Researchers at the Swiss Federal Labs for Materials Science (EMPA), ETH Zurich, and Zurich University Hospital are investigating whether an optical sensor tested on SARS could be used to reliably detect COVID-19 in the air in real time. The sensor combines an optical and thermal effect to detect the virus safely and reliably.
According to a an EPMA press release, the sensor is based on tiny structures of gold, so-called gold nanoislands, on a glass substrate. Artificially produced DNA receptors that match specific RNA sequences of the virus are grafted onto the nanoislands. The coronavirus is a so-called RNA virus: Its genome does not consist of a DNA double strand as in living organisms, but of a single RNA strand. Receptors on the surface of the sensor are therefore the complementary sequences to the virus' unique RNA sequences, which can reliably identify the virus.
The technology used for detection is localized surface plasmon resonance (LSPR), an optical phenomenon that occurs in metallic nanostructures. When excited, they modulate the incident light in a specific wavelength range and create a plasmonic near-field around the nanostructure. When molecules bind to the surface, the local refractive index within the excited plasmonic near-field changes. An optical sensor located on the back of the sensor can be used to measure this change and thus determine whether the sample contains the RNA strands in question.
In contrast, most laboratories use a molecular method called reverse transcription polymerase chain reaction, (RT-PCR for short), to detect viruses in respiratory infections. This method is well established and can detect even tiny amount of viruses, but at the same time it can be time consuming and prone to error.
The researchers are also investigating whether results from their method could be made more reliable by exciting the sensor with a laser beam, producing localized heat, which would enable the sensor to distinguish between two viruses with similar RNA sequences. The process is described in the press release.
Additional development work is needed before the sensor is ready to measure the corona virus concentration in the air. But researchers say that once ready, the principle could be applied to other viruses and help detect and stop epidemics at an early stage.
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