Millions of people have been tested for the new coronavirus, most using a PCR-based kit, a sensitive method that amplifies SARS-CoV-2 RNA from patient swabs so that tiny amounts of viruses can be detected.
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However, as the pandemic increases, this laboratory workhorse is showing signs of tension, according to research published in the journal ACS Nano.
Today, researchers, including those from the Institute of Environmental Engineering at ETH Zurich in Switzerland, have developed a potentially more precise diagnosis based on photothermal plasmon detection.
The method can detect interactions between molecules on the surface of a metallic nanostructure constructed as a local change in the refractive index.
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Health experts agree that expanded testing is essential to control the spread of COVID-19.
However, testing in many countries has been delayed due to the limited supply of certain reagents and a backlog of samples pending available PCR machines and laboratory staff.
A number of false negative and positive test results have been reported, the researchers said.
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Other methods, such as computed tomography (CT) and culture, do not provide quick or real-time results, they said.
Jing Wang of the Institute of Environmental Engineering, ETH Zurich, and colleagues wanted to develop a faster and potentially more accurate COVID-19 test to detect the SARS-CoV-2 virus, which could be a practical alternative to PCR.
The team fabricated DNA probes that recognized RNA sequences specific to SARS-CoV-2 and attached them to gold nanoparticles.
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When they add pieces of the viral genome, the RNA attached to complementary probes like a zipper is closed.
The team used a laser to heat the nanoparticles, making it more difficult to attach imperfectly matched sequences, thereby reducing false positives.
For example, a “zipper” of missing nucleic acid from a few teeth – indicating a partial offset – would unzip under these conditions.
In this way, researchers could distinguish between SARS-CoV-2 and its close relative, SARS-CoV-1.
The test detected less viral RNA than was found in respiratory swabs within minutes, the researchers said.
Although the test still needs to be tested on intact viral RNA from patient samples, it could help ease the current pressure on PCR-based tests, they said.