Metal-based environment-sensitive MRI contrast agents

Bonnet, Célia S.; Tóth, Éva

doi:10.1016/j.cbpa.2021.01.013

Cited by 16 publications

(15 citation statements)

References 63 publications

(78 reference statements)

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“…In solution, oxidation state changes of the MRI probe are readily detected through changes in probe signal, but there are additional considerations for more challenging in vivo applications. To optimize the response, a large difference in signal for the two states of the responsive probe is desirable. , Some of the probes described here have more favorable properties than others. For relaxivity probes, conversion of Mn(II) to Mn(III) complexes results in reduced relaxivity upon oxidation with hydrogen peroxide with relaxivity changes of typically about 3-fold .…”

Section: Outlook For In Vivo Studiesmentioning

confidence: 99%

“…Magnetic resonance imaging (MRI) contrast agents are paramagnetic metal complexes that are administered to enhance the images produced in diagnostic procedures. − Contrast agents modulate the proton resonances of water in soft tissue and are used to image blood flow, characterize tumors and lesions, and map heart function for augmenting the high-resolution images that characterize MRI . However, interest in determining disease prognosis and monitoring therapeutic response has given rise to a demand for a newer type of contrast agent which is called a molecular or responsive magnetic resonance imaging agent. , These agents produce signals in response to the biological environment including changes in pH, redox status, metal ion concentrations, or protein targets. , Such molecular agents (or probes) are challenging to produce but present a great opportunity for synthetic inorganic chemists.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to the advantage of being essential elements that are also earth abundant, transition-metal complexes have certain advantages in the development of responsive probes. One of the most obvious is the existence of multiple stable metal-based oxidation and spin states, something which is lacking for Gd(III) complexes. , The ability to switch between oxidation and corresponding spin states in response to redox-related changes in the biological environment is a powerful tool for molecular imaging. ,, For example, diseases such as cancer, stroke, and atherosclerosis are characterized by chronic inflammation which involves a perturbed biological redox environment. − …”

Section: Introductionmentioning

confidence: 99%

“…6,7 These agents produce signals in response to the biological environment including changes in pH, redox status, metal ion concentrations, or protein targets. 8,9 Such molecular agents (or probes) are challenging to produce but present a great opportunity for synthetic inorganic chemists.…”

Section: Introductionmentioning

confidence: 99%

“…10,14 The ability to switch between oxidation and corresponding spin states in response to redox-related changes in the biological environment is a powerful tool for molecular imaging. 8,15,16 For example, diseases such as cancer, stroke, and atherosclerosis are characterized by chronic inflammation which involves a perturbed biological redox environment. 17−19 In this viewpoint, we focus on the coordination chemistry of first-row transition-metal complexes and their use as redoxresponsive probes with an emphasis on iron and cobalt complexes that undergo oxidation state changes at the metal center.…”

Section: Introductionmentioning

confidence: 99%

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Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

et al. 2022

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The presence of multiple oxidation and spin states of first-row transition-metal complexes facilitates the development of switchable MRI probes. Redox-responsive probes capitalize on a change in the magnetic properties of the different oxidation states of the paramagnetic metal ion center upon exposure to biological oxidants and reductants. Transition-metal complexes that are useful for MRI can be categorized according to whether they accelerate water proton relaxation (T 1 or T 2 agents), induce paramagnetic shifts of 1 H or 19 F resonances (paraSHIFT agents), or are chemical exchange saturation transfer (CEST) agents. The various oxidation state couples and their properties as MRI probes are summarized with a focus on Co(II)/Co(III) or Fe(II)/Fe(III) complexes as small molecules or as liposomal agents. Solution studies of these MRI probes are reviewed with an emphasis on redox changes upon treatment with oxidants or with enzymes that are physiologically important in inflammation and disease. Finally, we outline the challenges of developing these probes further for in vivo MRI applications.

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Section: Outlook For In Vivo Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

et al. 2022

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Design Strategies for Responsive Fluorine‐19 Magnetic Resonance Probes Using Paramagnetic Metal Complexes

2022

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Magnetic resonance imaging (MRI) is a powerful and widely used in vivo imaging technique that enables whole body imaging without ionizing radiation. In clinical practice, 1 H MRI is employed for imaging anatomical and physiological states via monitoring of protons in water and lipids. In order to monitor biochemical processes at the molecular level, several research groups are exploring responsive MRI agents that alter their signal upon interaction with an analyte or biological environment of interest. Fluorine ( 19 F) MRI agents are promising due to the 19 F nucleus having similar magnetic resonance (MR) properties to proton and the absence of endogenous 19 F in living systems, resulting in no background signal. In order to make responsive 19 F MR agents for molecular imaging and analysis, fluorinated platforms must be developed in which their 19 F MR signal changes after interacting with a target analyte. A promising strategy is to use paramagnetic metals to modulate the 19 F MR signal by altering the relaxation rates and/or chemical shift of an appended 19 F imaging tag. In this concept, we provide an overview of the theoretical principles and molecular design strategies that have been exploited in the design of responsive 19 F MR agents, with a specific focus on agents based on small molecule paramagnetic metal ion chelates.

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Fluorinated Mn(III)/(II)‐Porphyrin with Redox‐Responsive ¹H and ¹⁹F Relaxation Properties

Pinto,

Ferreira,

Teixeira

et al. 2023

Chemistry A European J

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A new fluorinated manganese porphyrin, (Mn‐TPP‐p‐CF3) is reported capable of providing, based on the Mn(III)/Mn(II) equilibrium, dual 1H relaxivity and 19F NMR response to redox changes. The physical‐chemical characterization of both redox states in DMSO‐d6/H2O evidenced that the 1H relaxometric and 19F 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 19F 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 19F NMR. The broad 1H and 19F NMR signals of Mn(III)‐TPP‐p‐CF3 disappear in the presence of 1 equivalent ascorbate replaced by a shifted and broadened 19F NMR signal from Mn(II)‐TPP‐p‐CF3. Phantom 19F 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. 1H 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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Metal-based environment-sensitive MRI contrast agents

Cited by 16 publications

References 63 publications

Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

Design Strategies for Responsive Fluorine‐19 Magnetic Resonance Probes Using Paramagnetic Metal Complexes

Fluorinated Mn(III)/(II)‐Porphyrin with Redox‐Responsive ¹H and ¹⁹F Relaxation Properties

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Metal-based environment-sensitive MRI contrast agents

Cited by 16 publications

References 63 publications

Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

Redox-Responsive MRI Probes Based on First-Row Transition-Metal Complexes

Design Strategies for Responsive Fluorine‐19 Magnetic Resonance Probes Using Paramagnetic Metal Complexes

Fluorinated Mn(III)/(II)‐Porphyrin with Redox‐Responsive 1H and 19F Relaxation Properties

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Fluorinated Mn(III)/(II)‐Porphyrin with Redox‐Responsive ¹H and ¹⁹F Relaxation Properties