Dataset Information

Production, Collection, and Purification of 47Ca for the Generation of 47Sc through Isotope Harvesting at the National Superconducting Cyclotron Laboratory.

ABSTRACT: An experiment was performed at the National Superconducting Cyclotron Laboratory using a 140 MeV/nucleon 48Ca beam and a flowing-water target to produce 47Ca for the first time with this production route. A production rate of 0.020 ± 0.004 47Ca nuclei per incoming beam particle was measured. An isotope harvesting system attached to the target was used to collect radioactive cationic products, including 47Ca, from the water on a cation-exchange resin. The 47Ca collected was purified using three separation methods optimized for this work: (1) DGA extraction chromatography resin with HNO3 and HCl, (2) AG MP-50 cation-exchange resin with an increasing concentration gradient of HCl, and (3) AG MP-50 cation-exchange resin with a methanolic HCl gradient. These methods resulted in ?99 ± 2% separation yield of 47Ca with 100% radionuclidic purity within the limits of detection for HPGe measurements. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to identify low levels of stable ions in the water of the isotope harvesting system during the irradiation and in the final purified solution of 47Ca. For the first time, this experiment demonstrated the feasibility of the production, collection, and purification of 47Ca through isotope harvesting for the generation of 47Sc for nuclear medicine applications.

SUBMITTER: Abel EP

PROVIDER: S-EPMC7643120 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Production, Collection, and Purification of 47Ca for the Generation of 47Sc through Isotope Harvesting at the National Superconducting Cyclotron Laboratory.

Abel E Paige EP Domnanich Katharina K Clause Hannah K HK Kalman Colton C Walker Wes W Shusterman Jennifer A JA Greene John J Gott Matthew M Severin Gregory W GW

ACS omega 20201022 43

An experiment was performed at the National Superconducting Cyclotron Laboratory using a 140 MeV/nucleon 48Ca beam and a flowing-water target to produce 47Ca for the first time with this production route. A production rate of 0.020 ± 0.004 47Ca nuclei per incoming beam particle was measured. An isotope harvesting system attached to the target was used to collect radioactive cationic products, including 47Ca, from the water on a cation-exchange resin. T ...[more]

PMID: 33163769

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Project description:BackgroundIn molecular imaging and nuclear medicine, theranostic agents that integrate radionuclide pairs are successfully being used for individualized care, which has led to rapidly growing interest in their continued development. These compounds, which are radiolabeled with one radionuclide for imaging and a chemically identical or similar radionuclide for therapy, may improve patient-specific treatment and outcomes by matching the properties of different radionuclides with a targeting vector for a particular tumor type. One proposed theranostic radionuclide is scandium-47 (47Sc, T1/2 = 3.35 days), which can be used for targeted radiotherapy and may be paired with the positron emitting radionuclides, 43Sc (T1/2 = 3.89 h) and 44Sc (T1/2 = 3.97 h) for imaging. The aim of this study was to investigate the photonuclear production of 47Sc via the 48Ti(γ,p)47Sc reaction using an electron linear accelerator (eLINAC), separation and purification of 47Sc, the radiolabeling of somatostatin receptor-targeting peptide DOTATOC with 47Sc, and in vitro receptor-mediated binding of [47Sc]Sc-DOTATOC in AR42J somatostatin receptor subtype two (SSTR2) expressing rat pancreatic tumor cells.ResultsThe rate of 47Sc production in a stack of natural titanium foils (n = 39) was 8 × 107 Bq/mA·h (n = 3). Irradiated target foils were dissolved in 2.0 M H2SO4 under reflux. After dissolution, trivalent 47Sc ions were separated from natural Ti using AG MP-50 cation exchange resin. The recovered 47Sc was then purified using CHELEX 100 ion exchange resin. The average decay-corrected two-step 47Sc recovery (n = 9) was (77 ± 7)%. A radiolabeling yield of > 99.9% of [47Sc]Sc-DOTATOC (0.384 mg in 0.3 mL) was achieved using 1.7 MBq of 47Sc. Blocking studies using Octreotide illustrated receptor-mediated uptake of [47Sc]Sc-DOTATOC in AR42J cells.Conclusions47Sc can be produced via the 48Ti(γ,p)47Sc reaction and separated from natural Ti targets with a yield and radiochemical purity suitable for radiolabeling of peptides for in vitro studies. The data in this work supports the potential use of eLINACs for studies of photonuclear production of medical radionuclides and the future development of high-intensity eLINAC facilities capable of producing relevant quantities of carrier-free radionuclides currently inaccessible via routine production pathways or limited due to costly enriched targets.

