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Kelderman CAA, Maclean RC, Hungnes IN, Davey PRWJ, Salimova E, de Veer M, Patel N, Ma MT, Paterson BM. Technetium Nitrido Complexes of Tetradentate Thiosemicarbazones: Kit-Based Radiolabeling, Characterization, and In Vivo Evaluation. Inorg Chem 2023; 62:20791-20805. [PMID: 37855107 DOI: 10.1021/acs.inorgchem.3c02650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
Bis(thiosemicarbazone) and pyridylhydrazone-thiosemicarbazone chelators have demonstrated utility in nuclear medicine. In particular, the 64Cu2+ complexes have been extensively developed for hypoxia imaging and molecular imaging of peptide and protein markers of disease. However, the chemistry and application of bis(thiosemicarbazone) and pyridylhydrazone-thiosemicarbazone chelators in combination with 99mTc, the most widely used radionuclide in nuclear medicine, is underexplored. Herein, a series of bis(thiosemicarbazone) and pyridylhydrazone-thiosemicarbazone chelators were radiolabeled with nitrido-technetium-99m in an optimized one-pot synthesis from [99mTc]TcO4-. Optimization of the radiochemical syntheses allowed for production of the complexes in >90% radiochemical conversion with apparent molar activities of 3.3-5 GBq/μmol. Competition experiments demonstrated the excellent stability of the complexes. The nitrido-technetium-99 complexes were synthesized, and the chemical identities were investigated using mass spectrometry, spectroscopy, and density functional theory calculations. Complexation of nitrido-rhenium(V) was achieved with the N4-dialkylated bis(thiosemicarbazones). Planar imaging and ex vivo biodistribution studies of the five 99mTc complexes were conducted on healthy BALB/c mice to determine in vivo behavior. The lipophilic nature of the complexes resulted in uptake of 1.6-5.7% ID g-1 in the brain at 2 min postinjection and retention of 0.4-1.7% ID g-1 at 15 min postinjection. The stability of the complexes and the biodistribution data demonstrate that these chelators are ideal platforms for future production of radiopharmaceutical candidates.
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Affiliation(s)
| | - Rachel C Maclean
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Ingebjørg N Hungnes
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom
| | - Patrick R W J Davey
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Ekaterina Salimova
- Monash Biomedical Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Michael de Veer
- Monash Biomedical Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Natasha Patel
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom
| | - Michelle T Ma
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas' Hospital, London SE1 7EH, United Kingdom
| | - Brett M Paterson
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, Queensland 4072, Australia
- Monash Biomedical Imaging, Monash University, Clayton, Victoria 3800, Australia
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Design, Synthesis and Preclinical Assessment of 99mTc-iFAP for In Vivo Fibroblast Activation Protein (FAP) Imaging. Molecules 2022; 27:molecules27010264. [PMID: 35011496 PMCID: PMC8746441 DOI: 10.3390/molecules27010264] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 12/29/2021] [Accepted: 12/30/2021] [Indexed: 02/04/2023] Open
Abstract
Fibroblast activation protein (FAP) is expressed in the microenvironment of most human epithelial tumors. 68Ga-labeled FAP inhibitors based on the cyanopyrrolidine structure (FAPI) are currently used for the detection of the tumor microenvironment by PET imaging. This research aimed to design, synthesize and preclinically evaluate a new FAP inhibitor radiopharmaceutical based on the 99mTc-((R)-1-((6-hydrazinylnicotinoyl)-D-alanyl) pyrrolidin-2-yl) boronic acid (99mTc-iFAP) structure for SPECT imaging. Molecular docking for affinity calculations was performed using the AutoDock software. The chemical synthesis was based on a series of coupling reactions of 6-hidrazinylnicotinic acid (HYNIC) and D-alanine to a boronic acid derivative. The iFAP was prepared as a lyophilized formulation based on EDDA/SnCl2 for labeling with 99mTc. The radiochemical purity (R.P.) was verified via ITLC-SG and reversed-phase radio-HPLC. The stability in human serum was evaluated by size-exclusion HPLC. In vitro cell uptake was assessed using N30 stromal endometrial cells (FAP positive) and human fibroblasts (FAP negative). Biodistribution and tumor uptake were determined in Hep-G2 tumor-bearing nude mice, from which images were acquired using a micro-SPECT/CT. The iFAP ligand (Ki = 0.536 nm, AutoDock affinity), characterized by UV-Vis, FT-IR, 1H–NMR and UPLC-mass spectroscopies, was synthesized with a chemical purity of 92%. The 99mTc-iFAP was obtained with a R.P. >98%. In vitro and in vivo studies indicated high radiotracer stability in human serum (>95% at 24 h), specific recognition for FAP, high tumor uptake (7.05 ± 1.13% ID/g at 30 min) and fast kidney elimination. The results found in this research justify additional dosimetric and clinical studies to establish the sensitivity and specificity of the 99mTc-iFAP.
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Kaur A, New EJ, Sunde M. Strategies for the Molecular Imaging of Amyloid and the Value of a Multimodal Approach. ACS Sens 2020; 5:2268-2282. [PMID: 32627533 DOI: 10.1021/acssensors.0c01101] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Protein aggregation has been widely implicated in neurodegenerative diseases such as Alzheimer's disease, frontotemporal dementia, Parkinson's disease, and Huntington disease, as well as in systemic amyloidoses and conditions associated with localized amyloid deposits, such as type-II diabetes. The pressing need for a better understanding of the factors governing protein assembly has driven research for the development of molecular sensors for amyloidogenic proteins. To date, a number of sensors have been developed that report on the presence of protein aggregates utilizing various modalities, and their utility demonstrated for imaging protein aggregation in vitro and in vivo. Analysis of these sensors highlights the various advantages and disadvantages of the different imaging modalities and makes clear that multimodal sensors with properties amenable to more than one imaging technique need to be developed. This critical review highlights the key molecular scaffolds reported for molecular imaging modalities such as fluorescence, positron emission tomography, single photon emission computed tomography, and magnetic resonance imaging and includes discussion of the advantages and disadvantages of each modality, and future directions for the design of amyloid sensors. We also discuss the recent efforts focused on the design and development of multimodal sensors and the value of cross-validation across multiple modalities.
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Affiliation(s)
- Amandeep Kaur
- The University of Sydney, School of Medical Sciences, Faculty of Medicine and Health, Sydney, New South Wales 2006, Australia
- The University of Sydney, Nano Institute (Sydney Nano), The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Elizabeth J. New
- The University of Sydney, Nano Institute (Sydney Nano), The University of Sydney, Sydney, New South Wales 2006, Australia
- The University of Sydney, School of Chemistry, Faculty of Science, Sydney, New South Wales 2006, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Margaret Sunde
- The University of Sydney, School of Medical Sciences, Faculty of Medicine and Health, Sydney, New South Wales 2006, Australia
- The University of Sydney, Nano Institute (Sydney Nano), The University of Sydney, Sydney, New South Wales 2006, Australia
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Abstract
The knowledge on element 43 (Tc) of the periodic table, built over the years through the contributions given by the close relationship between chemistry and nuclear medicine, allowed the development of new and increasingly effective radiopharmaceuticals useful both as perfusion and target specific imaging agents for SPECT (single photon emission tomography). Among the manifold Tc-compounds, Tc(V) nitrido complexes played a relevant role in the search for new technetium-99m radiopharmaceuticals, providing efficient labeling procedures that can be conveniently exploited for the design and synthesis of agents, also incorporating small organic molecules or peptides having defined structural features. With this work, we present an overview of four decades of research on the chemistry and on the nuclear medicine applications of Tc(V) nitrido complexes.
