Synthesis of a novel lipopeptide with alpha-melanocyte-stimulating hormonepeptide ligand and its effect on liposome stability

Introduction of liposomes into target cells is important for drug delivery systems. For this purpose, the surface of the liposome is equipped with lig and peptides, which may bind to specific receptors on the cell membrane. An artificial novel lipopeptide (MSH-C4A2) containing the alpha-melanocyte-st imulating hormone (alpha-MSH) sequence and two long alkyl chains was design ed and synthesized, and the liposome, composed of egg phosphatidylcholine ( EPC) and MSH-C4A2, was prepared. The stability of the liposome was estimate d by measuring calcein leakage from the liposome inner phase. The stability of the liposome decreased upon addition of MSH-A4C2, which seemed to be at tributable to the amphiphilic property of the peptide moiety (a-MSH) of MSH -A2C4. The stability was, however, recovered fairly well upon addition of c holesterol (Ch) or phosphatidylglycerol (PG). It was concluded therefore th at the ternary system, MSH-C4A2/Ch/EPC or MSH-C4A2/PG/EPC, is suitable for preparing the functional liposome.