Project description:BackgroundRadiotheragnostics makes use of the same molecular targeting vectors, labeled either with a diagnostic or therapeutic radionuclide, ideally of the same chemical element. The matched pair of scandium radionuclides, 44Sc and 47Sc, satisfies the desired physical aspects for PET imaging and radionuclide therapy, respectively. While the production and application of 44Sc was extensively studied, 47Sc is still in its infancy. The aim of the present study was, therefore, to investigate and compare two different methods of 47Sc production, based on the neutron irradiation of enriched 46Ca and 47Ti targets, respectively.Methods47Sc was produced by thermal neutron irradiation of enriched 46Ca targets via the 46Ca(n,γ)47Ca → 47Sc nuclear reaction and by fast neutron irradiation of 47Ti targets via the 47Ti(n,p)47Sc nuclear reaction, respectively. The product was compared with regard to yield and radionuclidic purity. The chemical separation of 47Sc was optimized in order to obtain a product of sufficient quality determined by labeling experiments using DOTANOC. Finally, preclinical SPECT/CT experiments were performed in tumor-bearing mice and compared with the PET image of the 44Sc labeled counterpart.ResultsUp to 2 GBq 47Sc was produced by thermal neutron irradiation of enriched 46Ca targets. The optimized chemical isolation of 47Sc from the target material allowed formulation of up to 1.5 GBq 47Sc with high radionuclidic purity (>99.99%) in a small volume (~700 μL) useful for labeling purposes. Three consecutive separations were possible by isolating the in-grown 47Sc from the 46/47Ca-containing fraction. 47Sc produced by fast neutron irradiated 47Ti targets resulted in a reduced radionuclidic purity (99.95-88.5%). The chemical purity of the separated 47Sc was determined by radiolabeling experiments using DOTANOC achievable at specific activities of 10 MBq/nmol. In vivo the 47Sc-DOTANOC performed equal to 44Sc-DOTANOC as determined by nuclear imaging.ConclusionThe production of 47Sc via the 46Ca(n,γ)47Ca nuclear reaction demonstrated significant advantages over the 47Ti production route, as it provided higher quantities of a radionuclidically pure product. The subsequent decay of 47Ca enabled the repeated separation of the 47Sc daughter nuclide from the 47Ca parent nuclide. Based on the results obtained from this work, 47Sc shows potential to be produced in suitable quality for clinical application.

