Uptake of Archaeobacterial Liposomes and Conventional Liposomes by Phagocytic Cells

Abstract

Liposomes in the 200 nm size range were prepared from the ether lipids extracted from various Archaeobacteria (coined archaeosomes), and from conventional lipids. The entrapment of peroxidase or carboxyfluorescein was used to compare the in vitro uptake of various liposomes by murine peritoneal macrophages, J774A.1 macrophages and several non phagocytic cell lines. While liposomes composed of ester lipids dipalmitoylphosphatidylcholine, or dimyristoylphosphatidylcholine: dimyristoylphosphatidylglycerol: cholesterol (1.8:0.2:1.5, molar ratio) were taken up by macrophage species, the uptake of archaeosomes was 3 to 53 times greater. Uptake by non phagocytic HEp-2, HeLa, and EJ/28 cells was considerably less. Evidence from time-course studies using cytochalasins B+D, sub-optimal temperature or formaldehyde treatments of macrophages, indicated that the archaeosomes lost structural integrity following internalization within the J774A. 1 phagocytic cells. No cytotoxicity was observed in viability or growth assays with J774A. 1 cells, using high doses of three representative types of archaeosomes and one type of conventional-liposome. Therefore, archaeosomes may be well suited to applications where phagocytic cells are a target site.