Effect of archaeal lipids from A. pernix K1 on the in vitro stability and active loading efficiency of liposomes composed of sphingomyelin and cholesterol.

Archaeal lipids offer a useful strategy for improving liposomal systems because of their inherent stability under extreme conditions. Incorporating lipids from Aeropyrum pernix K1 allowed us to optimize sphingomyelin-cholesterol formulation. These archaeal lipids enabled complete recovery of liposome morphology after destabilization with 4 mM Ca2+ followed by EDTA, indicating that membrane integrity is maintained in the presence of calcium. This is noteworthy given the anionic nature of the archaeal lipids, which in this case provide colloidal stability without increasing sensitivity to Ca2+. The addition of 2 mol% archaeal lipids also supported high encapsulation efficiency of 95% for active vincristine loading and performed better than the binary mixture when vesicles were prepared by extrusion without cosolvents. Furthermore, reducing the archaeal lipid fraction preserved biological stability provided by sphingomyelin-cholesterol, as confirmed by flow cytometry and fluorescence microscopy, whereas pure archaeosomes composed entirely of archaeal lipids have been reported to show poor stability in biological systems.