Inhalable Bioadhesive Hydrogel Protects Lungs from Viruses

Ke Cheng, University of North Carolina, Chapel Hill, and North Carolina State University, Raleigh, NC, USA, and colleagues, have developed an inhalable powder that can help protect the lungs and airways from viruses. This powder, called Spherical Hydrogel Inhalation for Enhanced Lung Defence (SHIELD), works by strengthening the body’s mucosal layer, reducing the risk of viral invasion. The powder has been found to reduce infection in mice and non-human primates over 24 hours and can be taken repeatedly without affecting normal lung function.

The inhalable powder is made of microparticles consisting of gelatin and poly(acrylic acid) grafted with the non-toxic ester N-(Acryloyloxy)-succinimid. When these microparticles enter a moist environment, such as the airways and lungs, they swell and stick to the mucus layer, increasing its “stickiness.” As viruses need to penetrate the mucus to infect cells, the inhalable bio-adhesive binds with the body’s own mucus, preventing viruses from reaching the lung cells. The effect is strongest in the first eight hours after inhalation. SHIELD is biodegradable and completely excreted from the body within 48 hours.

Tests on mice showed that SHIELD blocked SARS-CoV-2 pseudovirus particles with 75 % efficiency four hours after inhalation, which dropped to 18% after 24 hours. The researchers also achieved similar results in tests against pneumonia and H1N1 viruses. In a non-human primate model, SHIELD-treated subjects had 50- to 300-fold lower viral loads than controls for both the SARS-CoV-2 WA1 (original) and B.1.617.2 (Delta) variants.

The researchers looked at potential toxicity both in vitro and in vivo, and found that 95 % of cell cultures exposed to a high concentration (10 mg ml^-1) of SHIELD remained healthy, and mice given daily doses for a fortnight maintained normal lung and respiratory functions.

According to the researchers, SHIELD works protectively in situations where wearing a mask is difficult, such as during vigorous exercise, eating or drinking, or close social contact. People can also use SHIELD in addition to physical masking for better protection. The researchers are investigating whether it can also be used to protect against allergens or air pollution.