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Inorganics
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Advanced Applications of Technetium Chemistry
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Advanced Applications of Technetium Chemistry

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Bioinorganic Chemistry".

Deadline for manuscript submissions: closed (31 August 2019) | Viewed by 19832

Special Issue Editor

Prof. Dr. Adriano Duatti

E-Mail Website
Guest Editor
Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via L. Borsari, 46, 44121 Ferrara, Italy
Interests: inorganic chemistry; radiopharmaceutical chemistry; radiometals; molecular imaging; radionuclide therapy

Special Issue Information

Dear Colleagues,

The first ever discovered artificial element, technetium, has played a pivotal role in promoting the growth and remarkable success of nuclear diagnostic imaging in the past decades. Actually, a group of radiopharmaceuticals labelled with the gamma-emitting radioisotope technetium-99m are still employed as standard imaging agents in the routine clinical practice of different medical specialties, ranging from cardiology to oncology, for the diagnosis of a number of diseases. Despite current overwhelming emphasis on positron emission tomography (PET), it is interesting to note that one of the first-line approaches for the assessment of coronary artery disease (CAD) is still based on the use of technetium-99m myocardial imaging agents, the impact of PET tracers in this field being still limited. It is easy to recognize that the most important reason for this long-lasting success of technetium-99m radiopharmaceuticals resides in the richness of the chemistry of this transition element. Only the existence of a multitude of stable chemical motifs and structural arrangements for technetium complexes has allowed investigation of the biological and diagnostic properties of a large spectrum of coordination compounds and eventually the discovery of useful imaging agents. Thus, the study of the inorganic chemistry of technetium has been at the root of the success of this class of radiopharmaceuticals.

Today, we are at the verge of a new era for technetium-99m radiopharmaceuticals after many years of obscurity. New outstanding technological developments are progressively narrowing the gap between single photon emission tomography (SPECT) and PET. Ultra-fast SPECT cameras with sub-millimetre resolutions are expected to replace old cameras, thus opening tantalizing clinical opportunities for technetium-99m diagnostic agents. In this scenario, in order to fully exploit the huge potential of these new technologies, unprecedented categories of technetium complexes might be required. Therefore, it seems worthy to review the status of technetium chemistry and to summarize the most remarkable results that have been unearthed during the last years. The aim of this Special Issue is to collect a number of contributions that can illustrate the still-flourishing field of technetium coordination chemistry and its applications to diagnostic medicine.

Prof. Dr. Adriano Duatti
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Inorganics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • technetium
  • technetium-99m
  • coordination complexes
  • technetium chemistry
  • metallic functional groups
  • radiometals
  • radiopharmaceuticals
  • imaging agents
  • SPECT

Published Papers (6 papers)

