Smart dual <i>T</i><sub>1</sub> MRI-optical imaging agent based on a rhodamine appended Fe(<scp>iii</scp>)-catecholate complex

Maheshwaran, Duraiyarasu; Nagendraraj, Thavasilingam; Balaji, T Sekar; Ganesan, Kumaresan; Kumaran, Senthil; Mayilmurugan, Ramasamy

doi:10.1039/d0dt02364g

Cited by 15 publications

(18 citation statements)

References 58 publications

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“…For example, a recent study shows the formation of dimeric μ-hydroxy Fe(III) complexes in solution that have reduced r 1 relaxivity . Other examples of Fe(III) agents require the addition of cosolvents to solubilize the complexes for solution studies or have low stability under physiological conditions including neutral pH. − …”

Section: Introductionmentioning

confidence: 99%

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

et al. 2021

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Four high-spin Fe(III) macrocyclic complexes, including three dinuclear and one mononuclear complex, were prepared toward the development of more effective iron-based magnetic resonance imaging (MRI) contrast agents. All four complexes contain a 1,4,7-triazacyclononane macrocyclic backbone with two hydroxypropyl pendant groups, an ancillary aryl or biphenyl group, and a coordination site for a water ligand. The pH potentiometric titrations support one or two deprotonations of the complexes, most likely deprotonation of hydroxypropyl groups at near-neutral pH. Variable-temperature 17O NMR studies suggest that the inner-sphere water ligand is slow to exchange with bulk water on the NMR time scale. Water proton T 1 relaxation times measured for solutions of the Fe(III) complexes at pH 7.2 showed that the dinuclear complexes have a 2- to 3-fold increase in r 1 relaxivity in comparison to the mononuclear complex per molecule at field strengths ranging from 1.4 T to 9.4 T. The most effective agent, a dinuclear complex with macrocycles linked through para-substitution of an aryl group (Fe2(PARA)), has an r 1 of 6.7 mM–1 s–1 at 37 °C and 4.7 T or 3.3 mM–1 s–1 per iron center in the presence of serum albumin and shows enhanced blood pool and kidney contrast in mice MRI studies.

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Section: Introductionmentioning

confidence: 99%

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

et al. 2021

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“…44,45 Very recently, a system based on a Fe(III) ion coordinated to three catecholate ligands bearing a rhodamine moiety on their surface was reported to display, through the binding to HSA, relaxometric enhancement properties similar to the ones herein reported for Fe(DFX) 2 . 46 As mentioned above, the assignment of the observed relaxation enhancement for Fe(DFX) 2 in serum to the closest protons on second sphere water molecules may represent an oversimplification as likely other mobile protons on the protein in the proximity of the interaction site may contribute. The involved protons (whatever is their origin) are in fast exchange with the bulk solvent as demonstrated by the decrease of the observed relaxivity upon the increase of the temperature.…”

Section: ■ Discussionmentioning

confidence: 96%

“…It follows that the reorientational motion of the second sphere water molecules becomes relevant to determine the relaxivity enhancement when the magnetic field strength is increased. The exploitation of the lengthening of T 1e was a common practice in the case of slowly moving GBCAs displaying relaxivity peaks at around 1 T where the correlation times for the electronic relaxation of Gd(III) ions approach the value of the molecular reorientational time (for HSA bound complexes, τ R is the range of 3–20 ns). , Very recently, a system based on a Fe(III) ion coordinated to three catecholate ligands bearing a rhodamine moiety on their surface was reported to display, through the binding to HSA, relaxometric enhancement properties similar to the ones herein reported for Fe(DFX) 2 …”

