SAN DIEGO—RNA vaccines packaged in tiny fatty containers called nanoparticles saved tens of millions from COVID-19. Now, researchers are trying to use similar nanoparticles to fight two other major killers, respiratory failure caused by lung infections such as flu and the atherosclerosis that leads to heart attacks and strokes. In both conditions, the endothelial cells that line blood vessels malfunction, turning down key genes. New research presented at the American Chemical Society (ACS) meeti...