Who doesn't know it? The throat is scratchy, a feeling of listlessness spreads. Have you been infected with Corona? You can quickly check this at home using rapid antigen tests -– but the accuracy of these tests leaves a lot to be desired. Many infections remain undetected, and false positive results can also occur. For reliable detection, a PCR test is indispensable, but this is both much more expensive and more time-consuming.
Fast and reliable results
A network of researchers from the Fraunhofer Institute for Production Technology IPT, the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB and the Fraunhofer Center for Manufacturing Innovation CMI in Boston (USA) now wants to change this. The three institutes are jointly developing thea Pathogen Analyzer SECURIGEL (Fig. below left) and combine the advantages of antigen and PCR tests: speed and accuracy.
Amplification at constant temperature
To amplify the genetic material, the institutes use a different method than the PCR test. The result is now available after about 30 minutes. The core of the technology is the encapsulation and on-chip storage of pathogen-specific diagnostics using RT-LAMP (reverse transcription loop-mediated isothermal amplification) in a patented, printable hydrogel (Fig. below middle). The reaction for amplifying the viral RNA takes place at a constant temperature of 62 °C –- the heating and cooling of the sample liquid required in PCR is not necessary.
Multiplexing by hydrogel
For this purpose, we at Fraunhofer IGB and Fraunhofer CMI have printed numerous small hydrogel droplets on a test chip similar in size to a rapid antigen test (Fig. below middle). These biogel nanosensors are arranged in 1500 individual 500 pL spots, with 500 additional spots each for simultaneous positive and negative controls, which increases the accuracy and reliability of the results. The hydrogel was optimizsed at the Fraunhofer IGB for the adhesion of the droplets to the chip surface and the reaction for a correct test result. Accordingly, our hydrogel (Fig. below right and above right) is characterizsed by five features: Spatial multiplexing capability, lower detection limits, on-chip storage of reagents, longer shelf life and scalability. The key advantage of our approach is a simplified sample preparation and discretizsation –- i.e. obtaining finitely many ("discrete") data from a continuous flow of information –- of RT-LAMP to significantly reduce false positives.
Parallel detection of multiple pathogens
On the one hand, such a multiplexing approach increases reliability; on the other hand, it makes it possible to detect up to twelve different types of viruses simultaneously with one sampling and one chip. Since we developed the system as a modular system, it can be quickly adapted to new pathogens and thus new situations.