It is now possible to turn a coffee cup into a cheap and sustainable COVID-19 test device. This was demonstrated by research conducted by Vittorio Saggiomo, assistant professor in the BioNanoTechnology group (BioNT) of Wageningen University & Research, in collaboration with TNO. The new test system, which was named "CoronaEspresso", is an ordinary aluminium Nespresso-type coffee cup filled with a cheap paraffin-based phase change material. The cup is covered with a 3D-printed sample holder with space for four test samples at a time.
It is a reusable device and the test consists of inserting a small (PCR or LAMP) tube into the CoronaEspresso. Called an Eppendorf tube, this contains a mixture of chemicals and enzymes to which the test sample is added, just like in large-scale testing lanes. For half an hour, the entire unit is placed in water that has just finished boiling. The paraffin warms the samples to 65 degrees and keeps them at that temperature for 25 minutes. This allows a so-called LAMP reaction to take place and, after that time, the result can be read from a colour change in the samples. The test result can be determined without the need for another lab.
LAMP (loop mediated isothermal amplification) is similar to the well-known PCR test but is cheaper, less demanding in terms of laboratory infrastructure, and yields results faster. This makes it possible to work at a constant process temperature. This is in contrast to a closely defined sequence of temperatures and actions required by the current PCR method. Furthermore, that is only possible with special equipment and in well-equipped labs. The CoronaEspresso mini-lab can be used for any RNA/DNA detection using LAMP. In collaboration with microbiologists from TNO in Zeist, the CoronaEspresso has been successfully tested, both with synthetic (SARS-CoV-2) RNA and with real human samples. It proved to be a reliable indicator of the presence or absence of the virus.
Centralised testing not always useful
When the coronavirus spread around the world in early 2020, it soon became clear that extensive testing and source and contact tracing were important in combating the pandemic. At first, efforts focused on centralised, fast-acting facilities and the associated sampling, storage, transport, testing, and other logistical bottlenecks.
“Centralised testing is only useful and feasible in terms of capacity to a certain extent. There were no good alternatives available for more efficient and effective decentralised testing (at home, at school, at work),” Saggiomo explains. “The currently available home tests are antibody-based tests. This is another technique that works particularly well with high virus concentrations, but people with lower virus concentrations will get a negative test result. A LAMP-type test you can take at home that has comparable reliability to the PCR test is of very beneficial. Furthermore, antibody-type tests can only be used once and then they are discarded. That is exactly what we do not want.”
Reusable, recyclable, and inexpensive
In order to use it on a large scale for testing, very little hardware is required for production and the production protocol is very simple. The aluminium cups and the special paraffin are widely available and cheap. CoronaEspresso can also be produced locally at low cost. The aluminium cups are already produced in large quantities and, more importantly, the process and logistics for recycling them are already in place because large quantities of Nespresso-type coffee cups are used worldwide. The phase-transition material is a kind of wax and can be reused in candles and other items. The 3D-printed holder is biodegradable. It is also easy to design alternatives if a 3D printer is not available.
The CoronaEspresso is not a single-use tool: it can be used several times to warm up samples as long as the wax does not come into contact with water and the cup remains undamaged. The researchers think that, in addition to testing at home, the CoronaEspresso is particularly interesting for use in more remote locations, in lower-income countries, etc.
Tested among researchers
The BioNanoTechnology group has now made hundreds of CoronaEspressos and distributed them among researchers who want to try them out. Looking to the future, Saggiomo and co-workers are trying to optimise the sampling (based on nose/throat swabs or saliva) and the practical matters regarding LAMP reaction mixtures.