Aptamers directly radiolabeled with technetium-99m as a potential agent capable of identifying carcinoembryonic antigen (CEA) in tumor cells T84.

Aptamers are small oligonucleotides that are selected to bind with high affinity and specificity to a target molecule. Aptamers are emerging as a new class of molecules for radiopharmaceutical development. In this study a new method to radiolabel aptamers with technetium-99m ((99m)Tc) was developed. Two aptamers (Apt3 and Apt3-amine) selected against the carcinoembryonic antigen (CEA) were used. Labeling was done by the direct method and the developed complex was subjected to quality control tests. Radiochemical purity and stability were monitored by Thin Layer Chromatography. Binding and specificity assays were carried out in the T84 cell line (CEA+) to evaluate tumor affinity and specificity after radiolabeling. Aptamers were successfully labeled with (99m)Tc in high radiochemical yields, showing in vitro stability in presence of plasma and cystein. In binding assays the radiolabeled aptamer Apt3-amine showed the highest affinity to T84 cells. When evaluated with HeLa cells (CEA-), lower uptake was observed, suggesting high specificity for this aptamer. These results suggest that the Apt3-amine aptamer directly labeled with (99m)Tc could be considered a promising agent capable of identifying the carcinoembryonic antigen (CEA) present in tumor cells.