EDTMP ligand-enhanced water interactions endowing iron oxide nanoparticles with dual-modal MRI contrast ability

Abstract

Single-modal magnetic resonance imaging (MRI) contrast agents sometimes cause signal confusion in clinical diagnosis. Utilizing ligands to endow iron oxide nanoparticles (IO NPs) with excellent dual-modal MRI contrast efficiency might be an effective strategy to improve diagnostic accuracy. This work presents the development of a special ligand-assisted one-pot approach for the preparation of super-hydrophilic magnetic NPs with excellent water dispersion, biocompatibility and T₁–T₂ dual-modal contrast enhancement properties. In addition, the strong binding capacity between the ethylenediamine tetramethylenephosphonic acid (EDTMP) ligand and water molecules induced by the presence of abundant hydrogen bonds significantly improves spin–lattice (T₁) and spin–spin (T₂) imaging of the IO core. After being modified with the EDTMP ligand, the T₂ relaxation rate of the IO core is dramatically increased from 71.78 mM⁻¹ s⁻¹ to 452.38 mM⁻¹ s⁻¹, and a moderate T₁ relaxation rate (11.61 mM⁻¹ s⁻¹) is observed simultaneously, implying that the NPs with an average size of 9.7 nm may be potential candidates as high-efficiency T₁–T₂ MRI contrast agents. This fundamental technique of using super-hydrophilicity ligands to endow IO NPs with dual-modal contrast properties without size change and damage in the T₂ contrast effect may provide a useful strategy to facilitate the application of magnetic NPs in the field of medical diagnosis.