Preparation, characterization and radiolabeling of a new amphiphilic derivative of DTPA.

A new derivative (1) of diethylenetriamine pentaacetic acid (DTPA) is described. Compound 1 contains a hydrophobic unit (a triphenyl methyl group) and a hydrophilic unit (a DTPA ester), and therefore behaves as an amphiphile in aqueous solution. Compound 1 appears to form a stable inclusion complex with 99mTc. A rabbit model was used in a scintigraphic study of the biodistribution of the complex 99mTc-1, using 99mTc-DTPA as a control. The resulting images revealed marked differences: 99mTc-1 showed rapid uptake in the liver followed by excretion in the gallbladder and intestines within 1 h, whereas 99mTc-DTPA appears, as expected, in the renal-pelvico system and in the bladder. These findings are significant as they provide more insight into the complex relationship between structural and physicochemical properties of radiopharmaceuticals and their biodistribution. Knowledge of such relationships is absolutely mandatory with respect to the development of new radiopharmaceuticals with increased efficacy and/or specificity.