Radiolabeling optimization of a cysteine-dextran lymph node seeking molecule using 99mTc-tricarbonyl core

1923 Objectives Technetium-99m-labeled dextran is a useful radiopharmaceutical for lymphoscintigraphy. The aim of this study was the radiolabeling optimization of a chemically modified dextran molecule using 99mTc-tricarbonyl core. Methods 99mTc-carbonyl was prepared using Isolink kit. Different variables such as temperature, concentration of Dextran-cysteine, volume of 99mTc(CO)3 and time for reaction were studied. Tricarbonyl ion radiochemical purity as well as 99mTc-Cys-Dextran purity was assessed in multiple chromatographic systems using TLC in order to allow quantification of byproducts. Radiochemical purity was also checked by HPLC and in a PD-10 column. Results Radiochemical purity of the 99mTc-tricarbonyl core was higher than 90%. Chromatography on a PD-10 column provided 99mTc-cysteine-dextran in fractions 7 to 12. Best conditions for cysteine-dextran radiolabeling were 20 μg of the molecule, 100 ml of 99mTc(CO)3, 100 oC and 20 min. Labeling yield was 92.3 +/-2.7 %. The radiochromatographic system that best defined all radio species was composed by SG-Al sheets in MeOH/6N HCl (95/5), Whatman n.1 in Acetone and ITLC-SG in MeOH/HCl 99:1. Conclusions Chemically modified dextran with cysteine was successfully radiolabeled. Radiochemical and chemical controls to guarantee the quality of this new potential radiotracer were also established. Research Support We want to thank IAEA for supporting this study.