GRAPHENE SENSOR TRACKS DOWN CANCER BIOMARKERS
An ultrasensitive
biosensor made from the wonder material graphene has been used to detect
molecules that indicate an increased risk of developing cancer
The biosensor has been
shown to be more than five times more sensitive than bioassay tests currently
in use, and was able to provide results in a matter of minutes, opening up the
possibility of a rapid, point-of-care diagnostic tool for patients.
The biosensor has been
presented today, 19 September, in IOP Publishing's journal 2D Materials.
To develop a viable
bionsensor, the researchers, from the University of Swansea, had to create
patterned graphene devices using a large substrate area, which was not possible
using the traditional exfoliation technique where layers of graphene are stripped
from graphite.
Instead, they grew
graphene onto a silicon carbide substrate under extremely high temperatures and
low pressure to form the basis of the biosensor. The researchers then patterned
graphene devices, using semiconductor processing techniques, before attaching a
number of bioreceptor molecules to the graphene devices. These receptors were
able to bind to, or target, a specific molecule present in blood, saliva or
urine.
The molecule,
8-hydroxydeoxyguanosine (8-OHdG), is produced when DNA is damaged and, in
elevated levels, has been linked to an increased risk of developing several
cancers. However, 8-OHdG is typically present at very low concentrations in
urine, so is very difficult to detect using conventional detection assays,
known as enzyme-linked immunobsorbant assays (ELISAs).
In their study, the
researchers used x-ray photoelectron spectroscopy and Raman spectroscopy to
confirm that the bioreceptor molecules had attached to the graphene biosensor
once fabricated, and then exposed the biosensor to a range of concentrations of
8-OHdG.
When 8-OHdG attached
to the bioreceptor molecules on the sensor, there was a notable difference in
the graphene channel resistance, which the researchers were able to record.
Results showed that
the graphene sensor was capable of detecting 8-OHdG concentrations as low as
0.1 ng mL-1, which is almost five times more sensitive compared with ELISAs.
The graphene biosensor was also considerably faster at detecting the target
molecules, completing the analysis in a matter of minutes.
Moving forward, the
researchers highlight the potential of the biosensor to diagnose and monitor a
whole range of diseases as it is quite simple to substitute the specific
receptor molecules on the graphene surface.
Co-author of the study
Dr Owen Guy said: "Graphene has superb electronic transport properties and
has an intrinsically high surface-to-volume ratio, which make it an ideal
material for fabricating biosensors.
Now that we've created
the first proof-of-concept biosensor using epitaxial graphene, we will look to
investigate a range of different biomarkers associated with different diseases
and conditions, as well as detecting a number of different biomarkers on the
same chip."
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