Engineering Liposomes in Microfluidic Mixing: The Critical Role of Lipid Membrane Properties in Formation and Precise Size Control

Microfluidic methods have gained attention for liposome preparation, as they enable the production of liposomes with monodispersed size distribution. Lipid membrane properties have been identified as critical parameters affecting particle size in microfluidic liposome preparation. Nevertheless, the correlation between membrane properties and particle size remains not fully understood. In this study, we investigate the relationship between the particle size and lipid membrane properties within a microfluidic environment. Four different ratios of 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphocholine, cholesterol, and egg sphingomyelin were used for preparing different characteristics of liposomes. Lipid membrane properties, hydrophobicity, and rigidity were estimated using the fluorescence probes 6-dodecanoyl-<i>N</i>,<i>N</i>-dimethyl-2-naphthylamine (Laurdan) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The effects of the lipid membrane properties were examined under different conditions, including total flow rate, flow rate ratio, and lipid concentration. By comparing a theoretical model, we discuss the liposome formation mechanism and its impact on the particle size. Our results highlight significant roles of membrane properties in liposome formation and particle size in microfluidic systems, offering insights for optimizing liposome preparation.