Preparation, radiolabeling with 99m Tc and 67 Ga and biodistribution studies of albumin nanoparticles covered with polymers.

Objective: To optimize radiolabeling with Tc-99m and Ga-67 of albumin nanoparticles coated with 4 differents synthetic polymers and to evaluate their stability in vivo and in vitro, as well as their biodistribution in vivo after intravenous administration. Material and methods: The nanoparticles were prepared using albumin and NOTA-modified albumin by the desolvation method and coated with 4 different polymers: HPMC, GMN2, GPM2 and GTM2. They were purified, lyophilized and characterized. Radiolabelling with Tc-99m was perfomed with 74 MBq of Tc-99m sodium pertechnetate, previously reduced with and acid solution of tin chloride at different concentrations (0.003, 0.005, 0.007, 0.01, 0.05 and 0.1 mg/ml) and at different times (5, 10, 15,30 and 60 minutes) and temperatures (room temperature, 40 degrees C and 60 degrees C). Radiolabelling with Ga-67 was perfomed by incubation of the nanoparticles with 37 MBq of (67)Gallium chloride (obtained from commercial gallium-(67) citrate) at different times (10 and 30 minutes) and temperatures (room temperature, 30 degrees C and 60 degrees C), and posterior purification with microconcentrators. The radiochemical purity was evaluated by TLC. Stability studies of radiolabeled nanoparticles in physiological serum and blood plasma were perfomed. Biodistribution studies of nanoparticles coated with GPM2 polymer were carried out in Wistar rats after intravenous administration of the nanoparticles. Control animals were carried out with 99mTc sodium pertechnetate and Ga-67 chloride. To do so, the animals were killed and activity in organs was measured in a gamma counter. Results: Tc-99m labeling was carried out optimally with a tin concentration of 0.007 mg/ ml for the GPM2 nanoparticles and 0.005 mg / ml for the rest of the formulations, with a radiolabelling time of 10 minutes at room temperature. In the case of Ga-67 the label was optimized at 30 degrees C temperature and 30 minutes of incubation. In both cases the radiochemical purity obtained was greater than 97%. The nanoparticles showed high stability in vitro after 48 hours of labeling (70% nanoparticles labeled with Tc-99m and 90% those labeled with Ga-67). Biodistribution studies of nanoparticles Tc-99m -GPM2 and Ga-67 -NOTA-GPM2 showed a high accumulation of activity in the liver at 2 and 24 hours after intravenous administration. Conclusion: The labeling procedure with Tc-99m and Ga-67 of albumin and albumin modified with NOTA nanoparticles allows obtaining nanoparticles with high labeling yields and adequate in vitro stability, allowing their use for in vivo studies. (C) 2020 Sociedad Espanola de Medicina Nuclear e Imagen Molecular. Published by Elsevier Espana, S.L.U. All rights reserved.