Disposable microchip could simplify disease diagnosis
Doctors could soon be able to test patients for 100 different conditions at once using a disposable microchip under development in the UK.
The ‘e-Gnosis’ chip could allow doctors to easily check samples of blood or saliva for different types of diseases, such as cancers, sexually transmitted infections or even allergies, using a rapid pregnancy-test-style reader connected to a smartphone or computer.
Like many new diagnosis technologies, the chip works by detecting molecules in the body that act as markers for a specific condition. But because it can also determine their concentration, it can check instantly for diseases that would otherwise need laboratory tests.
‘Although such systems exist to some degree, the fact that almost all of them rely on optical readers makes the setup cost, or the upfront cost, quite expensive,’ said the chip’s designer Dr Peter Kollensperger, a researcher at Imperial College London and recipient of a Royal Academy of Engineering enterprise fellowship.
‘That’s fine if you are a hospital running the same tests over and over again, but if you are a GP, or an outreach nurse, that may not be feasible. The chip could also be used in home monitoring, where patients take readings themselves instead of going to their GP or hospital.’
The e-Gnosis chip could also be used to detect other substances, such as drugs or pesticides in water, and Kollensperger believes targeting the sports market might be the easiest way to commercialise the technology before developing it for medical use.
The technology is based around a semiconductor sensor comprising an insulating layer covered in millions of nanometre-sized wells, which separates two sets of electrodes.
As the sample fluid is delivered to the chip, the molecular biomarkers get trapped in the wells, constricting their size and altering the current that passes between the electrodes.
The points where the electrodes intersect are known as pixels, each of which are around 100µm² in size and contain more than 100,000 nanowells filled with a specific type of antibody.
These antibodies each correspond to and bind with a specific biomarker and so different pixels can be used to detect different diseases on a single chip. The number of tests depends on the size of the pixel but a 3mm² chip could run 100 tests.
Using biomarkers and antibodies has become a common way of developing rapid tests but the technology is usually designed to produce a colour change, which only indicates whether or not a biomarker is present.
The e-Gnosis technology can use the current reading to calculate the concentration of the biomarkers, which is necessary for diagnosing some diseases such as prostate cancer but could also indicate how much medication is needed.
Kollensperger is hoping to produce a prototype chip running one or two tests over around 12 pixels by March next year.
‘In order to keep the chips as cheap as possible you want them as small as possible, which means you want to have the electrodes as close together as possible,’ he said. ‘And at some point, it becomes quite difficult to do larger readings of these in parallel to modify them chemically.
‘But the smaller you make the pixel, the fewer molecules you’d need to get a larger signal. These things are all interconnected and it depends what you’re looking for. Some tests might not be achievable for us.’