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Raymond JJ, Chowdhury MSI, Crawley MR, Morrow JR. Co(II) Macrocyclic Complexes with Amide-Glycinate Pendants as ParaCEST and Liposomal CEST Agents. Chemistry 2024; 30:e202401638. [PMID: 38861702 DOI: 10.1002/chem.202401638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Revised: 05/28/2024] [Accepted: 06/11/2024] [Indexed: 06/13/2024]
Abstract
Macrocyclic Co(II) complexes with appended amide-glycinate groups were prepared to develop paramagnetic Co(II) chemical exchange saturation transfer (CEST) agents of reduced overall charge. Complexes with reduced charge and lowered osmolarity are important for their loading into liposomes and to provide complexes that are highly water soluble and well tolerated in animals. Co(L1) has two non-coordinating benzyl groups and two amide-glycinate pendants, whereas Co(L2) has two unsubstituted amide pendants and two amide-glycinate pendants on cyclam (1,4,8,11-tetraazacyclododecane). The 1H NMR spectrum of Co(L1) is consistent with a single cis-pendant isomer with both amide protons in the trans-configuration, as supported by an X-ray crystal structure. Co(L2) has a mixture of different isomers in solution, including the trans-1,4 and 1,8 pendant isomers. The Z-spectrum of Co(L1) shows one highly-shifted CEST peak, whereas Co(L2) exhibits six CEST peaks. Encapsulation of 40 mM Co(L1) in a liposome with osmotically-induced shrinking at 300 mOsm/L produces a liposomal CEST agent with saturation frequency offset of 3 ppm. Addition of the amphiphilic 1,4,7-triazacyclononane-based complex Co(L5) to the liposomal bilayer at 18 mM with Co(L1) encapsulated in the liposome at 50 mM changes the sign and increases the magnitude of the saturation frequency offset to -7.5 ppm at 300 mOsm/L.
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Affiliation(s)
- Jaclyn J Raymond
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260
| | - Md Saiful I Chowdhury
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260
| | - Matthew R Crawley
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260
| | - Janet R Morrow
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260
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2
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Kras EA, Cineus R, Crawley MR, Morrow JR. Macrocyclic complexes of Fe(III) with mixed hydroxypropyl and phenolate or amide pendants as T 1 MRI probes. Dalton Trans 2024; 53:4154-4164. [PMID: 38318938 PMCID: PMC10897765 DOI: 10.1039/d3dt04013e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/29/2024] [Indexed: 02/07/2024]
Abstract
High-spin Fe(III) complexes of 1,4,7-triazacyclononane (TACN) with mixed oxygen donor pendants including hydroxypropyl, phenolate or amide groups are prepared for study as T1 MRI probes. Complexes with two hydroxypropyl pendants and either amide (Fe(TOAB)) or phenolate (Fe(PTOB)) groups are compared to an analog with three hydroxypropyl groups (Fe(NOHP)), in order to study the effect of the third pendant on the coordination sphere as probed by solution chemistry, relaxivity and structural studies. Solution studies show that Fe(PTOB) has two ionizations with the phenol pendant deprotonating with a pKa of 1.7 and a hydroxypropyl pendent with pKa of 6.3. The X-ray crystal structure of [Fe(PTOB)]Br2 features a six-coordinate complex with two bound hydroxypropyl groups, and a phenolate in a distorted octahedral geometry. The Fe(TOAB) complex has a single deprotonation, assigned to a hydroxypropyl group with a pKa value of 7.0. Both complexes are stabilized as high-spin Fe(III) in solution as shown by their effective magnetic moments and Fe(III)/Fe(II) redox potentials of -390 mV and -780 mV versus NHE at pH 7 and 25 °C for Fe(TOAB) and Fe(PTOB) respectively. Both Fe(PTOB) and Fe(TOAB) are kinetically inert to dissociation under a variety of challenges including phosphate/carbonate buffer, one equivalent of ZnCl2, two equivalents of transferrin or 100 mM HCl, or at basic pH values over 24 h at 37 °C. The r1 relaxivity of Fe(TOAB) at 1.4 T, pH 7.4 and 33 °C is relatively low at 0.6 mM-1 s-1 whereas the r1 relaxivity of Fe(PTOB) is more substantial and shows an increase of 2.5 fold to 2.5 mM-1 s-1 at acidic pH. The increase in relaxivity at acidic pH is attributed to protonation of the phenolate group to provide an additional pathway for proton relaxation.
