Long-circulating non-toxic blood pool imaging agent based on hyperbranched polyglycerols

PurposeCurrently, in vivo or in vitro99mTc-radiolabelled red blood cells are the standard blood pool imaging agents. Due to risks associated with handling of blood and the problems with the current 99mTc shortage, we were interested in a long-circulating biocompatible synthetic macromolecule that would be simple to prepare and could also be used for PET imaging.MethodsA high molecular weight hyperbranched polyglycerol (HPG) of 500 kDa was derivatized to coordinate radioactive gallium and to establish its labelling efficiency, stability and pharmacokinetics.ResultsThe resulting radiopharmaceutical in kit form was labelled rapidly within a couple of minutes at room temperature, was stable in transferrin and EDTA challenge tests, and was non-toxic in both cell viability and different hemocompatibility assays. A pharmacokinetic biodistribution study showed that the 67Ga–HPGN was confined to the blood compartment with a biological half life of 50.7 h.Conclusion67Ga–HPGN is thus a simple to prepare blood pool imaging agent for applications where a long biological half-life is essential, i.e., the diagnosis of internal bleeding. Since radiolabelling of the same kit with 68Ga was also confirmed, we plan to evaluate it shortly as a PET blood pool imaging agent for cardiac applications.

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