Nanostructure-enhanced water interaction to increase the dual-mode MR contrast performance of gadolinium-doped iron oxide nanoclusters

Rational structure design benefits the development of new classes of contrast agents (CAs) with excellent magnetic resonance imaging performance. In this work, hydrogenated silica with a net nanostructure (HSiO2) was fabricated and used to modify gadolinium-doped iron oxide nanoclusters (GdIONCs) to form a core-shell nanoplatform (HSiO2@GdIONC) with enhanced T1 and T2 contrast ability. In this nanoplatform, the HSiO2 shell showed a strong binding capacity for water molecules because of the presence of hydrogen bonds, oxygen vacancies, and high specific surface areas, and the strong binding capacity significantly improved the spin-spin (T2) and spin-lattice (T1) imaging of the GdIONC core. In addition, the T1 relaxation rate of the GdIONC core dramatically increased from 30.8 mM−1 s−1 to 38.2 mM−1 s−1 after being coated with the HSiO2 shell, and the r2 to r1 ratio decreased from 10.9 to 8.3, which is an appropriate ratio (r2/r1: 5–10) for dual-mode contrast. Cell and animal experiments suggested that HSiO2@GdIONC exhibited a better T1- and T2-weighted MR imaging effect than the bare GdIONC core, confirming that this strategy for modifying GdIONCs is a beneficial and promising approach for obtaining highly efficient dual-mode CAs.