Formation of 99mTc-immunoglobulin G complexes free from radiocolloids, quality controlled by radioimmunoelectrophoresis.

A method for the formation of 99mTc-human immunoglobulin G(99mTc-IgG) complexes free from radiocolloids is described. A concentrated hydrochloric acid reduction/vacuum evaporation/gentisic acid method was applied. Although no preparative chromatography was performed, no sign of 99mTc-radiocolloids was observed in the chemical quality controls of the 99mTc-IgG formation. High radiochemical purities of 99mTc-IgG were obtained either by precipitation in 32 vol.% ethanol in water at -10 degrees C, or by removal of other 99mTc-complexes by simply adding a suspension of sterilized Dowex 1 in gentisic acid solution. Besides gel chromatography and thin layer chromatography, the 99mTc-IgG formation was quality controlled by radioimmunoelectrophoresis in agarose gel with rabbit anti-human IgG-antibodies present in the gel. The 99mTc-IgG complexes were complex bound to the rabbit anti-human IgG antibodies, and precipitated as rockets in the gel. These rockets could be scintigraphed and their radioactivities could be quantified, thereby a quantitatively radio-chemical quality control based on the antigenicities of the 99mTc-IgG complexes was obtained. The 99mTc-IgG complexes were highly stable with no sign of dissociation even when the radioimmunoelectrophoresis was performed for 24 h. Improvements of the radioimmunoelectrophoretic system for the quality control of 99mTc-complexes with specific purified antibodies, are proposed.