Sensor measures virus concentration in the air

Swiss scientists have developed a new type of sensor for detecting the SARS-CoV-2 virus. In future, it could measure the virus concentration in the environment, for example in places where many people are present or in hospital ventilation systems.

Jing Wang and his team at the Swiss Federal Laboratories for Materials Testing and Research (EMPA) and the Swiss Federal Institute of Technology (ETH) in Zurich usually conduct research on measuring, analysing and reducing air pollutants such as aerosols and artificially produced nanoparticles. However, the current challenge currently facing the whole world is also changing the goals and strategies in the research laboratories. The new focus: a sensor that can quickly and reliably identify a specific virus such as SARS-CoV-2 - the new corona virus. 

Background: Most laboratories have so far used a molecular method called "Reverse Transcription Polymerase Chain Reaction", or RT-PCR for short, for their Covid-19 tests to detect viruses in respiratory infections. This method is well established and can already detect tiny amounts of the viruses - but at the same time the tests are often time-consuming.

An optical sensor for RNA samples

Jing Wang and his team 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, so-called gold nanoislands, on a glass substrate. Artificially produced DNA sequences that match certain RNA sequences of the SARS-CoV-2 virus are applied to the nanoislands. The new coronavirus is a so-called RNA virus: Its genome does not consist of DNA double strands, as is the case in humans, animals and plants, but of a single RNA strand. The artificial DNA receptors on the sensor are therefore the complementary sequences to the virus' unique RNA genome sequences that can uniquely identify the virus.

The technology used by the researchers for virus detection is called LSPR ("localized surface plasmon resonance"). This is an optical phenomenon that occurs in metallic nanostructures: In the excited state, these modulate the incident light in a specific wavelength range and create a so-called plasmonic near-field around the nanostructure. When molecules dock on the surface, the optical refractive index in this plasmonic near field changes exactly at this point. This can be measured with an optical sensor located on the back of the sensor and thus determine whether the sample contains the RNA strands you are looking for.
 

1. Sensor measures virus concentration in the air
2. Warmth increases reliability