Scientist brews up home Covid-19 test
TRANSITIONING to working from home and barred from his lab, you might expect the reasearch of organic chemist Vittorio Saggiomo, from the Bionanotechnology group at Wageningen University & Research in the Netherlands, to have come to a grinding halt.
But Saggiomo wondered if he could turn common household appliances to good use in the Covid-19 fight.
More specifically, could he create a cheap, highly sensitive home test for the virus? It turns out he could.
At the moment, there are two main types of Covid-19 test: the PCR test and lateral flow test (LFT). The gold-standard PCR test checks for the presence of the virus by detecting its genetic material, RNA. But the material has to be converted into DNA and amplified before it can be detected, achieved by the “polymerase chain reaction” – what PCR stands for.
The process involves repeated cycling through a range of temperatures between 50°C and 90°C. The amplified material is then detected with fluorescent labels that attach themselves to the viral DNA sequences.
As such, PCR is a highly sensitive technique, but it needs specialist materials and equipment to perform. This is why the tests are sent off to a lab.
The second test is the lateral flow test (LFT). It detects fragments of viral protein shells. Embedded within the strips of the LFT are antibodies that bind to the virus. They are labelled with tiny gold particles, which appear red, allowing you to see them on the test device.
The LFTs are fast, cheap and easy to use but nowhere near as sensitive as the PCR tests – they will only identify people with high viral loads. Thus many infected people will get a false negative result.
Ideally, we need a home test that’s as easy to use as the LFT but as sensitive as the PCR test. An excellent candidate is the loop-mediated isothermal amplification (Lamp)method. It works along similar principles to PCR, but has some key advantages. When the Lamp reaction occurs, it increases in the acidity of the sample.
That means you can add a substance that changes colour according to pH value, providing a visual indication of a positive or negative result. Another advantage is that Lamp reactions are carried out at a fixed temperature (65°C) instead of a range of temperatures. Nevertheless, Lamp still needs fine temperature control. But making and shipping new electronic thermostats designed for home Lamp tests is impractical (especially amid a pandemic).
So Saggiomo tried to find a way around this. He hit upon substances called phase change materials, that absorb energy (heat) as they melt and so maintain a constant temperature.
After finding a wax that melted at exactly the required temperature, Saggiomo constructed a device to house the Lamp reaction tubes and wax. This needed to be inserted into some other material that could be heated. The perfect housing turned out to be … Nespresso coffee machine capsules.
The final step was finding the right way to heat the capsules. After trying the dishwasher, microwave oven and cups of hot water, Saggiomo settled on a pan of simmering water on a stove top. The resulting “CoroNaspresso” device, when testing swabs from six people, correctly identified three Covid-19 cases (these had a different colour to the negative tests).
The test would be easy to produce in millions. People could then swab for genetic material at home and heat the capsules to get their results. These devices are cheap (€0.20) (about R3.40), easy to make, easy to use and largely recyclable. Maybe we’ll see the CoroNespresso tests in our homes soon.