Stability of liposomes in vitro and their uptake by rat Peyer's patches following oral administration.

To evaluate the usefulness of liposomes as a carrier for the targeted delivery of antigens to gut-associated lymphoid tissue, liposomal stability and uptake by rat Peyer's patches were investigated. Liposomes composed of distearoylphosphatidylcholine, phosphatidylserine, and cholesterol (DSPC-liposome), or dipalmitoylphosphatidylcholine, phosphatidylserine, and cholesterol were stable in acidic solution (pH 2.0), diluted bile, and pancreatin solution. Following the oral administration of liposomes to rats, rhodamine B-PE incorporated in the lipid phase of DSPC-liposomes was preferentially taken up by Peyer's patches in the lower ileum. The uptake of rhodamine B-PE from DSPC-liposomes larger than 374 nm in mean diameter was high. Orally administered DSPC-liposomes of a large diameter thus appear to serve effectively as a vehicle for delivering antigens to Peyer's patches.