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

Abstract

PurposeTo optimize radiolabeling with 99mTc of mannosylated Gantrez® 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 MethodsMan-NP-HS nanoparticles were prepared by the solvent displacement method. They were purified, lyophilized and characterized. Then, they were radiolabeled with 74MBq of 99mTcO4− 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 a control of free 99mTcO4−. Thus, animals were humanly killed at 2 and 24h after the ocular administration and activity in organs was measured in a Gamma counter. ResultsRadiolabeling yield obtained was greater than 90%. Biodistribution studies of 99mTc-Man-NP-HS showed radioactivity accumulated at 2 and 24h in nasal and ocular mucosa and gastrointestinal tract, in contrast to biodistribution of free 99mTcO4− that remained concentrated in the skin around the eye and gastrointestinal tract. ConclusionBiodistribution studies of 99mTc-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.