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 nanotechnology.