Carrier Activity of Sonicated Small Liposomes Containing Melphalan to Regional Lymph Nodes of Rats

Abstract

Tissue distribution following subcutaneous injection of liposomes containing melphalan (MPL) was studied in rats using 14C-MPL and 3H-phosphatidylcholine. Two types of liposomes, prepared by either a brief or a prolonged sonication, were compared. Brief sonication formed large liposomes of various sizes, while liposomes obtained after a prolonged sonication were small and relatively uniform in size (34 nm in mean diameter). Subcutaneous injection of small liposomes produced a strikingly high and sustained concentration of MPL equivalents in regional lymph nodes. In contrast, most liposomes prepared by a brief sonication appeared to remain at the injection site, and there was only a slight increase in the lymph node concentration of MPL equivalents over the plasma level during the 24-hour experiments.