We have demonstrated the capacity of non-phospholipid liposomes composed primarily of dioxyethylene acyl ethers and cholesterol to fuse with membranes composed primarily of phospholipid. Phase-contrast microscopy, freeze-fracture electron microscopy and a macromolecular probe indicate that these non-phospholipid liposomes can fuse with the plasma membranes of erythrocytes and fibroblasts, Furthermore, fluorescence probe experiments have demonstrated fusion between phosphatidylcholine liposomes and nonphospholipid liposomes. Mixing of internal contents was shown by a terbium/dipicolinate assay. Mixing of membrane lipid components was demonstrated by measuring (i) fluorescence resonance energy transfer between N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidyl- ethanolamine and N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine, after phosphatidylcholine liposomes were mixed with non-phospholipid liposomes, and (ii) reduced concentration quenching of rhodaminephosphatidylethanolamine and octadecylrhodamine incorporated into phosphatidylcholine liposomes after mixing with the non-phospholipid liposomes. The degree of apparent fusion reported by the different probe techniques ranged from 25% to 64%.
El Baraka, M., Pécheur, E. I., Wallach, D. F. H., & Philippot, J. R. (1996). Non-phospholipid fusogenic liposomes. Biochimica et Biophysica Acta - Biomembranes, 1280(1), 107–114. https://doi.org/10.1016/0005-2736(95)00286-3