Surface-modified liposomes for syndecan 2–targeted delivery of edelfosine

Abstract

Here, we report that the modification of liposome surfaces with AG73 peptides enhances delivery of the lipophilic anticancer drug, edelfosine, to tumor cells overexpressing the cell-surface receptor, syndecan 2. To test the effect of liposomal surface density of AG73 peptides on cellular uptake, we synthesized AG73 peptide-conjugated polyethylene glycol (MW 2000) lipid and incorporated it into fluorescence dye-labeled anionic liposomes with different ligand densities (1, 2, or 5 mol% of total lipids). Cellular uptake of AG73-peptide–modified liposomes gradually increased in proportion to the surface ligand density. The percentages of cells positive for AG73-modified, fluorescent-dye–labeled liposomes were 19.8 ± 2.0%, 23.1 ± 5.0%, and 99.2 ± 1.0%, for ligand mole percentages of 1, 2, and 5, respectively. The cell-targeting ability of AG73-modified liposomes was not significantly altered by the serum content of culture media. In keeping with the observed enhanced cellular uptake, AG73-peptide–modified liposomes entrapping edelfosine exhibited greater cancer cell-killing effects compared with unmodified liposomes. Following intravenous administration into tumor-bearing mice, AG73-peptide–modified liposomes showed 2.1-fold greater accumulation in tumors than unmodified liposomes. These results support the feasibility of using syndecan 2–directed liposomes for delivery of edelfosine.