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Cardoso ME, Tejería E, Rey Ríos AM, Terán M. Development and characterization of a 99m Tc-labeled Neuropeptide Y short analog with potential application in breast cancer imaging. Chem Biol Drug Des 2019; 95:302-310. [PMID: 31709766 DOI: 10.1111/cbdd.13644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 09/03/2019] [Accepted: 09/29/2019] [Indexed: 12/26/2022]
Abstract
The aim of this work was to develop and evaluate a 99m Tc-labeled neuropeptide Y derivative with affinity toward Y1-receptor. The selected amino acid sequence included nine amino acids derived from the C-terminal portion of the NPY complemented with the addition of one cysteine-mercaptoacetic acid moiety to bind the radiometal. Labeling was achieved through the preparation of a 3 + 1 nitrido complex. Physicochemical evaluation, cell uptake, internalization and externalization studies, and competitive assays were performed. Biodistribution experiments were carried out in normal and tumor-bearing mice. A single product with radiochemical purity >90% and high stability was obtained. In vitro analysis showed specific cellular uptake, IC50 of 73.2 nM, and a high internalization rate (80%). Biodistribution studies showed low blood and renal uptake and combined hepatobiliary and urinary elimination. Preliminary studies in mice bearing induced breast tumors rendered promising uptake values.
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Affiliation(s)
- María Elena Cardoso
- Área de Radioquímica, Facultad de Química, Universidad de la República (UdelaR), Montevideo, Uruguay
| | - Emilia Tejería
- Área de Radioquímica, Facultad de Química, Universidad de la República (UdelaR), Montevideo, Uruguay
| | - Ana María Rey Ríos
- Área de Radioquímica, Facultad de Química, Universidad de la República (UdelaR), Montevideo, Uruguay
| | - Mariella Terán
- Área de Radioquímica, Facultad de Química, Universidad de la República (UdelaR), Montevideo, Uruguay
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Tejería E, Giglio J, Fernández L, Rey A. Development and evaluation of a 99mTc(V)-nitrido complex derived from estradiol for breast cancer imaging. Appl Radiat Isot 2019; 154:108854. [PMID: 31442798 DOI: 10.1016/j.apradiso.2019.108854] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/02/2019] [Accepted: 08/11/2019] [Indexed: 01/10/2023]
Abstract
Estrogen receptors are overexpressed in 70% of breast cancer and identification of their presence is important to select the appropriate treatment. This work proposes the preparation and evaluation of an estradiol derived as potential ER imaging agent. Ethinylestradiol was derivatized to introduce a dithiocarbamate function for Tc coordination. Labeling was achieved through the formation of a symmetric Tc(V)-nitrido complex with a radiochemical purity (RCP) > 95%. Physicochemical evaluation, cell uptake, biodistribution in normal animals and in nude mice bearing induced ER + breast tumors showed promising results.
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Affiliation(s)
- Emilia Tejería
- Área de Radioquímica, Facultad de Química, General Flores 2124, Universidad de La República, 11800, Montevideo, Uruguay
| | - Javier Giglio
- Área de Radioquímica, Facultad de Química, General Flores 2124, Universidad de La República, 11800, Montevideo, Uruguay.
| | - Leticia Fernández
- Área de Radioquímica, Facultad de Química, General Flores 2124, Universidad de La República, 11800, Montevideo, Uruguay
| | - Ana Rey
- Área de Radioquímica, Facultad de Química, General Flores 2124, Universidad de La República, 11800, Montevideo, Uruguay.
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Yoshimura T, Nagata K, Shiroyama T, Kino Y, Takayama T, Sekine T, Shinohara A. A luminescent dicyanidonitridotechnetium(v) core with tridentate ligand coordination sites. Dalton Trans 2018; 47:16027-16030. [PMID: 30311926 DOI: 10.1039/c8dt02935k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A novel, luminescent technetium complex, [TcN(CN)2bpa] (bpa = bis-(2-pyridylmethyl)amine), with tridentate ligand coordination sites was synthesized and characterized. Photoemission with a maximum wavelength at 666 nm was observed in the solid-state at 296 K.
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Affiliation(s)
- Takashi Yoshimura
- Radioisotope Research Center, Institute for Radiation Sciences, Osaka University, Suita, Osaka 565-0871, Japan.
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8
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Khan AU, Khan MR, Shah SQ. 99mTc-prulifloxacin in artificially infected animals. Nuklearmedizin 2017; 50:134-40. [DOI: 10.3413/nukmed-0334-10-07] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Accepted: 01/10/2011] [Indexed: 11/20/2022]
Abstract
SummaryAim: The radiosynthesis of 99mTc-Prulifloxacin (99mTc-PRN) was assessed in terms of stability, binding with Staphylococcus aureus (S. aureus), biodistribution in rats (RT) and scintigraphic profile in rabbits (RB). Animals, material, methods: 99mTc-PRN was synthesized by mixing 25 μg of stannous fluoride (SnF2) with 18.5 MB of sodium pertechnetate. Thereafter, 0.5 mg of the prufloxacin (PRN) was added to the reaction mixture and the pH was set at 5.1 with 0.01 mol/l HCl. The reaction mixture was incubated at room temperature. The same process was repeated by increasing the concentration of the stannous fluoride from 25 to 250 μg, sodium pertechnetate from 18,5 to 185 MBq and the PRN from 0.5 to 5 mg. The radiochemical stability of the 99mTc-PRN was investigated in higher concentration of the cystein. In-vitro binding investigation was performed using living and heat killed S. aureus to verify specificity of the 99mTc-PRN. Biodistribution was evaluated in artificially infected rats and scintigraphic precision in rabbits at different interval. Results: The 99mTc-RPN prepared by mixing 2 mg of PRN, 74 MBq sodium pertechnetate, 100 μg stannous fluoride at pH 5.4, appeared to be more than 90% stable with a maximum radiochemical yield of 98.15 ± 0.25% at 30 min. The 99mTc-PRN showed higher stability in serum and satisfactory in-vitro binding to living as compared to heat killed S. aureus. 14.25 ± 0.15% of the injected dose was accumulated in the infected muscle of the model RT. Infected to normal muscle ratio was 5.12 and inflamed to normal muscle was 1.2. The biodistribution was validated by the scintigraphic localization of infection in rabbits. Conclusion: This investigation of 99mTc-PRN confirmed its momentous radiochemical immovability in saline, serum, preferential in-vitro binding to living bacteria, higher uptake in the infected muscle of model RT and precise localization in the infected muscle of model RB.
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Salvarese N, Refosco F, Seraglia R, Roverso M, Dolmella A, Bolzati C. Synthesis and characterization of rhenium(iii) complexes with (Ph 2PCH 2CH 2) 2NR diphosphinoamine ligands. Dalton Trans 2017; 46:9180-9191. [PMID: 28675225 DOI: 10.1039/c7dt01032j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis and characterization of a new series of neutral, six-coordinated compounds [ReIIIX3(PNPR)], where X is Cl or Br and PNPR is a diphosphinoamine having the general formula (Ph2PCH2CH2)2NR (R = H, CH3, CH2CH3, CH2CH2CH3, CH2CH2CH2CH3 and CH2CH2OCH3) are reported. Stable [ReIIIX3(PNPR)] complexes were synthesized, in variable yields, starting from precursors where the metal was in different oxidation states (iii and v), by ligand-exchange and/or redox-substitution reactions. The compounds were characterized by elemental analysis, proton NMR spectroscopy, cyclic voltammetry, UV/vis spectroscopy, positive-ion electrospray ionization mass spectrometry (ESI(+)-MS) and X-ray diffraction analysis. Although the formulation of the complexes allows either meridional or facial isomers, the latter arrangement was prevalent both in the solid and solution states. Only [ReCl3(PNPH)] showed a meridional configuration both in solution and in the crystalline state. [ReBr3(PNPme)] prefers the meridional configuration in the crystalline state and the facial one in solution. While ESI(+)-MS and voltammetric data seem to indicate some dependency from the nature of the alkyl substituent at the nitrogen, the available structural data of the complexes show only slight differences both for angles and bond lengths upon change of the alkyl chain tethered to the nitrogen.
