Pathogen Analyzer Combines Advantages of Antigen and PCR Testing

Rapid antigen tests can quickly provide results at home or at a testing site although the accuracy of these tests leaves a lot to be desired. Protein-based tests, where viral antigens are recognized on the chip, are simply not as accurate as nucleic acid-based tests. In other words: Many infections go undetected and false positive results are also possible. A PCR test is needed to get a reliable result; however, this is both significantly more expensive and more time consuming – it can take up to two days for the result to be available. This dilemma over choosing between speed and accuracy could soon become a thing of the past.

A group of researchers from the Fraunhofer Society (Munich, Germany) has developed a Pathogen Analyzer that combines the advantages of antigen and PCR testing to deliver fast and reliable results. Since the Pathogen Analyzer detects the genetic material of the viruses directly, as in a PCR test, the results are extremely accurate. However, it uses 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 degrees Celsius in a compact and mobile analyzer. 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 personalized test results, patients can connect a smartphone app to the analyzer. A light signal in the analyzer detects the amount of the pathogen’s genetic material and sends the final result directly to the affected person.

Another innovative feature of the Pathogen Analyzer is that it can simultaneously detect 12 types of viruses in a single sweep. 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. In the long term, the test should also function without an analyzer, being fully usable with just a smartphone: Cellphones 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.

One of the challenges was to help develop the subsequent manufacturing processes for the test and ensure that they were inexpensive – after all, the test should not cost more than one euro when mass-produced. For the chip itself, the researchers are therefore relying on roll-to-roll processing. The individual sample biosensors can be printed using either a 3D printer or the established screen printing process.

“As we developed the system to be modular, it can be quickly adapted to test for new pathogens,” said Daniel Reibert, a scientist at Fraunhofer IPT. “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.”

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