Coffee capsules put to use for coronavirus tests

It was an invention born out of frustration, says Vittorio Saggiomo, who works at Wageningen University & Research. Stuck at home during the first pandemic lockdown, Saggiomo saw that there were bottlenecks in testing for the novel coronavirus. What if, he thought, he could help build an option for at-home testing? His solution is a coffee capsule filled with wax. It might not sound like much, but in a preprint that has not undergone peer review, Saggiomo and his collaborators show that the technology can reliably detect the signature RNA sequences of the SARS-CoV-2 virus (ChemRxiv 2021, DOI: 10.26434/chemrxiv.14224481.v1).

The test uses LAMP, which stands for loop-mediated isothermal amplification. Unlike polymerase chain reaction (PCR) tests, which require temperature oscillations to work, LAMP amplifies target nucleic acid sequences—in this case a sequence unique to SARS-CoV-2—using an enzyme that works at a constant temperature of around 65 °C. That makes LAMP-based tests faster and cheaper to run than PCR tests. LAMP is the technology behind the first at-home COVID-19 test to receive an emergency use authorization from the US Food and Drug Administration. That test, however, costs about $50.

“We need lots of innovations to bring the price of diagnostics down,” says Manu Prakash of Stanford University, who is also working on low-cost testing options. “What is the point of having phenomenal tools if only a small portion of people can afford them?” he adds.

With experts worldwide working to reduce the cost of various steps in the LAMP-testing process, Saggiomo decided to work on simplifying the process’s heating step, seeking a way to keep the reaction mixture at a steady 65°C for the 25 min needed for test to run. After trying various options in his home, Saggiomo settled on filling small, aluminum, Nespresso-compatible coffee capsules with a phase-change material rather than their more usual cargo. The inexpensive phase-change material is paraffin based and maintains the right constant temperature because its melting point is between 63 and 65 °C. The coffee capsules are thin enough that when a pod is floated in just-boiled water, the temperature ramps up quickly and starts melting the material. The pod holds a few grams of the waxy substance, which sustains the constant temperature just long enough for the reaction to run.

Each capsule can hold four small vials for running the LAMP reaction, held in place with a 3D-printed holder that Saggiomo made at home. He also added some packaging foam to the outside, which helps the capsule float in the hot water.

Saggiomo admits his coffee capsule tech is just one part of LAMP testing. Samples still need to be taken, processed, and mixed with reagents before the heating stage. In this work, a diagnostic testing team did those steps using leftover sample material from tests they were running in the Netherlands, the results of which were used for comparison. Saggiomo’s LAMP tests matched the results of the diagnostic PCR tests. His team is now trying to make a one-step system that works directly on saliva without extra processing steps.

Vicente Pelechano Garcia’s team at the Karolinska Institute has developed more affordable reagents for SARS-CoV-2 LAMP tests (Sci. Rep. 2021, DOI: 10.1038/s41598-020-80352-8). He thinks the new work is a “nice improvement,” but for home users, more needs to be done to make testing foolproof, something Prakash also mentions. “Making a system where the user cannot make mistakes,” Pelechano Garcia says, “it is not easy.”

In the meantime, Saggiomo has hundreds of capsules at home. These could be used for any type of LAMP test, he says, not just for COVID-19 testing, and he’s already sending them out to people interested in trying his device for themselves.