Synthesis of PEG‐Iodine‐Capped Gold Nanoparticles and Their Contrast Enhancement in In Vitro and In Vivo for X‐Ray/CT

We designed gold nanoparticles (AuNPs) capped with iodine and polyethylene glycol (PEG) to provide effective enhancement for X‐ray CT imaging. The methoxy PEG‐iodine‐capped AuNPs were prepared through the chemisorption of iodine and substitution of methoxy PEG‐SH onto the surface of gold nanoparticles, and severe aggregation in TEM was not observed. The binding energies of Au 4f 7/2 and I 3d 5/2 of the methoxy PEG‐iodine‐capped AuNPs were obtained as 84.1 eV and 619.3 eV, respectively. The binding energy shift of methoxy PEG‐iodine‐capped AuNPs would be resulted from the chemisorption between gold nanoparticles and iodine atoms. The methoxy PEG‐iodine‐capped AuNPs have higher enhancement compared to PEG‐capped gold nanoparicles in the same amount of gold in vitro . After postinjection of methoxy PEG‐iodine‐capped AuNPs into the mice, dramatic contrast enhancement at the heart, aorta, liver, and kidney was observed, this was maintained up to 5 days, and there was no evidence of apparent toxicity. In conclusion, methoxy PEG‐iodine‐capped AuNPs might be a good candidate as a CT contrast agent for blood pool imaging, and this will also contribute to the prolongation of a blood circulation time for X‐ray CT imaging.