Researchers at Eindhoven University of Technology in The Netherlands and Keio University in Japan have developed a paper-based diagnostic test, which can be used to rapidly and inexpensively test for a variety of infectious diseases. A clinician can apply a drop of blood to the paper strip and detect the color of the emitted light using a smartphone camera, revealing if a patient has a specific infection, such as flu, HIV, or dengue fever.
In low-resource settings, such as remote areas in developing countries, healthcare workers often struggle to provide adequate healthcare. If they suspect that someone has an infectious disease, often the only way to confirm their diagnosis is to take a blood sample, transport it back to the nearest hospital lab, perform expensive lab tests, and then travel back to the patient to provide medication.
Researchers have dedicated significant efforts towards developing point-of-care diagnostic tests, which rapidly and inexpensively provide a clear answer for clinicians out in the field. This international research collaboration has developed such a diagnostic device, made using mostly paper. While paper might seem like an unusual choice, it is inexpensive and readily absorbs blood samples.
The device tests for the presence of antibodies to specific pathogens in the blood, and is simple to use. A clinician applies a drop of blood, waits 20 minutes, and then uses a smartphone camera to measure a color change. “A biochemical reaction causes the underside of paper to emit blue-green light,” said Maarten Merkx, a researcher involved in the study. “The bluer the color, the higher the concentration of antibodies.”
The paper is laced with a luminous sensor protein that emits blue light when it encounters blood, but in a second step this is converted to green light. However, if the blood contains a specific antibody, such as an antibody against the flu that might be present during a flu infection, it will bind to the sensor protein. This prevents the blue light from being converted to green. Therefore, lots of antibodies in the blood means that the light is mostly blue, whereas greener light indicates very few antibodies.
A smartphone camera can calculate the ratio between the blue and green light, helping a clinician to work out the concentration of an antibody in the blood. So far, the team has made a prototype that can test for three infections at once – flu, dengue fever, and HIV. The researchers hope that the test will be available commercially within a few years.
Study in Angewandte Chemie: Paper‐Based Antibody Detection Devices Using Bioluminescent BRET‐Switching Sensor Proteins…
Photos credit: Bart van Overbeeke