Super-rapid COVID test uses new technology

Sticking swabs up our noses and down our throats to confirm or deny whether we’re infected with the coronavirus—almost all of us have done it multiple times over the past few years.

The methods used to detect and prevent the spread of the virus were the same around the world, either:

• the expensive, time-consuming but very accurate PCR method, which detects the DNA of the virus in our mucous membranes, or
• the simpler and faster method that only indicates whether we have developed antibodies against the virus.

Ultra-fast detection

However, both methods have their weaknesses. The PCR method is expensive and time-consuming, while the antibody method says nothing about whether we actually have the virus in our bodies. A simple and inexpensive method of detecting the virus that gives a quick result would therefore be helpful.

Now researchers from NTNU, Oslomet and the University of Tabriz in East Azerbaijan have demonstrated a method to detect coronavirus in blood samples using nanosensors.

“Much of the research is focused on finding methods for rapidly isolating infected individuals that can break the chain of infection. Nanosensors have attracted a lot of attention due to their unique properties for ultra-fast detection of particles like viruses,” says Amir Maghoul. He is a researcher and first author of the article “An Optical Modeling Framework for Coronavirus Detection Using Graphene-Based Nanosensor”. When he started his work, he was a postdoctoral fellow at NTNU.

A first step towards developing a separate nanosensor for the coronavirus is to identify the optical properties that distinguish the coronavirus from other particles in our blood.

Ingve Simonsen, physics professor at NTNU, explains. Most people have seen the coronavirus as a round nucleus or ball with red “spikes” or protruding stalks. “We wanted to see what role the length and size of these ‘spikes’ play in how the cells reflect light and whether the size of the nucleus plays a role,” says Simonsen.

Suppresses resonance

To find answers to their questions, the researchers used mathematical models. The optical behavior of the virus – i.e. how the virus cell reflects light in the form of resonance – was simulated and analyzed across the entire light spectrum.

“We observed that reflectivity varies with the length of the spike proteins. As the length of the spikes increases, the reflectivity decreases, while at the same time the resonance shifts to higher wavelengths,” says Simonsen.

The researchers observed the same response when they varied the size of the virus core in the models. The width of the spike protein had less of an impact on how the light was reflected. In this way, the researchers were able to find out in which part of the wavelength spectrum the coronavirus differs from other particles in the blood.

“At certain wavelengths, we get a different optical response depending on whether viruses are present or not. We call this the optical signature of the corona virus,” says Simonsen.

“We know that the optical properties of particles change depending on their environment. They behave differently when they are in water or in a vacuum, when several particles are next to each other, or when the surface is covered with a thin layer of another substance.”

Example pregnancy test

In 1908, the German scientist Gustav Mie first described in general terms how spherical particles reflect light waves.

“As is well known, ordinary light consists of a spectrum of wavelengths. This is what we see when we look at a rainbow or when light passes through a glass prism. The light hits water molecules in the atmosphere or in the prism and is reflected in the different wavelengths of light that we see as the color spectrum,” says Simonsen.

Mie showed how small spheres or nuclei react differently to light.

“For example, small metal particles have a very strong optical response. This property is used in certain types of pregnancy tests that measure the optical response to small gold particles,” says Simonsen.

“The hormone you’re looking for in your urine – which you only have when you’re pregnant – collects on the surface of the gold particle on the test stick and changes the particle’s resonant frequency. The result is a color change to blue, showing you’re pregnant.”

Example rose painting

Another example of how small particles react to light can be seen in stained glass, such as in the large rose window in Nidaros Cathedral. The bold red, blue and green colors are all the result of the optical reaction of the metal particles used in the glass. And it is this property that can be used to detect coronaviruses in blood samples.

“What you’re doing is placing a network of thin, cylindrical gold particles over a very thin layer of graphene. Graphene is a nanomaterial with many intriguing properties, including the fact that it conducts electricity well and with low losses.”

When blood containing the coronavirus flows over the gold particles, the particles’ resonant frequency changes, which in turn creates an electromagnetic field. This field builds up a current in the sensor that can be easily measured.

“By examining the current curves for certain frequency ranges of the incident light, we can determine whether the blood contains corona viruses or not,” says Simonsen.

Great potential for nanotechnology

Nanosensors have the potential to be very sensitive. The “smart” graphene material in the nanodisk acts as an amplifier, explains Amir Maghoul.

“Nanotechnology has not been used for this type of sensor before, so this development is new technology. What we’ve done here is to create the first optical framework for detecting coronavirus and showing how the virus behaves in the optical spectrum,” says Maghoul.

The next step is to set up a company that can develop a laboratory prototype for the nanosensor.

“We need to raise money so we can go ahead and develop a sensor for general use. The collaboration between NTNU and Oslomet has shown that if the work is funded, we have facilities with significant potential to develop and manufacture this type of nanosensor for biomedical use,” says Maghoul.