Lung-targeting RNA-carrying lipid nanoparticles (LNPs) are often intravenously administered and accumulate in the pulmonary endothelium. However, most respiratory diseases are localized in the airway or the alveolar epithelium. Inhalation has been explored as a more direct delivery method, but it presents its own challenges. We believe that one reason LNPs have failed to transfect RNA into alveolar epithelial cells is their interaction with the lung surfactant (LS). We propose that inhalable LNP design should take inspiration from biological agents and other nanoparticles to overcome this barrier. Screening should first focus on LS penetration and then be optimized for cell uptake and endosomal release. This will enable more efficient applications of RNA-LNPs in lung diseases.
Keywords: RNA; alveoli; epithelium; lipid nanoparticles; lung surfactant; pneumocytes.