Liposomes labeled with Indium-111 by a novel surface labeling method exhibits good biodistribution in vivo

Radioliposomes have potential applications as theranostic nanoparticles. Several techniques have been developed to label liposomes with radionuclides. Methods: In this study, a new In-111 surface labeling method for 1,4,7,10-tetraazacyclododecane-N, N′, N″, N′″-tetraacetic acid (DOTA) derivative liposomes (DLs) is described. The in vitro stability and in vivo molecular imaging properties of the labeled liposomes were compared with those of conventional 111 In-liposomes ( 111 In-Ls) prepared by a remote loading method. In vitro stability tests were performed in normal saline, rat plasma, and human plasma at 37°C. Imaging characteristics of both radioliposomal preparations were determined in LS174T tumor-bearing mice. Results: The labeling efficiency of In-111-labeled DL ( 111 In-DLs) was greater than 95%; accordingly, no post-labeling purification was required, in contrast to the 111 In-Ls. The specificity of 111 In-DLs was higher (>10 111 In per liposome) than that of 111 In-Ls ( 111 In per liposome). The two radioliposomes showed similar in vitro stability. Non-invasive longitudinal monitoring by micro-single-photon emission computed tomography/computed tomography showed a similar in vivo tumor distribution for the two radioliposomes (48 h post-injection, P > 0.05). Conclusion: The new 111 In surface labeling method for liposomes was rapid, efficient, highly specific activity, and easy to perform. Although the two radioliposomes showed similar in vitro and in vivo characteristics, 111 In-DLs have benefits for clinical drug preparation, and this surface labeling method is a promising platform for radioliposomal theranostic nanoparticle preparation.