A new method for radiochemical separation of arsenic from irradiated germanium oxide

Vrije Universiteit Brussel, Bruxelles, Brussels Capital, Belgium
Applied Radiation and Isotopes (Impact Factor: 1.23). 10/2005; 63(3):343-51. DOI: 10.1016/j.apradiso.2005.04.005
Source: PubMed


Radioarsenic labelled radiopharmaceuticals could be a valuable asset to Positron Emission Tomography (PET). In particular, the long half-lives of (72)As (T(1/2)=26 h) and (74)As (T(1/2)=17.8 d) allow to investigate slow physiological or metabolical processes, like the enrichment and distribution of antibodies in tumor tissue. This work describes the direct production of no-carrier-added (nca) arsenic isotopes *As, with *=71, 72, 73, 74 or 77, the reaction to [*As]AsI(3) and its radiochemical separation from the irradiated solid germanium oxide via polystyrene-based solid-phase extraction. The germanium oxide target, irradiated at a cyclotron or a nuclear reactor, is dissolved in concentrated HF and Ge is separated almost quantitatively (99.97%) as [GeF(6)](2-). [*As]AsI(3) is formed by addition of potassium iodide. The radiochemical separation yield for arsenic is >90%. [*As]AsI(3) is a versatile radioarsenic labelling synthon.

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    • " to [ 77 As ] As ( III ) . The reduced nca [ 77 As ] As is extracted into benzene ( Fischer et al . , 1954 ] . Thus , 77 As is obtained as As ( III ) in benzene ; this could be dried and taken up into various vehicles for the preparation of various types of nca arsenic compounds including the most important labeling synthon , nca [ 77 As ] AsI 3 ( Jennewein et al . , 2005 ) . Due to its high solubility in different organic solvents such as benzene , toluene , xylene , chloroform and carbon disulfide ( Zingaro , 1994 ) , it is possible to reconstitute the nca [ 77 As ] AsI 3 obtained from the separated nca [ 77 As ] As ( III ) into in any vehicle of choice for further labeling applica - tions relevant to "
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    ABSTRACT: A method for the separation of no-carrier-added (nca) arsenic radionuclides from bulk amounts of irradiated germanium oxide (GeO2) target was developed in view of their potentialities in different biological and nuclear medicine applications. The beta- emitting 77As radionuclide, produced by the decay of 77Ge through the natGe(n,gamma)77Ge nuclear reaction, was used for standardization of the radiochemical separation procedure. The radiochemical separation was performed by precipitation followed by solvent extraction. About 99% post-irradiation recovery of the GeO2 target material, in a form suitable for reuse in future irradiation, was achieved. The developed method was suitable for the production of nca arsenic radionuclides either as trivalent or pentavalent arsenic in various vehicles which provided flexibility of formulations of different kinds of compound. The overall radiochemical yield for the complete separation of 77As was 90%. The separated nca 77As was of high radionuclidic purity and did not contain detectable amounts of the target material. This method can be adopted for the radiochemical separation of other different arsenic radionuclides produced from GeO2 through cyclotron as well as reactor irradiation.
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    ABSTRACT: Radioarsenic labelled radiopharmaceuticals could be a valuable asset to positron emission tomography. In particular, the long half-lives of As-72 (T-1/2 = 26 h) and As-74 (T-1/2 = 17.8 d) allow to investigate slow physiological or metabolical processes, like the enrichment and distribution of monoclonal antibodies (mab) in tumour tissue. In this work, a new method for the labelling of proteins with various radioactive arsenic isotopes was developed. For this purpose, two proteins, namely a chimeric IgG(3) monoclonal antibody, ch3G4, directed against anionic phospholipids, and Rituxan (Rituximab), were labelled as a proof of principle with no-carrier-added radioarsenic isotopes (As-74 and As-77). The developed labelling chemistry gives high yields (> 99.9%), is reliable and could easily be transferred to automated labelling systems in a clinical environment. At least for the mab used in this work, this route of radioarsenic labelling does not affect the immunoreactivity of the product. The arsenic label stays stable for up to 72 h at the molecular mass of the monoclonal antibody, which is in particular relevant to follow the pharmacology and pharmacokinetics of the labelled mab for several days. (c) 2006 Elsevier B.V. All rights reserved.
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