In vivo 212 Pb/ 212 Bi generator using indium-DTPA-tagged liposomes

• Published in: Radiochimica acta Vol. 99; no. 11; pp. 743 - 749
• Main Authors: Le Du, A., Mougin-Degraef, M., Botosoa, E., Rauscher, A., Faivre Chauvet, A., Barbet, Jacques, Montavon, G.
• Format: Journal Article
• Language: English
• Published: 01.11.2011
• ISSN: 0033-8230
• DOI: 10.1524/ract.2011.1871

Abstract Indium-DTPA-tagged liposomes were studied in the present work as carriers of in vivo 212 Pb/ 212 Bi generator to be used in targeted alpha therapy. The liposomal uptake of 212 Pb, into preformed liposomes, was investigated using different lipophilic chelate (DCP, 2,3-dimercapto-1-propanol (BAL), sodium acetate, and A23187), as a function of various parameters (temperature, concentrations of lipids, Pb, DTPA, ...) with 212 Pb as a tracer. Different formulations of liposomes were tested to evaluate the radiolabeling efficiency. No complexing agent was necessary for the passage of Pb 2+ through the membrane. It occurs naturally via a partial permeability of the lipid bilayer, which increases with the temperature. A complexing agent (DTPA) appears necessary to concentrate Pb in the internal compartment of the liposomes. Conditions were found ( T =65 ºC, internal DTPA concentration of 0.025 M, pH 7.4, ...) yielding a high and rapid uptake of 212 Pb in liposomes. The protocol established provides a novel method for the efficient entrapment of about 2–3 Pb atoms per liposome with a yield of 75% in conditions relevant for nuclear medicine.