Liposomal systems can be improved by archaeal lipids, whose unique structure enables archaeans to survive in extreme conditions. By adding lipids from the archaeon Aeropyrum pernix K1, we optimized the established liposomal formulation of sphingomyelin and cholesterol. Dynamic light scattering analysis revealed that even small additions (2 mol%) of archaeal lipids allow for the formation of monodisperse liposomes with a mean diameter below 100 nm via sonication, while also reducing the zeta potential to values that ensure colloidal stability. Fluorescence probe anisotropy showed that archaeal lipids proportionally increase liposomal fluidity as their concentration increases. Archaeal lipids also enable complete reversibility of the morphological parameters of liposomes after destabilization with 4 mM Ca²⁺ followed by the addition of EDTA, indicating the liposomal integrity is preserved in the presence of calcium ions. The release of calcein from liposomes with added archaeal lipids at elevated temperatures and during long-term storage at lower temperatures was comparable to, or better than in control samples without archaeal lipids. Furthermore, the addition of 2 mol% archaeal lipids facilitated an excellent encapsulation efficiency (95%) for active loading of vincristine and improved the biological stability of liposomes compared to archaeosomes composed solely of archaeal lipids, as confirmed by flow cytometry and fluorescence microscopy.
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