Real-time monitor can detect SARS-CoV-2 in indoor air within 5 minutes

Now that the emergency phase of the COVID-19 pandemic is over, scientists are looking for ways to monitor indoor environments in real time for viruses. By combining recent advances in aerosol sampling technology and an ultra-sensitive biosensing technique, researchers at Washington University in St. Louis have created a real-time monitor that can detect any of the virus variants. SARS-CoV-2 in a room in about 5 minutes.

The inexpensive, proof-of-concept device could be used in hospitals and healthcare facilities, schools, and public settings to help detect CoV-2 and potentially monitor other respiratory virus aerosols, such as influenza and respiratory syncytial virus (RSV). The results of their work on the monitor, which they say is the most sensitive detector available, are published July 10 in Nature Communication.

The interdisciplinary team of researchers from the McKelvey School of Engineering and School of Medicine consists of Rajan Chakrabarty, Harold D. Jolley Career Development Associate Professor of Energy, Environmental, and Chemical Engineering at McKelvey Engineering; Joseph Puthussery, postdoctoral research associate in Chakrabarty’s lab; John Cirrito, professor of neurology at the School of Medicine; and Carla Yuede, Associate Professor of psychiatry at the faculty of medicine.

There is nothing yet that tells us how safe a coin is. If you’re in a room with 100 people, you don’t want to know five days later whether you might be sick or not. The idea with this device is that you can basically know in real time, or every 5 minutes, if there is a live virus.”

John Cirrito, Professor of Neurology, School of Medicine, Washington University in St. Louis

Cirrito and Yuede had previously developed a microimmunoelectrode (MIE) biosensor that detects beta-amyloid as a biomarker for Alzheimer’s disease and wondered if it could be converted into a sensor for SARS-CoV-2. They contacted Chakrabarty, who assembled a team including Puthussery, who had expertise in building real-time instruments to measure air toxicity.

To convert the biosensor from beta-amyloid detection to the coronavirus, the researchers swapped the antibody that recognizes beta-amyloid for a llama nanobody that recognizes the spike protein of the SARS-CoV-2 virus. David Brody, MD, PhD, a former faculty member in the School of Medicine’s Department of Neurology and author of the paper, developed the nanobody in his laboratory at the National Institutes of Health (NIH). The nanobody is small, easy to replicate and modify, and inexpensive to manufacture, the researchers said.

“The nanobody-based electrochemical approach is faster to detect the virus because it doesn’t need a reagent or many processing steps,” Yuede said. “SARS-CoV-2 binds to nanobodies on the surface, and we can induce tyrosine oxidation on the surface of the virus using a technique called square wave voltammetry to get a measure of the amount of virus in the virus. sample.”

Chakrabarty and Puthussery integrated the biosensor into an air sampler that works based on wet cyclone technology. Air enters the sampler at very high velocities and mixes by centrifugation with the fluid lining the walls of the sampler to create a surface vortex, thereby trapping viral aerosols. The wet cyclone sampler has an automated pump that collects fluid and sends it to the biosensor for transparent virus detection by electrochemistry.

“The challenge with airborne aerosol detectors is that the level of virus in the indoor air is so dilute that it even pushes it towards the polymerase chain reaction (PCR) detection limit and it’s like finding a needle in a haystack,” Chakrabarty said. “The wet cyclone’s high virus recovery can be attributed to its extremely high throughput, which allows it to sample a greater volume of air over a 5-minute sample collection compared to commercially available samplers. “

Most commercial bioaerosol samplers operate at relatively low flow rates, Puthussery said, while the team’s monitor has a flow rate of around 1,000 liters per minute, making it one of the fastest-flowing devices. higher available. It’s also compact at about 1 foot wide and 10 inches tall and lights up when a virus is detected, alerting administrators to increase airflow or circulation in the room.

The team tested the monitor in the apartments of two COVID-positive patients. Real-time PCR results from room air samples were compared to air samples taken from a virus-free control room. The devices detected virus RNA in room air samples but did not detect any in control air samples.

In lab experiments that aerosolized SARS-CoV-2 in a room-sized chamber, the wet cyclone and biosensor were able to detect different levels of airborne virus concentrations after just a few minutes. sampling.

“We’re starting with SARS-CoV-2, but there are plans to also measure influenza, RSV, rhinovirus and other high-profile pathogens that regularly infect people,” Cirrito said. “In a hospital setting, the monitor could be used to measure staphylococci or streptococci, which cause all kinds of complications for patients. It could really have a major impact on people’s health.”

The team is working on the commercialization of the air quality monitor.