Browsing by Author "Fuchs, A"

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    Evaluation of radioisotope quality aspects for preparation of high specific activity [Ga-68]-NOTA-AnnexinA1.
    (Elsevier, 2010-09-08) Fuchs, A; Greguric, I; Roe, G
    The bi-functional chelator NOTA-(p-Bn)-NCS permits radio-labelling heat sensitive proteins with Ga-68 (t1/2=68 min) for positron emission tomography. Complexation at room temperature (RT) completes within minutes and in vivo transmetalation is negligible. Here, influences of trace metal cations, on radiochemical yield (RCY) and specific radioactivity (SRA) are assessed. Conjugation of NOTA-(p-Bn)-NCS to AnnexinA1 was performed at varying stoichiometries and conjugates purified by size exclusion high-performance liquid chromatography. Available complexation sites per protein were identified by colorimetric assay and titration with carrier added Ga-67. The complexation of Ga-68 by NOTA-AnnexinA1 at RT and 37°C was systematically studied with and without addition of competing trace metal cations. Ga-67 was used for confirmation of observed trends. Integrity of the radio-conjugate was assessed by addition of up to 104 fold excess of metal cations or apo-transferin and exposure to human serum at 37°C. Gallium-68 gave RCY of N99% within minutes at RT whereas, Ga-67 yielded max 85% dropping as the stock decayed. Presence of Fe(III) showed significant influence on RCY. Once formed, the radio-conjugate showed negligible loss of radioactivity under even the most extreme conditions investigated. SRA and RCY of the radio-conjugate depend significantly on absence of particularly Fe(III) during complexation. © 2020 Elsevier B.V
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    Feasibility of incorporating cations and anions expected in radioactive waste streams in metakaolin-based geopolymers.
    (Electrical Components International, 2007-03-25) Perera, DS; Vance, ER; Aly, Z; Fuchs, A; Kiyama, S; Davis, J; Smith, SV
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    Insight into the mechanisms of metal ion binding in hexagonal tungsten bronze
    (American Physical Society, 2006-03) Kennedy, SJ; Smith, SV; Avdeev, M; Fuchs, A
    Tungsten trioxides and their alkali-metal-intercalated products MzWO3+ show potential for application in electrodes, as ion exchangers, catalysts and the treatment of radioactive waste. Hexagonal tungsten bronze (HTB) was selected for the present work because its structure features hexagonal channels, of diameter ∼0.54 nm, that may be useful for selective and reversible binding of metal ions. X-ray and neutron powder diffraction were used to provide an insight into the mechanisms of metal ion binding of the Mo doped HTB's. Combined Rietveld refinement of the X-ray and neutron diffraction shows that doping with Mo degrades the crystallinity of HTB, in particular by creating a high degree of disorder in the a-b planes. Structural information combined with solution chemistry indicates several potential mechanisms of binding and metal ion exchange sites. This type of investigation provides invaluable information for new strategies in the design of inorganic sorbents and their optimization for metal ion separation.
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    Probing solid-liquid interfaces using radiotracer technology: characterization of functionalized microspheres.
    (American Chemical Society, 2008-08-26) Huang, S; Joso, R; Fuchs, A; Barner, L; Smith, SV
    This study explores the use of nuclear probes (radiolabeling techniques) for the quantification of available, reactive groups on solid surfaces and their role in the engineering of materials for biosensor applications. Microspheres were synthesized with reactive carboxylate groups as conjugation sites for proteins. The carboxylate groups were reacted with three bifunctional ligands, sarar, aminobenzyl-cyclen, and aminobenzyl-dota. The reaction conditions used were similar to that employed for the conjugation of proteins and optimized for the concentration of reactants (bifunctional ligand and EDC), pH, and time at 21°C. Of the three bifunctional ligands conjugated to the microsphere, sarar proved to be the most efficient. Optimum reaction conditions employed molar ratios of 1:20:100 for microspheres (estimated carboxylate groups of 1.1 × 10−7 per milligram of microspheres):sarar:EDC at pH 5.0 for 1 h, followed by 57/natCo radiolabeling at pH 7.0. The study demonstrates how nuclear probes with high specificity and sensitiviy can provide invaluable information on available reactive sites on solid surfaces at extremely low concentrations (>10−10 M) in a range of media. More importantly the nuclear probes enable the characterization of the surfaces of new materials in a non-destructive manner under conditions relevant to the engineering of the materials and ultimately the desired biosensor. © 2008, American Chemical Society