Fast, open PCR platform to fight future pandemics

To ensure that we are better equipped to fight pandemics, we need highly sensitive, on-the-spot tests that can indicate the presence of infections as clearly as possible in just a few minutes and transfer the results directly to the decision-makers digitally.

The Fraunhofer Institute for Microengineering and Microsystems IMM and Fraunhofer Institute for Experimental Software Engineering IESE are now developing a rapid test system of this kind as part of the OPEN-POCT project, aiming to combine the sensitivity of PCR tests with the low price point and rapid results of on-the-spot antigen tests that are sold in chemists and supermarkets. Fraunhofer IESE is focusing on data transfer, data security and data ownership, while Fraunhofer IMM is coordinating the project and has responsibility for the hardware and the integration of suitable detection reactions.

“It is not currently possible to use PoC [point-of-care] PCR systems to contain or even prevent a pandemic, because the test kits would have to be available immediately in large quantities and would also have to allow for cheap mass testing; for example, in test centres at airports. The goal of the OPEN-POCT project is to call this apparent dogma into question,” explained Dr Christian Freese, a researcher at Fraunhofer IMM.

“Only a sensitive, rapidly available alternative to PCR testing in the lab that is suitable for use anywhere will make it possible to effectively break chains of infection in the event of an outbreak and to contain a pandemic in its early stages, before the global movement of people makes this impossible.”

The problem is that cost-effective antigen tests that can be produced in large quantities cannot be made available immediately after an outbreak of a new infectious disease that could cause a pandemic — the development time required is simply too long. On the other hand, current PoC PCR tests are up to 30 times more expensive than antigen tests, due to factors including low production volumes, high investment costs, sophisticated logistics solutions and complex microfluidic structures. As a result, they are not suitable for mass testing or for use at the point of care.

“We aim to bring PCR testing out of the lab and into a rapid test system that can be used on the spot for large numbers of tests,” Freese said. “This is why we are designing our solution as an open system to allow multiple manufacturers to produce the components, eg, cartridges and reagents.”

The team’s device, which is only 15 x 15 x 20 cm in size, has a simple design. In addition to a microfluidic cartridge and pump, it includes heating structures and a fluorescence camera as a detector. No expensive components are needed, and the platform can be adapted for use with other viruses.

The researchers also hope to reduce the time needed for the PCR process down to only a few minutes. The problem with this is that the PCR methodology requires two temperatures — the reagents with the sample fluid must be heated and cooled, which is very time-consuming. The heating block in the PCR devices is initially heated to over 90°C so that the DNA strands can be separated. It is then cooled to around 60°C. After this, the virus genome is duplicated: one DNA strand becomes two and in the next stage two become four and so on. This allows the virus to be detected.

To avoid the need for the long-winded process of constant heating and cooling, Freese and his team use two different heat zones — one hot chamber and one cooler chamber. The sample fluid is pumped back and forth between them by means of the pump in the cartridge. The fluid moves from one heat zone to the other in the detection cartridge through loop-shaped microfluidic channels. As a result, it is stretched out, which gives it a large surface-to-volume ratio and, therefore, allows for rapid heat transport.

“This means that the system reaches the necessary temperature for the PCR process quickly and we no longer have to constantly adjust the heat block to the two different temperatures,” Freese said. The researchers’ preliminary tests with purified virus RNA were much quicker than standard PCR lab tests, with results available after only 15 minutes while achieving the same level of sensitivity.

The platform also allows for the digitalised, automated transfer of positive test results directly to the health authorities, which is important to enable a pandemic to be contained quickly. The project partners have drawn up a comprehensive white paper for decision-makers that covers diagnostic and data protection considerations as well as regulatory issues. The team also plans to expand the digital transfer solutions to include a link with Germany’s Corona-Warn-App.

“In principle, this is all about developing an administrative and regulatory ecosystem for a scalable, open, digitalised PoC PCR test system to detect infectious agents that could cause pandemics,” Freese said.

Image caption: The on-the-spot, rapid PCR test system developed by the Fraunhofer IMM with a microfluidic analysis cartridge for the rapid detection of infectious diseases. Image ©Fraunhofer IMM.

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