Uptake of Transition Metal Ions Using Liposomes Containing Dicetylphosphate as a Ligand

Abstract

The uptake of Cu²⁺ was investigated using various types of liposomes composed of phosphatidylcholine (PC), cholesterol (Chol) and dicethylphosphate (DCP). DCP played a role as a ligand for Cu²⁺. Multilamellar vesicles (MLVs) were more effective for the uptake of Cu²⁺ compared to unilamellar vesicles prepared by the extrusion technique. The uptake efficiency of MLVs for Cu²⁺ was dependent on the molar ratio of DCP in MLVs. The uptake percent of Cu²⁺ was 92% using MLVs having a PC:DCP:Chol molar ratio of 4:3:3; 95% of the total vesicle Cu²⁺ was bound to DCP of the outer membrane surface of the MLVs, and the remaining 5% of the total Cu²⁺ was distributed into the interior side of the MLVs. MLVs having a PC:DCP:Chol molar ratio of 4:3:3 were also effective as separation media for Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺. The uptake efficiency of the MLVs for the transition-metal ions increased in the order Co²⁺ < Zn²⁺ < Ni²⁺ < Mn²⁺ < Cu²⁺.