In vivo PET imaging and biodistribution of radiolabeled gold nanoshells in rats with tumor xenografts

Here we report the radiolabeling of gold nanoshells (NSs) for PET imaging in rat tumor model. A conjugation method was developed to attach NSs with the radionuclide, 64Cu. The resulting conjugates showed good labeling efficiency and stability in PBS and serum. The pharmacokinetics of 64Cu-NS and the controls (64Cu-DOTA and 64Cu-DOTA-PEG2K) were determined in nude rats with a head and neck squamous cell carcinoma xenograft by radioactive counting. Using PET/CT imaging, we monitored the in vivo distribution of 64Cu-NS and the controls in the tumor-bearing rats at various time points after their intravenous injection. PET images of the rats showed accumulation of 64Cu-NSs in the tumors and other organs with significant difference from the controls. The organ biodistribution of rats at 46 h post-injection was analyzed by radioactive counting and compared between the 64Cu-NS and the controls. Different clearance kinetics was indicated. Neutron activation analysis (NAA) of gold concentration was performed to quantify the amount of NSs in major tissues of the dosed rats and the results showed similar distribution. Overall, PET images with 64Cu had good resolution and therefore can be further applied to guide photothermal treatment of cancer.