Comparison of phosphonate, hydroxypropyl and carboxylate pendants in Fe(III) macrocyclic complexes as MRI contrast agents

Kras, Elizabeth A.; Abozeid, Samira M.; Eduardo, Waldine; Spernyak, Joseph A.; Morrow, Janet R.

doi:10.1016/j.jinorgbio.2021.111594

Cited by 16 publications

(45 citation statements)

References 54 publications

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“…For both LipoA and LipoB, the r 1 relaxivity decreases with temperature from 24 to 45 or 50 °C, respectively. This is similar to the decrease in relaxivity with an increase in temperature that is observed for Fe(L1) and for other closed-coordination sphere Fe(III) complexes . Such a decrease with increasing temperature is attributed to decreasing correlation times from rotational motion and the electronic relaxation time of the Fe(III) center .…”

Section: Resultssupporting

confidence: 84%

“…41,42 The proton r 1 relaxivity of Fe(L1) is attributed predominately to second-sphere and outer-sphere water interactions (Table 1, Figure S1). 42,46 Notably, the dinuclear Fe(III) complex has a 2.6-fold greater relaxivity per molecule compared to Fe(L1) at 4.7 T. The greater relaxivity of the Fe(III) centers of the dinuclear complex is attributed to the open coordination sites that allow for an inner-sphere water molecule. The exchange of the inner-sphere water on Fe 2 (L2) is slow on the NMR time scale, yet the complex still produces higher relaxivity than the complexes that lack the bound water.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…This is similar to the decrease in relaxivity with an increase in temperature that is observed for Fe(L1) and for other closed-coordination sphere Fe(III) complexes. 46 Such a decrease with increasing temperature is attributed to decreasing correlation times from rotational motion and the electronic relaxation time of the Fe(III) center. 66 However, at higher temperatures (>45 °C for LipoA and >50 °C for LipoB1), the r 1 relaxivity increases with temperature.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…17 Two of the Fe(III) complexes lack inner-sphere water 42 but have protons on the hydroxypropyl groups to facilitate second-sphere water interactions or proton exchangebased T 1 relaxation. 46 The dinuclear Fe(III) complex has one bound water per iron center. 41 LipoA and LipoB are studied as T 1 and T 2 MRI probes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Two different types of liposomes are studied here, including LipoA with internally loaded Fe(III) coordination complex and LipoB with internally loaded Fe(III) complex and an amphiphilic Fe(III) complex that incorporates into the bilayer . Two of the Fe(III) complexes lack inner-sphere water but have protons on the hydroxypropyl groups to facilitate second-sphere water interactions or proton exchange-based T 1 relaxation . The dinuclear Fe(III) complex has one bound water per iron center .…”

Section: Introductionmentioning

confidence: 99%

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Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes

Abozeid

Chowdhury

Asik

et al. 2021

ACS Appl. Bio Mater.

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Paramagnetic liposomes containing Fe(III) complexes were prepared by incorporation of mononuclear (Fe(L1) or Fe(L3)) or dinuclear (Fe2(L2)) coordination complexes of 1,4,7-triazacyclononane macrocycles containing 2-hydroxypropyl pendant groups. Two different types of paramagnetic liposomes were prepared. The first type, LipoA, has the mononuclear Fe(L1) complex loaded into the internal aqueous core. The second type, LipoB, has the amphiphilic Fe(L3) complex inserted into the liposomal bilayer and the internal aqueous core loaded with either Fe(L1) (LipoB1) or Fe2(L2) (LipoB2). LipoA enhances both T1 and T2 water proton relaxation rates. Treatment of LipoA with osmotic gradients to produce a nonspherical liposome produces a liposome with a chemical exchange saturation transfer effect as shown by an asymmetry analysis but only at high osmolarity. LipoB1, which contains an amphiphilic complex in the liposomal bilayer, produced a broadened Z-spectrum upon treatment of the liposome with osmotic gradients. The r 1 relaxivity of LipoB1 and LipoB2 were higher than the r 1 relaxivity of LipoA on a per Fe basis, suggesting an important contribution from the amphiphilic Fe(III) center. The r 1 relaxivities of paramagnetic liposomes are relatively constant over a range of magnetic field strengths (1.4–9.4 T), with the ratio of r 2/r 1 substantially increasing at high field strengths. MRI studies of LipoB1 in mice showed prolonged contrast enhancement in blood compared to the clinically employed Gd(DOTA), which was injected at a 2-fold higher dose per metal than the Fe(III)-loaded liposomes.

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Section: Resultssupporting

confidence: 84%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes

Abozeid

Chowdhury

Asik

et al. 2021

ACS Appl. Bio Mater.

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Enzyme Control Over Ferric Iron Magnetostructural Properties

et al. 2021

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Fe3+ complexes in aqueous solution can exist as discrete mononuclear species or multinuclear magnetically coupled species. Stimuli‐driven change to Fe3+ speciation represents a powerful mechanistic basis for magnetic resonance sensor technology, but ligand design strategies to exert precision control of aqueous Fe3+ magnetostructural properties are entirely underexplored. In pursuit of this objective, we rationally designed a ligand to strongly favor a dinuclear μ‐oxo‐bridged and antiferromagnetically coupled complex, but which undergoes carboxylesterase mediated transformation to a mononuclear high‐spin Fe3+ chelate resulting in substantial T1‐relaxivity increase. The data communicated demonstrate proof of concept for a novel and effective strategy to exert biochemical control over aqueous Fe3+ magnetic, structural, and relaxometric properties.

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Enzyme Control Over Ferric Iron Magnetostructural Properties

et al. 2021

View full text Add to dashboard Cite

Fe 3 + complexes in aqueous solution can exist as discrete mononuclear species or multinuclear magnetically coupled species. Stimuli-driven change to Fe 3 + speciation represents a powerful mechanistic basis for magnetic resonance sensor technology, but ligand design strategies to exert precision control of aqueous Fe 3 + magnetostructural properties are entirely underexplored. In pursuit of this objective, we rationally designed a ligand to strongly favor a dinuclear μoxo-bridged and antiferromagnetically coupled complex, but which undergoes carboxylesterase mediated transformation to a mononuclear high-spin Fe 3 + chelate resulting in substantial T 1 -relaxivity increase. The data communicated demonstrate proof of concept for a novel and effective strategy to exert biochemical control over aqueous Fe 3 + magnetic, structural, and relaxometric properties.

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Comparison of phosphonate, hydroxypropyl and carboxylate pendants in Fe(III) macrocyclic complexes as MRI contrast agents

Cited by 16 publications

References 54 publications

Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes

Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes

Enzyme Control Over Ferric Iron Magnetostructural Properties

Enzyme Control Over Ferric Iron Magnetostructural Properties

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