Physico-chemical characterisation of 99mTc-tin fluoride colloid agent used for labelling white cells

Tc-99m-tin fluoride colloid is an agent used to label leucocytes, for the imaging and diagnosis of inflammatory conditions including Crohn's disease. Despite previous investigations, this radiolabelling agent is still poorly characterised. The aim of this work was to examine the process of formation and stability of Tc-99m-tin fluoride colloid using mass spectrometry, membrane filtration and atomic absorption spectrophotometric techniques. Tin-oxide bonds in tin clusters were identified in the stannous fluoride reagent vial by mass spectrometry. From radioactive particle size distribution experiments, the facile disruption of radiocolloid particles with excess oxygen gas contrasted to the partial hydrolysis of Sn(II) during the formation process. Under the standard conditions, 10% of particles were determined as 1-3 mu m, and this population coordinated 96% of the Tc-99m added. Colloid particle formation and the reduction of Tc-99m-pertechnetate is discussed. Sodium fluoride may optimise 1-3 mu m radioactive particle size, by regulating particle growth. Tc-99m-tin fluoride colloid is affected by positive or negative charge, as either Al, Mo ions or solid membranes, resulting in either coagulation and/or deflocculation of the particles. Copyright (c) 2006 John Wiley & Sons, Ltd.