Novel Gadolinium-Free Ultrasmall Nanostructured Positive Contrast for Magnetic Resonance Angiography and Imaging

21 February 2023, Version 1


Nanostructured contrast agents are promising alternatives to Gd(III)-based chelates in magnetic resonance (MR) imaging techniques. A novel ultrasmall paramagnetic nanoparticle (UPN) was strategically designed to maximize the number of exposed paramagnetic sites and r1 while minimizing r2, by decorating 3 nm large titanium dioxide nanoparticles with suitable amounts of iron oxide. Its relaxometric parameters are comparable to that of gadoteric acid (GA) in agar phantoms, and the r2/r1 ratio of 1.38 at 3T is close to the ideal unitary value. The good contrast effect was confirmed by T1-weighted MR images of Wistar rats after intravenous bolus injection of UPN. Those results associated with good biocompatibility and a much longer contrast effect before renal excretion indicate its high potential as alternative blood-pool contrast agent to the GA gold standard for MR angiography, especially for patients with severe renal impairment.


Ultrasmall Nanoparticle
Contrast Agent
Iron Oxide

Supplementary materials

Additional results of UPNs colloidal stability and T1-weighted MR images (PDF).
Results showing the UPNs colloidal stability in cellular culture medium assessed by DLS. Images showing the absence of precipitates. Measured Zeta potentials of the UPNs with different functionalizations. T1-weighted MR images of Wistar rats after i.v. bolus injection of UPNs. Images suggest that UPNs are filtered by the kidneys and eliminated by urinary excretion.


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