The labelling of human serum transferrin with 99mTc and a study concerning uptake of the complex by tumour cells.
The direct labelling of serum transferrin (sTf) with 99mTc on high-affinity binding sites, producing a complex of excellent stability, is described. The high-affinity binding sites were prepared by pre-treating sTf with 2-mercaptoethanol. For the radiolabelling step, thiourea was used as an exchange ligand and a filtration procedure used to remove 99mTc that had not complexed with the protein. RT112 bladder tumour cells incubated in the presence of labelled sTf showed a rapid initial uptake of 99mTc, reaching a plateau after about 20 min. Radiolabelling was also carried out without a pre-reduction step in an attempt to form a co-ordination complex between 99mTc and the Fe3+-binding site of sTf, analogous to that formed by Fe3+. The tumour cell uptake of sTf labelled without pre-reduction was then examined. In contrast to 59Fe3+ and other radio-metals co-ordinated with the Fe3+-binding site which show a continuous increase in incorporation with time, the uptake of 99mTc rapidly reached a plateau.
Smith
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TA
Department of Chemistry, Innovation Centre, University of York, UK.
Walton
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PH
D006801:Humans; D007553:Isotope Labeling / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013667:Technetium / Q000493:pharmacokinetics*; D014168:Transferrin / Q000493:pharmacokinetics*; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000378:metabolism*
D019275:Radiopharmaceuticals; D014168:Transferrin; D013667:Technetium