In order to infect cells and cause respiratory disease, viruses, such as SARS-CoV-2, must get through the mucus layer that coats and protects the respiratory tract. Despite our natural defenses, previous research has shown that SARS-CoV-2 is difficult to remove from the airway through mucociliary clearance, making it easier for the virus to spread throughout the respiratory system. Now, researchers from NC State University have developed a bioadhesive hydrogel that can be inhaled as a powder and reinforces the mucus layer, impeding SARS-CoV-2 infection in the lungs.
The powder, named Spherical Hydrogel Inhalation for Enhanced Lung Defense (SHIELD), comprises microparticles made from poly(acrylic acid) grafted with the non-toxic N-hydroxysuccinimide ester and gelatin. In the moist environment of the lungs and respiratory tract, the microparticles swell and stick to the mucosal layer, increasing its adhesiveness and enhancing its ability to trap pathogens, such as SARS-CoV-2 and other viruses. The hydrogel biodegrades over time and is completely cleared from the body after about 48 hours. The researchers tested the efficacy of SHIELD for preventing SARS-CoV-2 infection in mouse and non-human primate models, and further assessed its biocompatibility and potential toxicity in mice and human bronchial epithelial cell culture.
The team found that SHIELD blocked a SARS-CoV-2 pseudovirus with 75% efficiency in mice four hours after inhalation, which fell to 18% after 24 hours. In the non-human primate experiments, African green monkeys treated with SHIELD and exposed to SARS-CoV-2 or its Delta variant had viral loads 50 to 300-fold lower than untreated monkeys and none of the symptoms commonly seen in primates infected with the virus, such as lung inflammation and fibrosis. In the mouse models, SHIELD was also efficient at blocking the H1N1 flu and mouse pneumonia viruses. Biocompatibility tests in cell cultures showed 95% of cells exposed to 10 mg ml-1 of shield remained healthy after three days, and mice administered shield every day for two weeks retained normal lung and respiratory function with no sign of injury. This study was published in Nature Materials.
“SHIELD is easier and safer to use than other physical barriers or anti-virus chemicals,” said corresponding author Ke Cheng. “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.”
According to Cheng, the researchers are also looking into whether SHIELD could protect against other potential health threats such as allergens or air pollution. The researchers have filed a patent for the technology and are working toward having it approved by the Food and Drug Administration (FDA) for human use.