Project description:BackgroundTerbium-155 [T1/2 = 5.32 d, Eγ = 87 keV (32%) 105 keV (25%)] is an interesting radionuclide suitable for single photon emission computed tomography (SPECT) imaging with potential application in the diagnosis of oncological disease. It shows similar decay characteristics to the clinically established indium-111 and would be a useful substitute for the diagnosis and prospective dosimetry with biomolecules that are afterwards labeled with therapeutic radiolanthanides and pseudo-radiolanthanides, such as lutetium-177 and yttrium-90. Moreover, terbium-155 could form part of the perfect "matched pair" with the therapeutic radionuclide terbium-161, making the concept of true radiotheragnostics a reality. The aim of this study was the investigation of the production of terbium-155 via the 155Gd(p,n)155Tb and 156Gd(p,2n)155Tb nuclear reactions and its subsequent purification, in order to obtain a final product in quantity and quality sufficient for preclinical application. The 156Gd(p,2n)155Tb nuclear reaction was performed with 72 MeV protons (degraded to ~ 23 MeV), while the 155Gd(p,n)155Tb reaction was degraded further to ~ 10 MeV, as well as performed at an 18 MeV medical cyclotron, to demonstrate its feasibility of production.ResultThe 156Gd(p,2n)155Tb nuclear reaction demonstrated higher production yields of up to 1.7 GBq, however, lower radionuclidic purity when compared to the final product (~ 200 MBq) of the 155Gd(p,n)155Tb nuclear reaction. In particular, other radioisotopes of terbium were produced as side products. The radiochemical purification of terbium-155 from the target material was developed to provide up to 1.0 GBq product in a small volume (~ 1 mL 0.05 M HCl), suitable for radiolabeling purposes. The high chemical purity of terbium-155 was proven by radiolabeling experiments at molar activities up to 100 MBq/nmol. SPECT/CT experiments were performed in tumor-bearing mice using [155Tb]Tb-DOTATOC.ConclusionThis study demonstrated two possible production routes for high activities of terbium-155 using a cyclotron, indicating that the radionuclide is more accessible than the exclusive mass-separated method previously demonstrated. The developed radiochemical purification of terbium-155 from the target material yielded [155Tb]TbCl3 in high chemical purity. As a result, initial cell uptake investigations, as well as SPECT/CT in vivo studies with [155Tb]Tb-DOTATOC, were successfully performed, indicating that the chemical separation produced a product with suitable quality for preclinical studies.

Project description:Both scandium-44 and yttrium-86 are popular PET isotopes with appropriate half-lives for immuno-positron emission tomography (immuno-PET) imaging. Herein, a new bifunctional H4pypa ligand, H4pypa-phenyl-NCS, is synthesized, conjugated to a monoclonal antibody, TRC105, and labeled with both radionuclides to investigate the long-term in vivo stability of each complex. While the 44Sc-labeled radiotracer exhibited promising pharmacokinetics and stability in 4T1-xenograft mice (n = 3) even upon prolonged interactions with blood serum proteins, the progressive bone uptake of the 86Y-counterpart indicated in vivo demetallation, obviating H4pypa as a suitable chelator for Y3+ ion in vivo. The solution chemistry of [natY(pypa)]- was studied in detail and the complex found to be thermodynamically stable in solution with a pM value 22.0, ≥3 units higher than those of the analogous DOTA- and CHX-A''-DTPA-complexes; the 86Y-result in vivo was therefore most unexpected. To explore further this in vivo lability, Density Functional Theory (DFT) calculation was performed to predict the geometry of [Y(pypa)]- and the results were compared with those for the analogous Sc- and Lu-complexes; all three adopted the same coordination geometry (i.e. distorted capped square antiprism), but the metal-ligand bonds were much longer in [Y(pypa)]- than in [Lu(pypa)]- and [Sc(pypa)]-, which could indicate that the size of the binding cavity is too small for the Y3+ ion, but suitable for both the Lu3+ and Sc3+ ions. Considered along with results from [86Y][Y(pypa-phenyl-TRC105)], it is noted that when matching chelators with radionuclides, chemical data such as the thermodynamic stability and in vitro inertness, albeit useful and necessary, do not always translate to in vivo inertness, especially with the prolonged blood circulation of the radiotracer bound to a monoclonal antibody. Although H4pypa is a nonadentate chelator, which theoretically matches the coordination number of the Y3+ ion, we show herein that its binding cavity, in fact, favors smaller metal ions such as Sc3+ and Lu3+ and further exploitation of the Sc-pypa combination is desired.

Dataset Information

Production, Collection, and Purification of 47Ca for the Generation of 47Sc through Isotope Harvesting at the National Superconducting Cyclotron Laboratory.

Publications

Production, Collection, and Purification of <sup>47</sup>Ca for the Generation of <sup>47</sup>Sc through Isotope Harvesting at the National Superconducting Cyclotron Laboratory.

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