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Research

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19 pages, 3098 KiB  
Article
Synthesis and Evaluation of 99mTc-Tricabonyl Labeled Isonitrile Conjugates for Prostate-Specific Membrane Antigen (PSMA) Image
by Nadeem Ahmed Lodhi, Ji Yong Park, Kyuwan Kim, Mi Kyung Hong, Young Joo Kim, Yun-Sang Lee, Gi Jeong Cheon, Keon Wook Kang and Jae Min Jeong
Inorganics 2020, 8(1), 5; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics8010005 - 14 Jan 2020
Cited by 7 | Viewed by 3831
Abstract
Prostate-specific membrane antigen (PSMA) is a biomarker expressed on the surface of prostate cancer (PCa). In an effort to improve the detection and treatment of PCa, small urea-based PSMA inhibitors have been studied extensively. In the present study, we aimed to develop 99m [...] Read more.
Prostate-specific membrane antigen (PSMA) is a biomarker expressed on the surface of prostate cancer (PCa). In an effort to improve the detection and treatment of PCa, small urea-based PSMA inhibitors have been studied extensively. In the present study, we aimed to develop 99mTc-tricabonyl labeled urea-based PSMA conjugates containing isonitrile (CN-R)-coordinating ligands ([99mTc]Tc-15 and [99mTc]Tc-16). Both the PSMA conjugates were obtained at high radiochemical efficiency (≥98.5%). High in vitro binding affinity was observed for [99mTc]Tc-15 and [99mTc]Tc-16 (Kd = 5.5 and 0.2 nM, respectively) in PSMA-expressing 22Rv1 cells. Tumor xenografts were conducted using 22Rv1 cells and rapid accumulation of [99mTc]Tc-16 (1.87 ± 0.11% ID/g) was observed at 1 h post-injection, which subsequently increased to (2.83 ± 0.26% ID/g) at 4 h post-injection. However, [99mTc]Tc-15 showed moderate tumor uptake (1.48 ± 0.18% ID/g), which decreased at 4 h post-injection (0.81 ± 0.09% ID/g). [99mTc]Tc-16 was excreted from non-targeted tissues with high tumor-to-blood (17:1) and tumor-to-muscle ratio (41:1) at 4 h post-injection at approximately 4 times higher levels than [99mTc]Tc-15. Uptakes of [99mTc]Tc-15 and [99mTc]Tc-16 to PSMA-expressing tumor and tissues were significantly blocked by co-injection of 2-(Phosphonomethyl)-pentandioic acid (2-PMPA), suggesting that their uptakes are mediated by PSMA specifically. Whole-body single photon emission computed tomography imaging of [99mTc]Tc-16 verified the ex vivo biodistribution results and demonstrated clear visualization of tumors and tissues expressing PSMA compared to [99mTc]Tc-15. In conclusion, using [99mTc]Tc-16 rather than [99mTc]Tc-15 may be the preferable because of its relatively high tumor uptake and retention. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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10 pages, 695 KiB  
Article
Technetium Nitrido-Peroxo Complexes: An Unexplored Class of Coordination Compounds
by Micol Pasquali, Emilija Janevik-Ivanovska and Adriano Duatti
Inorganics 2019, 7(12), 142; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics7120142 - 11 Dec 2019
Viewed by 2750
Abstract
The purpose of this work was to further expand the chemistry of mixed technetium nitrido-peroxo complexes, a still poorly explored class of compounds containing the Tc(VII) moiety, [99gTc][Tc(N)(O2)2]. A number of novel complexes of the formula [ [...] Read more.
The purpose of this work was to further expand the chemistry of mixed technetium nitrido-peroxo complexes, a still poorly explored class of compounds containing the Tc(VII) moiety, [99gTc][Tc(N)(O2)2]. A number of novel complexes of the formula [99gTc][Tc(N)(O2)2(L)] with bidentate ligands (L) (where L = deprotonated alanine, glycine, proline) were prepared by reacting a solution of nitrido-technetic(VI) acid with L in the presence of a source of H2O2. Alternatively, the complex [99gTc][Tc(N)(O2)2X]− (X = Cl, Br) was used as a precursor for substitution reactions where the halogenide ion was replaced by the bidentate ligand. The new complexes were characterized by elemental analysis and mass spectroscopy. The preparation of the analogous [99mTc][Tc(N)(O2)2] moiety, radiolabeled with the metastable isomer Tc-99m, was also studied at a no-carrier-added level, using S-methyl-N-methyl-dithiocarbazate as the donor of the nitrido nitrogen atoms. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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20 pages, 3437 KiB  
Article
Towards 99mTc- and Re-Based Multifunctional Silica Platforms for Theranostic Applications
by Michel A. Wuillemin, Michael J. Reber, Thomas Fox, Bernhard Spingler, Dominik Brühwiler, Roger Alberto and Henrik Braband
Inorganics 2019, 7(11), 134; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics7110134 - 09 Nov 2019
Cited by 5 | Viewed by 2951
Abstract
Taking advantage of the radiation properties of 99mTc and 186/188Re and the photophysical characteristics of the {M(CO)3}+ moiety (M = Re), we developed a multifunctional silica platform with the theranostic pair 99mTc/Re with high potential for (nano)medical [...] Read more.
Taking advantage of the radiation properties of 99mTc and 186/188Re and the photophysical characteristics of the {M(CO)3}+ moiety (M = Re), we developed a multifunctional silica platform with the theranostic pair 99mTc/Re with high potential for (nano)medical applications. Starting with a general screening to evaluate the most suitable mesoporous silica construct and the development of appropriate chelate systems, multifunctional mesoporous silica microparticles (SBA-15) were synthesized. These particles act as a model towards the synthesis of the corresponding nanoconstructs. The particles can be modified at the external surface with a targeting function and labeled with the {M(CO)3}+ moiety (M = 99mTc, Re) at the pore surface. Thus, a silica platform is realized, whose bioprofile is not altered by the loaded modalities. The described synthetic procedures can be applied to establish a target-specific theranostic nanoplatform, which enables the combination of fluorescence and radio imaging, with the possibility of radio- and chemotherapy. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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14 pages, 1612 KiB  
Article
Cysteine Derivatized 99mTc-Labelled Fatty Acids as β-Oxidation Markers
by Theodoros Tsotakos, Charalambos Triantis, Christos Kiritsis, Aggeliki Panagiotopoulou, Dimitrios Psimadas, Patricia Kyprianidou, Maria Pelecanou, Minas Papadopoulos and Ioannis Pirmettis
Inorganics 2019, 7(11), 133; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics7110133 - 08 Nov 2019
Cited by 1 | Viewed by 2178
Abstract
With the aim of developing 99mTc-labeled fatty acids intended for myocardial metabolism imaging we report herein the synthesis and characterization of two novel derivatives of undecanonoic and hexadecanonoic acid that have been functionalized at the ω-site by cysteine through the formation of [...] Read more.
With the aim of developing 99mTc-labeled fatty acids intended for myocardial metabolism imaging we report herein the synthesis and characterization of two novel derivatives of undecanonoic and hexadecanonoic acid that have been functionalized at the ω-site by cysteine through the formation of a thioether bond (Cys–FA11 and Cys–FA16). Equimolar amounts of each ligand and the [NEt4]2[Re(CO)3Br3] precursor generated the respective hexacoordinated neutral complexes in which the ligand coordinated to the metal through the SNO donor system of cysteine. The rhenium complexes were characterized by elemental analysis, IR and NMR spectroscopies. The analogous technetium-99m complexes, 99mTc–Cys–FA11 and 99mTc–Cys–FA16 were prepared by incubation of the ligand with the precursor [99mTc(CO)3(H2O)3]+ (radiochemical yield ≥98%). Their structure was established by comparative HPLC techniques. In vivo studies in mice showed high initial heart uptake for both 99mTc complexes (7.4 ± 0.53 and 7.07 ± 0.73 percentage of injected dose (%ID)/g at 1 min post injection. Rapid clearance (0.60 ± 0.02 %ID/g) was observed for 99mTc–Cys–FA11 while the clearance of the longer fatty acid 99mTc–Cys–FA16 was slower (2.31 ± 0.09 %ID/g at 15 min p.i.). Metabolite analysis study indicated that complexes were catabolized through the β-oxidation process. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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Review

