Lanthanopolyoxometalate-Silica Core/Shell Nanoparticles as Potential MRI Contrast Agents
authors Carvalho, RFS; Pereira, GAL; Rocha, J; Castro, MMCA; Granadeiro, CM; Nogueira, HIS; Peters, JA; Geraldes, CFGC
nationality International
journal EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
author keywords Contrast agents; Core-shell nanoparticles; Lanthanides; Paramagnetic relaxation; Polyoxometalates
keywords NMR TRANSVERSAL RELAXIVITY; MAGNETIC-RESONANCE; GOLD NANOPARTICLES; HETEROPOLYTUNGSTATE COMPLEXES; GADOLINIUM COMPLEX; GD(III) COMPLEXES; SI-29 NMR; PARTICLES; COORDINATION; SUSPENSIONS
abstract The NMR relaxivities of the decatungstolanthanoate core-shell nanoparticles, prepared by encapsulating [Ln(W5O18)(2)](9-) polyoxometalates (LnPOM) within amorphous silica shells (K-9[Ln(W5O18)(2)]@SiO2), were studied along the Ln series. The relaxivity of GdPOM is slightly higher than for Gd-DTPA due to second-sphere relaxation effects, but the values for the other paramagnetic LnPOMs are much smaller due to the short T-1e values of their Ln(3+)-ions. The NPs have core-shell spherical structures, with LnPOM-containing cores with 9.5-28 nm diameters, and 4.0-11.0 nm thick amorphous silica shells. In water suspensions, the NPs have negative zeta potentials (-32.5 to -40.0 mV) and time-dependent hydrodynamic diameters (31-195 nm) reflecting the formation of aggregates. The relaxivities of GdPOM@SiO2 NPs suspensions (r(1)=10.97 (mM Gd)(-1) s(-1), r(2)=12.02 (mM Gd)(-1) s(-1), 0.47 T, 25 degrees C) are considerably larger than for the GdPOM solutions, indicating that their silica shell is significantly porous to water. This increase is limited by the agglomeration of the complexes in the NPs core, limiting their access to water to those at the core surface. Replacing half of the Gd3+ ions by Eu3+ decreases the NPs r(1) and r(2) relaxivities at 0.47 T to 20 % and 35 % of their initial values, which are still considerable, but does not affect the efficient luminescence properties of the Eu3+ centers. This indicates that the mixed NPs have potential as dual modality MRI/optical imaging contrast agents.
publisher WILEY-V C H VERLAG GMBH
issn 1434-1948
isbn 1099-0682
year published 2021
volume 2021
issue 34
beginning page 3458
ending page 3465
digital object identifier (doi) 10.1002/ejic.202100445
web of science category 8
subject category Chemistry, Inorganic & Nuclear
unique article identifier WOS:000687128000001
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journal impact factor 2.529
5 year journal impact factor 2.284
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