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10
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Clinical translation of a PSMA inhibitor for 99m Tc-based SPECT. Nucl Med Biol 2017; 48:36-44. [DOI: 10.1016/j.nucmedbio.2017.01.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 11/22/2022]
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11
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Radiolabeling, biological evaluation and molecular docking of delafloxacin: a novel methicillin-resistant Staphylococcus aureus infection radiotracer. J Radioanal Nucl Chem 2015. [DOI: 10.1007/s10967-015-4586-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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12
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Radiocomplexation and evaluation of the 99mTc-Gemifloxacin in artificially Escherichia coli infected mice. J Radioanal Nucl Chem 2015. [DOI: 10.1007/s10967-015-4515-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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13
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El-Kawy OA, Farah K. Radiocomplexation and biological evaluation of nemonoxacin in mice infected with multiresistant Staphylococcus aureus and penicillin-resistant Streptococci. J Radioanal Nucl Chem 2015. [DOI: 10.1007/s10967-015-4069-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Deiser F, Kraus F, Schmidbaur H. Bis(triphenylphosphine)silver( i) perrhenate, a cyclic dimer. Chem Commun (Camb) 2015; 51:6746-8. [DOI: 10.1039/c5cc01446h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 1 : 4 and 1 : 2 complexes of silver perrhenate and triphenylphosphine, [(Ph3P)4Ag]+ReO4−and [(Ph3P)2AgReO4]2, have been prepared and their structures determined in the solid state by X-ray diffraction.
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Affiliation(s)
- F. Deiser
- Department Chemie
- Technische Universität München
- 85747 Garching b. M
- Germany
| | - F. Kraus
- Department Chemie
- Technische Universität München
- 85747 Garching b. M
- Germany
- Fachbereich Chemie
| | - H. Schmidbaur
- Department Chemie
- Technische Universität München
- 85747 Garching b. M
- Germany
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Salvarese N, Morellato N, Rosato A, Meléndez-Alafort L, Refosco F, Bolzati C. Novel [99mTcIII(PS)2(Ln)] Mixed-Ligand Compounds (PS = Phosphino-thiolate; L = Dithiocarbamate) Useful in Design and Development of TcIII-Based Agents: Synthesis, in Vitro, and ex Vivo Biodistribution Studies. J Med Chem 2014; 57:8960-70. [DOI: 10.1021/jm501088w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nicola Salvarese
- Dipartimento
di Scienze Chirurgiche, Oncologiche e Gastroenterologiche, Università degli Studi di Padova, via Gattamelata 64, 35138 Padua, Italy
| | - Nicolò Morellato
- Dipartimento
di Scienze del Farmaco, Università degli Studi di Padova, Via Marzolo 5, 35131 Padua, Italy
| | - Antonio Rosato
- Dipartimento
di Scienze Chirurgiche, Oncologiche e Gastroenterologiche, Università degli Studi di Padova, via Gattamelata 64, 35138 Padua, Italy
- Istituto Oncologico Veneto, via
Gattamelata 64, 35138 Padua, Italy
| | - Laura Meléndez-Alafort
- Dipartimento
di Scienze Chirurgiche, Oncologiche e Gastroenterologiche, Università degli Studi di Padova, via Gattamelata 64, 35138 Padua, Italy
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Kit preparation and biokinetics in women of 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 for breast cancer imaging. Nucl Med Commun 2014; 35:423-32. [DOI: 10.1097/mnm.0000000000000065] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Hayne DJ, Lim S, Donnelly PS. Metal complexes designed to bind to amyloid-β for the diagnosis and treatment of Alzheimer's disease. Chem Soc Rev 2014; 43:6701-15. [PMID: 24671229 DOI: 10.1039/c4cs00026a] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Alzheimer's disease is the most common form of age-related neurodegenerative dementia. The disease is characterised by the presence of plaques in the cerebral cortex. The major constituent of these plaques is aggregated amyloid-β peptide. This review focuses on the molecular aspects of metal complexes designed to bind to amyloid-β. The development of radioactive metal-based complexes of copper and technetium designed as diagnostic imaging agents to detect amyloid burden in the brain is discussed. Separate sections of the review discuss the use of luminescent metal complexes to act as non-conventional probes of amyloid formation and recent research into the use of metal complexes as inhibitors of amyloid formation and toxicity.
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Affiliation(s)
- David J Hayne
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, 3010, Australia.
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Design and biological evaluation of ⁹⁹mTc-N₂S₂-Tat(49-57)-c(RGDyK): a hybrid radiopharmaceutical for tumors expressing α(v)β(3) integrins. Nucl Med Biol 2013; 40:481-7. [PMID: 23618768 DOI: 10.1016/j.nucmedbio.2013.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Revised: 01/08/2013] [Accepted: 01/15/2013] [Indexed: 11/21/2022]
Abstract
UNLABELLED The α(ν)β(3) integrin is over-expressed in the tumor neovasculature and the tumor cells of glioblastomas. The HIV Tat-derived peptide has been used to deliver various cargos into cells. The aim of this research was to synthesize and assess the in vitro and in vivo uptake of (99m)Tc-N₂S₂-Tat(49-57)-c(RGDyK) ((99m)Tc-Tat-RGD) in α(ν)β(3) integrin positive cancer cells and compare it to that of a conventional (99m)Tc-RGD peptide ((99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2). METHODS The c(RGDyK) peptide was conjugated to a maleimidopropionyl (MP) moiety through Lys, and the MP group was used as the branch position to form a thioether with the Cys(12) side chain of the Tat(49-57)-spacer-N₂S₂ peptide. (99m)Tc-Tat-RGD was prepared, and stability studies were carried out by size exclusion HPLC analyses in human serum. The in vitro affinity for α(v)β(3) integrin was determined by a competitive binding assay. In vitro internalization was determined using glioblastoma C6 cells. Biodistribution studies were accomplished in athymic mice with C6 induced tumors that had blocked and unblocked receptors. Images were obtained using a micro-SPECT/CT. RESULTS (99m)Tc-Tat-RGD was obtained with a radiochemical purity higher than 95%, as determined by radio-HPLC and ITLC-SG analyses. Protein binding was 15.7% for (99m)Tc-Tat-RGD and 5.6% for (99m)Tc-RGD. The IC50 values were 6.7 nM ((99m)Tc-Tat-RGD) and 4.6 nM ((99m)Tc-RGD). Internalization in C6 cells was higher in (99m)Tc-Tat-RGD (37.5%) than in (99m)Tc-RGD (10%). Biodistribution studies and in vivo micro-SPECT/CT images in mice showed higher tumor uptake for (99m)Tc-Tat-RGD (6.98% ± 1.34% ID/g at 3h) than that of (99m)Tc-RGD (3.72%±0.52% ID/g at 3h) with specific recognition for α(v)β(3) integrins. CONCLUSIONS Because of the significant cell internalization (Auger and internal conversion electrons) and specific recognition for α(v)β(3) integrins, the hybrid (99m)Tc-N₂S₂-Tat(49-57)-c(RGDyK) radiopharmaceutical is potentially useful for the imaging and possible therapy of tumors expressing α(v)β(3) integrins.
