Synthesis, characterization and evaluation of^99mTc-L, L-ethylenecysteine dimer to assess regional cerebral blood flow

Abstract

L,L-ethylenecysteine dimer (L,L-ECD) compound was synthesized with an overall yield 31.2% and a melting point 197–198°C. A systematic study has been carried out on the labelling of L,L-ECD with technetium-99m by ligand exchange via^99mTc-EDTA. The percent labelling yield of L,L-ECD was found ≥95% when 0.75 2.0 mg and 100 μg of L,L-ECD, disodium-EDTA and tin (II) were used, respectively, at pH 5.5. The produced^99mTc-L,L-ECD complex is stable, neutral and lipid soluble. The^99mTc-L,L-ECD complex penetrate the blood-brain barrier following intravenous injection in the tail vein of mice with an initial brain uptake equal to 0.9% at 2 minutes and a slow washout equal to 0.65% after 25 minutes. High uptake in the gastrointestinal tract (GIT) was observed. It reaches up to 38.9% at 2 minutes and increased as time pass reaching 48.3% at 60 minutes. These results indicate that this ligand is suitable for brain imaging and has a tendency to be excreted via liver and GIT due to its lipophilicity.