Comparative Study of a Series of ^99mTc(CO)₃ Mannosylated Dextran Derivatives for Sentinel Lymph Node Detection

Sentinel lymph node detection (SLND) is rapidly entering common practice in the management of patients with tumors. The introduction of mannose molecules to ^99mTc-labeled dextrans, so far, showed that the sentinel node could trap these agents due to their recognition by the mannose receptors of lymph node macrophages. The current study aimed to synthesize, characterize, and biologically evaluate a series of mannosylated dextran derivatives labeled with ^99mTc for potential use in SLND. The compounds were designed to have a dextran with a molecular weight of 10-500 kDa as a backbone, S-derivatized cysteines, efficient SNO chelators, and mannose moieties for binding to mannose receptors. They were successfully synthesized, thoroughly characterized using NMR techniques, and labeled with the fac-[^99mTc(CO)₃]⁺ synthon. Labeling with high yields and radiochemical purities was achieved with all derivatives. In vivo biodistribution and imaging studies demonstrated high uptake in the first lymph node and low uptakes in the following node and confirmed the ability to visualize the SLN. Among the compounds studied, ^99mTc-D75CM demonstrated the most attractive biological features, and in combination with the high radiochemical yield and stability of the compound, its further evaluation as a new radiopharmaceutical for sentinel lymph node detection was justified.