Biodistribution of Different Sized Nanoparticles Assessed by Positron Emission Tomography: A General Strategy for Direct Activation of Metal Oxide Particles

The extraordinary small size of NPs makes them difficult to detect and quantify once distributed in a material or biological system. We present a simple and straightforward method for the direct proton beam activation of synthetic or commercially available aluminum oxide NPs (Al2O3 NPs) via the O-16(p,alpha)N-13 nuclear reaction in order to assess their biological fate using positron emission tomography (PET). The radiolabeling of the NPs does not alter their surface or structural properties as demonstrated by TEM, DLS, and zeta-potential measurements. The incorporation of radioactive N-13 atoms in the Al2O3 NPs allowed the study of the biodistribution of the metal oxide NPs in rats after intravenous administration via PET. Despite the short half-life of N-13 (9.97 min), the accumulation of NPs in different organs could be measured during the first 68 min after administration. The percentage amount of radioactivity per organ was calculated to evaluate the relative amount of NPs per organ. This simple and robust activation strategy can be applied to any synthetic or commercially available metal oxide particle.