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Affiliation(s)
- Elizabeth A Kras
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260, USA.
| | - Roy Cineus
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260, USA.
| | - Matthew R Crawley
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260, USA.
| | - Janet R Morrow
- Department of Chemistry, University at Buffalo, the State University of New York, Amherst, NY 14260, USA.
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3
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Pinto SMA, Ferreira ARR, Teixeira DSS, Nunes SCC, Batista de Carvalho ALM, Almeida JMS, Garda Z, Pallier A, Pais AACC, Brett CMA, Tóth É, Marques MPM, Pereira MM, Geraldes CFGC. Fluorinated Mn(III)/(II)-Porphyrin with Redox-Responsive 1 H and 19 F Relaxation Properties. Chemistry 2023; 29:e202301442. [PMID: 37606898 DOI: 10.1002/chem.202301442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Indexed: 08/23/2023]
Abstract
A new fluorinated manganese porphyrin, (Mn-TPP-p-CF3 ) is reported capable of providing, based on the Mn(III)/Mn(II) equilibrium, dual 1 H relaxivity and 19 F NMR response to redox changes. The physical-chemical characterization of both redox states in DMSO-d6 /H2 O evidenced that the 1 H relaxometric and 19 F NMR properties are appropriate for differential redox MRI detection. The Mn(III)-F distance (dMn-F =9.7-10 Å), as assessed by DFT calculations, is well tailored to allow for adequate paramagnetic effect of Mn(III) on 19 F T1 and T2 relaxation times. Mn-TPP-p-CF3 has a reversible Mn(II)/Mn(III) redox potential of 0.574 V vs. NHE in deoxygenated aqueous HEPES/ THF solution. The reduction of Mn(III)-TPP-p-CF3 in the presence of ascorbic acid is slowly, but fully reversed in the presence of air oxygen, as monitored by UV-Vis spectrometry and 19 F NMR. The broad 1 H and 19 F NMR signals of Mn(III)-TPP-p-CF3 disappear in the presence of 1 equivalent ascorbate replaced by a shifted and broadened 19 F NMR signal from Mn(II)-TPP-p-CF3 . Phantom 19 F MR images in DMSO show a MRI signal intensity decrease upon reduction of Mn(III)-TPP-p-CF3 , retrieved upon complete reoxidation in air within ~24 h. 1 H NMRD curves of the Mn(III)/(II)-TPP-p-CF3 chelates in mixed DMSO/water solvent have the typical shape of Mn(II)/Mn(III) porphyrins.
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Affiliation(s)
- Sara M A Pinto
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Ana R R Ferreira
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Daniela S S Teixeira
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Sandra C C Nunes
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Ana L M Batista de Carvalho
- Molecular Physical Chemistry R&D Unit Department of Chemistry, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal
- Department of Life Sciences, Faculty of Science and Technology, Calçada Martim de Freitas, 3000-393, Coimbra, Portugal
| | - Joseany M S Almeida
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- CEMMPRE, University of Coimbra, Pinhal de Marrocos, 3030-788, Coimbra, Portugal
| | - Zoltan Garda
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France
| | - Agnés Pallier
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France
| | - Alberto A C C Pais
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Christopher M A Brett
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- CEMMPRE, University of Coimbra, Pinhal de Marrocos, 3030-788, Coimbra, Portugal
| | - Éva Tóth
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, Université d'Orléans, Rue Charles Sadron, 45071, Orléans Cedex 2, France
| | - Maria P M Marques
- Molecular Physical Chemistry R&D Unit Department of Chemistry, University of Coimbra, Rua Larga, 3004-535, Coimbra, Portugal
- Department of Life Sciences, Faculty of Science and Technology, Calçada Martim de Freitas, 3000-393, Coimbra, Portugal
| | - Mariette M Pereira
- University of Coimbra, CQC-IMS, Department of Chemistry, P-3004-535, Coimbra, Portugal
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
| | - Carlos F G C Geraldes
- Coimbra Chemistry Center, University of Coimbra, Rua Larga Largo D. Dinis, 3004-535, Coimbra, Portugal
