RGD-Conjugated Nanoscale Coordination Polymers for Targeted T1- and T2-weighted Magnetic Resonance Imaging of Tumors in Vivo

Development of multifunctional nanoscale coordination polymers (NCPs) allowing for T-1- and T-2-weighted targeted magnetic resonance (MR) imaging of tumors could significantly improve the diagnosis accuracy. In this study, nanoscale coordination polymers (NCPs) with a diameter of approximate to 80 nm are obtained with 1,1-dicarboxyl ferrocene (Fc) as building blocks and magnetic gadolinium(III) ions as metallic nodes using a nanoprecipitation method, then further aminated through silanization. The amine-functionalized Fc-Gd@SiO2 NCPs enable the covalent conjugation of a fluorescent rhodamine dye (RBITC) and an arginine-glycine-aspartic acid (RGD) peptide as a targeting ligand onto their surface. The formed water-dispersible Fc-Gd@SiO2(RBITC)-RGD NCPs exhibit a low cytotoxicity, as confirmed by MTT assay. They have a longitudinal relaxivity (r(1)) of 5.1 mM(-1) s(-1) and transversal relaxivity (r(2)) of 21.7 mM(-1) s(-1), suggesting their possible use as both T-1-positive and T-2-negative contrast agents. In vivo MR imaging experiments show that the signal of tumor over-expressing high affinity (v3) integrin from T-1-weighted MR imaging is positively enhanced 47 +/- 5%, and negatively decreased 33 +/- 5% from T-2-weighted MR imaging after intravenous injection of Fc-Gd@SiO2(RBITC)-RGD NCPs.