Experimental study of 99mTc-depreotide preparation and its affinity with A549 cell

The (99m)Tc-labeled agent, ((99m)TcO)depreotide, has received regulatory approval in the United States and Europe for use in the detection of cancer. It is essential to establish a simple and reliable method of direct radiolabeling of (99m)Tc-depreotide and to investigate its specific receptor binding properties with human non small cell lung cancer (NSCLC) A549 cell in vitro. So we made some researches as follow: Depreotide was labeled with (99m)Tc using SnCl2 as a reductant. Labeling efficiencies at different pH values and temperatures were compared. Radioreceptor assay was used to observe the uptake kinetics, stagnation and retention half time of (99m)Tc-depreotide in A549 cells. As the results of the investigation ,many facts is shown below: The labeling rate of pH 6.0 group was higher than that of pH 5.0 and pH7.0 groups. The labeling rate decreased when temperature increased from 15 °C to 50 °C. The uptake rate increased with rising temperature, and the maximum uptake was observed at 60 min at 37 °C. The cleaning curves were similar at different temperatures, and the half cleaning time at 37 °C was 48 min. The results showed that the optimal conditions for labeling depreotide with (99m)Tc was found to be below 15 °C at a pH lower than 6.0. Furthermore, at 37 °C, (99m)Tc-depreotid may have the potential as an ideal imaging agent for somatostatin receptors.