Evaluation of labelling conditions, quality control and biodistribution study of 99mTc-5-aminolevulinic acid (5-ALA): a potential liver imaging agent

Labelling of 5-aminolevulinic acid (5-ALA) with 99mTc was achieved by using SnCl2·2H2O as reducing agent. Radiochemical purity and labelling efficiency was determined by instant thin layer chromatography/paper chromatography. Efficiency of labelling was dependent on many parameters such as amount of ligand, reducing agent, pH, and time of incubation. 99mTc labelled 5-ALA remained stable for 24 h in human serum. Tissue biodistribution of 99mTc-5-ALA was evaluated in Sprague–Dawley rats. Biodistribution study (% ID/g) in rats revealed that 99mTc-5-ALA was accumulated significantly in liver, spleen, stomach and intestine after half hour, 4 and 24 h. Significant activity was noted in bladder and urine at 4 h. High liver uptake of 99mTc-5-ALA makes it a promising liver imaging agent.