Angew. Chem. Int. Ed. http://doi.org/f2nzkd (2013)

Radiolabelled nanoparticles for use as imaging agents in positron emission tomography (PET) usually rely on macrocyclic chelators to attach the radiolabels, for example 64Cu, to the nanoparticles. This arrangement can easily dissociate in vivo, however, resulting in reduced diagnostic accuracy. Now, Zhao et al. report an improvement in the radiolabel stability of 64Cu-doped gold nanoparticles by the direct incorporation of 64Cu into the lattice structure of the nanoparticles (64CuAuNPs). The 64CuAuNPs, prepared using 64CuCl2 as a precursor, have 64Cu integrated throughout and their activity can be controlled by altering the initial activity of 64CuCl2. In a cancer mouse model, Zhao et al. use PET imaging to show that the 64CuAuNPs passively target and heterogeneously distribute within the tumour. In vivo pharmacokinetic studies indicate that most of the 64CuAuNPs are retained within systemic circulation at 1 hour, but are rapidly cleared by the liver and spleen at 24 hours. These factors result in accumulative uptake in the tumour and an increased tumour-to-muscle ratio at extended PET imaging times.