'Pathogen Analyzer' a cost-effective alternative to PCR

Researchers from the Fraunhofer Institute for Production Technology IPT, the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB and the Fraunhofer USA - Center for Manufacturing Innovation are developing a COVID-19 test that combines the accuracy of PCR testing with the speed of rapid antigen testing. In future, they believe this assay will be able to simultaneously detect up to 11 other pathogens.

“With our Pathogen Analyzer, we combine the advantages of antigen and PCR testing,” said Daniel Reibert, a scientist at Fraunhofer IPT. “As we detect the genetic material of the viruses directly, as in a PCR test, the results are extremely accurate. However, we use a different method to duplicate the genetic material, which means that the result is available after just 20 to 40 minutes.”

To do this, the researchers printed multiple small hydrogel droplets onto a test chip, which is similar in size to a rapid antigen test; experts call these droplets ‘biosensors’. The sample — which, as with previous tests, is obtained via a nasopharyngeal swab and transferred to a buffer solution — is applied to this chip. The test chip is then heated to 62°C in a compact and mobile analyser.

The buffer solution and the high temperature expose the genetic material of the virus and multiply the nucleic acids for quantitative detection within the biosensors. This reaction takes place at a constant temperature — the heating and cooling of the sample liquid that is biochemically necessary for a PCR test is not required. To receive their personalised test results, patients can connect a smartphone app to the analyser. A light signal in the analyser detects the amount of the pathogen’s genetic material and sends the final result directly to the affected person.

“Each biosensor contains capture molecules that emit fluorescent radiation of a different wavelength when irradiated with light if they have captured the appropriate pathogen. As such, each biosensor is like a small individual test,” Reibert said. Taking a multiplexing approach not only increases the reliability of the results but also makes it possible to detect up to 12 different types of viruses simultaneously using a single sample and a single test chip.

“As we developed the system to be modular, it can be quickly adapted to test for new pathogens.”

One of the challenges was to help develop the subsequent manufacturing processes for the test and ensure that they were inexpensive — ideally costing no more than €1 when mass-produced. For the chip itself, the researchers are relying on roll-to-roll processing. The individual sample biosensors can be printed using either a 3D printer or the established screen printing process.

In the long term, the test could also function without an analyser, being fully usable with just a smartphone. Mobile phones already come equipped with a light source and camera, and the heating element can be integrated into the test chip itself. Then, the researchers hope, the test could provide fast, inexpensive and reliable results not only in central locations such as stadiums or doctors’ offices but also directly at home — and for a wide range of pathogens.

Image caption: The test chip is placed in the analyser after applying the sample. Here it is heated to 62°C so that the reaction can take place. Image ©Fraunhofer IPT.

Please follow us and share on Twitter and Facebook. You can also subscribe for FREE to our weekly newsletters and bimonthly magazine.