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36 pages, 10334 KiB  
Review
Nitrido Technetium-99 m Core in Radiopharmaceutical Applications: Four Decades of Research
by Cristina Bolzati and Alessandro Dolmella
Inorganics 2020, 8(1), 3; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics8010003 - 31 Dec 2019
Cited by 13 | Viewed by 4477
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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16 pages, 1455 KiB  
Review
99mTc Labelling Strategies for the Development of Potential Nitroimidazolic Hypoxia Imaging Agents
by Javier Giglio and Ana Rey
Inorganics 2019, 7(11), 128; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics7110128 - 23 Oct 2019
Cited by 13 | Viewed by 3042
Abstract
Technetium-99m has a rich coordination chemistry that offers many possibilities in terms of oxidation states and donor atom sets. Modifications in the structure of the technetium complexes could be very useful for fine tuning the physicochemical and biological properties of potential 99mTc [...] Read more.
Technetium-99m has a rich coordination chemistry that offers many possibilities in terms of oxidation states and donor atom sets. Modifications in the structure of the technetium complexes could be very useful for fine tuning the physicochemical and biological properties of potential 99mTc radiopharmaceuticals. However, systematic study of the influence of the labelling strategy on the “in vitro” and “in vivo” behaviour is necessary for a rational design of radiopharmaceuticals. Herein we present a review of the influence of the Tc complexes’ molecular structure on the biodistribution and the interaction with the biological target of potential nitroimidazolic hypoxia imaging radiopharmaceuticals presented in the literature from 2010 to the present. Comparison with the gold standard [18F]Fluoromisonidazole (FMISO) is also presented. Full article
(This article belongs to the Special Issue Advanced Applications of Technetium Chemistry)
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