it effectively does is miniaturises and compacts
all the different processes that a researcher or a technician in the
diagnostic lab uses."
The lab-on-a-chip shrinks the pipettes,
beakers and test tubes of a modern chemistry lab onto a microchip-sized
wafer of glass or plastic. Perhaps you want to know which viruses are
in a sample of blood? Or, on the battlefield, which biological warfare
agent is present in a soldier's bloodstream? Put in a drop of blood at
one end and the carefully carved channels take its constituent molecules
past a circuit of nanometre-sized chemical and physical tests that
poke, prod and characterise them to answer your question, however
complicated. A chip developed by the University of Alberta, for example,
can screen for chromosome mutations that cause a range of cancers.
The platform blurs
nanotechnology,
biotechnology and micro-electronics. And it is not specific to medicine
– it is being developed for environmental monitoring of pollutants and,
increasingly, in basic scientific research to speed up the once-tedious
aspects of examining genes or testing the properties of new materials.
Prof
Tom Duke at the London Centre for Nantechnology has been working on a
chip that can detect whether a blood sample contains HIV. Current tests
require testing in large laboratories staffed by skilled clinicians,
which is a hindrance if you want to test people in resource-poor
countries where the disease is rife.
Duke's chip simplifies that
process using a sensor that only requires a drop of blood at one end.
The blood is separated into its parts by an array of nanometre-sized
silicon pillars in the sensor and the biggest bits – such as blood cells
and large proteins – are trapped. Any virus particles pass between the
pilars to the other end of the sensor, where they are attracted to a
series of tiny cantilevers coated with antibodies. These are, in
essence, mini diving boards that bend when something lands on them, and
that deflection can be measured by bouncing a laser off them. The more
the diving boards are deflected, the more virus is present. "This
platform can be used for pretty much any viral or bacterial disease,"
says Duke.
There are several advantages to the lab-on-a-chip
approach, beyond the convenience of being able to test in the field. The
test sample required is much smaller because of the sensitivity of the
chip, which is useful if you need to measure trace gases in the
atmosphere or the very earliest stages of a disease when the chemical
markers in the blood are low in number and would probably be missed by
standard tests.
"Potentially you can detect the presence of, for
example, cancer or diabetes at a much earlier stage and then treat it
more effectively," says Morrison. "If you treat the disease earlier on,
you have a much greater chance of success."
The Simbas chip,
designed by a team of researchers led by Ivan Dimov at the University of
California, Berkeley, can detect a biological component in blood at a
concentration of around 1 part per 40 billion. "That can be roughly
thought of as finding a fine grain of sand in a 1,700-gallon sand pile,"
says Dimov. The self-contained chip can get results from a drop of
blood in 10 minutes, without the need for any external pumps, tubes or
power supply.
Researchers interested in basic physiology are also
finding a use for these sophisticated mini laboratories. Scientists at
Harvard University have created a lung on a chip that contains several
types of tissue and can be used in experiments to understand basic
function. They can simulate flowing blood, introduce pollutants and
toxins to see how the "lung" reacts and even stretch and contract the
cells to simulate breathing.
The technology will no doubt get
faster, cheaper and more abundant. But there are some ethical questions
coming along the pipeline, along with the technical ones. Most
important, while it is still in its infancy and still relatively
expensive, who gets access to it? And, since many of the devices will be
used to test for an individual's susceptibility to specific genetic
diseases, another question is who should be able to access to that
information? "As a scientist I'd say screen everybody for every disease
because then you know who is going to get something and you can treat
them early on," says Morrison. "But that's maybe looking at it from a
utopian point of view."
The dystopian alternative is a
precautionary note rather than an inevitability and, in any case,
debates around future access to genetic and medical data are already
under way, thanks to a rapidly improving arsenal of medical and
environmental sensors. Miniature laboratories on silicon and glass chips
are another, invaluable tool in that arsenal.
The Guardian is working in association with the European Union's NanoChannels project to create a portal for information on the technical and ethical challenges associated with nanotechnol