Labelling and optimization of PHOTOFRIN^® with ^99mTc

Abstract

Abstract PHOTOFRIN ® was labelled with 99m Tc using SnCl 2 ·2H 2 O as reducing agent. Instant thin layer chromatography (ITLC-SG) in 0.05 M NaOH was used for evaluation of radiochemical purity. Labelling efficiency was dependent on various factors that include the ligand/reductant ratio, pH and time of incubation. Therefore, optimum conditions of labelling were also determined. The stability of 99m Tc-PHOTOFRIN ® in serum was checked by using fresh human serum. Tissue distribution of 99m Tc-PHOTOFRIN ® was evaluated in Sprague Dawley rats. PHOTOFRIN ® was labelled with an efficiency of >95% under optimum conditions, which were PHOTOFRIN ® : 200 μg, pH: 3–4, SnCl 2 ·2H 2 O: 15 μg and 30 min incubation at room temperature. The 99m Tc-labelled PHOTOFRIN ® remained stable in human serum for 24 h. Biodistribution study in rats revealed maximum concentration of the labelled compound in liver, lungs and spleen at 0.5 h, and significant activity was also seen in the bladder and urine, indicating the mode of urinary excretion of PHOTOFRIN ® .