STUDIES ON THE INSTANT LABELING METHOD OF ^99mTc-HUMAN SERUM ALBUMIN

Abstract

Recent progress in radiopharmaceuticals have developed many useful ^99mTc labeled compounds. To minimize body irradiation through the labeling procedures and to produce uniform compounds, development of instant labeling kit is quite desirable. Various factors concerning with development of ^99mTc albumin kit have been investigated. Besides ^99mTc albumin, the labeled compound might contain free pertechnetate and colloidal components. The quality of the material was checked by Sephadex gel filtration and paper chromatography. Finally established procedures were as follows : into 50mg albumin solution 0.05 mg ofacidic stannous chloride was added, pH was adjusted to 2.5〜3.0,after 15 min. pH was brought back to neutral, passed through 0.22μ Millipor filter, then gassed by nitrogen before and after lyophilization, stoppered and kept refrigerated until use. When needed, labeling was effectively completed within 2 min. of mixing with ^99mTc pertechnetate. Using 1mg of tin, more than 33mg of albumin was found necessary to minimize contamination of colloid and pertechnetate. Against 50mg of albumin, increasing amount of tin resulted in increasing formation of colloid, and labeling efficiencies of higher than 90% could be achived by 0.05mg of stannous chloride. As to the duration of storage, gassation and lyophilization were found important. Freezed samples without gassation were not good enough after 1 week and gassed and freezed samples were useful for 2 weeks, but gassed and lyophilized samples provided excellent products even after 9 weeks.