Development of [103Pd]-labeled-bis(N4-methylthiosemicarbazone) complexes as possible therapeutic agents

Due to interesting tumor seeking properties of bis-thiosemicarbazones, two radio palladium-bis-thio-semicarbazone complexes, i.e., [ 103 Pd]-pyruvaldehyde-bis(N 4 -methylthiosemicarbazone) ([ 103 Pd] PTSM) and [ 103 Pd]-di-acetyl-bis(N 4 -methylthiosemicarbazone) ([ 103 Pd]ATSM) were prepared according to the analogy of radio copper homologs. Palladium-103 (t 1/2 =16.96 d) was produced via the 103 Rh(p, n) 103 Pd nuclear reaction with proton energy 18 MeV. The final activity was eluted in form of Pd(NH 3 ) 2 Cl 2 in order to react with bis-thiosemicarbazones to yield [ 103 Pd]-labeled compounds. Chemical purity of the product was confirmed to be below the accepted limits by polarography. [ 103 Pd]-labeled bis-thiosemicarbazones were prepared with a radiochemical yield of more than 80% at room temperature after 60-90 min by vortexing a mixture of thiosemicarbazones and Pd activity in ethanol. The purification of the labeled compounds performed by reverse phase column chromatography using C 18 plus Sep-Pak. Radiochemical purity of more than 99% specific activity of about 12500-13000Ci/mol was obtained. The stability of the complexes was checked in final product and presence of human serum at 37°C up to 48 h. The partition co-efficients of the final complexes were determined. The initial physico-chemical properties of the labeled compounds were compared to those of their copper homologues.