Gastrointestinal uptake of liposomes. I. In vitro and in situ studies

Abstract

The stability of -[alpha]-phosphatidylcholine distearoyl/cholesterol and egg lecithin/cholesterol multilamellar liposomes at acidic pH values, in the presence of bile salts and in the presence of pancreatic lipase, was studied by determining the leakage rates of entrapped markers. Substantial loss of entrapped glucose and complete loss of entrapped carboxyfluorescein were observed under conditions similar to what would be expected in the gastrointestinal tract. Transport studies using in vitro diffusion cells and everted-sac experiments suggest that intact liposomes are not taken up by epithelial cells and that liposomal entrapment does not facilitate the transport of non-absorbable drugs and prevents the transport of absorbable ones. In situ studies seem to confirm this viewpoint since almost all of the liposomes and their entrapped markers remain in the intestine even after 3 h.