preparation & evaluation of [201tl](iii)-dtpa-higg for inflammation detection

background: radiolabeled polyclonal human immunoglubins are useful in the detection of inflammations. in this work a novel approach has been presented to use thallium-201 as a comlexed nuclide for the development of radioimmunoconjugates. materials and methods: thallium-201 (t1/2=3.04 d) in tl+ form was converted to tl3+ cation in presence of o3 in 6m hcl, controlled by rtlc/gel electrophoresis methods and used in the labeling of human polyclonal antibody (higg) after residulation with freshly prepared cyclic dtpa-dianhydride. the best results of the conjugation were obtained by the addition of 1 ml of a higg pharmaceutical solution (5 mg/ml, in phosphate buffer, ph=7) to a glass tube, which was pre-coated with dtpa-dianhydride (0.01 mg) at 25c with continuous mild stirring for 30 min. results: the final isotonic [201tl](iii)-dtpa-higg complex was checked by radio-tlc using several solvent systems to ensure the formation of only one species, and it was followed by filtration through a 0.22 µm filter (specific activity= 33.7 tbq/mm, radiochemical purity95%). preliminary bio-distribution studies in normal and inflammation-bearing rats were performed. the target/skin and target/blood ratios were 4 and 6 after 28h, respectively, showing the selectivity of the radiopharmaceutical for the inflammatory lesions. conclusion: the incorporation of tl(iii) cation into a immunoconjugate was performed using the known methods. the biodistribution of the immunocomplex was shown to be consistent with a stable complex for the detection of inflammations. significant inflammation detection was observed for the final complex in rats with turpentine oil-induced inflammation.