Synthesis, stability, and cellular uptake of (131)I-estradiol against MCF7 and T-47D human cell lines as a radioligand for binding assay

Estradiol is a steroid hormone that works as an agonist estrogen receptor (ER). This compound is widely used as a ligand and bind specifically to the ERα. Radioligand binding assay is an in vitro method for drug development from natural products by synthesizing estradiol through radiolabeling using the radioiodination method. Synthesis of (131)I-estradiol was perfomed by direct method using chloramine T as an oxidizer and by indirect labeling using (131)I-histamine. The purity of chemical was determined by thin-layer chromatography and paper electrophoresis, as well as its stability for 30 days of storage in refrigerator, freezer and room temperature. The cellular uptake test of the radioligands from both methods was carried out with MCF7 and T-47D cell lines at 60 min. The results exhibited that (131)I-estradiol was succesfully obtained with radiochemical purity greater than 95% and more stable in the refrigerator until 21 days than freezer and room temperature. (131)I-estradiol and (131)I-his-estradiol were internalized higher in T-47D cells than MCF7 cells (44.34 ± 5.93% vs. 17.27 ± 1.71% and 45.34 ± 6.42% vs. 4.92 ± 1.59%, respectively). Furthermore, the radioligands can be used to binding assay in determining the agonist or antagonist to ER of new drugs development.