6533b82ffe1ef96bd1294f25

RESEARCH PRODUCT

Separation and purification of no-carrier-added arsenic from bulk amounts of germanium for use in radiopharmaceutical labelling

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AbstractRadioarsenic labelled radiopharmaceuticals could add special features to molecular imaging with positron emission tomography (PET). For example the long physical half-lives of72As (T1/2=26 h) and74As (T1/2=17.8 d) in conjunction with their high positron branching rates of 88% and 29%, respectively, allow the investigation of slow physiological or metabolical processes, like the enrichment and biodistribution of monoclonal antibodies in tumour tissue or the characterization of stem cell trafficking. A method for separation and purification of no-carrier-added (nca) arsenic from irradiated metallic germanium targets based on distillation and anion exchange is developed. It finally converts the arsenic into an*As(III) synthon in PBS buffer and pH 7 suitable for labelling of proteinsviaAs-S bond formations. The method delivers radioarsenic in high purity with separation factors of 106from germanium and an overall yield from target to labelling synthon of >40%. In a proof-of-principle experiment, the monoclonal antibody Bevacizumab, directed against the human VEGF receptor, was labelled with a radiochemical yield >90% within 1 h at room temperature with nca72/74/77As.