UPTAKE OF LIPOSOMES WHICH INCORPORATE A GLYCOPEPTIDE FRACTION OF ASIALOFETUIN BY HepG2 CELLS

Abstract

We examined the interaction between liposomes which incorporate a fraction triantennary glycopeptide (AF2) of asialofetuin and human hepatoma cells (HepG2) in vitro. HepG2 cells are known to express the asialoglycoprotein receptor.For liposome preparation AF2 was cleaved from asialofetuin, purified and conjugated with different length (C12,C16 and C18) fatty acids (FA). The conjugates were subsequently incorporated into pre-formed sonicated liposomes using a mild cholate incubation method. Interactions between AF2/FA-liposomes as well as control-liposomes (with no ligand) and cells (in the presence of serum) were measured at different lipid doses after incubating HepG2 cells with liposomes at 4°C and 37°C, in the absence and presence of galactose, and also evaluated by fluorescence microscopy. More extensive studies were performed with the AF2/C18-liposomes which were previously found to incorporate higher amounts of ligand and be the most stable of the formulations prepared.Results from both, morphological and quantitative studies, demonstrate that AF2/C16 and especially AF2/C18-liposomes are bound and taken up by the cells by a galactose specific mechanism. The AF2/C12-liposomes-which were previously found to incorporate low amounts of ligand in a non-stable way- were taken up by the cells in amounts similar to those of the control liposomes (without ligand) while this uptake was not reduced by galactose and therefore possibly non-specific. The intracellular localization of AF2/C18-liposomes was further evidenced by intracellular acidification using NH4Cl. These conclusions, justify the importance of further in vivo studies in order to demonstrate the capability of the proposed system to target hepatocytes.