Nav: Home

A new biosensor for the COVID-19 virus

April 21, 2020

Jing Wang and his team at Empa and ETH Zurich 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 SARS-CoV-2 - 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, 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 in such a way that it could reliably identify a specific virus was born. The sensor will not necessarily replace the established laboratory tests, but could be used as an alternative method for clinical diagnosis, and more prominently to measure the virus concentration in the air in real time: For example, in busy places like train stations or hospitals.

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, or RT-PCR for short, to detect viruses in respiratory infections. This 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.

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 receptors that match specific RNA sequences of the SARS-CoV-2 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. 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 LSPR, short for localized surface plasmon resonance. This is 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.

Heat increases reliability

However, it is important that only those RNA strands that match exactly the DNA receptor on the sensor are captured. This is where a second effect comes into play on the sensor: the plasmonic photothermal (PPT) effect. If the same nanostructure on the sensor is excited with a laser of a certain wavelength, it produces localized heat.

And how does that help reliability? As already mentioned, the genome of the virus consists of only a single strand of RNA. If this strand finds its complementary counterpart, the two combine to form a double strand - a process called hybridization. The counterpart - when a double strand splits into single strands - is called melting or denaturation. This happens at a certain temperature, the melting temperature. However, if the ambient temperature is much lower than the melting temperature, strands that are not complementary to each other can also connect. This could lead to false test results. If the ambient temperature is only slightly lower than the melting temperature, only complementary strands can join. And this is exactly the result of the increased ambient temperature, which is caused by the PPT effect.

To demonstrate how reliably the new sensor detects the current COVID-19 virus, the researchers tested it with a very closely related virus: SARS-CoV. This is the virus that broke out in 2003 and triggered the SARS pandemic. The two viruses - SARS-CoV and SARS-CoV2 - differ only slightly in their RNA. And validation was successful: "Tests showed that the sensor can clearly distinguish between the very similar RNA sequences of the two viruses," explains Jing Wang. And the results are ready in a matter of minutes.

At the moment, however, the sensor is not yet ready to measure the corona virus concentration in the air, for example in Zurich's main railway station. A number of developmental steps are still needed to do this - for example, a system that draws in the air, concentrates the aerosols in it and releases the RNA from the viruses. "This still needs development work," says Wang. But once the sensor is ready, the principle could be applied to other viruses and help to detect and stop epidemics at an early stage.
-end-


Swiss Federal Laboratories for Materials Science and Technology (EMPA)

Related Rna Articles:

New kind of CRISPR technology to target RNA, including RNA viruses like coronavirus
Researchers in the lab of Neville Sanjana, PhD, at the New York Genome Center and New York University have developed a new kind of CRISPR screen technology to target RNA.
Discovery of entirely new class of RNA caps in bacteria
The group of Dr. Hana Cahová of the Institute of Organic Chemistry and Biochemistry of the CAS, in collaboration with scientists from the Institute of Microbiology of the CAS, has discovered an entirely new class of dinucleoside polyphosphate 5'RNA caps in bacteria and described the function of alarmones and their mechanism of function.
New RNA mapping technique shows how RNA interacts with chromatin in the genome
A group led by scientists from the RIKEN Center for Integrative Medical Sciences (IMS) in Japan have developed a new method, RADICL-seq, which allows scientists to better understand how RNA interacts with the genome through chromatin--the structure in which the genome is organized.
Characterising RNA alterations in cancer
The largest and most comprehensive catalogue of cancer-specific RNA alterations reveals new insights into the cancer genome.
A new approach to reveal the multiple structures of RNA
The key of the extraordinary functionality of ribonucleic acid, better known as RNA, is a highly flexible and dynamic structure.
RNA modification -- Methylation and mopping up
Ludwig-Maximilian-Universitaet (LMU) in Munich researchers have discovered a novel type of chemical modification in bacterial RNAs.
New RNA molecules may play a role in aging
Using a new sequencing method, this class of previously invisible RNA molecules were found to be abundantly expressed.
AI reveals nature of RNA-protein interactions
A deep learning tool could help in structure-based drug discovery.
Uncovering the principles behind RNA folding
Using high-throughput next-generation sequencing technology, Professor Julius Lucks found similarities in the folding tendencies among a family of RNA molecules called riboswitches, which play a pivotal role in gene expression.
A new, unified pathway for prebiotic RNA synthesis
Adding to support for the RNA world hypothesis, Sidney Becker and colleagues have presented what's not been shown before -- a single chemical pathway that could generate both the purine and pyrimidine nucleosides, the key building blocks of RNA.
More RNA News and RNA Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.