Self-Limiting Growth Nanoscale Coordination Polymers for Fluorescence and Magnetic Resonance Dual-Modality Imaging

The size and shape of coordination polymers (CPs) are often tuned by external factors including reaction temperature, reaction time, precursor ratio, auxiliary ligand, and surfactant. Here, a self-limiting growth of uniform nanoscale CPs (NCPs) spheres with Gd3+ and Ru[4,4'-(COOH)(2) bipyridyl(bpy)](3)(2+) (L-Ru) as precursors is reported. Sexadentate L-Ru and nine-coordinating Gd3+ play key roles in the formation of the NCPs via a simple and robust self-limiting procedure. Therefore, the formation of NCP spheres is almost unaffected in the reaction temperature of 100-160 degrees C for 1-6 h. Moreover, no auxiliary ligand or surfactant is required, whereas high yield and simple procedure are obtained. The red fluorescence of L-Ru and high longitudinal relaxivity of Gd3+ remain in the NCPs, which are therefore examined as fluorescence-magnetic resonance (MR) dual-modality imaging probes. The structural merits of the NCPs enable high MR contrast efficiency. Red emission avoids the auto-fluorescence and light scattering from tissues and realizes low-background imaging. The low toxicity and background, and high imaging efficiency of the NCPs are confirmed using HepG2 cells, zebrafish, and tumor-bearing mice as models.