New sensor detects pneumonia based on patient’s breath

The development is a portable sensor on a microchip that detects synthetic molecules – so-called biomarkers of diseases. These markers are initially attached to inhaled nanoparticles and are only released when they interact with specific clues, such as enzymes associated with a particular disease. It is assumed that the patient first inhales such nanoparticles – much the same as asthma medications. If a person is healthy, they are excreted from the body unchanged. But when there is an infection, such as pneumonia, enzymes produced during the course of the disease separate the biomarkers from the nanoparticles. These molecules are then exhaled and can be detected by the device, indicating the presence of a disease.

Previously, identifying such biomarkers required sophisticated laboratory equipment that is rarely found in regular medical offices. Now the researchers have shown that their new portable device is capable of detecting such molecules even in very low concentrations. The device is called PlasmoSniff, and in the future they plan to integrate it into a compact diagnostic device that can be used both in clinics and at home. The development is based on a field of science known as Plasmonics – the study of the interaction of light with matter at the nanoscale. The scientists used Raman spectroscopy, which allows them to identify molecules by the characteristic vibrations of their chemical bonds. However, it is not easy to detect the necessary biomarkers because they are very few among the many other molecules in the exhaled air. According to the researchers, it’s like looking for a needle in a haystack.

To solve the problem, the team created a sensor that amplifies the signal of the desired molecules. Its base is a thin gold film coated with a layer of gold nanoparticles with a porous silica shell. There is a gap of only about five nanometers between the particles and the film. The sensor surface is modified to bind to water molecules, which in turn “stick” to the biomarkers. This structure amplifies light through plasmon resonance: electrons in gold nanostructures begin to collectively oscillate under the influence of light, concentrating the electromagnetic field in a microscopic gap. Once there, the biomarkers produce a much stronger signal of scattered light, which can be measured and compared with the characteristic “fingerprint” of a particular molecule.

During the experiments, scientists tested the sensor on samples of lung fluid from healthy mice, adding biomarkers of pneumonia. The samples were heated to simulate exhaled air, and the sensor recorded the molecules passing through it along with the vapor. The results showed that the device was able to rapidly detect biomarkers of pneumonia even at very low concentrations of clinical significance.