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19
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Salvarese N, Morellato N, Venzo A, Refosco F, Dolmella A, Bolzati C. Synthesis and Characterization of [MIII(PS)2(L)] Mixed-Ligand Compounds (M = Re, 99Tc; PS = Phosphinothiolate; L = Dithiocarbamate) as Potential Models for the Development of New Agents for SPECT Imaging and Radiotherapy. Inorg Chem 2013; 52:6365-77. [DOI: 10.1021/ic400094s] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- N. Salvarese
- Dipartimento di Scienze del
Farmaco, Università di Padova, Via
Marzolo 5, 35131 Padova, Italy
| | - N. Morellato
- Dipartimento di Scienze del
Farmaco, Università di Padova, Via
Marzolo 5, 35131 Padova, Italy
| | - A. Venzo
- ISTM-CNR, Via Marzolo 1, 35131 Padova,
Italy
| | - F. Refosco
- ICIS-CNR, Corso Stati Uniti, 4, 35127 Padova, Italy
| | - A. Dolmella
- Dipartimento di Scienze del
Farmaco, Università di Padova, Via
Marzolo 5, 35131 Padova, Italy
| | - C. Bolzati
- ICIS-CNR, Corso Stati Uniti, 4, 35127 Padova, Italy
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Hickey JL, Donnelly PS. Diagnostic imaging of Alzheimer's disease with copper and technetium complexes. Coord Chem Rev 2012. [DOI: 10.1016/j.ccr.2012.03.035] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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RGD conjugates of the H2dedpa scaffold: synthesis, labeling and imaging with 68Ga. Nucl Med Biol 2012; 39:785-94. [DOI: 10.1016/j.nucmedbio.2012.01.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/29/2011] [Accepted: 01/10/2012] [Indexed: 11/20/2022]
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Radiosynthesis of (99m)Tc(CO)3-Clinafloxacin Dithiocarbamate and Its Biological Evaluation as a Potential Staphylococcus aureus Infection Radiotracer. Nucl Med Mol Imaging 2011; 45:248-54. [PMID: 24900014 DOI: 10.1007/s13139-011-0106-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 08/21/2011] [Accepted: 08/23/2011] [Indexed: 10/17/2022] Open
Abstract
BACKGROUND Clinafloxacin dithiocarbamate (CNND) was radiolabeled with technetium-99m ((99m)Tc) using [(99m)Tc(CO)3(H2O)3](+) and assessed for its radiochemical stability in saline and serum, its in vitro binding with methicillin-resistant Staphylococcus aureus (MRSA) and biodistribution in female nude mice (FNM) artificially infected with live and heat-killed MRSA. METHODS In normal saline (NS) the (99m)Tc(CO)3-clinafloxacin dithiocarbamate ((99m)Tc(CO)3-CNND) showed radiochemical stability with a maximum value of 99.10 ± 0.20% and remained stable up to 4 h (92.65 ± 0.18%). RESULTS In human serum at 37°C within 16 h of incubation, 14.85% side products as a result of de-tagging developed. Incubation with MRSA gave saturated binding with a maximum value of 72.75 ± 1.20%. Almost six-fold higher uptake was seen in the infected muscle of the FNM as compared to the inflamed and normal muscle. The (99m)Tc(CO)3-CNND complex showed a normal route of excretion from the body of the FNM model. CONCLUSION The higher stability in NS, HS, saturated in vitro binding with a live strain of MRSA and six-fold higher uptake in the target organ showed the (99m)Tc(CO)3-CNND complex to be a potential MRSA infection radiotracer.
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Shah SQ, Khan MR. 99mTcN–gatifloxacin dithiocarbamate complex: a novel multi-drug-resistance Streptococcus pneumoniae (MRSP) infection radiotracer. J Radioanal Nucl Chem 2011. [DOI: 10.1007/s10967-011-1180-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shah SQ, Khan MR. Radiosynthesis and biodistribution of the 99mTc-trovafloxacin complex as a potential methicillin resistant Staphylococcus aureus infection radiotracer. J Radioanal Nucl Chem 2011. [DOI: 10.1007/s10967-011-0991-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Shah SQ, Khan MR. Radiosynthesis and characterization of the 99mTc-fleroxacin complex: a novel Escherichia coli infection imaging agent. TRANSIT METAL CHEM 2011. [DOI: 10.1007/s11243-011-9467-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Synthesis of 99mTcV ≡ N-Pazufloxacin dithiocarbamate complex and biological evaluation in Wister rats artificially infected with Escherichia coli. J Radioanal Nucl Chem 2011. [DOI: 10.1007/s10967-010-0954-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Chatterjee S, Del Negro AS, Edwards MK, Twamley B, Krause JA, Bryan SA. trans-K(3)[TcO(2)(CN)(4)]. Acta Crystallogr Sect E Struct Rep Online 2010; 66:i61-i62. [PMID: 21588082 PMCID: PMC3007308 DOI: 10.1107/s1600536810028205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 07/14/2010] [Indexed: 05/30/2023]
Abstract
The structure of the title compound, tripotassium trans-tetra-cyanidodioxidotechnetate(V), is isotypic with its Re analogue. The [TcO(2)(CN)(4)](3-)trans-tetra-cyanido-dioxido-technetate anion has a slightly distorted octa-hedral configuration. The Tc atom is located on a center of inversion and is bound to two O atoms in axial and to four cyanide ligands in equatorial positions. The Tc-O distance is consistent with a double-bond character. The two potassium cations, one located on a center of inversion and one in a general position, reside in octa-hedral or tetra-hedral environments, respectively. K⋯O and K⋯N inter-actions occur in the 2.7877 (19)-2.8598 (15) Å range.
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Affiliation(s)
- Sayandev Chatterjee
- Radiochemical Processing Laboratory, Pacific Northwest National Laboratory, Richland, WA 99357, USA
| | - Andrew S. Del Negro
- Radiochemical Processing Laboratory, Pacific Northwest National Laboratory, Richland, WA 99357, USA
| | - Matthew K. Edwards
- Radiochemical Processing Laboratory, Pacific Northwest National Laboratory, Richland, WA 99357, USA
| | - Brendan Twamley
- Department of Chemistry, University of Idaho, Moscow, ID 83844, USA
| | - Jeanette A. Krause
- Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA
| | - Samuel A. Bryan
- Radiochemical Processing Laboratory, Pacific Northwest National Laboratory, Richland, WA 99357, USA
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Bolzati C, Cavazza-Ceccato M, Agostini S, Tisato F, Bandoli G. Technetium and rhenium in five-coordinate symmetrical and dissymmetrical nitrido complexes with alkyl phosphino-thiol ligands. Synthesis and structural characterization. Inorg Chem 2009; 47:11972-83. [PMID: 19007158 DOI: 10.1021/ic801436d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reactivity of bulky alkylphosphino-thiol ligands (PSH) toward nitride-M(V, VI) (M = Tc/Re) precursors was investigated. Neutral five-coordinate monosubstituted complexes of the type [M(N)(PS)Cl(PPh(3))] (Tc1-4, Re1-2) were prepared in moderate to high yields. It was found that these [M(N)(PS)Cl(PPh(3))] species underwent ligand-exchange reactions under mild conditions when reacted with bidentate mononegative ligands having soft donor atoms such as dithiocarbamates (NaL(n)) to afford stable dissymmetrical mixed-substituted complexes of the type [M(N)(PS)(L(n))] (Tc5,8-10, Re5-9) containing two different bidentate chelating ligands bound to the [M[triple bond]N](2+) moiety. In these reactions, the dithiocarbamate replaced the two labile monodentate ligands (Cl and PPh(3)) leaving the [M(N)(PS)](+) building block intact. In the above reactions, technetium and rhenium were found to behave in a similar way. Instead, under more drastic conditions, reactions of PSH with [M(N)Cl(2)(PPh(3))(2)] gave a mixture of monosubstituted [M(N)(PS)Cl(PPh(3))] and bis-substituted species [M(N)(PS)(2)] (Tc11-14) in the case of technetium, whereas only monosubstituted [M(N)(PS)Cl(PPh(3))] complexes were recovered for rhenium. All isolated products were characterized by elemental analysis, IR and multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopies, ESI MS spectrometry, and X-ray crystal structure determination of the representative monosubstituted [Tc(N)(PStbu)Cl(PPh(3))] (Tc4) and mixed-substituted [Re(N)(PScy)(L(3))] (Re7) and [Re(N)(PSiso)(L(4))] (Re9) complexes. The latter rhenium complexes represent the first example of a square-pyramidal nitrido Re species with the basal plane defined by a PS(3) donor set. Monosubstituted [M(N)(PS)Cl(PPh(3))] species bearing the substitution-inert [M(N)(PS)](+) moieties act as suitable building blocks proposed for the construction of new classes of dissymmetrical nitrido compounds with potential application in the development of essential and target specific (99m)Tc and (188)Re radiopharmaceuticals for imaging and therapy, respectively.
