Gd(iii) complex conjugated ultra-small iron oxide as an enhanced T1-weighted MR imaging contrast agent

Abstract

In this work, ultra-small iron oxide nanoparticles were synthesized using high temperature pyrolysis. For further functionalization, dopamine was anchored onto the surface of ultra-small iron oxide nanoparticles (Fe₃O₄@DOPA NPs). Gd(III) ions were chelated with diethylenetriaminepentaacetic acid (DTPA) which was linked with dopamine. The resulting Gd(III) complex conjugated ultra-small Fe₃O₄ NPs [Fe₃O₄@DOPA(Gd-DTPA) NPs] were characterized by XRD pattern and TEM. The longitudinal relaxivity (r₁) of Fe₃O₄@DOPA(Gd-DTPA) NPs was 9.97 mM⁻¹ S⁻¹. Compared to ultra-small Fe₃O₄ NPs and Gd(III) complexes, Fe₃O₄@DOPA(Gd-DTPA) NPs showed a significant improvement of the T₁-weighted MR image in aqueous solution, in vitro and in vivo.