The use of redox polymers in labelling procedures of proteins and peptides with 99mTc. II. Technique of preparation of kits for protein labelling by 99mTc and its effect on the stability and radiochemical purity

Abstract

BACKGROUND: Our research into new methods of labelling biologically active substances with technetium (^99mTc) to be used in nuclear medicine is focused on proteins and peptides whose labelling is difficult and continues to pose a problem. Use of redox polymers is the gentlest method as there is no need to use other compounds to modify reaction conditions, as is the way with the currently employed methods.
METHODS: Kits containing proteins, e.g., human immunoglobulin (IgG), human leukocytes dialysate (HLD), were labelled with ^99mTc using a redox polymer (RP-IDA) and/or using reduction of pertechnetate (^99mTc) with stannous chloride. The radiochemical purity was evaluated using paper and/or electrophoresis of the labelled proteins. The results were confirmed by column chromatography of the labelled IgG.
RESULTS: Use of a redox polymer for labelling raises the stability of ^99mTc labelled proteins so that labelling efficiency remains virtually the same (96-98%) after 30 hours while it is about 45% with the routine method using stannous chloride. The stability of protein-containing kits prepared using redox polymers was improved; the labelling efficiency of HLD and IgG after 300 days of kit storage was over 97% and 87%, respectively.
CONCLUSIONS: The labelling procedure using redox polymers can be used in formulating protein- and peptide-based radiopharmaceuticals to improve their stability and ^99mTc labelling efficiency.