Mutations in SARS-CoV-2, the virus that causes COVID-19, continue to produce new virus variants. Some of these mutations may confer resistance to the immunity induced by vaccines or prior SARS-CoV-2 infections. Thus, there is a need for strategies that could prevent infection by a range of SARS-CoV-2 variants.
Physical barriers, such as the mucus lining of the airways, provide the first line of defense against infections. A research team led by Dr. Ke Cheng at North Carolina State University set out to develop a way to reinforce this mucus barrier. They described their method, which they dubbed spherical hydrogel inhalation for enhanced lung defense, or SHIELD, in Nature Materials on February 9, 2023.
SHIELD consists of an inhalable powder of fine particles, less than 5 μm across, made from an absorbent polymer. Upon contact with moisture, the particles absorb water, which causes them to swell. Within 10 minutes, they link with each other to form a hydrogel. Electron microscope imaging showed that mucus with SHIELD added formed a denser and stiffer gel, with smaller pores, than mucus alone. Virus-sized particles didn’t cross through this denser gel as easily as through ordinary mucus.