An instant kit method for labeling antimyosin Fab' with technetium-99m: evaluation in an experimental myocardial infarct model.

An instant kit method for labeling antibody Fab' fragments was developed. The method utilizes a ligand exchange reaction between the intermediate complex 99mTc-D-glucarate and the free sulfhydryl groups on the antibody Fab' fragment. Radiolabeling of the Fab' using generator eluate achieves quantitative 99mTc incorporation in less than 30 min at room temperature. The radiolabel is stable in human plasma for at least 24 hr and stable to incubation with 10 mM diethylene-triaminepentaacetic acid (24 hr) and 1 mM diaminodithiol agent (up to 3 hr). Mouse biodistribution of 99mTc-antimyosin shows faster blood clearance and lower uptake in the lungs, liver, and spleen in comparison to 111In-antimyosin. Technetium-99m-antimyosin and 111In-antimyosin showed equivalent ability to detect myocardial infarct in a canine model.