Respuesta :
Answer:
Asymmetric liposomes have different lipids in outer and inner leaflets, which would greatly increase the flexibility of vesicle in drug delivery systems. It has been well known that the phospholipid distribution in natural membranes is asymmetric. For example, phosphatidyl tcholine and sphingomyelin concentrate at the outer leaflet whereas phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine are mainly localized in the inner leaflet. Typically, Lipids are self-assembled symmetrically in artificial liposomes regardless of the preparation methods. As drug delivery carriers, asymmetric liposomes with advanced functions are appealing candidates for targeted accumulation and controlled drug release. Their outer and inner leaflet could be manipulated depending on the nature of encapsulated drug molecules. For example, asymmetric liposomes help deliver negatively charged siRNA to target organs by having positively charged inner layer that encapsulates siRNA with high efficiency, and negatively charged outer surface prevents nonspecific uptake of the asymmetric liposomes. The unique tunability of asymmetric liposomes opens a wide door for multi-site functionalization, resulting in highly engineered liposomes as advanced drug delivery vesicles
