Comparative studies of S-bridged complexes of 99mTc with fac(S)-[M(aet)3] (M=RhIII, IrIII; aet=2-aminoethanethiolate)

Abstract

fac (S)-[Ir(aet) 3 ] (aet=2-aminoethanethiolate) is N3S3 metalloligand, which forms S-bridged polynuclear complexes with transition metal ions. A complex analogous to [Re{Ir(aet 3 )} 2 ] 3+ was formed by the reaction of 99m TcO 4 Na and fac (S)-[Ir(aet) 3 ] in the presence of SnCl 2 2H 2 O. A simple method for radiollabelling of fac (S)-[Ir(aet) 3 ] with 99m Tc was developed with radiolabelling efficiency higher than 99%. Effects of SnCl 2 ·2H 2 O concentration, time and pH on the radiolabelling efficiency were determined and compared with 99m Tc-[Rh(aet) 3 ]. 99m Tc-[Ir(aet) 3 ] was also characterized by electrophoresis, HPLC, biodistribution studies in rats and scintigraphy in rabbit. Higher uptake by kidneys showed rapid distribution of the labelled fac (S)-[Ir(aet) 3 ]. Scintigrams show that liver, bladder and skeletal uptake were significant. The results of biodistribution showed that 99m Tc-[Ir(aet) 3 ] uptake is quite rapid as compared to 99m Tc-[Rh(aet) 3 ].