We prepared the liposomes, changed the entrapped amount of adriamycin (ADR) per the amount of liposome composing lipid, and after the addition of these liposomes with the same concentration of ADR(therefore, different dose of lipid), the tumor cell uptake of ADR was examined. The high entrapped amount of ADR demonstrated the usefulness in the tumor cell uptake of the ADR liposome in vitro. The cell uptake of the liposome depended on additional amount of ADR and liposomal lipid. Next, using ADR contained liposome and irinotecan contained liposome, its usefulness on tumor cell uptake by the polyethyleneglycol (PEG) modification of the surface on the liposome in vitro examined. In both liposome, PEG modification of the surface on the liposome facilitated the initial rate of the liposome uptake into the tumor cell. We have considered that this facilitation was attributed to the lipo-hydrophilic property of PEG and the fixed aqueous layer around the liposome. Therefore, PEG modification of the surface on the liposome, prevents the adhesion of serum opsonine and avoids reticuloendothelial system, does not inhibit tumor cell uptake rather facilitates. From the results of dextran sulfate contained liposome, it is expected that these liposome passed through the membrane of the tumor cell. Therefore, a higher entrapped amount of antitumor agents in the liposome and PEG modification have been confirmed to be beneficial in the tumor cell uptake.
