(172a) Evaluation of Stability in Liposomes Composed of Mixed Phospholipids

Lipid vesicles, also referred to as liposomes, are enclosed spherical structures wherein the shell is a lipid bilayer membrane. It is critical to understand factors that affect liposome size, drug capacity, stability, and drug release in order to best design liposomes for various pharmaceutical and biomedical applications. Our focus is on liposome stability, in particular, because this characteristic directly translates to shelf-life of liposomal drug products. Specifically, this poster presents our work on the physical and chemical stability of two mixed-phospholipid systems where one lipid is saturated and the other is unsaturated (System 1: DMPC-DOPC, System 2: DPPC-DOPC). Liposomes are prepared using thin film hydration, freeze-thaw cycling, and extrusion to yield mostly unilamellar liposomes with diameters of ca. 100 nm in all cases. Once prepared, liposomes are exposed to accelerated aging conditions, namely elevated temperature, and aliquots are collected at regular intervals for analysis. The physical stability of liposomes is tracked through dynamic and static light scattering (DLS/SLS), as well as, light transmittance. The chemical stability of liposomes is assessed using high-performance liquid chromatography (HPLC). This poster will present these data and draw conclusions about the role of lipid composition in controlling liposome stability, thus providing essential insights for future liposome-based drug delivery system design.