Scientists invent home COVID-19 test using coffee machine capsules

The transition to working from home has had its challenges for all of us, but when your job is to research biological applications for nanotechnology, those trials are a little more complicated than juggling the use of broadband in the household. If excluded from his lab, you can reasonably expect to find an organic chemist Vittorio Saggiomo, from the Bionanotechnology group in Wageningen University and Research in the Netherlands, to have stopped abruptly.

But Saggiomo is a creative and imaginative type, so he started to wonder if he could make good use of common household appliances in the fight against COVID-19. Specifically, could it create a very sensitive and inexpensive home test for the virus? It turns out he could. His team has now posted the idea on a preprint server, ChemArxiv. The document has yet to be reviewed by other scientists.

Currently, there are two main types of COVID-19 test: the PCR test and the lateral flow test (LFT). The reference PCR test checks for the presence of the virus by detecting its genetic material called RNA. But there are very small amounts of viral material in a swab, so the material has to be converted into DNA and amplified before it can be detected. And this is achieved by the “polymerase chain reactionIs what PCR stands for.

The process involves repeated cycles through a temperature range between 50 ° C and 90 ° C. During each cycle, the amount of DNA doubles, so after 30 cycles more than a billion copies of viral material can be created from a single strand of starting material. The amplified material is then detected with fluorescent markers which bind to the viral DNA sequences.

As such, PCR is a very sensitive technique, but it requires specialized materials and equipment to function. This is why the tests are sent to a lab, and it takes a day or two to get the result.

The second common test is the lateral flow test (LFT). These work by detecting fragments of the shells of viral proteins. LFT bands contain antibodies that bind to the virus. These antibodies are marked with tiny particles of gold, which appear in red, allowing you to see them on the test device. The labeled antibodies accumulate in separate bands on the LFT depending on whether the virus is present or not.

LFTs are fast, inexpensive, and easy to use, making them ideal for community and home testing. But they are far from being as sensitive than PCR tests – they will only identify people with a high viral load. This means that many infected people will get a false negative result from these tests.

CoroNaspresso tests

Ideally, we need a home test that is as easy to use as LFTs but as sensitive as the PCR test. An excellent candidate is a method called loop-mediated isothermal amplification (Lampe). It works on very similar principles to PCR, producing multiple copies of the starting genetic material – which you can get from a swab – but has some key advantages.

For example, it can be combined with a convenient “color reading”. When the lamp reaction occurs, it causes an increase in the acidity of the sample. This means that you can add a substance that changes color depending on the pH value in the reaction mixture, providing a visual indication of a positive or negative result. Another advantage is that the lamp reactions are carried out at a fixed temperature (around 65 ° C) instead of needing a constant cycle through a range of temperatures.

Nevertheless, Lamp still needs precise temperature control. Temperature control systems – whether they are in a PCR machine, lamp instrument, or home oven – are typically made with electronic thermostats. However, making and shipping new electronics specially designed for home lamp testing is not practical (especially in the midst of a pandemic). So Saggiomo tried to find a way around it. He discovered substances called phase change materials which absorb energy (heat) while melting and thus maintain a constant temperature.

After finding a wax made of such a material that melted at exactly the required temperature, Saggiomo set out to build a device to house the lamp’s reaction tubes and pieces of wax. This then had to be inserted into another material that could be heated. The perfect case turned out to be staring him in the face as he brewed his morning coffee: the capsules from the Nespresso machine.

The last step was just to find the right way to heat the capsules. After trying the dishwasher (it worked but the samples got lost), the microwave (failed because the tubes overheated and the lids popped out) and cups full of hot water (not enough control over the temperature), Saggiomo settled down on a simple pot of simmering water on a stove. The resulting “CoroNaspresso” device, when tested by other team members, with swabs from six people, correctly identified three cases of COVID-19 (these were a different color from the tests negative).

Covid test at home.
Tweet by @V_Saggiomo

The test, including capsules, phase change wax, and vials to insert genetic material into, would be easy to produce by the millions. People could then take genetic material at home and heat the capsules to get their results. These devices are also inexpensive (around € 0.20), easy to manufacture, easy to use and largely recyclable. Maybe we will see the CoroNespresso tests in our homes soon, don’t confuse them with your usual coffee pods.

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About Jeffery L. Parker

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