- Department of Life Sciences, Faculty of Science and Technology, Calçada Martim de Freitas, 3000-393, Coimbra, Portugal
- CIBIT/ICNAS, University of Coimbra, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
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Chowdhury MSI, Kras EA, Turowski SG, Spernyak JA, Morrow JR. Liposomal MRI probes containing encapsulated or amphiphilic Fe(III) coordination complexes. Biomater Sci 2023; 11:5942-5954. [PMID: 37470467 DOI: 10.1039/d3bm00029j] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Liposomes containing high-spin Fe(III) coordination complexes were prepared towards the production of T1 MRI probes with improved relaxivity. The amphiphilic Fe(III) complexes were anchored into the liposome with two alkyl chains to give a coordination sphere containing mixed amide and hydroxypropyl pendant groups. The encapsulated complex contains a macrocyclic ligand with three phosphonate pendants, [Fe(NOTP)]3-, which was chosen for its good aqueous solubility. Four types of MRI probes were prepared including those with intraliposomal Fe(III) complex (LipoA) alone, amphiphilic Fe(III) complex (LipoB), both intraliposomal and amphiphilic complex (LipoC) or micelles formed with amphiphilic complex. Water proton relaxivities r1 and r2 were measured and compared to a small molecule macrocyclic Fe(III) complex containing similar donor groups. Micelles of the amphiphilic Fe(III) complex had proton relaxivity values (r1 = 2.6 mM-1 s-1) that were four times higher than the small hydrophilic analog. Liposomes with amphiphilic Fe(III) complex (LipoB) have a per iron relaxivity of 2.6 mM-1 s-1 at pH 7.2, 34 °C at 1.4 T whereas liposomes containing both amphiphilic and intraliposomal Fe(III) complexes (lipoC) have r1 of 0.58 mM-1 s-1 on a per iron basis consistent with quenching of the interior Fe(III) complex relaxivity. Liposomes containing only encapsulated [Fe(NOTP)]3- have a lowered r1 of 0.65 mM-1 s-1 per iron complex. Studies show that the biodistribution and clearance of the different types liposomal nanoparticles differ greatly. LipoB is a blood pool agent with a long circulation time whereas lipoC is cleared more rapidly through both renal and hepatobiliary pathways. These clearance differences are consistent with lower stability of LipoC compared to LipoB.
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Affiliation(s)
- Md Saiful I Chowdhury
- Department of Chemistry, University at Buffalo, The State University of New York, Amherst, NY 14260, USA.
| | - Elizabeth A Kras
- Department of Chemistry, University at Buffalo, The State University of New York, Amherst, NY 14260, USA.
| | - Steven G Turowski
- Department of Cell Stress Biology, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, USA
| | - Joseph A Spernyak
- Department of Cell Stress Biology, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, USA
| | - Janet R Morrow
- Department of Chemistry, University at Buffalo, The State University of New York, Amherst, NY 14260, USA.
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Kadakia RT, Ryan RT, Cooke DJ, Que EL. An Fe complex for 19F magnetic resonance-based reversible redox sensing and multicolor imaging. Chem Sci 2023; 14:5099-5105. [PMID: 37206407 PMCID: PMC10189869 DOI: 10.1039/d2sc05222a] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 04/14/2023] [Indexed: 05/21/2023] Open
Abstract
We report a first-in-class responsive, pentafluorosulfanyl (-SF5)-tagged 19F MRI agent capable of reversibly detecting reducing environments via an FeII/III redox couple. In the FeIII form, the agent displays no 19F MR signal due to paramagnetic relaxation enhancement-induced signal broadening; however, upon rapid reduction to FeII with one equivalent of cysteine, the agent displays a robust 19F signal. Successive oxidation and reduction studies validate the reversibility of the agent. The -SF5 tag in this agent enables 'multicolor imaging' in conjunction with sensors containing alternative fluorinated tags and this was demonstrated via simultaneous monitoring of the 19F MR signal of this -SF5 agent and a hypoxia-responsive agent containing a -CF3 group.
