Synthesis and properties of neutral gadolinium and technetium-99m-labeled complexes

Diethylenetriaminepentaacetic di(L-dopa ethyl ester) ligand (DTPA-2LDEE) was synthesized by reaction between diethylenetriaminepentaacetic dianhydride (DTPAA) and L-dopa ethyl ester (LDEE). This ligand reacted with gadolinium chloride and sodium pertechnetate to make the corresponding neutral gadolinium complex Gd-DTPA-2LDEE and technetium-99m-labeled complex 99mTc-DTPA-2LDEE, respectively. The ligand and complexes were characterized and their properties in vitro and in vivo were also evaluated. Gd-DTPA-2LDEE possessed higher relaxation effectiveness and lower cytotoxicity to human hepatoma HepG-2 cells than Gd-DTPA. 99mTc-DTPA-2LDEE had enhanced single-photon emission computed tomography (SPECT) signal enhancements of the kidneys in rats and provided longer duration time than that of 99mTc-DTPA. Therefore, 99mTc-DTPA-2LDEE can be selectively excreted by the kidneys and used as a potential radioactive probe in SPECT.