Scientists in Ireland, Zurich and Madrid have developed a new kind of medical sensor that can detect minute traces of a substance down to the level of a molecule. They believe it may provide fast and accurate point-of-care detection for diseases such as Ebola, HIV or even the common cold.

The team has already proven the device will work when tested with fullerene molecules, explains Dr Damien Thompson, a lecturer in the department of physics and energy at the University of Limerick and a group leader in the university's Materials and Surface Science Institute.

“We can scan liquids for minute traces of chemicals. It is minute down to ultra low, one molecule is enough,” he said of the test device the researchers have developed.

The collaboration involves Dr Thompson and his group along with IMDEA-Nanoscience in Madrid and IBM Zurich. It arose in the way so many good projects have through personal contact while at a conference. Dr Thompson met IBM's Peter Nirmalraj and the two found they had much common ground in their research. The group sought funding and received it from Science Foundation Ireland, the EU and from IBM. Work only got under way late last year so the team has made rapid progress.

The goal is to have a device that can detect extremely low concentrations of biomarkers in a blood sample, say for cancer or a disease such as Ebola. The device should be able to detect this provided a unique biomarker molecule is available and should be able to do so to an extremely high level of accuracy, Dr Thompson says.

“If we can measure molecules more accurately and quickly without the need for expensive laboratories then we can quickly diagnose conditions in patients,” he says. “Imagine a situation where a life-threatening condition could be rapidly diagnosed in its incubation stage using a simple hand-held test outside of a lab environment.”

They describe their device in the current edition of the journal Nature Materials. Like any such device it has a sensor designed to detect a given molecule and the sensor sends back an electrical signal if the target is present in a sample.

The researchers wanted to develop a much more sensitive sensor, however, one that could detect very, very low levels of the target molecule. This in turn threw up challenges because much greater sensitivity comes at a cost. You run the risk that the target molecule will chemically interact with the sensor and confound the signal being returned by it.

“We want to spy on the molecule, we want to look at its energy levels without actually changing them,” says Dr Thompson.

Another problem to be overcome related to the target managing to sit on the sensor long enough to be detected. At higher concentrations this is not a problem, but at low concentrations the molecule gets buffeted about and won’t sit on the sensor long enough to allow confirmation of its presence.

The researchers came up with answers to these problems. For starters they used silicon oil as the carrier of the sample across the sensor. “We needed gloop to carry the interesting molecules around. We used silicon oil as liquid brakes to do this. Without the oil the molecule flies around the surface of the sensor but the oil damps down its motion,” he explains.

They also found a solution to the problem of chemical reactivity. They introduced a thin insulating layer just one atom thick onto the surface of the sensor. This blocked any physical reaction between the target and the sensor, but was not thick enough to stop the sensor from detecting the molecule and sending back its positive signal.

The researchers managed to go cheap and cheerful when it came to this insulating layer, which is formed by alkanes, inexpensive chains of carbon and hydrogen atoms that stop any interference with the sensor. The signal from the molecule is kept pure. “The molecule’s energy levels are not contaminated by noise from the sensor surface,” he says.

“The potential is very exciting and this research has unlocked what has been a long-standing issue for the diagnostics community – how to place molecules near conducting surfaces without perturbing the molecule’s electrical properties.”

Now they face a new challenge, adding a blood sample to the mix. It is a complex liquid, it is electrically polar, and makes it more difficult to detect a target with high sensitivity. It could take two years to overcome these issues and get close to delivering a proven diagnostic tool, Dr Thompson said.