US Pharm. 2020;45(5):HS-15-HS-16.

 A team of researchers from Empa, ETH Zurich, and Zurich University Hospital has succeeded in developing a novel sensor for detecting the new coronavirus. In the  future, it could be used to measure the concentration of the virus in the environment—for example, in places where there are many people or in hospital ventilation systems.

Dr. Jing Wang and his team at Swiss Federal Laboratories for Materials Science and Technology and ETH Zurich, Switzerland, usually work on measuring, analyzing, and reducing airborne pollutants such as aerosols and artificially produced nanoparticles. However, the challenge the whole world is currently facing is also changing the goals and strategies in the research laboratories. The new focus: a sensor that can quickly and reliably detect the new coronavirus.

But the idea is not quite so far removed from the group’s previous research work: Even before the COVID-19 began to spread, first in China and then around the world, Dr. Wang and his colleagues were researching sensors that could detect bacteria and viruses in the air. As early as January, the idea of using this basis to further develop the sensor to reliably identify a specific virus was born.

Fast and reliable tests for the new coronavirus are urgently needed to bring the pandemic under control as soon as possible. Most laboratories use a molecular method called reverse transcription polymerase chain reaction to detect viruses in respiratory infections. This is well established and can detect even tiny amounts of viruses but can be time-consuming and prone to error.

Dr. Wang and his colleagues have developed an alternative test method in the form of an optical biosensor. The sensor combines two different effects to detect the virus safely and reliably: an optical and a thermal one. The sensor is based on tiny structures of gold, called gold nanoislands, on a glass substrate. Artificially produced DNA receptors that match specific RNA sequences of COVID-19 are grafted onto the nanoislands. The coronavirus is an RNA virus. Its genome does not consist of a DNA double strand as in living organisms, but of a single RNA strand. The receptors on the sensor are therefore the complementary sequences to the virus’ unique RNA sequences, which can reliably identify the virus.

The technology the researchers use for detection is called localized surface plasmon resonance, 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.