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Affiliation(s)
- Rahul T Kadakia
- Department of Chemistry, University of Texas at Austin 105 E 24th St. Stop A5300 Austin TX 78712 USA
| | - Raphael T Ryan
- Department of Chemistry, University of Texas at Austin 105 E 24th St. Stop A5300 Austin TX 78712 USA
| | - Daniel J Cooke
- Department of Chemistry, University of Texas at Austin 105 E 24th St. Stop A5300 Austin TX 78712 USA
| | - Emily L Que
- Department of Chemistry, University of Texas at Austin 105 E 24th St. Stop A5300 Austin TX 78712 USA
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6
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Duraiyarasu M, Kumaran SS, Mayilmurugan R. Alkyl Chain Appended Fe(III) Catecholate Complex as a Dual-Modal T1 MRI-NIR Fluorescence Imaging Agent via Second Sphere Water Interactions. ACS Biomater Sci Eng 2023. [PMID: 37141045 DOI: 10.1021/acsbiomaterials.3c00203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The C12-alkyl chain-conjugated Fe(III) catecholate complex [Fe(C12CAT)3]3-, Fe(C12CAT)3 [C12CAT = N-(3,4-dihydroxyphenethyl)dodecanamide], was synthesized and characterized, reported as a dual-modal T1-MRI and an optical imaging probe. The DFT-optimized structure of Fe(C12CAT)3 reveals a distorted octahedral coordination geometry around the high spin Fe(III) center. The formation constant (-log K) of Fe(C12CAT)3 was calculated as 45.4. The complex exhibited r1-relaxivity values of 2.31 ± 0.12 and 1.52 ± 0.06 mM-1 s-1 at 25 and 37 °C, respectively, on 1.41 T at pH 7.3 via second-sphere water interactions. The interaction of Fe(C12CAT)3 with human serum albumin showed concomitant enhancement of r1-relaxivity to 6.44 ± 0.15 mM-1 s-1. The MR phantom images are significantly brighter and directly correlate to the concentration of Fe(C12CAT)3. Adding an external fluorescent marker IR780 dye to Fe(C12CAT)3 leads to the formation of self-assembly by C12-alkyl chains. It resulted in the fluorescence quenching of the dye, and its critical aggregation concentration was calculated as 70 μM. The aggregated matrix of Fe(C12CAT)3 and IR780 dye is spherical, with an average hydrodynamic diameter of 189.5 nm. This self-assembled supramolecular system is found to be non-fluorescent and was "turn-on" under acidic pH via dissociation of aggregates. The r1-relaxivity is found to be unchanged during the matrix aggregation and disaggregation. The probe showed MRI ON and fluorescent OFF under physiological conditions and MRI ON and fluorescent ON under acidic pH. The cell viability experiments showed that the cells are 80% viable at 1 mM probe concentration. Fluorescence experiments and MR phantom images showed that Fe(C12CAT)3 is a potential dual model imaging probe to visualize the acidic pH environment of the cells.
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Affiliation(s)
- Maheshwaran Duraiyarasu
- Department of Chemistry, and Department of Bioscience & Biomedical Engineering, Indian Institute of Technology Bhilai, Raipur, Chattisgarh 492015, India
| | - S Senthil Kumaran
- Department of NMR, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029, India
| | - Ramasamy Mayilmurugan
- Department of Chemistry, and Department of Bioscience & Biomedical Engineering, Indian Institute of Technology Bhilai, Raipur, Chattisgarh 492015, India
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7
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Belov AS, Belova SA, Efimov NN, Zlobina VV, Novikov VV, Nelyubina YV, Zubavichus YV, Voloshin YZ, Pavlov AA. Synthesis, X-ray structure and magnetic properties of the apically functionalized monocapped cobalt(II) tris-pyridineoximates possessing SMM behaviour. Dalton Trans 2023; 52:2928-2932. [PMID: 36811361 DOI: 10.1039/d2dt04073e] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The title cobalt(II) pseudoclathrochelate complexes possess an intermediate trigonal prismatic-trigonal antiprismatic geometry. As follows from PPMS data, they exhibit an SMM behaviour with Orbach relaxation barriers of approximately 90 K. Paramagnetic NMR experiments confirmed a persistence of these magnetic characteristics in solution. Therefore, a straightforward apical functionalization of this 3D molecular platform for its targeted delivery to a given biosystem can be performed without substantial changes.
