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(Nanowerk News) The quantum sensing capabilities of nanodiamonds can be used to improve the sensitivity of paper-based diagnostic tests, potentially enabling early detection of diseases such as HIV, according to a study by UCL researchers in the i-sense McKendry group.
Lateral flow tests on paper work the same way as a pregnancy test in that a strip of paper is dipped in a sample of fluid and a change in color – or fluorescent signal – indicates a positive result and protein detection. viral or DNA. They are widely used to detect viruses ranging from HIV to SARS-CoV-2 (lateral flow tests for Covid-19 are currently being tested across England) and can provide a quick diagnosis, as the results do not they must be processed in a laboratory.
The new research, published in Nature (“Biosensing with spin-enhanced nanodiamonds for ultra-sensitive diagnostics”), found that low-cost nanodiamonds could be used to signal the presence of an HIV disease marker with a sensitivity many thousands of times greater than gold nanoparticles widely used in these tests.
This increased sensitivity allows for lower viral loads to be detected, meaning the test could detect lower levels of disease or detect disease at an early stage, which is critical for reducing the risk of transmitting infected individuals and for effective treatment. of diseases such as HIV.
The research team is working to adapt the new technology to test for COVID-19 and other diseases in the coming months. A key next step is the development of a portable device that can “read” the results, as the technique was demonstrated using a microscope in a laboratory. Further clinical evaluation studies are also planned.
Lead author, Professor Rachel McKendry, professor of biomedical nanotechnology at UCL and director of i-sense EPSRC IRC, said: “Our proof-of-concept study shows how quantum technologies can be used to detect levels ultra low levels of viruses in a patient sample, allowing for very early diagnosis.
“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 working to adapt our approach to COVID-19. We believe this new transformative technology will go to benefit patients and protect populations from infectious diseases “.
The researchers used the quantum properties of nanodiamonds produced with a precise imperfection. This defect in a diamond’s highly regular structure creates what is called a nitrogen vacuum (NV) center. NV centers have many potential applications, from fluorescent biomarking for use in ultra-sensitive imaging to information processing qubits in quantum computing.
NV centers can signal the presence of an antigen or other target molecule by emitting bright fluorescent light. In the past, fluorescent markers were limited by background fluorescence, sample or test strip, making it more difficult to detect low concentrations of viral proteins or DNA that would indicate a positive test. However, the quantum properties of fluorescent nanodiamonds allow for selective modulation of their emission, which means that the signal can be fixed at a set frequency using a microwave field and can be effectively separated from the background fluorescence, addressing this limitation.
The optical results showed an improvement in sensitivity of up to five orders of magnitude (100,000 times) over gold nanoparticles (i.e., far fewer nanoparticles were required to generate a detectable signal). With the inclusion of a short 10-minute constant-temperature amplification step, in which copies of RNA were multiplied, the researchers were able to detect HIV RNA at the level of a single molecule in a sample model.
The work has been demonstrated in a laboratory setting, but the team hopes to develop the tests so that the results can be read with a smartphone or portable fluorescence reader. This means that testing could, in the future, be performed in low-resource contexts, making it more accessible to users.
First author, Dr Ben Miller (i-sense Postdoctoral Research Associate at the London Center for Nanotechnology at UCL) said: “Lateral flow tests on paper with gold nanoparticles do not require laboratory analysis, making them particularly useful in environments with few resources and where access to 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 the signal from the unwanted background fluorescence of the test strip, greatly improving sensitivity. ”
Co-author, Professor John Morton, director of UCL’s Quantum Science and Technology Institute (UCLQ), said, “This interdisciplinary collaboration between UCLQ and LCN’s i-sense team is a fantastic example of how fundamental work on quantum systems, such as the NV Center in Diamond, can evolve from the laboratory and play a crucial role in real-world applications in sensing and diagnostics. UCLQ researchers are exploring and enabling the impact of these and other quantum technologies by working with industry and other academic research groups. ”
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