Synthesis of Radioiodine-labeled Nanocarrier Composed of Poly(L-Lactic Acid)-block-Poly(Sarcosine) Amphiphilic Polydepsipeptide and Its Biodistribution in Tumor-bearing and Inflammation Model Mice

We have developed amphiphilic polydepsipeptide micelle “lactosome” as a novel nanocarrier with tumor accumulation properties for cancer imaging probes. In this study, radioiodine-labeled lactosomes were synthesized and evaluated to develop diagnostic radiotracers for in vivo imaging utilizing single photon emission computed tomography (SPECT). The 125I-labeled lactosome was obtained in sufficient yields for biodistribution studies. Radioactivity in the blood circulation was maintained at a high level between 2–48 h post-injection of 125I-labeled lactosome into BALB/c mice. Radioactivity uptake by the Colon-26 tumor implanted in the femur gradually increased. The uptake ratio of subcutaneous tumor/muscle increased to 16.7 at 48 h post-injection. Additionally, tumor SPECT imaging of 123I-labeled lactosome in mice was achieved. Radioactivity uptake of turpentine-induced inflamed tissue reached a maximum at 24 h and then decreased at 48 h post-injection. The mean uptake ratio of inflammatory tissue/muscle increased to 14.4 at 24 h. In conclusion, radioiodine-labeled lactosomes as nanocarriers may serve as potential candidates in facile and generic tumor or inflammation imaging techniques.