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Santos-Cuevas CL, Ferro-Flores G, Arteaga de Murphy C, Ramírez FDM, Luna-Gutiérrez MA, Pedraza-López M, García-Becerra R, Ordaz-Rosado D. Design, preparation, in vitro and in vivo evaluation of 99mTc-N2S2-Tat(49–57)-bombesin: A target-specific hybrid radiopharmaceutical. Int J Pharm 2009; 375:75-83. [DOI: 10.1016/j.ijpharm.2009.04.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Revised: 04/11/2009] [Accepted: 04/14/2009] [Indexed: 10/20/2022]
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Boros E, Häfeli UO, Patrick BO, Adam MJ, Orvig C. Design, Synthesis, and Imaging of Small Amphiphilic Rhenium and 99mTechnetium Tricarbonyl Complexes. Bioconjug Chem 2009; 20:1002-9. [DOI: 10.1021/bc900022c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eszter Boros
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146, East Mall, Vancouver, British Columbia, V6T 1Z3, Canada, and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
| | - Urs O. Häfeli
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146, East Mall, Vancouver, British Columbia, V6T 1Z3, Canada, and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
| | - Brian O. Patrick
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146, East Mall, Vancouver, British Columbia, V6T 1Z3, Canada, and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
| | - Michael J. Adam
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146, East Mall, Vancouver, British Columbia, V6T 1Z3, Canada, and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
| | - Chris Orvig
- Medicinal Inorganic Chemistry Group, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146, East Mall, Vancouver, British Columbia, V6T 1Z3, Canada, and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
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Gancheff JS, Kremer C, Denis PA, Giorgi C, Bianchi A. Thermodynamic study of proton transfer reactions of Re(V) trans-dioxocomplexes in aqueous solution. Dalton Trans 2009:8257-68. [DOI: 10.1039/b911121b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Katayev EA, Kolesnikov GV, Sessler JL. Molecular recognition of pertechnetate and perrhenate. Chem Soc Rev 2009; 38:1572-86. [PMID: 19587953 DOI: 10.1039/b806468g] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Evgeny A Katayev
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov st., 28, Moscow 119991, Russian Federation.
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First examples of neutral rhenium(V) complexes with a novel semi-rigid ligand containing a P,N,N,S donor atom set: Synthesis, characterisation and crystal structure. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.07.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Wolohan P, Reichert DE. Molecular modeling of hexakis(areneisonitrile)technetium(I), tricarbonyl eta5 cyclopentadienyl technetium and technetium(V)-oxo complexes: MM3 parameter development and prediction of biological properties. J Mol Graph Model 2007; 25:616-32. [PMID: 16769234 DOI: 10.1016/j.jmgm.2006.04.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 04/26/2006] [Accepted: 04/27/2006] [Indexed: 11/24/2022]
Abstract
Genetic algorithms (GA) were used to develop specific technetium metal-ligand force field parameters for the MM3 force field. These parameters were developed using automated procedures within the program FFGenerAtor from a combination of crystallographic structures and ab initio calculations. These new parameters produced results in good agreement with experiment when tested against a blind validation set. To illustrate the utility of these new force field parameters, quantitative structure-activity relationship (QSAR) models were developed to predict the P-glycoprotein uptake (log10 VI) of a series of hexakis(areneisonitrile)technetium(I) complexes and to predict their biodistribution. The log10 VI QSAR model, built using a training set of 16 Tc(I) isonitrile complexes, exhibited a correlation between the experimental log10 VI and 5 simple descriptors as follows: r2 = 0.94, q2 = 0.93. When applied to an external test set of six Tc(I) isonitrile complexes, the QSAR preformed with great accuracy q2 = 0.78 based on a leave-one-out cross-validation analysis. Further QSAR models were developed to predict the biodistribution of the same set of Tc(I) isonitrile complexes; a QSAR model to predict hepatic uptake exhibited a correlation between the experimental log10(Blood/Liver) with six simple descriptors as follows: r2 = 0.97, q2 = 0.96. A QSAR model to predict renal uptake exhibited a correlation between the experimental log10(Blood/Kidney) and six simple descriptors as follows: r2 = 0.85, q2 = 0.82. When applied to the external test set the QSAR models preformed with great accuracy, q2 = 0.78 and 0.56, respectively.
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Affiliation(s)
- Peter Wolohan
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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35
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Méndez-Rojas MA, Kharisov BI, Tsivadze AY. Recent advances on technetium complexes: coordination chemistry and medical applications¶. J COORD CHEM 2007. [DOI: 10.1080/00958970500324633] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Miguel A. Méndez-Rojas
- a Departamento de Química y Biología , Universidad de las Américas-Puebla , Ex-Hacienda de Sta. Catarina Martir, AP 100, Cholula 72820, Puebla, México
| | - Boris I. Kharisov
- b Facultad de Ciencias Químicas , Universidad Autónoma de Nuevo León , 66450 San Nicolas de los Garza 18-F, Nuevo León, México
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Cowley AR, Dilworth JR, Salichou M. Syntheses and structures of pyrazolylmethane complexes of rhenium(iii), (iv) and (v). Dalton Trans 2007:1621-9. [PMID: 17426864 DOI: 10.1039/b617549j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reaction of [ReOCl3(PPh3)(2)] with HCpz(3) (pz = pyrazole) in dichloromethane leads to the formation of a new Re(iv) complex [ReCl3(HCpz3)]X (X=Cl, [ReO4]) with loss of the rhenium-oxo group. We also report a convenient, high-yield synthetic route to complexes of the type [ReOXn(L)](3-n)+ (X=Cl, Br, n = 2, 3) by the reaction of bis(pyrazolylmethane) and bis(pyrazolylacetate) ligands with [ReOCl3(PPh3)2]. Dinuclear complexes containing the O=Re-O-Re=O group were also isolated and structurally characterised. We have also investigated the reactions of these ligands with diazenide precursors and isolated and characterised complexes of the type [ReClx(N2Ph) (L)(PPh3)] (x = 1,2). The potential applications of these complexes as radiopharmaeuticals is discussed.
