Polyelectrolyte-Stabilized Nanotemplates Based on Gd(III) Complexes with Macrocyclic Tetra-1,3-diketones as a Positive MR Contrast Agents

Abstract

The work presents for the first time aqueous colloids prepared from Gd(III) complexes with 1,3-diketone derivatives as promising candidates for positive MR contrast agents (CA). The obtained colloids are based on reprecipitation of water insoluble Gd(III) complexes from organic to aqueous phases with further stabilization via layer-by-layer deposition of oppositely charged polyelectrolytes. A complex of experimental techniques reveals amorphous 3-6 nm sized Gd(III)-based hard templates encapsulated into soft polyelectrolyte capsules. Magnetic field and coating effects on T 1 -and T 2 -relaxivities for colloids with mono-, bi-and tri-layer polyelectrolyte deposition onto Gd(III)-based templates are revealed. The relaxivities of the mono-layered colloids are greater than those of commercial mononuclear Gd (III) CA. Water molecular correlation times in aqueous solutions of novel Gd(III)-based nanoparticles were calculated. T 1 -and T 2weighted MRI data show strong positive contrast.

High performance magneto-fluorescent nanoparticles assembled from terbium and gadolinium 1,3-diketones

“…1g) are lower than those estimated by DLS measurements, because of their aggregation and swelling of polyelectrolyte coating in aqueous solutions. Moreover, the hard templates within the soft PSS coating are not uniform, consisting of smaller (2–10 nm sized) cores, as previously reported for PSS-stabilized Gd- 1 colloids43. The TEM images of PSS-stabilized Tb- 1 colloids confirm similar morphology (Fig.…”

“…The uniformity of both Gd- and Tb-based colloids is fully consistent with the isomorphism of Tb- 1 and Gd- 1 complexes. It is worth noting that the previously reported amorphous nature of the hard templates of PSS-stabilized Gd- 1 colloids results from metastability of the hard cores, probably due to reprecipitation of the complex from organic to aqueous solutions43. Similar XRD measurements (for detailed description of the procedure see SI) were performed here for PSS-stabilized Tb- 1 colloids.…”

“…According to our previous reports, the complex formation of 1 with both Gd(III)43 and Tb(III)44 occurs in 1:1 stoichiometry in alkaline DMF solutions. Our previous report43 on the synthesis of PSS-stabilized Gd- 1 colloids demonstrated the ability of keeping the full amount of Gd- 1 complex within NP shell, thanks to the poor solubility of the complex, experimentally confirmed by luminescence measurements of the supernatant solutions in the synthesis of PSS-stabilized Tb- 1 colloids. This tendency provides great synthetic advantage, since the Tb-to-Gd ratio in the colloids can be easily driven by their ratio in the organic (DMF) solution.…”

“…The DLS data reveal the size of hydrated PSS-coated colloids, while their functionality results from the hard cores inside the polyelectrolyte coating174345. The previously published reports1743 highlight hard-soft morphology of the colloids. The TEM image of the dried colloids presented in Fig.…”

“…The synthesis of europium-doped luminescent polyelectrolyte colloids was first described by Mustafina et al 41. and later applied to various terbium42, and gadolinium43 complexes.…”