AN EFFICIENT METHOD FOR LOADING IN-111 INTO LIPOSOMES USING ACETYLACETONE

  • 1 January 1982
    • journal article
    • research article
    • Vol. 23  (9) , 810-815
Abstract
The efficient loading of high levels of 111In into the inner aqueous compartment of liposomes can be achieved by using a water-soluble lipophilic chelate, acetylacetone. The loading method involves the incubation of the acetylacetone-111In complex with liposomes entrapping 1 mM nitrilotriacetic acid. The loading process is carried out in isotonic saline, 10 mM Tris-HCl, pH 7.6, at room temperature. Evidently, ions are concentrated in the internal aqueous compartment of liposomes by acetylacetone, which mediates the transport of 111In ions across the outermost lipid bilayer of liposomes, permitting subsequent transfer to the encapsulated nitrilotriacetic acid. As much as 90% of the acetylacetone-chelated 111In becomes internalized in the aqueous compartment of liposomes and bound by entrapped nitrilotriacetic acid. In liposomes made from bovine brain sphingomyelin/cholesterol, the loaded liposomes retained the entrapped internally bound 111In even after incubation with serum at 37.degree. C for 24 h.