Inhalable SHIELD Protects Lungs Against COVID-19

Investigators are working to build a physical barrier against COVID-19.

The inhalable bioadhesive hydrogel, spherical hydrogel inhalation for enhanced lung defense (SHIELD), densely coats the airway to restrict viral entry.

A new study, published in Nature Materials, reports how SHIELD reduced COVID-19 infection in both mouse and nonhuman primate models over a 24-hour period.

“The idea behind this work is simple,” said Ke Chong, corresponding author of the paper. “Viruses have to penetrate the mucus in order to reach and infect the cells, so we’ve created an inhalable bioadhesive that combines with your own mucus to prevent viruses from getting to your lung cells.”

The inhalable powder microparticles are made of gelatin and polyacrylic acid grafted with nontoxic ester. In the moist environment of the respiratory system, the microparticles swell and stick to the mucosal layer. Cheng explained, “Mucus is the body’s natural hydrogel barrier; we are just enhancing that barrier.”

The effects of SHIELD are most acutely felt in the first 8 hours after inhalation, dissipating over 24 hours. By 48 hours, SHIELD biodegrades and is completely cleared from the body. The investigators noted SHIELD is made with food-grade materials and does not affect normal respiratory function.

In mouse models, SHIELD was 75% effective at blocking COVID-19 pseudovirus particles in the first 4 hours after inhalation. This efficacy decreased to 18% after 24 hours, results that were consistent when SHIELD was tested against pneumonia and H1N1 viruses.

In a nonhuman primate model (African green monkeys), SHIELD recipients had a 50-300-fold reduction in viral loads. The SHIELD patients exhibited none of the symptoms commonly associated with primate COVID-19 infection, including lung inflammation and fibrosis.

The investigators found SHIELD provided protection against the original wild-type Wuhan COVID-19 strain (SARS-CoV-2 WA1), as well as the newer and more infectious Delta variant (B.1.617.2).

“SHIELD is easier and safer to use than other physical barriers or anti-virus chemicals,” Cheng said. “It works like an ‘invisible mask’ for people in situations where masking is difficult, for example during heavy exercise, while eating or drinking, or in close social interactions. People can also use SHIELD on top of physical masking to have better protection.”

The investigators have filed to patent SHIELD and are working toward Food and Drug Administration (FDA) approval for human use. The Nature Materials study was supported by the National Institutes of Health, the American Heart Association, and with special funding from the North Carolina State Provost’s Office.