Cells and Materials


In vitro stabilities of liposomes prepared from the total polar lipids (TPL) of various species of Archaeobacteria were compared with those made from egg phosphatidylcholine (EPC) and from mixtures of TPLIEPC. Stability was monitored by measuring the extent of leakage of entrapped dyes. Liposomes prepared from exclusively archaeobacteriallipids (coined archaeosomes), particularly those containing the bilayer spanning tetraether lipids, were generally stable to conditions such as storage at 37°C for greater than 7 days, exposure to phospholipase A2, incubation with serum, and, to some extent, exposure to bile salts. In contrast, EPC liposomes were generally unstable to these conditions, releasing, for example, 100% of the entrapped dye within 1.5 h of incubation at 37°C. Mixing EPC with archaeobacterial TPL modified stability of the liposomes to varying degrees, depending on the types of the archaeobacterial lipids, the mixing ratio, and the stress factor being tested. For some applications, incorporation of an ester lipid into the liposome layer may be used to modulate the stability of archaeosomes, and decrease the cost of production without necessarily compromising utility.