Section: Discussionmentioning

confidence: 99%

Fe(deferasirox)₂: An Iron(III)-Based Magnetic Resonance Imaging T₁ Contrast Agent Endowed with Remarkable Molecular and Functional Characteristics

et al. 2021

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The search for alternatives to Gd-containing magnetic resonance imaging (MRI) contrast agents addresses the field of Fe(III)-bearing species with the expectation that the use of an essential metal ion may avoid the issues raised by the exogenous Gd. Attention is currently devoted to highly stable Fe(III) complexes with hexacoordinating ligands, although they may lack any coordinated water molecule. We found that the hexacoordinated Fe(III) complex with two units of deferasirox, a largely used iron sequestering agent, owns properties that can make it a viable alternative to Gd-based agents. Fe(deferasirox) 2 displays an outstanding thermodynamic stability, a high binding affinity to human serum albumin (three molecules of complex are simultaneously bound to the protein), and a good relaxivity that increases in the range 20−80 MHz. The relaxation enhancement is due to second sphere water molecules likely forming H-bonds with the coordinating phenoxide oxygens. A further enhancement was observed upon the formation of the supramolecular adduct with albumin. The binding sites of Fe(deferasirox) 2 on albumin were characterized by relaxometric competitive assays. Preliminary in vivo imaging studies on a tumor-bearing mouse model indicate that, on a 3 T MRI scanner, the contrast ability of Fe(deferasirox) 2 is comparable to the one shown by the commercial Gd(DTPA) agent. ICP-MS analyses on blood samples withdrawn from healthy mice administered with a dose of 0.1 mmol/kg of Fe(deferasirox) 2 showed that the complex is completely removed in 24 h.

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“…The large relaxivities in human serum were then attributed to the water molecules in the second coordination sphere. The binding capacity of the complex to HSA was studied in detail by the titration experiments with different concentration of the complex or HSA [ 43 ]. The results indicated that three Fe(III)–(DFX) 2 units bind tightly to one molecule of HSA with an average apparent binding constant ( K a) of 2.8 × 10 5 M −1 .…”

Section: Mononuclear Fe(iii) Complexesmentioning

confidence: 99%

Low-Molecular-Weight Fe(III) Complexes for MRI Contrast Agents

Chen

Yang

2022

Molecules

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Fe(III) complexes have again attracted much attention for application as MRI contrast agents in recent years due to their high thermodynamic stability, low long-term toxicity, and large relaxivity at a higher magnetic field. This mini-review covers the recent progress on low-molecular-weight Fe(III) complexes, which have been considered as one of the promising alternatives to clinically used Gd(III)-based contrast agents. Two kinds of complexes including mononuclear Fe(III) complexes and multinuclear Fe(III) complexes are summarized in sequence, with a specific highlight of the structural relationships between the complexes and their relaxivity and thermodynamic stability. In additional, the future perspectives for the design of low-molecular-weight Fe(III) complexes for MRI contrast agents are suggested.

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Smart dual T₁ MRI-optical imaging agent based on a rhodamine appended Fe(iii)-catecholate complex

Abstract: The high spin Fe(iii) complex Fe(RhoCat)3 is reported as a smart dual-modal T1 MRI-optical imaging probe to visualize the NO molecule and an acidic pH environment.

Cited by 15 publications

References 58 publications

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

Fe(deferasirox)₂: An Iron(III)-Based Magnetic Resonance Imaging T₁ Contrast Agent Endowed with Remarkable Molecular and Functional Characteristics

Low-Molecular-Weight Fe(III) Complexes for MRI Contrast Agents

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Smart dual T1 MRI-optical imaging agent based on a rhodamine appended Fe(iii)-catecholate complex

Abstract: The high spin Fe(iii) complex Fe(RhoCat)3 is reported as a smart dual-modal T1 MRI-optical imaging probe to visualize the NO molecule and an acidic pH environment.

Cited by 15 publications

References 58 publications

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes

Fe(deferasirox)2: An Iron(III)-Based Magnetic Resonance Imaging T1 Contrast Agent Endowed with Remarkable Molecular and Functional Characteristics

Low-Molecular-Weight Fe(III) Complexes for MRI Contrast Agents

Contact Info

Product

Resources

About

Smart dual T₁ MRI-optical imaging agent based on a rhodamine appended Fe(iii)-catecholate complex

Fe(deferasirox)₂: An Iron(III)-Based Magnetic Resonance Imaging T₁ Contrast Agent Endowed with Remarkable Molecular and Functional Characteristics