Preparation of lipid vesicles containing high levels of entrapped radioactive cations.

The ionophore A23187 was incorporated into the lipid bilayer of unilamellar vesicles and used to earry externally added indium ions to a chelator, nitrilotriacetic acid, which was previously entrapped in the vesicles. The extent of vesicle loading was assayed by Sephadex chromatography and γ-ray perturbed angular correlation spectroscopy. Incubation conditions were developed which allow rapid loading of more than 90% of added ¹²¹In³⁺ with specific activities of 200–300 μCi/mg lipid.