Lab-on-a-chip analyses blood with optical detector
24 July 2009
The EU-funded NEMOSLAB project is developing an integrated ‘lab on a
chip’ that can simultaneously test a blood sample for several different
molecules at the point of care. It is being used to measure fertility
hormones and detect the genes associated with certain types of cancer.
Much of modern medicine relies on the testing of blood and other
samples for key molecules that confirm the presence of a specific
disease or other disorder. Samples need to be sent to a laboratory and
it may be several days before the result comes back. The project aims to
make it possible to obtain results within a few minutes of the sample
being taken, while the patient is still there with the doctor.
“The question was whether we could combine silicon or other
semiconductor technologies with the bioassay techniques and the
diagnostic technologies,” explains project coordinator Dr Konstantinos
Misiakos of the National Centre of Scientific Research in Athens. “Some
of the technologies were innovative or state of the art at the time the
project started, some others were more or less conventional.”
NEMOSLAB uses an optical technique to recognise the presence of
selected biological molecules. Light passes down a silicon nitride
waveguide — a flat rectangular pipe about 8 micrometres wide and 0.15
micrometres thick — to a detector which turns it into an electrical
The waveguide is coated with a probe molecule that can recognise
target molecules by binding to them. This could be an antibody, which
will bind with a specific protein, or a strand of DNA that will bind
with a complementary strand in the sample fluid.
“We chose the probes to be very selective for the molecules we want
to detect,” says Dr Sotiris Kakabakos who is working with Misiakos.
“They have been tested right on the chip but also with conventional
methods which select those probes to be very specific for the analyte to
A microfluidics system within the chip passes the sample — normally
blood serum — over the waveguide. When a target molecule in the sample
binds to the surface of the waveguide the optical properties are changed
and the amount of light arriving at the detector also changes. The step
in the signal is distinctive.
Each NEMOSLAB chip contains nine waveguides which are exposed to the
sample at the same time and can be primed to detect different molecules.
The entire chip is fabricated as a single unit.
An electronics package collects the signals from the waveguides and
produces the results within a few minutes of the sample being
“We can’t claim the physics is new,” says Misiakos, “but the
realisation of the physics into an integrated and small format through
the mature silicon technology is new. Our advantage is that we have all
the optical components monolithically integrated on the silicon chip.”
One of the partners, an infertility treatment centre in Dortmund, is
interested in using the device to monitor hormone levels in the blood of
women seeking to conceive a baby through in-vitro fertilisation. The
NEMOSLAB device can test for nine different hormones at the same time.
At present, women have to travel to the clinic every day for the
tests but with NEMOSLAB they could do the tests themselves at home.
The project has also developed a set of probes for detecting the
BRCA1 gene which is associated with breast and ovarian cancer. Several
different mutations of the gene can be sensed at the same time. This
opens up the possibility of screening for a predisposition to these
Many other applications are possible, too, and not just within
medicine. The portability of the device makes it ideal for environmental
monitoring. It could be used in field testing for agrochemicals in water
supplies and in food safety applications.
Although the NEMOSLAB results are promising, it is too early to move
towards commercialisation. “We don’t believe we can commercialise the
technology right away,” says Misiakos.
Further work is needed on aspects such as the sample preparation. “We
cannot just put in a drop of blood to get results. It has to be treated
and that is not yet integrated on the device.”
Further work is also needed on the read-out electronics so that the
whole device can be made more compact. “The read-out electronics are
quite small but we cannot claim that this is a hand-held device. It’s
portable at this time but not hand-held as we would like.”
There are also questions to be resolved about the long-term stability
of the molecular probes coating the waveguides.
The NEMOSLAB approach is not the only way of doing such tests. Other
groups are working on electrochemical, microbalance and acoustic methods
for detecting molecules.
“We are much more sensitive, though, compared to acoustic devices or
to several electrochemical devices,” says Kakabakos. “Also we have much
faster results. The unique feature is the fully integrated transducer.
This is unique at a worldwide level!”
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