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Affiliation(s)
- Andrew R Cowley
- Central Chemistry Department, University of Oxford, 12 Mansfield Road, Oxford, UK
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Tisato F, Porchia M, Bolzati C, Refosco F, Vittadini A. The preparation of substitution-inert 99Tc metal-fragments: Promising candidates for the design of new 99mTc radiopharmaceuticals. Coord Chem Rev 2006. [DOI: 10.1016/j.ccr.2006.01.022] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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38
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Banerjee SR, Babich JW, Zubieta J. A new bifunctional amino acid chelator targeting the glucose transporter. Inorganica Chim Acta 2006. [DOI: 10.1016/j.ica.2005.11.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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40
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Tzanopoulou S, Pirmettis IC, Patsis G, Raptopoulou C, Terzis A, Papadopoulos M, Pelecanou M. Oxorhenium(V) and Oxotechnetium(V) [NN][S]3Complexes of 2-Phenylbenzothiazole Derivatives. Inorg Chem 2006; 45:902-9. [PMID: 16411729 DOI: 10.1021/ic051538e] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of 2-(2'-pyridyl)benzothiazole, [NN], with the ReO(V)(3+) and TcO(V)(3+) cores in the presence of thiophenols, [S] (RC(6)H(4)SH, R = H, 4-CH(3), 4-OCH(3)), as coligands led to the isolation of hexacoordinated complexes of the MO[NN][S](3) type (M = Re, Tc). In all cases, two geometric mer isomers were formed, as evidenced by NMR spectroscopy and confirmed by X-ray crystallography. In both isomers, the coordination geometry about the metal ion is a distorted octahedral defined by the two nitrogen atoms of the bidentate ligand, the three sulfur atoms of the monodentate thiols, and the oxygen atom of the oxo group. The apical positions of the octahedron are occupied by the oxygen of the oxo group and, in one of the isomers, the nitrogen of the pyridyl moiety of 2-(2'-pyridyl)benzothiazole, while, in the second isomer, the imine nitrogen of 2-(2'-pyridyl)benzothiazole. The complexes are stable, neutral, and lipophilic. Complete (1)H and (13)C NMR assignments are reported for all complexes. The synthetic reaction was also successfully transferred at the technetium-99m tracer level by ligand exchange reaction using (99m)Tc-glucoheptonate as precursor in the presence of 2-(2'-pyridyl)benzothiazole and 4-CH(3)C(6)H(4)SH. The structure of the technetium-99m complex was established by high-performance liquid chromatographic comparison with the analogous oxotechnetium and oxorhenium complexes. The 2-(2'-pyridyl)benzothiazole ligand serves as a preliminary model for 2-(4-aminophenyl)benzothiazole, which possesses interesting properties for the development of technetium and rhenium radiopharmaceuticals for tumor imaging and/or radiotherapy as well as in vivo diagnosis of Alzheimer's disease.
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Affiliation(s)
- Stamatia Tzanopoulou
- Institutes of Biology, Radioisotopes-Radiodiagnostic Products, and Materials Science, National Centre for Scientific Research Demokritos, 15310 Athens, Greece
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He H, Lipowska M, Xu X, Taylor AT, Carlone M, Marzilli LG. Re(CO)(3) complexes synthesized via an improved preparation of aqueous fac-[Re(CO)(3)(H(2)O)(3)](+) as an aid in assessing (99m)Tc imaging agents. Structural characterization and solution behavior of complexes with thioether-bearing amino acids as tridentate ligands. Inorg Chem 2005; 44:5437-46. [PMID: 16022542 DOI: 10.1021/ic0501869] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Parallel studies of the preparation of Re and (99m)Tc agents aid in interpreting the nature of tracer (99m)Tc radiopharmaceuticals. Aqueous solutions of the fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) cation are gaining wide use and are readily prepared, but such solutions of the fac-[Re(CO)(3)(H(2)O)(3)](+) cation (1) are not so easily accessible. Herein we describe a new, reliable, and straightforward preparation of aqueous solutions of 1, characterized by HPLC and ESI-MS. Treatment of solutions of 1 with thioether-bearing amino acids, AAH = S-methyl-l-cysteine (MECYSH), S-propyl-l-cysteine (PRCYSH), and methionine (METH), gave high yields of fac-Re(CO)(3)AA complexes. X-ray crystallographic and NMR analyses indicated that MECYS(-), PRCYS(-), and MET(-) were bound in fac-Re(CO)(3)AA complexes as tridentate monoanionic ligands through amino, thioether, and alpha-carboxyl groups. In CD(3)OD, (1)H NMR spectra have broad signals but have two sets of signals at -10 degrees C, consistent with two isomers with different configurations at the pyramidal sulfur; these interconvert slowly on the NMR time scale at low temperatures. Indeed, the crystal structure of the fac-Re(CO)(3)(PRCYS) reveals a mixture of the two possible diastereoisomers. S-(Carboxymethyl)-l-cysteine (CCMH(2)) and 1 gave two products, 5A (kinetically favored) and 5B (thermodynamically favored). X-ray crystallographic analyses of a crystal of 5B and of a 1:1 cocrystal of 5A and 5B showed that 5A and 5B are diastereoisomers with the CCMH(-) alpha-carboxyl group dangling. In addition to the amino and thioether groups, the S-(carboxymethyl) carboxyl group is coordinated, a feature that slows interconversion of diastereoisomers relative to the other fac-Re(CO)(3)AA complexes because interconversion can now occur only after the rupture of Re-ligand bonds. These N, O, and S tridentate adducts are quite stable, and the grouping has promise in (99m)Tc(CO)(3) tracer development.
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Affiliation(s)
- Haiyang He
- Department of Radiology, Emory University, Atlanta, Georgia 30322, USA
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Banerjee SR, Maresca KP, Francesconi L, Valliant J, Babich JW, Zubieta J. New directions in the coordination chemistry of 99mTc: a reflection on technetium core structures and a strategy for new chelate design. Nucl Med Biol 2005; 32:1-20. [PMID: 15691657 DOI: 10.1016/j.nucmedbio.2004.09.001] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2004] [Revised: 08/31/2004] [Accepted: 09/01/2004] [Indexed: 11/26/2022]
Abstract
Bifunctional chelates offer a general approach for the linking of radioactive metal cations to macromolecules. In the specific case of 99mTc, a variety of technologies have been developed for assembling a metal-chelate-biomolecule complex. An evaluation of these methodologies requires an appreciation of the coordination characteristics and preferences of the technetium core structures and oxidation states, which serve as platforms for the development of the imaging agent. Three technologies, namely, the MAG3-based bifunctional chelates, the N-oxysuccinimidylhydrazino-nicotinamide system and the recently described single amino acid chelates for the {Tc(CO)3}1+ core, are discussed in terms of the fundamental coordination chemistry of the technetium core structures. In assessing the advantages and disadvantages of these technologies, we conclude that the single amino acid analogue chelates (SAAC), which are readily conjugated to small peptides by solid-phase synthesis methods and which form robust complexes with the {Tc(CO)3}1+ core, offer an effective alternative to the previously described methods.
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Affiliation(s)
- Sangeeta Ray Banerjee
- Department of Chemistry, Syracuse University, Center for Science and Technology, Syracuse, NY 13244, USA
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Tisato F, Refosco F, Porchia M, Bolzati C, Bandoli G, Dolmella A, Duatti A, Boschi A, Jung CM, Pietzsch HJ, Kraus W. The crucial role of the diphosphine heteroatom X in the stereochemistry and stabilization of the substitution-inert [M(N)(PXP)]2+ metal fragments (M = Tc, Re; PXP = diphosphine ligand). Inorg Chem 2005; 43:8617-25. [PMID: 15606213 DOI: 10.1021/ic049139r] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nature of the heteroatom X incorporated in the five-membered PXP-diphosphine bridging chain was found to play a primary unit role both in the overall stability and in the stereochemical arrangement of nitrido-containing [M(N)(PXP)](2+) metal fragments (M = Tc, Re). Thus, by mixing PXP ligands with labile [Re(N)Cl(4)](-) and Tc(N)Cl(2)(PPh(3))(2) nitrido precursors in CH(2)Cl(2)/MeOH mixtures, a series of neutral M(N)Cl(2)(PXP) complexes (M = Tc, 1-5; M = Re, 8, 9) was collected. In the resulting distorted octahedrons, PXP adopted facial or meridional coordination, and combination with halide co-ligands produced three different stereochemical arrangements, that is, fac,cis, mer,cis, and mer,trans, depending primarily on the nature of the diphosphine heteroatom X. When X = NH, mer,cis-Tc(N)Cl(2)(PNP1), 1, was the only isomer formed. Alternatively, when a tertiary amine nitrogen (X = NR; R = CH(3), CH(2)CH(2)OCH(3)) was introduced in the bridging chain, fac,cis-M(N)Cl(2)(PN(R)P) complexes (M = Tc, 2, 3; M = Re, 8f) were obtained. Isomerization into the mer,cis-Re(N)Cl(2)(PN(R)P), 8m, species was observed only in the case of rhenium when the tertiary amine group carried the less encumbering methyl substituent. fac,cis-Tc(N)Cl(2)(PSP), 4f, was isolated in the solid state when X = S, but a mixture of fac,cis-Tc(N)Cl(2)(PSP) and mer,trans-Tc(N)Cl(2)(PSP), 4m, isomers was found in equilibrium in the solution state. A similar equilibrium between fac,cis-M(N)Cl(2)(POP) (M = Tc, 5f; M = Re, 9f) and mer,trans-M(N)Cl(2)(POP) (M = Tc, 5m; M = Re, 9m) species was detected in POP-containing complexes. The molecular structure of all of these complexes was assessed by means of conventional physicochemical techniques including multinuclear NMR spectroscopy and X-ray diffraction analysis of representative mer,cis-Tc(N)Cl(2)(PN(H)P), 1, fac,cis-Tc(N)Cl(2)(PSP), 4f, and mer,cis-Re(N)Cl(2)(PN(Me)P), 8m, compounds.
