Tc99m fibrinogen: an optimization of the labelling conditions

The influence of pH and medium constituents on the labelling of fibrinogen with Tc-99m, is described. Fibrinogen stability in solution is strongly pH dependent. pH range for stability of fibrinogen is narrow (5.5-10). Consequently fibrinogen can not be labelled in acid conditions. Only neutral or alkaline conditions may be prepared. The best formulation for Tc-99m fibrinogen consists in 4mg of fibrinogen in 0.05 M carbonate buffer pH 9.8 (1 ml) 30 μg stannous chloride 2H2O. The labelling is performed by adding less than 1ml TcO4 Tc-99m. Citrate and phosphate buffers compete strongly with proteins for Tc-99m and decrease drastically the plasmatic half life of Tc-99m proteins. Small quantities of glycin or ammonium sulfate or epsilon amino-caproic acid have no effects on the isotopic coagulability of Tc-99m fibrinogen