SARS-CoV-2 aerosol detected indoors by air monitors in minutes

The importance of detecting viral aerosols, especially SARS-CoV-2, was brought to the forefront during the novel coronavirus disease (COVID-19) pandemic. To date, techniques for detecting viruses in indoor environments have been limited, require long turnaround times, and require skilled labor.

Now, researchers report creating a real-time monitor that can detect the SARS-CoV-2 virus (and its variants) indoors in about five minutes by combining aerosol sampling and ultrasensitive biosensing techniques. there is This proof-of-concept device could help detect SARS-CoV-2 in hospitals and healthcare facilities, schools and public places, and could help monitor other respiratory virus aerosols such as influenza and respiratory syncytial virus (RSV). .

This work, Nature Communications In newspapers,Real-time environmental monitoring of SARS-CoV-2 aerosols“

“At the moment, there is nothing to indicate how safe the room is,” said Dr. John Silito, professor of neurology at the Washington University School of Medicine in St. Louis. “If you’re in a room with 100 people, he doesn’t want to know five days later if he’s sick. means that we can know every five minutes.”

Cirrito et al. had previously developed a microimmunoelectrode (MIE) biosensor to detect amyloid-beta as a biomarker for Alzheimer’s disease. They wondered if it could be converted into a detector for SARS-CoV-2. To convert a biosensor that detects amyloid-beta into a coronavirus, the researchers swapped an antibody that recognizes amyloid-beta with a llama nanobody that recognizes the spike protein of the SARS-CoV-2 virus.

“Nanobody-based electrochemical approaches are faster for virus detection because they do not require reagents or many processing steps,” said Dr. Carla Yuede, associate professor of psychiatry at the School of Medicine. “SARS-CoV-2 can bind to surface nanobodies and induce oxidation of tyrosines on the virus surface using a technique called square-wave voltammetry to measure the amount of virus in a sample.”

A biosensor was integrated into an air sampler that operates based on wet cyclone technology. Air enters the sampler at very high velocity and is centrifugally mixed with the liquid lining the walls of the sampler to create surface vortices, thereby trapping viral aerosols. The Wet Cyclone Sampler has an automated pump that collects and delivers liquid to a biosensor and uses electrochemistry to seamlessly detect viruses.

“The challenge for airborne aerosol detectors is that the levels of viruses in indoor air have become so dilute that they are approaching the limits of polymerase chain reaction (PCR) detection, like finding a needle in a haystack. is,” said Rajan Chakrabarti. , Ph.D., Associate Professor of Energy, Environmental and Chemical Engineering at McKelvie Engineering. “The high virus recovery rate with the wet cyclone is likely due to the very high flow rate, which allows a larger volume of air to be sampled in a 5-minute sample collection compared to commercial samplers. increase.”

The team’s monitor has a flow rate of about 1,000 liters per minute, one of the highest flow devices available. It’s also compact, at about 1 foot wide and 10 inches tall, and lights up when a virus is detected to alert administrators to increase airflow and circulation in the room.

The team tested the monitors in the apartments of two COVID-19 positive patients. Real-time PCR results of air samples from bedrooms were compared to air samples collected from virus-free control rooms. The device detected viral RNA in air samples from bedrooms, but none in control air samples.

In laboratory experiments in which SARS-CoV-2 was aerosolized into a room-sized chamber, wet cyclones and biosensors were able to detect varying levels of airborne virus concentrations after just a few minutes of sampling. More specifically, this experiment demonstrates that the device has a sensitivity of 77-83% and a detection limit of 7-35 viral RNA copies/m.³ of air.

“We’re starting with SARS-CoV-2, but we also have plans to measure influenza, RSV, rhinovirus, and other major pathogens that infect people on a daily basis,” said Sirito. “Hospitals can use this monitor to measure staphylococci and streptococci that cause all sorts of complications in patients. The team is working on commercializing an air quality monitor.