Formation of99mTc-immunoglobulin G complexes free from radiocolloids, quality controlled by radioimmunoelectrophoresis

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Abstract
A method for the formation of99mTc-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 of99mTc-radiocolloids was observed in the chemical quality controls of the99mTc-IgG formation. High radiochemical purities of99mTc-IgG were obtained either by precipitation in 32 vol.% ethnnol in water at-10°C, or by removal of other99mTc-complexes by simply adding a suspension of sterilized Dowex 1 in gentisic acid solution. Besides gel chromatography and thin layer chromatography, the99mTc-IgG formation was quality controlled by radioimmunoelectrophoresis in agarose gel with rabbit anti-human IgG-antibodies present in the gel. The99mTc-IgG complexes were complex bound to the rabbit antihuman IgG antibodies, and precipitated as rockets in the gel. These rockets could be scintigraphed and their radioactivities could be quantified, thereby a quantitatively radiochemical quality control based on the antigenicities of the99mTc-IgG complexes was obtained. The99mTc-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 of99mTc-complexes with specific purified antibodies, are proposed.

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