To further our understanding of nanoparticle interactions with biological systems, it is important that highly sensitive, reliable and robust methods for labelling particles are established. We report here the application of a series of bi-functional cage ligands to radiolabel a range (i.e. shapes and sizes) of titanium dioxide (TiO2) particles. The cages were covalently attached to the surface of the particles via the use of a dopac derivative and then radiolabeled with a gamma emitting radioisotope. The final radiolabeled nanoparticles proved to be stable in solution and the method easy and robust. The application of a gamma emitter allows the radiolabeled particles to be tracked in vivo and in the environment.