Development of radiolabeled ¹¹¹In-albumin liposomes for long-term imaging of tumors.

BACKGROUND: The current study aims to develop a clinically applicable radiopharmaceutical agent for long-term imaging in the diagnosis and management of oncologic patients in the field of nuclear medicine. Liposomes, as pharmaceutical nanocarriers, have been extensively studied in pharmaceutical industry and depending on their structural characteristics could be formulated for accumulation in various pathological sites in the body. PEGylated liposomes have smaller volume of distribution and decreased clearance, consequently, due to their more prolonged presence in the bloodstream and their stability during this time, could be used for tumor imaging. STUDY DESIGN AND METHODS: In-oxine and their stability in serum medium was assessed and the rate of their biodistribution in C26-colon carcinoma tumor-bearing mice was evaluated by two approaches, quantitatively radioactivity measurement and qualitatively gamma scintigraphy imaging. RESULTS: In -radiolabeled liposomes having a size of about 130 nanometers, were capable of accumulating in tumor sites based on enhanced penetration and retention (EPR) phenomenon. These liposomes also have high stability for maintaining encapsulated albumin for a long time up to 96 h and even may be stable for longer time period. In the study of biodistribution of our formulation in tumor-bearing mice, they accumulated more in the kidney, liver, spleen and tumor sites, so that even after clearance of formulation in the bloodstream, they existed in significantly higher levels in the mentioned organs and likewise tumor sites up to 96 h. In gamma scintigraphy, organs with high activity resulted from accumulation, were visible in the form of hot spots demonstrating formulation stability in the tumor sites from time of administration to 96 h. CONCLUSIONS: Our in vitro and in vivo studies demonstrated that this PEGylated radiolabeled liposomal formulation have considerable stability and efficiency for long-term tumor imaging which merit further studies for its transformation into clinical application.