Researchers at the Paul Scherrer Institute (PSI) and the University of Basel have developed a rapid test for COVID-19 that is reliable, can simultaneously test for the presence of other diseases, and provides information about the patient’s immune response that may inform treatment.
Instead of detecting components of the COVID-19 virus—the method used by often-unreliable rapid antigen tests—the PSI test uses nanofluidics to test for antibodies. The team designed a small Plexiglass plate with three parallel channels. A mixture of blood, nanoparticles with the same structure as COVID-19 spike proteins, and fluorescent particles is injected into one side of the plate. As the capillary effect moves blood and added nanoparticles through the channels, the particles get stuck at predefined locations of varying channel diameter, depending on which pathogens are present in the blood.
If the individual is infected, the stuck particles create a light signal visible under a fluorescence microscope. The more antibodies the patient has formed, the brighter it is. “[Y]ou can use the signal strength to see whether the immune system is reacting well and a mild course can be expected—or whether it might be overreacting, meaning there is a risk of complications,” says Thomas Mortelmans, a doctoral candidate at the Swiss Nanoscience Institute of the University of Basel and first author of the study. The team is also working on a way to use a mobile phone camera to read the signals. “Modern devices are now capable of doing this,” Mortelmans adds.
The test could also be used to simultaneously diagnose other diseases by adding nanoparticles of different sizes and surface structures. “Our vision is a technology with which we can simultaneously diagnose several diseases and variants of COVID and flu reliably, quickly, and inexpensively via mobile phone. Our novel concept is capable of making this a reality,” says Yasin Ekinci, head of the Laboratory for X-ray Nanoscience and Technologies at PSI. He adds that the system is “in principle” similar to Legos, “in which you can combine different components.”
The test is described in a recent edition of ACS Applied Nanomaterials.