A novel approach to testing for the presence of the virus that causes Covid-19 may result in tests that are faster, less expensive, and potentially less prone to mistakes than current detection methods. Though the work, which is based on quantum effects, is still theoretical, the researchers believe that these detectors could be adapted to detect virtually any virus.
Changhao Li, an MIT doctoral student, Paola Cappellaro, a professor of nuclear science and engineering and physics, and Rouholla Soleyman and Mohammad Kohandel of the University of Waterloo describe the new approach in a paper published on December 16, 2021, in the journal Nano Letters.
Rapid tests that detect specific viral proteins and polymerase chain reaction (PCR) tests that take several hours to process are presently available for the SARS-CoV-2 virus. Neither of these tests can accurately determine the amount of virus present. Even gold-standard PCR tests may have a false-negative rate of more than 25%. In contrast, the team’s analysis indicates that the new test could have false negative rates of less than 1%. The test may also be sensitive enough to detect a few hundred strands of viral RNA in less than a second.
The new method makes use of nitrogen vacancy (NV) centres, which are atomic-scale defects in tiny bits of diamond. Because of quantum effects occurring in the diamond’s crystal lattice, these tiny defects are extremely sensitive to minute perturbations and are being investigated for a wide range of sensing devices that require high sensitivity.
The new method would involve coating the nanodiamonds containing these NV centres with a magnetically coupled material that has been treated to bond only with the virus’s specific RNA sequence. When virus RNA binds to this material, it disrupts the magnetic connection and causes changes in the fluorescence of the diamond that are easily detected with a laser-based optical sensor.
The sensor uses only low-cost materials (the diamonds involved are smaller than specks of dust), and the devices could be scaled up to analyze a whole batch of samples at once, the researchers say. The gadolinium-based coating with its RNA-tuned organic molecules can be produced using common chemical processes and materials, and the lasers used to read out the results are comparable to cheap, widely available commercial green laser pointers.
While this initial work was based on detailed mathematical simulations that proved the system can work in principle, the team is continuing to work on translating that into a working lab-scale device to confirm the predictions.
