Synthesis and bioevaluation of ¹²⁵I-labeled gold nanorods.

A novel technique is described for monitoring the in vivo behavior of gold nanorods (GNRs) using γ-imaging. GNRs were radiolabeled using [¹²⁵I] sodium iodide in a simple and fast manner with high yield and without disturbing their optical properties. Radiolabeled GNRs were successfully visualized by radioisotope tagging, allowing longitudinal in vivo studies to be performed repeatedly in the same animal. The preliminary biodistribution study showed that PEGylated GNRs have much longer blood circulation times and clear out faster, while bare GNRs accumulate quickly in the liver after systematic administration. The highly efficient method reported here provides an extensively useful tool for guidance of the design and development of new gold nanoparticles as target-specific agents for both diagnostics and photothermal therapy.