ИСТИНА

The complexation of alpha, beta and Auger emitting radionuclides is under investigation for the target delivering of them to tumor cells. One of the most common ligand used for binding of cationic species in nuclear medicine is 1,4,7,10-tetra-azacyclotetradecane-N,N′,N″,N‴-tetraacetic acid (H4DOTA). It forms thermodynamically and kinetically stable complexes with such cations as Ac3+, Y3+, Lu3+, Bi3+. However the kinetics of complexation is not always suitable in comparison with half-life periods of required nuclides. Consequently the search of new effective binding chelating molecules that would demonstrate fast kinetics of complex formation should be carried out among H4DOTA analogs. Water soluble new DOTA-like azamacrocyclic compounds show not only thermodynamic affinity for metal cations but also demonstrate “immediate” complex formation. This work presents complexation study of Y3+, Lu3+ and La3+ (as Ac3+ analog) by new diazamacrocylic ligand L. H4DOTA L Stability constants of ML complexes were determined by potentiometric titration of aqueous solutions of ligand in the presence of M3+ cations in water-jacketed titration vessel maintained at 25.0±0.1°C. The formation of 1:1 ML complex was observed. The protonation constants of the ligand L and the stability constants of the complexes were calculated from the electromotive force titration data with Hyperquad software: M=Y3+ lgβML=5.94±0.01; M=Lu3+ lgβML=5.87±0.01; M=La3+ lgβML=5.46±0.02. These values are in agreement with common tendency to stronger binding with cation hardness increasing. The change in UV absorbance spectrum of L before and after M3+ cation addition achieves in 3-5 minutes and does not modify during days that confirms fast complex formation. The work is supported by RFBR (project 13-03-01304 )