Since the start of the novel coronavirus pandemic, millions of people have been tested. Most people got tested with a kit that relies on the polymerase chain reaction (PCR), which can detect small amounts of the virus by amplifying the SARS-CoV-2 RNA from the patient. As the pandemic continues, it’s becoming evident that testing methods other than PCR are needed.
Testing is critical for controlling the spread of the COVID-19 disease, but testing has lagged in many countries around the world due to limited reagent supply and not enough PCR machines to run the tests. False positives and negatives have also been an issue. One of the other available methods, computed tomography (CT) scanning doesn’t provide real-time results.
Jim Wang and his team of researchers decided to develop a faster, more accurate test for detecting the SARS-CoV-2 virus. The basis for their test was something called localized surface plasmon resonance, which is the result of the confinement of a surface plasmon in a nanoparticle about the size of the wavelength of light used to excite the plasmon. The researchers made DNA probes that could recognize the novel coronavirus RNA sequences and attached them to gold nanoparticles. Then they added bits of the virus’ genome, and they found that the RNA attached to the probes and created the effect of a zipper closing. Then the researchers heated the nanoparticles with a laser which made it harder for the nanoparticles to remain attached, which in turn reduces false positives. In other words, if the “zipper” is missing some teeth, that indicates a partial mismatch. When heated with the laser, these mismatches would drop off, leaving only true positive results. It also allows the researchers to be able to distinguish SARS-CoV-2 from its cousin, SARS-CoV-1.
The new test was able to detect the virus using respiratory swabs in just minutes. The technique still must be tested on patients with an intact virus. But, according to researchers, this new test could take some of the strain off PCR. The team’s findings are published in ACS Nano.