Basu with 3D models of nasal passages
Assistant professor Saikat Basu of the Department of Mechanical Engineering is using his expertise in aerosol modeling to help design a mask with a reusable respirator that will actively capture and inactivate the coronavirus-carrying aerosol droplets.

Experience in modeling aerosol sprays designed to treat chronic sinus problems puts assistant mechanical engineering professor Saikat Basu in a unique position to tackle COVID-19. He is part of a multi-institutional team of researchers who will design and develop a mask with a reusable respirator that captures coronavirus-carrying droplets and kills the virus.

Basu was the first South Dakota State University faculty member to receive a grant for COVID-19 research through the National Science Foundation’s Rapid Response Research funding mechanism.  

“We envision the respirator will be a removable piece that can be washed each day and then reused,” explained Basu. To develop this respirator, he is collaborating with associate professor Sunghwan “Sunny” Jung of Cornell University and associate professor Leonardo Chamorro of the University of Illinois Urbana-Champaign. The project, which began in May, is supported by a $200,000 NSF grant.

Since April 2016, Basu has been modeling aerosol sprays designed to help patients with chronic sinus problems with a research group at the University of North Carolina Chapel Hill Medical School. He has published more than a dozen peer-reviewed journal papers on intranasal transport, topical drugs and nasal surgeries.

Mask on child, pig nostrils, mask on flexible nose in graphic
The internal structure of a new respirator mask designed to trap and kill coronaviruses will be modeled after the nasal passages of animals that have a sensitive sense of smell.

Developing virus-killing respirator

The new respirator will filter the air a wearer breathes, Basu explained. As one breathes, the respirator will actively capture and inactivate the virus-carrying aerosol droplets.

In contrast, N95 respirators use passive filters to prevent wearers from inhaling airborne particles. “They do nothing to kill the virus,” he pointed out. The new designs for the mask filter will also be more breathable and, hence, more comfortable to wear than the currently available face coverings.

The new respirator filter will have an internal structure modeled after the complex nasal passages of animals, such as pigs and rodents, which have a very sensitive sense of smell. This unique design will help isolate the droplets and embed them in the respirator, Basu explained. He will do 3D modeling of human breathing to figure out the best possible respirator design. One doctoral student is also working on the project.

In addition to its unique structure, the new respirator will use a combination of copper-based filters and temperature changes to help the droplets adhere to the respirator walls and to kill the virus.  “It takes about 50 minutes to inactivate the virus,” he said.

Once the prototype has been completed, the researchers will collaborate with a biosafety level 3 laboratory to test their design using live virus.

Modeling droplet transmission

To help identify what size droplets the respirator must capture, Basu developed a model that uses breathing rates to track the droplet sizes most likely to reach the most vulnerable area of the respiratory tract. That area is the nasopharynx, located in the upper part of the throat behind the nasal passages and above the esophagus and voice box.

The ciliated cells lining the nasopharynx have a surface receptor, known as ACE2, which the virus uses to enter the cells. The infection spreads from this initial infection site into the lungs through aspiration of the virus-laden nasopharyngeal fluids.

Basu developed CT-based digital models of the nasal airspace of several healthy adults and simulated four inhalation rates to determine which droplet sizes are most likely to reach the nasopharynx. The different airflow rates accounted for the differences in our inhalation process during resting state and forceful breathing.

“When viral transmission is averaged over different breathing rates, droplets ranging from 2.0 to 20 microns in size do the best job of landing at the nasopharynx,” he said, pointing out the droplet sizes are larger than expected.

“These are the droplet sizes that we need to make sure our new respirator design captures,” Basu said. This data is also useful for scientists developing inhaled COVID-19 antiviral therapeutics and targeted intranasal vaccines, because their effectiveness will, in part, depend on the aerosol medicine reaching that initial infection site—the nasopharynx.

BY CHRISTIE DELFANIAN

COURTESY OF: SDSU Marketing & Communications

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