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Self-assembly of Gd3+-bound keplerate polyanions into nanoparticles as the route for synthesis of positive MRI contrast agents. Impact of the structure on the magnetic relaxivity

Abstract

The present work introduces Gd3+ complexes with giant keplerate polyanions as promising basis for MRI contrast agents. The impact of Gd3+ binding with different building blocks of keplerates on magnetic relaxivity of the complexes is revealed by comparative study of the keplerates [{Mo6O21}12{Mo2O4(OAc)}30]42-, [{Mo6O21}12{Mo2O4(HPO4)}30]72-, and [{Mo6O21}12{Mo2O2S2(OAc)}30]42-. Unprecedentedly high longitudinal and transverse relaxivity values (up to 250 and 300 mM-1∙s-1 correspondingly) are achieved for the keplerates possessing edl{Mo2O4(OAc)} and {Mo2O4(HPO42-)} moieties under their 1:1 complex formation with Gd3+. The transformation of the external pores from Mo9O9 to Mo9O6S3 in the {Mo2O2S2(OAc)}-keplerate or the increase in the Gd3+-to-keplerate ratio the factors that decrease the relaxivity. The rapid degradation of the free keplerates in aqueous solutions restricts the use of the Gd3+-bound keplerates with 1:1 stoichiometry as MRI contrast agents. In this work, optimized stoichiometry of the complexes, their self-assembly into ultra-small nanoparticles and hydrophilic coating by a triblock copolymer are highlighted as the tools for increasing both the colloid and chemical stability of the keplerate complexes. Optimal keplerate compositions have been identified to achieve compromise low cytotoxicity and high stability; these Gd3+-bound keplerates exhibit longitudinal and transverse relaxivity values (95 and 114 mM-1∙s-1, respectively), well within the region of interest for MRI technique.

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Publication details

The article was received on 13 Jun 2018, accepted on 06 Sep 2018 and first published on 07 Sep 2018


Article type: Paper
DOI: 10.1039/C8SM01214H
Citation: Soft Matter, 2018, Accepted Manuscript
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    Self-assembly of Gd3+-bound keplerate polyanions into nanoparticles as the route for synthesis of positive MRI contrast agents. Impact of the structure on the magnetic relaxivity

    J. Elistratova, B. Akhmadeev, V. S. Korenev, M. N. Sokolov, I. Nizameev, A. T. Gubaidullin, A. D. Voloshina and A. Mustafina, Soft Matter, 2018, Accepted Manuscript , DOI: 10.1039/C8SM01214H

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