Abstract
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Objectives Several studies are available, which highlight the use of Schiff base ligands for radio-labeling, but very little work has been reported which has used Marcepto compounds, although it is desired to include such compounds in the design of radiopharmaceuticals due to their importance in the biological system.
Methods Equimolar L - cysteine and salicylaldehyde in distilled water and ethanol were heated at 40°C to form a white colored ligand. The product formed was analyzed using FT - IR, thermo gravimetric analysis and elemental analysis at Fc College. Radiolabeling of the ligand was performed at SKMCH&RC using 99mTc from 99Mo generator. SnCl2.H2O was used as a reducing agent at STP. Radio TLC was performed using SG plates and 0.9% NaCl and acetone as the mobile phases. Geiger Muller counter detected the counts on the SG plates and radiolabeling efficiency of the product was achieved. Quality control results of the radiolabeled product were performed before moving further. During Biodistribution study, product was injected IV into the animal ear. Scanning was performed under the gamma camera.
Results Ligand synthesis was verified from IR indicating the presence of the closed ring structure Thiozolidine ring 1 (Fig. 1). IR showed absence of chromophore group hence the ligand was colorless. DSC peaks indicated the reaction type as endothermic. Ligand appeared to be stable in DMSO. After optimizing various parameters effective radiolabeling up to 88 % was achieved at pH 5, using lyophilized tin chloride pyrophosphate cold kit in NaCl (0.9%). Animal study was carried out for Bio distribution of the radiopharmaceutical. 99mTc - ligand uptake was highlighted in the soft organs immediately after injection. The areas showing higher radiotracer uptake were kidney (20 %), liver (35 %), bones (15%) and brain (10 %) (Fig. 2). Delayed images showed the radiotracer retention in the soft organs as well as in the spine of the animals (Fig 3, 4). Comparative study was performed using 99mTc - MDP and 99mTc PHYTATE.
Conclusions Salicylaldicysteine is efficiently labeled with 99mTc and is suitable in simultaneous scanning of liver, kidney and brain. In this study, significant uptake is highlighted in brain in addition to soft tissues in dynamic flow followed with delay images, which is worth consideration. This indicates the ability of drug in crossing the blood brain barrier. This study also highlights the importance of sulfur containing ligands in brain scanning.