Researchers develop a faster, more accurate COVID-19 test

Millions of people have been tested for the novel coronavirus, most using a kit that relies on the polymerase chain reaction (PCR). This sensitive method amplifies SARS-CoV-2 RNA from patient swabs so that tiny amounts of the virus can be detected. However, as the pandemic surges, this laboratory workhorse is showing signs of strain. Now, researchers reporting a proof-of-concept study in ACS Nano have developed a potentially more accurate diagnostic based on plasmonic photothermal sensing.

Health experts agree that expanded testing is crucial for controlling the spread of COVID-19. However, testing in many countries, including the U.S., has lagged behind because of limited supplies of some reagents and a backlog of samples awaiting available PCR machines and laboratory personnel. In addition, a number of false-negative and -positive test results have been reported. Other methods, such as computed tomography (known as "CT") scanning and culturing, do not provide quick or real time results. Jing Wang and colleagues wanted to develop a faster, potentially more accurate COVID-19 test for detecting the SARS-CoV-2 virus that could be a practical alternative to PCR.

The researchers based their test on a technique called localized surface plasmon resonance, which can detect interactions between molecules on the surface of a constructed metallic nanostructure as a local change in refractive index. The team made DNA probes that recognized specific SARS-CoV-2 RNA sequences and attached them to gold nanoparticles. When they added pieces of the virus's genome, the RNA attached to the complementary probes like a zipper being closed. The team used a laser to heat up the nanoparticles, making it more difficult for imperfectly matched sequences to remain attached, reducing false-positives.

For example, a nucleic acid "zipper" missing a couple of teeth -- indicating a partial mismatch -- would unzip under these conditions. In this way, the researchers could discriminate between SARS-CoV-2 and its close relative, SARS-CoV-1. The assay detected amounts of viral RNA below those present in respiratory swabs in a matter of minutes. Although the test still needs to be tested on intact viral RNA from patient samples, it could help relieve the current pressure on PCR-based tests, the researchers say.

Source:
Journal reference:

Qiu, G., et al. (2020) Dual-Functional Plasmonic Photothermal Biosensors for Highly Accurate Severe Acute Respiratory Syndrome Coronavirus 2 Detection. ACS Nano. doi.org/10.1021/acsnano.0c02439.

Comments

  1. Christian Schoen Christian Schoen United States says:

    I was on a presentation for the CDC on new and upcoming technologies related to quickly detecting COVID 19.  This new technology called Plasmonic PCR uses gold nanoparticles (gold nanorods) as nanoheaters in the PCR reaction mixture to decrease the required PCR cycle times to less than a few seconds.  It can be used in LAMP, RT-PCR and conventional PCR modes.  The technology is described as being safer since samples can be prepared without handling, and that conventional fluorophores are no longer needed for quantitation.  The instrument is lightweight and can run on batteries since the bulky thermal heaters are no longer necessary.  They have published in multiple journals and are looking for partners to accelerate production.  Lets hope this new instrument can find its way to the point of care quickly.

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