Lipid nanoparticles (LNPs) have become the leading platform for nucleic acid delivery; yet, their therapeutic performance is strongly influenced by the membrane-based biological barriers they encounter in vivo. These barriers exist at multiple hierarchical levels, ranging from extracellular matrices and mucosal layers to endothelial interfaces, plasma membranes, and intracellular organelles. Each barrier imposes distinct physicochemical constraints that shape LNP transport, cellular entry, and cargo release. This review provides a mechanistic framework for understanding LNP-membrane interactions by integrating membrane biophysics, lipid chemistry, functional interfacial forces, and the acquired feature, i.e., protein corona. We also describe the interfaces encountered during major administration routes, including intramuscular, intravenous, intraperitoneal, inhaled, oral, and intratumoral delivery, and highlight how local architecture, fluid composition, and protein corona evolution influence biodistribution and targeting. At the cellular level, we compare the membrane properties of parenchymal, stromal, and immune cells, emphasizing how differences in surface chemistry, receptor expression, and endocytic pathways determine LNP binding and internalization. We then discuss the key organellar processes that regulate intracellular trafficking and mRNA release, including endosomal maturation, acid-triggered lipid protonation, fusion-driven membrane remodeling, and nonbilayer phase transitions. Moreover, we outline recent evidence for LNP transcytosis across restrictive barriers such as the blood-brain barrier, tumor vasculature, pulmonary epithelium, and intestinal mucosa, as well as the contribution of exocytosis and extracellular vesicles to secondary mRNA delivery. Finally, we highlight emerging experimental and computational tools for probing LNP-membrane interactions. By integrating molecular design considerations with membrane biophysics and nanobio interface chemistry, this review aims to provide a mechanistic and strategic perspective to guide the rational development of next-generation LNP delivery systems.
