A benzene-core trinuclear GdIII complex: towards the optimization of relaxivity for MRI contrast agent applications at high magnetic field.

Dalton transactions (Cambridge, England : 2003) · 2008 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3416

Study snapshot

PublicationDalton transactions (Cambridge, England : 2003) · 2008

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

A novel ligand, H(12)L, based on a trimethylbenzene core bearing three methylenediethylenetriamine-N,N,N'',N''-tetraacetate moieties (-CH(2)DTTA(4-)) for Gd(3+) chelation has been synthesized, and its trinuclear Gd(3+) complex [Gd(3)L(H(2)O)(6)](3-) investigated with respect to MRI contrast agent applications. A multiple-field, variable-temperature (17)O NMR and proton relaxivity study on [Gd(3)L(H(2)O)(6)](3-) yielded the parameters characterizing water exchange and rotational dynamics. On the basis of the (17)O chemical shifts, bishydration of Gd(3+) could be evidenced. The water exchange rate, k(ex)(298)=9.0+/-3.0 s(-1) is around twice as high as k(ex)(298) of the commercial [Gd(DTPA)(H(2)O)](2-) and comparable to those on analogous Gd(3+)-DTTA chelates. Despite the relatively small size of the complex, the rotational dynamics had to be described with the Lipari-Szabo approach, by separating global and local motions. The difference between the local and global rotational correlation times, tau(lO)(298)=170+/-10 ps and tau(gO)(298)=540+/-100 ps respectively, shows that [Gd(3)L(H(2)O)(6)](3-) is not fully rigid; its flexibility originates from the CH(2) linker between the benzene core and the poly(amino carboxylate) moiety. As a consequence of the two inner-sphere water molecules per Gd(3+), their close to optimal exchange rate and the appropriate size and limited flexibility of the molecule, [Gd(3)L(H(2)O)(6)](3-) has remarkable proton relaxivities when compared with commercial contrast agents, particularly at high magnetic fields (r(1)=21.6, 17.0 and 10.7 mM(-1)s(-1) at 60, 200 and 400 MHz respectively, at 25 degrees C; r(1) is the paramagnetic enhancement of the longitudinal water proton relaxation rate, referred to 1 mM concentration of Gd(3+)).

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Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

A trinuclear Gd(III) complex [Gd3L(H2O)6]3− was synthesized and characterized by multiple-field, variable-temperature 17O NMR and proton relaxivity measurements. The complex showed evidence of bishydration per Gd(III), a water exchange rate kex(298)=9.0±3.0 s−1 (about twice that of commercial [Gd(DTPA)(H2O)]2−), and high r1 relaxivities reported at 60, 200, and 400 MHz (25 °C).

Outcomes measured

MRI contrast agent proton relaxivity (r1)
Water exchange rate (kex)
Rotational correlation times (Lipari–Szabo global/local)
17O NMR chemical shifts / hydration state

View raw extracted JSON

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  "study_type": "other",
  "exposure": {
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  },
  "population": null,
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  "outcomes": [
    "MRI contrast agent proton relaxivity (r1)",
    "Water exchange rate (kex)",
    "Rotational correlation times (Lipari–Szabo global/local)",
    "17O NMR chemical shifts / hydration state"
  ],
  "main_findings": "A trinuclear Gd(III) complex [Gd3L(H2O)6]3− was synthesized and characterized by multiple-field, variable-temperature 17O NMR and proton relaxivity measurements. The complex showed evidence of bishydration per Gd(III), a water exchange rate kex(298)=9.0±3.0 s−1 (about twice that of commercial [Gd(DTPA)(H2O)]2−), and high r1 relaxivities reported at 60, 200, and 400 MHz (25 °C).",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "gadolinium",
    "Gd(III) complex",
    "MRI contrast agent",
    "relaxivity",
    "17O NMR",
    "water exchange",
    "rotational dynamics",
    "Lipari-Szabo",
    "high magnetic field"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1039/b717390c
PubMed: 18283380

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