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Tubaro M, Traldi P, Bolzati C, Tisato F, Refosco F, Benini E, Cavazza-Ceccato M. Characterisation via electrospray ionisation multistage mass spectrometry of three related series of nitrido technetium complexes containing phosphinothiolate and dithiocarbamate ligands. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2005; 19:1874-80. [PMID: 15945035 DOI: 10.1002/rcm.1998] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nine nitrido technetium compounds comprising bis-substituted Tc(N)(PS)(2) (1-4) (PS = bidentate phosphinothiolate ligands) and Tc(N)(dtc)(2) (5, 6) derivatives (dtc = bidentate dithiocarbamate), and mixed-ligand Tc(N)(PS)(dtc) (7-9) species, were subjected to electrospray ionisation mass spectrometry and MS(n) experiments. Bis-substituted phosphinothiolato complexes 1-4 lead to the straightforward formation of dinuclear species reasonably originating from proton bound dimers. These dinuclear species do not show, under collisionally induced fragmentation processes, the formation of monomeric units but cleavages related to the ligand framework, thereby proving the high stability of the [Tc--H(+)--Tc] bond. Bis-dithiocarbamate compounds 5 and 6 show, instead, abundant [M+H](+), [M+Na](+) and [2M+Na](+) ions, and their collisionally induced fragmentations are highly favoured with cleavages related to the C--N and C--S bonds. During these processes, the coordination of a water molecule to [MH-L](+) product ions is observed, as proved by the collisionally induced H(2)O loss detected for this species. Mixed-ligand compounds 7 and 8 show the protonated molecules and Na(+)-cationised ions with fragmentation processes related to the dithiocarbamate moiety. This behaviour indicates that coordination of ether- and ester-substituted dithiocarbamates to the [Tc [triple chemical bond] N] group is weaker than that of phosphinothiolates. Conversely, diethyldithiocarbamate inserted in mixed complex 9 enhances both C--N and Tc--S bonds, and fragmentation processes suggest that metal-phosphinothiolate and metal-dithiocarbamate show comparable strength.
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Affiliation(s)
- Michela Tubaro
- CNR, Istituto di Scienze e Tecnologie Molecolari, Corso Stati Uniti 4, I-35127 Padova, Italy
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Banerjee SR, Schaffer P, Babich JW, Valliant JF, Zubieta J. Design and synthesis of site directed maleimide bifunctional chelators for technetium and rhenium. Dalton Trans 2005:3886-97. [PMID: 16311643 DOI: 10.1039/b507096a] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new family of heterobifunctional linkers (L1-L9) containing a terminus consisting of a tridentate donor set for coordination of the {M(CO)(3)}(+) core (M = Tc, Re), and a thiol reactive maleimide group has been prepared conveniently and in high yield under Mitsunobu reaction conditions by the coupling of an appropriate alcohol derivative with maleimide. The rhenium complexes [Re(CO)(3)(Lx)]Br (x= 1-9) were prepared in good yields from the reactions of the ligands and (NEt(4))(2)[Re(CO)(3)Br(3)] in refluxing methanol. The ligands and their Re complexes were characterized by (1)H and (13)C NMR, IR, and ESI-MS. Ligand L4 and [Re(CO)(3)(L5)]Br have been structurally characterized by X-ray crystallography. Photoexcitation of solutions of the complexes [Re(CO)(3)(Lx)]Br (x= 4-6) gives rise to intense and prolonged luminescence at room temperature (fluorescence lifetimes of ca. 16 micros). The ligands and their Re complexes react smoothly at the maleimide linker with sulfhydryl groups of peptides and proteins at room temperature in phosphate-buffered saline (PBS, pH 7.4) to form stable thioether bioconjugates. The photoluminescence properties of the labeled conjugates are similar to those of the parent complexes, but with even longer lifetimes. The ligands can also be labeled at room temperature with (99m)Tc to give chemically robust complexes. The corresponding hydrazinonicotinamide derivative N-[5-(6'-hydrazinopyridine-3'-carbonyl)aminopentyl]maleimide (L10) was also prepared. While coupling of L10 to cysteine ethylester and synthesis of the rhenium derivative [ReCl(3)(HYNIC-maleimide)(2)] were successfully accomplished, attempts to couple [ReCl(3)(HYNIC-maleimide)(2)] to glutathione or BSA yielded intractable mixtures.
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Tisato F, Bolzati C, Porchia M, Refosco F. Contribution of electrospray mass spectrometry for the characterization, design, and development of nitrido technetium and rhenium heterocomplexes as potential radiopharmaceuticals. MASS SPECTROMETRY REVIEWS 2004; 23:309-332. [PMID: 15264232 DOI: 10.1002/mas.20000] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Diagnostic nuclear medicine (NM) is among the imaging procedures (together with X-ray, computerized tomography, magnetic resonance, and echography) the clinicians can routinely adopt to image organs or tissues and related disorders. (99m)Tc-based agents are the radiopharmaceuticals of election in diagnostic NM because of the ideal physical properties of the 99mTc nuclide (t1/2 6.01 hr; Egamma 142 keV), low cost, and easy availability through the commercial 99Mo/99mTc generator, and chemical versatility of the element. In the last two decades the synergistic work of clinics, pharmacologists, and coordination chemists has had a tremendous impact in the development of new 99mTc-based radiopharmaceuticals through the recognition of the structure at the molecular level of the agent utilized. This has been achieved by studying the physico-chemical properties of the long-lived 99gTc (t1/2 2.11 x 10(5) year; Ebeta 292 keV) and third-row congener Re isostructural compounds. Electrospray ionization mass spectrometry (ESI-MS) and collision experiments (MS/MS) represent valuable analytical techniques suitable for the characterization of both technetium and rhenium complexes relevant to NM. Unequivocal structural identification of these bioinorganic compounds, either simple coordination complexes ("essential radiopharmaceuticals") or more sophisticated structures carrying bioactive fragments ("receptor-specific" radiopharmaceuticals), can be realized in combination with multinuclear NMR spectroscopy. MS/MS experiments provide useful information on the different metal-ligand bond strength, and comparison of the fragmentation profiles of isostructural technetium and rhenium compounds give additional details on the role played by the metal in determining preferred decomposition channels. The analysis of these data contribute to design novel synthetic strategies for the obtainment of technetium and rhenium compounds relevant to NM. The chemistry underlying the production of a new class of potential radiopharmaceuticals including a terminal nitrogen bond and a mixed coordination sphere comprising heterodiphosphines and/or dithiocarbamates (DTC) is presented in detail together with the ESI-MS and MS/MS investigations.
