Radiolabeling FAU with 125I and its biodistribution in mice

Objective: The aim of this study was to label 2'-fluoro-2'-deoxy-l-β-D-arabinofuranosyluracil (FAU) with 125I, and to investigate the characteristics of the labeled compound as well as its bio-distribution in mice. Methods: FAU was radiolabeled with Na125I using the Iodogen method. The Sep-Pak C18 reverse phase column was used to purify the labeled product. The labeling efficiency, radiochemical purity, the in vitro stability and its biodistribution in mice were observed. Results: FAU was successfully labeled with Na125I with the labeling efficiency of (63.12±5.01)%. The radiochemical purity was (98.60 ± 0.52)%. 125I-5-iodo-FAU (FIAU) was stable in PBS and fresh human serum under 37 degree C and the radio-chemical purity remained more than 95.04% after 24 h. Mouse experiment showed that the radiolabeled product was washed out from blood quickly. The uptake expressed as percentage activity of injected dose per gram of tissue (% ID/g) was (4.33±1.00)% ID/g at 0.5 h and (0.71±0.06)% ID/g at 2 h after injection. The 125I-FIAU was mainly excreted through kidney. Conclusions: 125I-FIAU could be obtained by labeling FAU with the Iodogen method with satisfactory labeling efficiency, radiochemical purity and stability. Mouse biodistribution experiment showed it was mainly excreted through kidney. (authors)