Physicochemical Characterization, Manufacturing, and Stability of Liposomal Drug Delivery Systems: From Formulation Design to Pharmaceutical Translation

Liposomal drug delivery systems have evolved into clinically relevant platforms for delivering small molecules, biologics, and vaccines. Nevertheless, a persistent translational gap remains between promising laboratory-scale formulations and reproducible pharmaceutical products. This review provides a practical framework linking liposome formulation, physicochemical characterization, manufacturing, and stability to pharmaceutical translation. Particular emphasis is placed on relationships between critical process parameters and critical quality attributes, including vesicle size, polydispersity index, zeta potential, morphology, lamellarity, encapsulation efficiency, drug loading, and in vitro release behavior. Preparation and cargo-loading strategies are discussed across conventional research-scale methods and approaches with potential for scalable manufacturing. Microfluidic production of conventional liposomes is distinguished from the manufacture of structurally distinct RNA-loaded lipid nanoparticles. Purification strategies and analytical determination of encapsulation efficiency are examined, with attention to the distinction between separation techniques and quantitative analytical methods. Lamellarity is highlighted as a structural determinant of encapsulation capacity, membrane organization, and release behavior, with complementary assessment by cryo-TEM, 31P-NMR, and small-angle X-ray scattering. Quality-control challenges associated with aggregation, fusion, cargo leakage, phospholipid hydrolysis, oxidation, and sterilization are also considered. Dry-state stabilization through lyophilization and spray drying is discussed for its potential to improve long-term stability and reduce cold-chain dependence. Ligand-targeted liposomes introduce additional requirements for surface characterization and biological evaluation, while approved products and investigational formulations illustrate achievements and limitations in clinical translation. Overall, this review emphasizes the importance of establishing relationships between formulation composition, processing, structural organization, stability, and functional performance to support more reproducible development and informed pharmaceutical translation.