Radiolabeling and biodistribution studies of polymeric nanoparticles as adjuvants for ocular vaccination against brucellosis

Purpose: To optimize radiolabeling with Tc-99m of mannosylated Gantrez (R) nanoparticles loaded with the Brucella Ovis antigen (Man-NP-HS) and to carry out biodistribution studies in mice after ocular administration of the nanoparticles. Material and methods: Man-NP-HS nanoparticles were prepared by the solvent displacement method. They were purified, lyophilized and characterized. Following this, they were radiolabeled with 74 MBq of (TcO4-)-Tc-99m previously reduced with an acidic stannous chloride solution, working in absence of oxygen and at a final pH of 4. Radiolabeling yield was evaluated by TLC. Biodistribution studies were carried out in mice after ocular administration of the formulation and control of free (TcO4-)-Tc-99m. To do so, the animals were humanely killed at 2 and 24 hours after the ocular administration and activity in organs was measured in a Gamma counter. Results: Radiolabeling yield obtained was greater than 90%. Biodistribution studies of Tc-99m-Man-NP-HS showed radioactivity accumulated at 2 and 24 hours in nasal and ocular mucosa and gastrointestinal tract, in contrast to biodistribution of free (TcO4-)-Tc-99m that remained concentrated in the skin around the eye and gastrointestinal tract. Conclusion: Biodistribution studies of Tc-99m-Man-NP-HS after ocular instillation have made it possible to demonstrate its biodistribution in nasal mucosa and gastrointestinal tract. This characteristic is essential as an antigenic delivery system throughout the ocular mucosa. This, together with its elevated immune response, effective protection and intrinsic avirulence make them a suitable anti-Brucella vaccine candidate. (c) 2012 Elsevier Espana, S.L. and SEMNIM. All rights reserved.