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Affiliation(s)
- Alexander S Belov
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia. .,Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia
| | - Svetlana A Belova
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia. .,Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia
| | - Nikolay N Efimov
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia.
| | - Veronika V Zlobina
- Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia
| | - Valentin V Novikov
- Moscow Institute of Physics and Technology, National Research University, Institutsliy per. 9, Dolgoprudny, 141700 Moscow Region, Russia.,BMSTU Center of National Technological Initiative "Digital Material Science: New Material and Substances", Bauman Moscow State Technical University, 2nd Baumanskaya st. 5, 105005, Moscow, Russia
| | - Yulya V Nelyubina
- Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia.,BMSTU Center of National Technological Initiative "Digital Material Science: New Material and Substances", Bauman Moscow State Technical University, 2nd Baumanskaya st. 5, 105005, Moscow, Russia
| | - Yan V Zubavichus
- Synchrotron Radiation Facility SKIF, G.K. Boreskov Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences, 1 Nikolskii pr., 630559 Koltsovo, Russia
| | - Yan Z Voloshin
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia. .,Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia
| | - Alexander A Pavlov
- Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia.,BMSTU Center of National Technological Initiative "Digital Material Science: New Material and Substances", Bauman Moscow State Technical University, 2nd Baumanskaya st. 5, 105005, Moscow, Russia.,National Research University Higher School of Economics, 101000 Moscow, Russia
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8
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Kotková Z, Koucký F, Kotek J, Císařová I, Parker D, Hermann P. Copper(II) complexes of cyclams with N-(2,2,2-trifluoroethyl)-aminoalkyl pendant arms as potential probes for 19F magnetic resonance imaging. Dalton Trans 2023; 52:1861-1875. [PMID: 36448539 DOI: 10.1039/d2dt03360g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A series of Cu(II) complexes with cyclam-based ligands containing two N-(2,2,2-trifluoroethyl)-aminoalkyl pendant arms in 1,8-positions (L1: 1,2-ethylene spacer, L2: 1,3-propylene spacer; L3: 1,4-butylene spacer) was studied in respect to potential use as contrast agents for 19F magnetic resonance imaging (MRI). A number of structures of the complexes as well as of several organic precursors were determined by single-crystal X-ray diffraction analysis. Geometric parameters (especially distances between fluorine atoms and the central metal ion) were determined for each complex and the identity of isomeric complex species present in solution was established. The NMR longitudinal relaxation times (T1) of 19F nuclei in the ligands at clinically relevant fields and temperatures (1-2 s) were significantly shortened upon Cu(II) binding to 7-10 ms for [Cu(L1)]2+, 20-30 ms for [Cu(L2)]2+ and 20-50 ms for [Cu(L3)]2+. The trend of the relaxation time shortening is in accordance with the distance and number of chemical bonds between fluorine atoms and the Cu(II) ion. The signals show promising T2*/T1 ratios in the range 0.25-0.55, assuring their good applicability to 19F NMR/MRI. The results show that even the Cu(II) ion, with a small magnetic moment, causes significant relaxation enhancement with a long-range effect and can be considered as a highly suitable metal ion for efficient 19F MRI contrast agents.
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Affiliation(s)
- Zuzana Kotková
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 42 Prague 2, Czech Republic.
| | - Filip Koucký
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 42 Prague 2, Czech Republic.
| | - Jan Kotek
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 42 Prague 2, Czech Republic.
| | - Ivana Císařová
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 42 Prague 2, Czech Republic.
| | - David Parker
- Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong
| | - Petr Hermann
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 42 Prague 2, Czech Republic.
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