Radiolabeled liposomes for scintigraphic imaging

Liposomes have been investigated extensively as carriers for drugs in attem pts to achieve selective deposition and/or reduced toxicity. Liposomes radi olabeled with gamma emitters such as Ga-67, In-111 and Tc-99m, can be used for imaging purposes. Liposomes as formulated in the past, are rapidly take n up by cells of the mononuclear phagocyte system (MPS), primarily those lo cated in liver and spleen. The recent development of long-circulating lipos omes (LCLs), yielded liposomes that oppose recognition by the MPS. The deve lopment of these LCLs with enhanced circulatory half-lives has broadened th e potential of liposomes to scintigraphically visualize pathologic processe s in vivo. Liposomes have been proposed for tumor imaging, infection imagin g and blood pool imaging. Strategies have been developed that allow rapid, easy and efficient labeling of preformed liposomes with In-111 and Tc-99m. There is now a vast body of preclinical evidence showing that LCLs can be u sed to image a wide variety of tumors as well as inflammatory lesions. The first studies in patients show that radiolabeled liposomes can image tumor and inflammatory lesions with good sensitivity and good specificity. Here, the present status of liposome-based radiopharmaceuticals for scintigraphic application is reviewed. (C) 2000 Published by Elsevier Science Ltd.