Mesoporous silica nanoparticles functionalized with fluorescent and MRI reporters for the visualization of murine tumors overexpressing α_vβ₃ receptors

A novel fluorescein/Gd-DOTAGA containing nanoprobe for the visualization of tumors by optical and Magnetic Resonance Imaging (MRI) is reported herein. It is based on the functionalization of the surface of small mesoporous silica nanoparticles (MSNs) (∼30 nm) with the arginine-glycine-aspartic (RGD) moieties, which are known to target α_vβ₃ integrin receptors overexpressed in several tumor cells. The obtained nanoprobe (Gd-MSNs-RGD) displays good stability, tolerability and high relaxivity (37.6 mM^-1 s^-1 at 21.5 MHz). After a preliminary evaluation of their cytotoxicity and targeting capability toward U87MG cells by in vitro fluorescence and MR imaging, the nanoprobes were tested in vivo by T₁-weighted MR imaging of xenografted murine tumor models. The obtained results demonstrated that the Gd-MSNs-RGD nanoprobes are good reporters both in vitro and in vivo for the MR-visualization of tumor cells overexpressing α_vβ₃ integrin receptors.