Silica Nanoparticles for Bimodal MRI-Optical Imaging by Grafting Gd3+and Eu3+/Tb3+Complexes

Bimodal magnetic resonance imaging (MRI)/optical probes for bioimaging were obtained by grafting two types of lanthanide metal ions, Gd3+ and Eu3+/Tb3+, on the surface of SiO2 nanoparticles. The resulting systems were endowed with relaxometry and photoluminescent properties, respectively. Grafting a pyridine-based aromatic backbone on to the silica surface enhances the emission quantum yield of the Eu3+-containing nanoparticles fivefold compared to similar systems that bear no aromatic antennae. The emission properties of the mixed Ln3+/Gd3+-based nanoparticles are not influenced by the presence of Gd3+. The relaxometric properties of these samples are slightly better than the properties of commercial [Gd(DTPA)]2 (DTPA = diethylenetriaminepentaacetate). When taken up by RAW 264.7 cells (mouse macrophage cell line), such bimodal probes exhibit both T1-weighted MRI increased contrast and fluorescence tracking.