Blood tests for Covid-19 could be made “up to 100,000 times more sensitive” by using nanodiamonds

Pregnancy-style tests for diseases like Covid-19 and HIV may soon be updated with built-in “nanodiamonds” that improve their sensitivity by up to 100,000 times.

While PCR swabs are currently the most common way to test for coronavirus infection, other diagnostic methods are also under development.

These include “lateral flow” tests that work in the same way as pregnancy tests, in that they can detect virus proteins in body fluids, such as blood or urine.

Traditionally, lateral flow tests use gold nanoparticles, which absorb light and produce a red line to indicate a positive result.

However, the researchers say that replacing gold with diamond nanoparticles would result in this line emitting a bright fluorescent light, which is easier to detect, making the test up to 100,000 times more sensitive.

UCL researchers working on the project say this method, which is still in its early stages, could allow for early diagnosis and rapid treatment.

Paper lateral flow tests using gold nanoparticles are already in use as a method to rapidly diagnose HIV and are in the early stages of a preliminary study to see if they can detect SARS-CoV-2, the virus that causes Covid. -19 infection.

Hopefully these will be able to quickly provide a positive or negative result without the need for complex laboratory analysis.

However, diamonds can be designed to have a very slight and precise flaw in their rigid structure.

This deliberate “mistake” creates a so-called nitrogen vacuum center, which allows the diamond particle to shine. This unique property is currently being investigated in several fields, including biomarking and quantum computers.

In disease testing, these light-emitting vacuums shine brightly in a straight line when the diamond binds to a target molecule, such as viral antigen.

This glow is much brighter than the gold-impregnated test line, but it has another advantage; The quantum glow of the nanodiamond can also be easily distinguished from the background fluorescence.

This filters out the noise and amplifies the diamond’s signal, making the tests up to 100,000 times more sensitive than current methods in early tests, the researchers say.

UCL scientists have found that diamonds can be given a positive result by a single molecule of HIV genetic material after ten minutes of amplification.

Lead author, UCL Professor Rachel McKendry, said: ‘We have focused on HIV detection, but our approach is very flexible and can be easily adapted to other diseases and types of biomarkers.

‘We are already working to adapt our approach to Covid-19. We believe this new transformative technology could benefit patients and protect populations from infectious disease through much earlier disease diagnosis. “

Current methods are at the forefront of scientific innovation, but the researchers hope to miniaturize the technology so that it can be easily accessed.

They are now focusing on being able to read the bright diamond tests with a smartphone or portable fluorescence reader.

First author, Dr Ben Miller of UCL, said: “Lateral flow tests on paper with gold nanoparticles do not require laboratory analysis, which makes them particularly useful in contexts with few resources and where access. health care is limited.

‘They are low cost, portable and easy to use. However, these tests currently lack the sensitivity to detect very low levels of biomarkers.

“By replacing commonly used gold nanoparticles with fluorescent nanodiamonds in this new design and selectively modulating their (already bright) light output, we were able to separate their signal from the unwanted background fluorescence of the test strip, greatly improving the sensitivity. “

The full results are published in the journal Nature.