Comprehensive analysis of liposome formulation parameters and their influence on encapsulation, stability and drug...

An understanding of the factors that affect liposome size, drug loading, stability and drug release is critical for the rational design of liposomes with desired pharmacokinetics and biodistribution. This article presents a report on the formulation and characterization of BIIB093 (glibenclamide) liposomes as well as a detailed analysis of the influence of formulation methods and parameters on encapsulation efficiency, liposome size, charge (zeta potential, ZP), polydispersity index (PDI), and drug release. PEGylated liposomes containing BIIB093 were made using ethanol injection and calcium acetate remote loading. The critical formulation parameters investigated include: the effect of lipid chain length, lipid unsaturation, lipid phase transition temperature (Tc) and the amount of cholesterol. Liposomes generated in this study had low average particle size (130 ± 20 nm), PDI (0.15 ± 0.1) and ZP (-2 ± 1 mV). Liposomes made from lipids with long acyl chains showed enhanced drug loading, encapsulation efficiency and drug retention. Similarly, liposomes made from lipids with high degree of unsaturation and low T_c exhibited faster drug release rates. Additionally, increasing the amount of cholesterol in the liposome bilayer improved PDI, decreased drug incorporation and accelerated drug release but had negligible impact on liposome size and ZP. Furthermore, encapsulating the drug in the liposome core enabled sustained drug release.