A portable diagnostic device could help determine the likely severity of a disease

A portable device designed to detect not only the presence of an infection but also how the patient’s immune system is responding to it, could help doctors predict the likely severity of a disease.

The point of care sensor, which is being developed by an EU-funded consortium, can detect not only invading pathogens, but also small molecules produced by the immune system in response to the disease.

This can be used to predict how the disease will evolve in a particular patient, according to Leopold Georgi at the Technische Universitat Berlin, who is coordinating the Platform for ultra-sensitive Point-of-Care diagnostics for infectious diseases (PoC-ID) project.

A prototype device is being developed to detect the presence of respiratory syncytial infection (RSV) in children. The RSV virus, which infects nearly all children before their third birthday, usually mildly, can occasionally lead to severe conditions such as bronchiolitis and pneumonia.

“It’s quite hard to say with RSV if it will be severe enough for the infant to be hospitalised, or if it will be just a small fever,” said Georgi. “That is why we want to measure the immune response, because our immune system has the best biosensors you can have, better than any we technologists can make, so we want to combine the sensor technology of the body with sensors to identify the pathogen itself,” he said.

Pathogens and small molecules within a patient sample are first captured by RNA oligonucleotide molecules known as aptamers.

The researchers chose aptamers rather than antibodies as they are able to capture smaller molecules, making them more suitable for identifying an immune response, said Georgi.

“They are also easier to handle during production, because antibodies typically cannot survive temperatures of 45 degrees Celsius or higher, while aptamers are much more stable, and they are also more stable against enzymes in the body.”

The aptamers are placed on top of a graphene sensor, which can detect small changes in electrical charge along its surface caused by the presence of pathogens and small molecules.

However, since graphene is a two-dimensional material that is very difficult to bind to other surfaces, a layer of carbon nanomembrane is first placed in between. This membrane, which is just two nanometres thick, sticks tightly to the graphene as a result of intermolecular forces such as van der Waals force. The aptamers are then attached to the membrane.

The technology could be used to detect a range of infectious diseases, said Georgi.