Surface PEG Grafting Density Determines Magnetic Relaxation Properties of Gd-Loaded Porous Nanoparticles for MR Imaging Applications

Abstract

Surface PEGylation of nanoparticles designed for biomedical applications is a common and straightforward way to stabilize the materials for in vivo administration and to increase their circulation time. This strategy becomes less trivial when MRI active porous nanomaterials are concerned as their function relies on water/proton-exchange between the pores and bulk water. Here we present a comprehensive study on the effects of PEGylation on the relaxometric properties of nanozeolite LTL (dimensions of 20 × 40 nm) ion-exchanged with paramagnetic GdIII ions. We evidence that as long as the surface grafting density of the PEG chains does not exceed the “mushroom” regime (conjugation of up to 6.2 wt % of PEG), Gd-LTL retains a remarkable longitudinal relaxivity (38 s–1 mM–1 at 7 T and 25 °C) as well as the pH-dependence of the longitudinal and transverse relaxation times. At higher PEG content, the more compact PEG layer (brush regime) limits proton/water diffusion and exchange between the interior of LTL and the bulk, with detrimental consequences on relaxivity. Furthermore, PEGylation of Gd-LTL dramatically decreases the leakage of toxic GdIII ions in biological media and in the presence of competing anions, which together with minimal cytotoxicity renders these materials promising probes for MRI applications.

Nanoarchitectures for efficient IgE cross‐linking on effector cells to study amoxicillin allergy

“…The contour length (full extended length) is calculated as a product of the polymeric length (N) and length of the monomeric unit, 3.5 Å for PEG. 54 …”

On the Versatility of Nanozeolite Linde Type L for Biomedical Applications: Zirconium-89 Radiolabeling and In Vivo Positron Emission Tomography Study

“…As shown in Table 1, the small leakage of Gd III ions from Zr(oxalate)/Gd III -LTL and Zr(chloride)/Gd III -LTL nanoparticles in both media could be reduced upon PEGylation of their surface, as reported earlier for Gd III -LTL. 19 The leakage of Zr IV ions follows the same trend in PBS, while in serum, the difference between the two Zr-loading procedures becomes apparent for the non-PEGylated Zr(oxalate)/Gd III -LTL and Zr(chloride)/Gd III -LTL nanoparticles with 4.2 and 1.6 wt % released Zr IV ions, respectively. This moderate leakage indicates a strong binding of this tetravalent metal-ion to the LTL framework, whether on the surface or in the inner pores.…”

“…Surface functionalization of nanoparticles is a common way to stabilize them prior to in vivo applications. In our previous study, we have shown that this strategy not only provides the nanoparticles with the necessary colloidal stability but also prevents the leakage of toxic ions loaded in the porous LTL crystals . Thus, in the current study, the PEGylation step was adapted to the radiolabeling procedure.…”

Dual-Stimuli-Responsive Multifunctional Gd2Hf2O7 Nanoparticles for MRI-Guided Combined Chemo-/Photothermal-/Radiotherapy of Resistant Tumors

“…Fortunately, the relaxivity of Gd 2 Hf 2 O 7 @PDA@PEG-Pt-RGD NPs slightly enhanced to 38.28 mM –1 s –1 . It may be due to the fact that the PDA on the surface of MRI CA confines water molecules in the CA’s vicinity and then enhances the r 1 value. ,, Furthermore, Gd 2 Hf 2 O 7 and Gd 2 Hf 2 O 7 @PDA@PEG-Pt-RGD NPs provide considerably brighter images than Magnevist. It is demonstrated that Gd 2 Hf 2 O 7 @PDA@PEG-Pt-RGD NPs with higher relaxivity can obtain brighter images (Figure b), which is favorable for guiding tumor therapy.…”