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Affiliation(s)
- Francesco Tisato
- Istituto di Chimica Inorganica e delle Superfici, CNR, Corso Stati Uniti 4, 35127 Padova, Italy.
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Bolzati C, Benini E, Cazzola E, Jung C, Tisato F, Refosco F, Pietzsch HJ, Spies H, Uccelli L, Duatti A. Synthesis, Characterization, and Biological Evaluation of Neutral Nitrido Technetium(V) Mixed Ligand Complexes Containing Dithiolates and Aminodiphosphines. A Novel System for Linking Technetium to Biomolecules. Bioconjug Chem 2004; 15:628-37. [PMID: 15149191 DOI: 10.1021/bc0499782] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new biomolecule labeling method that utilizes the [(99m)Tc(N)(PNP)](2+) metal fragment is presented. Thus, a series of nitrido mixed-ligand M(V) complexes (M = (99m)Tc, (99g)Tc, Re), [M(N)(Ln)(PNP)], where Ln is the dianionic form of a dithiolate or substituted-dithiolate ligand and PNP is an aminodiphosphine, is described. (99m)Tc complexes can be prepared using either a two-step or a three-step procedure starting from generator-eluted pertechnetate through a prereduced mixture of [(99m)Tc(N)]-containing species, followed by sequential or contemporary addition of the relevant dithiolate and aminodiphosphine. The reactions of 2,3-dimercaptopropionic acid (H(2)L1) with [Tc(N)(PNP)](2+) were investigated in detail. It was found that this bidentate ligand coordinated the metal fragment through the [S(-),S(-)] donor atom pair, to yield neutral mixed-ligand complexes [(99m)Tc(N)(L1)(PNP)] in high specific activity. The additional carboxylic functional group was not involved in metal coordination, thus remaining available for conjugation to target-specific molecules. Dithiolates incorporating pendant functional group(s) gave rise to a 1:1 diastereoisomeric mixture of syn-[M(N)(Ln)(PNP)] and anti-[M(N)(Ln)(PNP)] derivatives, depending on the relative orientation of the dithiolate substituent(s) with respect to the terminal nitrido group, and no isomeric conversion was detected. (99m)Tc species had been proven to be identical with the (99g)Tc complexes prepared at the macroscopic level by comparison of the corresponding radiometric and UV/vis HPLC profiles. Challenge experiments with cysteine or glutathione indicated that these physiological agents had no effect on the stability of this class of mixed-ligand (99m)Tc-complexes. Biodistribution studies in rats of selected (99m)Tc-complexes showed a rapid clearance from the blood and tissues after 60 min pi.
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Arterburn JB, Corona C, Rao KV, Carlson KE, Katzenellenbogen JA. Synthesis of 17-alpha-substituted estradiol-pyridin-2-yl hydrazine conjugates as effective ligands for labeling with Alberto's complex fac-[Re(OH2)3(CO)3]+ in water. J Org Chem 2003; 68:7063-70. [PMID: 12946150 DOI: 10.1021/jo034780g] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of (99m)Tc-estradiol radiopharmaceuticals would be advantageous for the detection of estrogen receptor-positive breast tumors. Estradiol derivatives conjugated to organometallic tricarbonyl-Tc(I) and related Re(I) complexes are capable of achieving high receptor binding affinity, but effective methods for synthesizing radiolabeled complexes in water are not available. Our interest in the synthesis of 2-hydrazinopyridines as ligands for Tc and Re led us to investigate Pd-catalyzed amination reactions of halo-pyridine substrates with di-tert-butyl hydrazodiformate. Both 2- and 4-substituted halo-pyridine substrates undergo C-N coupling with di-tert-butyl hydrazodiformate to produce Boc-protected pyridine hydrazine derivatives. Only highly electrophilic 3-pyridine halides were converted to the hydrazine. The Boc-protected 5-bromopyridin-2-yl hydrazine substrate 3 was prepared by regioselective substitution at the 2-position of 2,5-dibromopyridine. This bifunctional chelate was attached to ethynyl or vinyl groups at the 17alpha position of estradiol, using Sonogashira and Suzuki/Miyaura coupling reactions to synthesize 1 and 2 in high yields, respectively. Deprotection of 1 under acidic conditions provided the hydrazine hydrochloride salt 25. The 17alpha-estradiol-tricarbonylrhenium(I) complex 4 was synthesized by labeling 25 with fac-[Re(OH(2))(3)(CO)(3)](+) in aqueous ethanol. This complex exhibited excellent stability and high receptor binding affinity for the estrogen receptor, and it is a promising model for evaluation of the analogous Tc-99m complexes as diagnostic imaging agents for breast tumors.
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Affiliation(s)
- Jeffrey B Arterburn
- Department of Chemistry and Biochemistry MSC 3C, New Mexico State University, P.O. Box 30001, Las Cruces, New Mexico 88003, USA.
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Arterburn JB, Bryant BK, Chen D. Synthesis of (pyridin-2-yl)hydrazine conjugates as bifunctional chelates using the Suzuki-Miyaura reaction. Chem Commun (Camb) 2003:1890-1. [PMID: 12932018 DOI: 10.1039/b304153k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Palladium catalyzed C-C couplings were used to connect (pyridin-2-yl)hydrazine to organic substrates, including a phenylalanine derivative, providing a new method for introducing this important ligand.
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Affiliation(s)
- Jeffrey B Arterburn
- Department of Chemistry & Biochemistry MSC 3C, New Mexico State University, Box 30001, Las Cruces, New Mexico 88003, USA.
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Meléndez-Alafort L, Ramírez FDM, Ferro-Flores G, Arteaga de Murphy C, Pedraza-López M, Hnatowich DJ. Lys and Arg in UBI: a specific site for a stable Tc-99m complex? Nucl Med Biol 2003; 30:605-15. [PMID: 12900286 DOI: 10.1016/s0969-8051(03)00055-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The aim of this study was to help establish if ubiquicidin peptide 29-41 fragment (UBI) contains a specific site for 99mTc labeling by a new direct method under alkaline conditions. Since this peptide does not have cysteine residues, it is possible that neighboring arginine and lysine in the peptide amino acid sequence (Thr-Gly-Arg-Ala-Lys-Arg-Arg-Met-Gln-Tyr-Asn-Arg-Arg) could be a specific coordination site to form a stable 99mTc-UBI complex. Following direct labeling, the in vitro stability of 99mTc-UBI was compared to UBI radiolabeled by one indirect method using HYNIC/tricine and HYNIC/tricine/EDDA. Radiochemical purity of 99mTc-UBI averaged 97% compared to 88% for 99mTc-HYNIC-UBI/tricine and 98% for 99mTc-HYNIC-UBI/tricine/EDDA. Both 99mTc-HYNIC-UBI (tricine or EDDA) and 99mTc-UBI showed stability in human serum and solutions of cysteine. 99mTc-UBI radiochemical purity 24 h after dilution in 0.9% NaCl was greater than 90% at pH 9 and greater than 95% at pH 6.5. Under one set of experimental conditions, in vitro binding to bacteria of 99mTc-UBI was 35% and identical to that of 99mTc-HYNIC-UBI/tricine and 99mTc-HYNIC-UBI/tricine/EDDA at 32% and 31% respectively. The biodistribution of 99mTc-UBI in mice showed a rapid renal clearance. To help identify the site(s) of 99mTc binding following direct labeling, molecular mechanics and quantum-mechanical calculations were performed which showed that the amine groups of Arg(7) and Lys are the most probable site. The calculations show that these groups can form a square pyramid with two water molecules for the Tc cation (dxysp(3)). It will be necessary to isolate and characterize the 99Tc(V)(O)-UBI.(H2O)n complex to confirm these results.
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